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Ecological theory predicts that specialist insect herbivores are more likely to locate and colonize host plants growing in relatively sparse or pure stands compared to host plants growing amongst diverse non-host vegetation. We tested the hypothesis that increasing the apparency and accessibility of milkweed (Asclepias spp.) host plants in small polyculture gardens would boost their colonization by the monarch butterfly (Danaus plexippus), an iconic native species of conservation concern. We established replicated gardens containing the identical mix of milkweeds, flowering nectar sources, and non-host ornamental grasses but arranged in three different spatial configurations that were monitored for monarch colonization over two successive growing seasons. Monarch eggs and larvae were 2.5–4 times more abundant in gardens having milkweeds evenly spaced in a 1 m corridor around the perimeter, surrounding the nectar plants and grasses, than in gardens in which milkweeds were surrounded by or intermixed with the other plants. Predator populations were similar in all garden designs. In a corollary open-field experiment, female monarchs laid significantly more eggs on milkweed plants that were fully accessible than on milkweeds surrounded by non-host grasses of equal height. In addition, we monitored monarch usage of 22 citizen-planted gardens containing milkweed and nectar plants in relation to their botanical composition, layout, and surrounding hardscape. Multivariate analysis explained 71% of the variation, with significantly more eggs and larvae found in gardens having milkweeds spatially isolated as opposed to closely intermixed with non-host plants, and in gardens having 100 m north/south access unimpeded by structures. Numerous programs encourage citizens to establish gardens with milkweed and nectar plants to help offset habitat loss across the monarch's breeding range. Our findings suggest guidelines for garden design that can help make the urban sector's contributions to monarch habitat restoration more rewarding for participants, and of greater potential value to monarch recovery.

E-mail to the authors, 8 April 2015: I am a beekeeper who has a good relationship with area golf courses. Recently the golf pros approached me about the idea of naturalizing the roughs with a low maintenance drought tolerant grass/wild-flower mixture. They would also like me to put honey bee hives on their courses to encourage pollination. It would be a great opportunity to diversify the flora as well as educate the public on the importance of floral variety for pollinators. Is there any chance the UK Entomology department would like to extend their Operation Pollinator Project to our county? The highly publicized decline of bees, monarch butterflies, and other iconic pollinators inspires broad public empathy and can be a springboard for outreach education about insects and engaging local user groups in grassroots insect conservation (Colding et al. 2006, Xerces Society 2012, MonarchWatch 2015). This article highlights opportunities for entomologists to partner with golf courses (among the most ubiquitous open-space urban and peri-urban land types) for pollinator conservation, outreach education, teaching, and research. Forging such natural links can engage diverse target audiences, including golf industry staff, golfers, club members and guests, neighborhood associations, community groups, undergraduate and graduate students, and the general public. Golf courses are often just a short drive away from urban university campuses, making them accessible as sites for …

Plant secondary chemicals can alter herbivore suitability for parasitoids by weakening or stunting the host, delaying its development, or when larval parasitoids encounter ingested phytotoxins in the body of their host. Experiments with different parasitoids that exploit the same host species feeding on the same plant may provide insight about how parasitoid life history affects the strength of such interactions. The encyrtid wasp Copidosoma bakeri, a slow-developing polyembryonic egg-larval parasitoid, and the tachinid fly Linnaemya comta, a fast-developing solitary species, both parasitize Agrotis ipsilon, a generalist noctuid. We tested the hypothesis that of the two parasitoid species, the encyrtid, because of its more prolonged developmental association with the host, would suffer greater fitness costs when A. ipsilon feeds on perennial ryegrass containing an alkaloid-producing fungal endophyte. Indeed, fewer parasitized cutworms yielded C. bakeri broods, and those host mummies were smaller, formed more slowly, and contained fewer adults when the hosts fed on endophytic as opposed to endophyte-free grass. In contrast, L. comta fitness parameters were similar regardless of the type of grass upon which their host fed. Our results highlight that the outcome of endophyte-mediated tritrophic interactions may differ for different parasitoid species. Implications for integrating the use of endophytic grasses and biological control are discussed.

Ontogenetic changes in feeding behavior of armyworms, Pseudaletia unipucta (Haworth), were compared on tall fescue [Schedonorus arundinaceus (Schreb.) Dumort] cultivars with spiny-, intermediate-, or smooth-edged leaf blades to clarify whether the edge spines deter caterpillars, in which case release of modified, smooth-edged forage grasses for improved livestock performance might aggravate armyworm damage to pastures. Edge biting, success initiating edge-feeding, and propensity to window- or edge-feed were observed for individual 2nd, 3rd, or 4th instars on grass leaf blades with intact margins. Early second instars bit smooth and spiny leaf edges with equal frequency but were unable to initiate edge-feeding. They fed on leaf edges after margins were cut away, but not when leaf juice was applied to intact edges, indicating the leaf margin is a barrier. Third and 4th instars mostly edge-fed on smooth leaves, but on the grasses with spiny margins they compensated for the difficulty of edge-feeding by prolonging their window-feeding. There was no developmental cost to window-feeding by 3rd instars, but 4th instars suffered reduced weight gain on spiny grass apparently because, unlike earlier instars, their mandibles are too large and not well shaped for efficient window-feeding between the parallel vascular bundles. Armyworms display behavioral plasticity in feeding mode in response to spiny- versus smooth-edged grasses. Greater use of smooth-bladed pasture grasses may result in proportionately more edge-feeding by armyworms but is unlikely to result in markedly greater pasture losses because this grass-feeding specialist so effectively exploits conventional tall fescue despite its structural characteristics.

Root-feeding grubs (Coleoptera: Scarabaeidae) were sampled from damaged areas of 61 irrigated roughs on 32 Kentucky golf courses to determine species composition and natural enemy incidence, the first such survey in the United States' transitional turfgrass climatic zone. Masked chafers (Cyclocephala lurida Bland and C. borealis Arrow) and Japanese beetle (Popillia japonica Newman) accounted for ≈73 and 26% of grubs found in an autumn survey, with Cyclocephala spp. predominating at most sites, although mixed infestations were common. Only a few Phyllophaga spp., and no exotic species other than P. japonica were found. Cyclocephala spp. also predominated in seasonal and statewide surveys regardless of whether a course had cool- or warm-season grass fairways. Pathogenic bacteria, Paenibacillus and Serratia spp., and the autumn-active parasitoid Tiphia pygidialis Allen were the main enemies associated with Cyclocephala spp. Predominant enemies of P. japonica were Paenibacillus, Serratia, and Metarhizium spp. in autumn, and eugregarines, Stictospora sp. (probably S. villani Hays and Clopton) and Tiphia vernalis Rohwer in spring. Entomopathogenic nematodes and the microsporidian Ovavesicula popilliae Andreadis & Hanula were nearly absent in our samples. No predictive relationships were found between soil parameters and proportionate abundance of Cyclocephala or P. japonica, or with natural enemy incidence at particular sites. Although incidence of individual enemies was generally low (

Polyembryonic parasitoids producing single-sex broods of clonal offspring provide an unusually clear window into the classic tradeoff between the number and size of offspring. We conducted a laboratory study of the encyrtid parasitoid Copidosoma bakeri parasitizing the noctuid Agrotis ipsilon to examine the way that size and number of offspring tradeoff in broods of each sex and to determine how the fit between host and parasitoid brood is achieved. We found that brood mass (wasp body massbrood size) was proportional to host mass, independent of brood sex, indicating a tight fit between brood and host and ensuring a sizenumber tradeoff. By correcting brood size and body mass of each brood for host mass, we demonstrated the expected inverse relationship between wasp variables. We postulated that the wasp brood might achieve the fit to the host by (1) adjusting brood size based on information available early in host development before and during division of the embryo, (2) manipulating host size late in host development after completion of embryo division, or (3) simply adjusting individual wasp mass to fill the host. We evaluated host responses to parasitismand correlations between brood size and host growth early and late in developmentfor broods of each sex. The data are consistent with adjustment of brood size to the amount of host growth early in host development and with manipulation of host mass late in host development. The tight link between host mass and brood mass also suggests a final adjustment by parasitoid growth to achieve complete filling. Within the tight fit, female broods were smaller but contained larger individuals than male broods. The sex-specific balance point of the tradeoff and sex differences in balancing mechanisms and responses to host size suggest different selection pressures on each sex requiring future investigation.

The Japanese beetle, Popillia japonica Newman, has an unusually broad host range among deciduous woody plants, yet it feeds only sparingly, or not at all, on certain species in the field. We evaluated beetles' preference, survival over time and fecundity on eight woody plant species historically rated as susceptible or resistant and, after verifying those ratings, tested whether resistance is correlated with so-called quantitative defense traits including leaf toughness, low nutrient content (water, nitrogen, and sugars), and relatively high amounts of tannins or saponins, traditionally associated with such plants. We further tested whether species unsuitable for Japanese beetles are also rejected by fall webworms, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), the expected outcome if the aforementioned traits serve as broad-based defenses against generalists. Choice tests supported historical resistance ratings for the selected species: tuliptree, lilac, dogwood, and Bradford callery pear were rejected by Japanese beetles, whereas sassafras, cherry plum, Virginia creeper, and littleleaf linden were readily eaten. Rejected species also were unsuitable for survival over time, or egg-laying, indicating beetles' inability to overcome the resistance factors through habituation, compensatory feeding, or detoxification. None of the aforementioned leaf traits was consistently higher or lower in the resistant or susceptible plants, and plant species rejected by Japanese beetles often were not rejected by fall webworms. Specialized secondary chemistry, not quantitative defenses, likely determines the Japanese beetle's dietary range among deciduous woody plant species it may encounter.

Neotyphodium and Epichloe species (Ascomycota: Clavicipitaceae) are fungal symbionts (endophytes) of grasses. Many of these endophytes produce alkaloids that enhance their hosts' resistance to insects or are toxic to grazing mammals. The goals of eliminating from forage grasses factors such as ergot alkaloids that are responsible for livestock disorders, while retaining pasture sustainability, and of developing resistant turf grasses, require better understanding of how particular alkaloids affect insect herbivores. We used perennial ryegrass Lolium perenne L. (Poaceae) symbiotic with Neotyphodium lolii x Epichloe typhina isolate Lp1 (a natural interspecific hybrid), as well as with genetically modified strains of Lp1 with altered ergot alkaloid profiles, to test effects of ergot alkaloids on feeding, growth, and survival of the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), a generalist grass-feeding caterpillar. Neonates or late instars were provided clippings from glasshouse-grown plants in choice and rearing trials. Wild-type endophytic grass showed strong antixenosis and antibiosis, especially to neonates. Plant-endophyte symbiota from which complex ergot alkaloids (ergovaline and lysergic acid amides such as ergine) or all ergot alkaloids were eliminated by endophyte gene knockout retained significant resistance against neonates. However, this activity was reduced compared to that of wild-type Lp1, providing the first direct genetic evidence that ergot alkaloids contribute to insect resistance of endophytic grasses. Similarity of larval response to the two mutants suggested that ergovaline and/or ergine account for the somewhat greater potency of wild-type Lp1 compared to the knockouts, whereas simpler ergot alkaloids contribute little to that added resistance. All of the endophyte strains also produced peramine, which was probably their primary resistance component. This study suggests that ergot alkaloids can be eliminated from an endophyte of perennial ryegrass while retaining significant insect resistance.

We investigated the biology of Tiphia pygidialis Allen, a previously unstudied native parasitoid of masked chafer, Cyclocephala spp. grubs, in central Kentucky and the seasonal dynamics of Tiphia vernalis Rohwer, an introduced parasitoid of Japanese beetle, Popillia japonica Newman. T. pygidialis was active from mid-August to early October, parasitizing third-instar masked chafers, whereas T. vernalis attacked overwintered third-instar P. japonica from mid-April to early June. Adult T. vernalis were attracted to modified Japanese beetle traps and yellow pan traps and to 10% sugar water sprayed on tree foliage. Spraying sugar water directly on turf most effectively monitored T. pygidialis wasps. Parasitism rates as high as 33 and 58% were observed for T. pygidialis and T. vernalis, respectively. In the laboratory, T. pygidialis larvae progressed through five instars to cocoon formation in ≈22 d. They overwinter as prepupae. Field-collected female wasps lived 32 ± 4 d, parasitizing 22 ± 6 grubs. In...

We examined the effects of supplemental food sources on parasitism of turf-infesting white grubs (Coleoptera: Scarabaeidae) by tiphiid wasps (Hymenoptera: Tiphiidae). Survival of spring active Tiphia vernalis Rohwer and late summer active Tiphia pygidialis Allen, parasitoids of Japanese beetle, Popillia japonica Newman, and masked chafer, Cyclocephala spp., grubs, respectively, was significantly increased when wasps were provided with 10% sugar water in the laboratory. Presence of a grub for host feeding did not affect wasp longevity. Sugar sprays applied directly to turf were examined as a method for increasing grub parasitism rates. Large numbers of T. pygidialis visited turf sprayed with sugar water to feed. Parasitism of Cyclocephala spp. grubs by T. pygidialis was reduced in sugar-sprayed turf, but higher in turf plots located near sugar-sprayed turf. T. vernalis, which feeds on homopteran honeydew secretions, was never observed feeding on sugar-sprayed turf, nor did such treatments affect i...

The Japanese beetle (Popillia japonica Newman), a polyphagous scarab, feeds on certain palatable plants that are toxic, or reputedly toxic. Paralysis of the beetle after consumption of flowers of zonal geranium (Pelargonium × hortorum L. H. Bailey) has been documented, but factors affecting expression and range of this phenomenon are poorly known. Published anecdotes regarding toxicity of two other hosts, larkspur (Delphinium sp.) and bottlebrush buckeye (Aesculus parviflora Walt.), have not been empirically tested. For zonal geraniums, we compared toxicity with P. japonica of flowers versus leaves, sun-grown and shaded plants, and different-colored flowers. The progression of paralysis and recovery, as well as survival of paralyzed beetles under laboratory and field conditions, also were evaluated. Beetles became paralyzed after feeding on flowers of zonal geranium, but not by consuming leaves, suggesting the active compound is unique to flowers. Shaded or sun-grown flowers, and red-, white-, or...

We tested the hypothesis that early-season defoliation of flowering crabapple, Malus sp., by eastern tent caterpillars, Malacosoma americanum F., induces localized or systemic resistance to Japanese beetles, Popillia japonica Newman, feeding on the same trees in late June. ‘Candymint Sargent’ crabapple trees were inoculated with M. americanum egg masses, resulting in extensive defoliation during March and April. Second flush leaves of defoliated trees were smaller and thinner than those of control trees. In laboratory feeding assays with non-damaged foliage, beetles generally preferred fully expanded leaves over partially expanded ones, regardless of whether or not the source tree had been defoliated. Detached first flush leaves with caterpillar damage were fed upon less than comparable non-damaged leaves, suggesting that early-season wounding causes some within-leaf reduction in palatability to P. japonica. Other assays with detached first- and second-flush leaves, however, indicated absence of induced, systemic resistance. Previously-defoliated and control trees sustained comparable damage from natural beetle populations in the field. Our results suggest that defoliation of Malus sp. by tent caterpillars in early spring is unlikely to reduce feeding damage by Japanese beetles later in the same growing season.

We studied effects of parasitism by two Tiphia species (Hymenoptera: Tiphiidae) on burrowing behavior of their respective scarabaeid hosts and tested the hypothesis that parasitoid alteration of host hormones accounts for the observed behavioral change. In turf field-plots, third-instar masked chafer grubs, Cyclocephala sp., parasitized by native Tiphia pygidialis Allen burrowed to depths of 12-16 cm within 21 d, whereas nonparasitized grubs remained in the upper 4 cm of soil. Grubs bearing an egg or early-instar Tiphia larva were found relatively close to the surface, whereas those with a fourth- or fifth-instar parasitoid were deeper. Experiments in soil-filled, vertical observation chambers confirmed downward movement by parasitized Cyclocephala, and similar response in third-instar Japanese beetle, Popillia japonica Newman, parasitized by Tiphia vernalis Rohwer. Removal of the Tiphia egg from masked chafers was followed by initial downward movement of grubs and then a gradual ascent, suggesting that host behavior is affected both by the venomous sting and feeding by the wasp larva. Significant but inconsistent differences were found in juvenile hormone-III (JH III) titers in hemolymph taken from nonparasitized grubs or grubs parasitized for 1 or 14 d. Topical application of JH III and methoprene acid resulted in grubs moving deeper into the soil, whereas injection of 20-hydroxyecdysone did not affect grub behavior. Failure to dig deeply enough in soil when sampling for parasitized scarab grubs or Tiphia cocoons likely will result in underestimation of parasitism rates.

Cues used in below-ground host-searching behaviour and host discrimination were examined for Tiphia vernalis Rohwer and Tiphia pygidialis Allen (Hymenoptera: Tiphiidae), ecto-parasitoids of root-feeding larvae of the Japanese beetle, Popillia japonica Newman, and masked chafers, Cyclocephala spp. (Coleoptera: Scarabaeidae), respectively. Response to potential stimuli was compared in dual choice tests in an observation chamber filled with soil. Each wasp showed species-specific, directed movement along residual body odor trails made by dragging its respective host through the soil. Presence of a grub was not necessary for wasps to follow such trails. Frass from either host- or non-host grubs elicited trail-following, but each Tiphia species followed frass trails from its respective host when a choice was presented. Frass trails elicited stronger responses than body odor trails. The combination of host frass and body odor elicited the strongest trail-following responses. Our results suggest that once in the soil, Tiphia spp. locate their hosts using contact kairomones present in grub body odor trails and frass.

▪ Abstract The Japanese beetle, Popillia japonica Newman, an introduced scarab, has become the most widespread and destructive insect pest of turf, landscapes, and nursery crops in the eastern United States. It also damages many fruit, garden, and field crops. This review emphasizes recent research on the beetle's biology and management. Adults feed on leaves, flowers, or fruits of more than 300 plant species. Adaptations mediating their host finding, dietary range, mating, and oviposition are discussed. We also address abiotic and biotic factors affecting population dynamics of the root-feeding larvae. Japanese beetle grubs are widely controlled with preventive soil insecticides, but options for remedial control of adults and larvae presently are limited. Advances in understanding host plant resistance, entomopathogens, and other biorational approaches may provide more options for integrated management. Despite ongoing regulatory efforts, the Japanese beetle remains a threat as an invasive species.

We tested the potential for the Japanese beetle, Popillia japonica Newman, to habituate to a neem-based feeding deterrent applied to foliage of linden, Tilia cordata L., a preferred host for the adults. Female beetles' consumption of control foliage versus foliage treated with either a low or high rate of neem insecticide, corresponding to 9 or 39 pm azadirachtin, respectively, was tested in a series of 4-h choice or no-choice tests over four successive days. In another experiment, females were conditioned for 22 h with either control foliage, leaves treated with the low rate, or a mixture of both treated and untreated leaves. Deterrence of either the low or high rate of neem to these beetles was then evaluated in choice tests with control foliage, as before. In choice tests, mean consumption of control foliage was always greater than for treated foliage, regardless of rate. There was, however, proportionately more feeding on foliage treated with the high rate upon successive exposures. In no-choice tests, beetles initially deterred by the low rate were not significantly deterred by that rate by the third and fourth days of the experiment. Finally, beetles conditioned by exposure to leaves treated with the low rate were not deterred by that rate in a subsequent choice test, although they were deterred by the higher rate. Despite these trends, we suggest that Japanese beetles' polyphagy and mobility probably would reduce the likelihood for habituation to neem-based feeding deterrents in the field.

Patterns of feeding by Japanese beetles, Popillia japonica Newman, were studied in relation to time of day or night and to ambient temperature (Ta). We also measured beetles’ thoracic temperatures (Tth) at rest, during preflight warm up, and during flight, and observed their within-plant distributions in relation to sunlight or shade to gain insight regarding whether their in-field behavior involves physiological and behavioral thermoregulation. Finally, we studied startle response as affected by Ta and time of morning. Japanese beetles fed most extensively within trees from midmorning until late afternoon, but also substantially in evening (1800–2200 hours) and sparingly throughout the night so long as Ta was >15°C. Beetles in the field were capable of endothermy, maintaining elevated Tth independent of basking. At low to moderate Ta (19–32°C), nonflying beetles in shade or direct sunlight had Tth as much as 3.75 or 5.5°C higher, respectively, than Ta. Thoracic temperature was elevated during fl...

Callirhytis cornigera (Osten Sacken) is a gall wasp that has alternating agamic and sexual generations that develop in large, woody stem galls and small, blister-like leaf galls, respectively, on pin oak, Quercus palustris Muenchhausen. We assessed the spatial distribution of the leaf galls within leaves, shoots, canopy levels, and whole trees, and examined the relationship between leaf gall density and various tree parameters. Within leaves, proportionately more galls were located on primary lateral veins (59.5%) or midveins (38.1%), as compared with the petioles (2.0%) or secondary lateral veins (0.4%). As many as 18 galls occurred on individual leaves, but most leaves contained 0–4 galls. Some current-year shoots contained as many as 132 leaf galls, but most shoots had

Published anecdotal reports suggest that Japanese beetles, Popillia japonica Newman, feed more heavily on host plants growing in full sun than on shaded plants. We studied the effects of shading on foliar characteristics of roses (Rosa variety floribunda ‘Class Act’) and determined preference and fecundity of beetles provided with sun- or shade-conditioned leaves. Defoliation by P. japonica also was compared between sun-grown and experimentally shaded roses in the field. Leaves from plants grown in full sun were smaller and thicker than ones from shaded plants, with slightly higher tannins. Leaf toughness and nitrogen levels were not affected by shading, but leaves from sun-grown plants had relatively higher sugar content. Beetles consistently consumed more foliage from sun-grown plants than from shade-grown plants in laboratory preference tests. However, beetles fed continuously for 2 wk on leaves from sun- or shade-grown plants had similar fecundity. In the field, beetles fed somewhat more heav...

Populations of Callirhytis cornigera (Osten Sacken) and its associated community of natural enemies and inquilines were monitored on pin oak, Quercus palustris Muenchhausen, in Lexington, KY, from 1997 to 1999. The gall wasp has alternating agamic and sexual generations that differ morphologically and develop in multichambered galls on branches and single-chambered galls on leaves, respectively. There was a strong association between maximum gall diameter and the number of total stem gall inhabitants, such that proportionately more C. cornigera survived and fewer were parasitized as stem gall diameter increased. The most abundant natural enemies of the agamic generation included the hymenopteran parasitoids Sycophila spp. (Eurytomidae) and Ormyrus labotus Walker (Ormyridae), and the clerid predator Phyllobaenus verticalis (Say). The most abundant inquilines in stem galls were the cynipids Synergus sp. near lignicola and Ceroptres sp., and the dogwood borer, Synanthedon scitula (Harris) (Lepidoptera: Sesiidae). In leaf galls, Aprostocetus sp. was the most abundant parasitoid, and Ceroptres sp. was the only inquiline. The unique aspects of the C. cornigera gall system are discussed, including the relative abundance, emergence phenology, and host relationships of C. cornigera and its associated natural enemies and inquilines.

We studied ant predation on eggs and larvae of the black cutworm, Agrotis ipsilon (Hufnagel), and on eggs of the Japanese beetle, Popillia japonica Newman, on golf courses and lawns in central Kentucky. Lasius neoniger Emery accounted for >99% of the ant mounds on golf putting greens and collars. Although often regarded as a nuisance pest, L. neoniger preyed heavily upon A. ipsilon eggs on turfgrass cores implanted into putting greens, collars, fairways, and roughs. Predation on eggs was lower in fairways than in roughs, and in plots where ant populations were reduced by insecticides. When 1,600 individual 1st-instar cutworms were placed near L. neoniger nests on putting greens, 62% were attacked and killed upon their 1st encounter with the ants. Third- and 4th-instar cutworms generally fended off attacks by L. neoniger and Formica pallidifulva nitiventris Emery, but were invariably killed during encounters with Formica schaufussi Mayr and Formica subsericea Say, larger ants that are common in lawns and golf roughs. Predation on implanted Japanese beetle eggs also tended to be greater in roughs than in fairways, and fewer grubs were found in areas of golf roughs where ants were abundant than where ants had been controlled. This study suggests that predation by indigenous ants provides an important buffer against pest outbreaks on lawns and golf courses.

It is commonly held that food-aversion learning should be more prevalent in polyphagous herbivores than in specialists. We tested the ability of Popillia japonica, a polyphagous scarab, to learn avoidance of a palatable but illness-inducing plant. Beetles that feed on flowers of geranium, Pelargonium × hortorum, became paralyzed, although most recovered within 24 h. In choice tests, naive beetles strongly preferred geranium petals over leaves of linden, Tilia cordata, a highly suitable host. Experienced beetles maintained this preference although it resulted in repeated bouts of paralysis. Fecundity was >10 times higher for beetles fed linden foliage for 2 wk than for those fed only geranium. Nevertheless, when a surplus of both foods was provided, the beetles fed mainly on geranium, resulting in greatly reduced fecundity. These results contradict the view that generalists should show propensity for food-aversion learning. Indeed, in this case, P. japonica continued to prefer the toxic plant, compromising its fitness.

The basis for resistance of Bradford callery pear, Pyrus calleryana Decaisne ‘Bradford,’ [Rosaceae] to the Japanese beetle, Popillia japonica Newman, was investigated. Chloroform-dipping rendered leaves palatable, initially suggesting that deterrent waxes had been removed. However, extracts containing surface waxes were not deterrent. Subsequent experiments showed that increased palatability of solvent-dipped leaves is associated with enzymatic tissue browning, characteristic of polyphenol oxidases, rather than simply release of phagostimulants from surface disruption of damaged leaves. Frozen and thawed leaves showed similar browning, becoming increasingly palatable for several hours after thawing. Palatability changes were temperature- and aerobic-sensitive, further evidence that oxidizing enzymes are involved. Juice from leaves that had been frozen and thawed stimulated feeding on glass fiber disks, whereas fresh leaf juice did not. Survival and fecundity were much higher for beetles fed frozen and thawed or chloroform-dipped Bradford pear leaves than for beetles fed normal leaves. We hypothesize that decompartmentalization of deterrent compounds, possibly phenolics, followed by enzymatic oxidation and altered leaf chemistry may explain the increased palatability of chloroform-dipped or frozen and thawed Bradford pear tissue to P. japonica. This approach may be helpful in identifying specific compounds responsible for resistance of woody plants to generalist insects.

Attraction of Japanese beetles, Popillia japonica Newman, to 17 compounds typical of those released by undamaged and insect-damaged angiosperm leaves was compared in replicated field trials. Eight compounds attracted significantly more beetles than did an unbaited trap; however, the 2 most attractive single compounds, phenylacetonitrile and ( Z )-jasmone, were only ≍10% as effective as geraniol, a component of commercial lures. Progressive pairwise addition of less attractive volatiles to a blend of phenylacetonitrile and ( Z )-jasmone resulted in increasing beetle capture. The relative attractiveness of blends of conifer/eucalyptus, fruit-like, and floral odors, plus a complete mixture of these, also was tested. Although the floral, fruit-like, and complete mixtures captured more beetles than did the conifer/eucalyptus blend or phenylacetonitrile alone, our results suggest that this polyphagous insect is likely to be attracted to many naturally occurring plant volatiles, and that as the number of components in a volatile blend increases, so will its attractiveness. The complete mixture of volatile compounds also attracted more green June beetles, Cotinis nitida (L)., than did the fruit-like, floral, or conifer/eucalyptus blends.

We studied the close range olfactory response of Japanese beetles, Popillia japonica Newman, to constitutive or feeding-induced volatiles from leaves of 4 maple species differing in susceptibility to defoliation. In pitfall arenas, intact leaves of susceptible species, Acer palmatum Thunberg and A. platanoides L., were not significantly more attractive than those of resistant maples, A. rubrum L. and A. saccharinum L. Consistent with these results, the compounds emitted by intact maple leaves were generally similar across resistance groupings. For each maple species, leaves that had been damaged overnight by Japanese beetles attracted significantly more beetles than did undamaged leaves. Beetles did not discriminate between damaged leaves of susceptible and resistant maple species. Significant differences were noted, however, in the types of feeding-induced compounds emitted by susceptible and resistant maple leaves. Specifically, leaves of susceptible species emitted relatively higher amounts of esters with fruit-like odors and the floral fragrance compound linalool, whereas leaves of resistant maples emitted more terpene hydrocarbons. Possible roles of volatile compounds as attractants and feeding stimulants, or as feeding deterrents, for the Japanese beetle are discussed.

The hypothesis that feeding-induced plant volatiles are responsible for aggregation of Japanese beetles, Popillia japonica Newman, on leaves was tested using clonal grape plants, Vitis Labrusca L. The attractiveness of undamaged vines, undamaged vines with nonfeeding beetles, vines with fresh feeding damage, and vines with overnight feeding damage was compared in replicated field trials by placing the treatments in the field in the morning and counting the number of beetles that landed on the plants throughout the day. Many more beetles were recruited to vines with overnight feeding damage than to any of the other treatments, indicating attraction to feeding-induced volatiles. Furthermore, the low number of beetles attracted to vines with nonfeeding beetles or freshly damaged vines provided evidence against the existence of a putative aggregation pheromone. Subsequently, we examined the emission of volatiles from grape vines in situ. During the period of peak emission (1200–1500 hours), emission from vines with overnight feeding damage was almost 65 times higher than from undamaged vines. Aliphatic compounds and terpenoids were the major classes of compounds emitted by the beetle-damaged vines. The implications of feeding-induced volatiles in host-finding and mate location by this polyphagous insect are discussed.

The volatile compounds emitted by leaves of four crabapple cultivars susceptible to damage by Japanese beetles and four relatively resistant cultivars were examined. Twelve compounds, mostly terpene hydrocarbons, were identified from intact leaves. The terpenes (E)-β-ocimene, caryophylene, germacrene D and (E,E)-α-farnesene occurred in significantly higher levels in susceptible cultivars, whereas resistant cultivars produced greater amounts of (E)-4,8-dimethyl 1,3,7-nonatriene and linalool. The relative attractiveness of the cultivars as determined in a pitfall bioassay, however, was not related to their susceptibility to the Japanese beetle as previously determined by defoliation sustained in the field. The attractiveness of individual cultivars was found to be positiviely correlated with linalool as a percent of the total volatile blend emitted by leaves. This study and previous work suggest that variation in susceptibility of crabapple cultivars to defoliation by Japanese beetles is not due to the attractiveness of the individual cultivars but rather to nonvolatile components of susceptibility and/or resistance. A scenario for host location by the Japanese beetle is presented.

The Japanese beetle, Popillia japonica Newman, an introduced polyphagous scarabaeid, is an important pest of woody landscape plants and fruit crops in the eastern United States. A striking aspect of the beetle’s behavior is its tendency to congregate on particular plants, often nearly defoliating them, while other suitable hosts in the vicinity are only lightly damaged (Fleming, 1972). Feeding almost always begins at the top of a plant, regardless of its height, and proceeds downward (Fleming, 1972).

Adult females of the southern masked chafer, Cyclocephala lurida Bland, produce a volatile sex pheromone that attracts conspecific males. Previously we documented that extracts of 3rd-instar Cyclocephala spp. grubs contain one or more compounds that attract males and stimulate copulatory attempts when these males arrive at the source of the odor. Attraction of males to larvae appears to be undocumented for any other insect species. We examined developmental expression of the production of this attractant within Cyclocephala spp., and evaluated hexane extracts of other species of scarabaeid grubs for attractiveness to C. lurida or conspecifics. We found that the attractant is not limited to the postoverwintering last instar, but rather is present in all larval stages and in male and female pupae. Extracts of Cyclocephala spp. grubs also attracted males of the northern masked chafer, Cyclocephala borealis Arrow. Hexane extracts of 3rd instars of Japanese beetles, Popillia japonica Newman, and green June beetles, Cotinis nitida L., were not attractive to male C. lurida , indicating that there is some phylogenetic specificity to this unusual production of a sex-specific attractant. Third instars of C. nitida do not attract conspecific males. Studies of male attraction to conspecific immature stages in Cyclocephala spp. and other Scarabaeidae may provide insights into the evolutionary origins of chemical communication systems.

The tremendous diversity of insect species is paralleled by diverse forms of communication between the sexes (Lewis 1984). A survey of insect fauna would soon reveal that every sensory modality is used in communication, from the obvious visual signals of brightly colored butterflies and acoustic signals of cicadas to the less obvious, but equally important, substrate-borne vibrational signals of leafhoppers and chemical signals used by many moths and beetles. The diversity of these signals has been shaped by evolutionary processes tied to sexual selection and speciation (Otte ' Endler 1989). Though the issues surrounding the role of sexual communication in speciation have not been resolved, studies of the evolution of communication have focused, in large part, on this diversification. An even more elusive evolutionary question concerns how sexual communication originates. The origin of functional communication is enigmatic because, by definition, it involves two parties, the signaler and the receiver. The physiological and behavioral requirements for signal production and signal reception are always different, yet both are necessary. Why would a firefly flash unless other fireflies could respond to that flash? Why would a male cricket sing if females did not have the potential to respond to that signal? How could a chemical signal originate, when the receiver often must have thousands of specialized receptors to respond?

Feeding preferences of Japanese beetle, Popillia japonica Newman, and southern masked chafer, Cyclocephala lurida Bland, grubs for six common cool-season turfgrasses were evaluated in choice tests in the greenhouse. On the basis of larval distributions, Popillia japonica consistently preferred perennial ryegrass, Lolium perenne L., over all other turfgrasses tested. In contrast, C. lurida showed no consistent pattern of preference. Presence of one grub species did not affect distribution of the other species. Grubs did not discriminate between tall fescue, Festuca arundinacea Schreb., infected with the endophyte Acremonium coenophialum Morgan-Jones & Gams and endophyte-free tall fescue.

Ant-exclusion to facilitate biocontrol by endemic natural enemies was investigated for suppressing infestations of two coccids, calico scale, Eulecanium cerasorum (Cockerell), and magnolia scale, Neolecanium cornuparvum (Thro), in landscape settings. Application of sticky bands combined with basal trunk sprays resulted in 92-100% reduction in counts of honeydew-seeking ants, mainly Formica subsericea Say, ascending large, scale-infested sugar maple (Acer saccharum Marshall) trees. Ant-exclusion was associated with increased numbers of green lacewing, mainly Chrysoperla rufilabris (Burmeister), larvae and spiders on multiple sample dates, and 54 and 69% fewer surviving scale nymphs after the first and second growing seasons. Foliar sooty mold accumulation was also significantly reduced where ants were excluded. In feeding trials, C. rufilabris larvae collected from the tree canopies consumed large numbers of settled scale nymphs. On another site, ant-exclusion led to 82% reduction in magnolia scale densities on Magnolia stellata (Siebold & Zuccarini) Maximowicz, compared with controls, after 1 yr. Nine and 10 ant species were found tending calico and magnolia scales, respectively, at landscape sites in central Kentucky, and in situ observation trials showed that many of them aggressively attack approaching lacewing larvae. Our results suggest that where ants are closely associated with soft scales on woody landscape plants, ant-exclusion has potential as a sustainable pest management strategy.

Turfgrass culture, a multibillion dollar industry in the United States, poses unique challenges for integrated pest management. Why insect control on lawns, golf courses, and sport fields remains insecticide-driven, and how entomological research and extension can best support nascent initiatives in environmental golf and sustainable lawn care are explored. High standards for aesthetics and playability, prevailing business models, risk management–driven control decisions, and difficulty in predicting pest outbreaks fuel present reliance on preventive insecticides. New insights into pest biology, sampling methodology, microbial insecticides, plant resistance, and conservation biological control are reviewed. Those gains, and innovations in reduced-risk insecticides, should make it possible to begin constructing holistic management plans for key turfgrass pests. Nurturing the public's interest in wildlife habitat preservation, including beneficial insects, may be one means to change aesthetic perceptions and gain leeway for implementing integrated pest management practices that lend stability to turfgrass settings.

Sticky traps baited with crude female extract of the southern masked chafer, Cyclocephala lurida Bland, were tested at 28 sites on a golf course and on 27 individual home lawns to determine if the numbers of males captured in short-term trapping could be used to predict subsequent grub densities. Hexane rinses of female beetles were effective in luring males to traps. There was no correlation between male captures and local densities of grubs on the golf course, where movement of beetles between adjacent areas may have confounded our ability to discriminate among high- and low-density sites. In contrast, there was significant, albeit weak correlation (r2 = 0.25) between male captures and subsequent larval populations in home lawns, even though trapping was restricted to only two nights due to limited availability of crude female extract. Identification and synthesis of the C. lurida sex attractant would allow season-long trapping, which could provide a more accurate assessment of beetle populations and prediction of grub densities at particular turfgrass sites. The fact that most home lawns sampled did not develop damaging infestations underscores the need for improved methods of sampling and risk assessment to avoid unnecessary preventative treatments.

We tested the response of wood and phloem boring Coleoptera to traps baited with ethanol alone, and to ethanol baits augmented with oak logs. The logs provided a source of natural oak volatiles, and we hypothesized that these volatiles would increase attraction of borers to ethanol. Ethanol baited traps augmented with oak logs attracted 2.3 times more cerambycid adults than ethanol alone, and 4.9 times more cerambycids than logs alone. Logs alone were not attractive to Scolytidae, nor did they enhance attractiveness of ethanol alone to scolytids. Although many saprophagous wood and phloem feeding Coleoptera are attracted to ethanol, these results suggest that for some groups of borers, other tree emitted volatiles may also aid host location.

Restricted infection of a lower leaf of cucumber, Cucumis sativus L., with the anthracnose fungus Colletotrichum lagenarium has been previously shown by others to induce persistent, systemic resistance to the same fungus and to at least 12 other diverse plant pathogens. The non-specificity of pathogen-induced resistance has fueled speculation that it might also affect arthropod herbivores. However, we found that immunization of cucumber with C. lagenarium had no effect on population growth of twospotted spider mites, Tetranychus urticae Koch, reared on foliage for which induced resistance to the same pathogen was confirmed. Similarly, immunization with C. lagenarium had no systemic effect on weight gain, duration of development, or pupal weight of fall armyworms, or on progeny production by melon aphids. In reciprocal tests, previous feeding injury from spider mites or fall armyworms did not induce systemic resistance to C. lagenarium. These results indicate that, at least for cucumber, pathogen-activated induced resistance is specific to plant pathogens, suggesting separate mechanisms of induced resistance to pathogens or herbivores. Resume Est-ce que l'immunization du concombre contre l'anthracnose par Colletotrichum lagenarium affecte ses proprietes d'hote vis-a-vis des arthropodes? Dans une etude de resistance induite, l'infection basale des feuilles du concombre, Cucumis sativus L., avec Colletotrichum lagenarium, le champignon de l'anthracnose, a genere une induction systemique et persistante, non seulement au meme champignon, mais aussi et surtout a l'egard de douze autres. La nature non-specifique de cette resistance a des lors engendre une hypothese, celle de savoir si cette non-specificite pourrait s'entendre au niveau d'arthropodes phytophages. Cependant, nos travaux ont demontre que l'immunite vis-a-vis de C. lagenarium n'affecte ni la population de tetraniques, Tetranychus urticae Koch, elevee sur des feuilles resistantes de concombre; ni le gain ponderal, ni la duree de developpement, ni le poids nymphal de Spodoptera frugiperda, ou la fertilite des aphides de melon. De ces resultats, il peut-etre deduit que, au moins chez le concombre, l'induction de resistance due a C. lagenarium demeure specifique aux champignons saprophytes, c'est a dire qu'il existe des mecanismes separes pour la resistance, soit aux champignons, soit aux arthropodes phytophages.

Chestnut blight fungus, Cryphonectria (Endothia) parasitica , causes bark and wood deformity to the lower bole of scarlet oak, Quercus coccinea L., but does not kill the tree. We tested the hypothesis that C. parasitica infection stresses the tree and predisposes it to attack by the twolined chestnut borer, Agrilus bilineatus (Weber). Scarlet oaks with obvious disease symptoms attracted significantly more A. bilineatus , cerambycids, and scolytids than did apparently healthy trees. However, only 9 of 21 diseased trees were successfully colonized. Total nitrogen and tannin concentrations of the phloem did not differ significantly between diseased and control trees; however, phenolic concentrations were significantly higher in the phloem of diseased trees that were colonized by borers. Total carbohydrate concentrations of xylem and phloem in July did not differ significantly between diseased and control trees, even in those diseased trees that were colonized. However, starch concentrations of the outer sapwood were slightly lower in all diseased trees. This tree decline complex is unusual in that the apparent predisposing stress, C. parasitica , did not reduce radial growth or total carbohydrates, which are generally regarded as indicators of tree vigor.

Many generalist herbivores, especially adult beetles, are facultative florivores, feeding on leaves but readily accepting floral tissues when available. We speculated that day-flying beetles with high energetic requirements would benefit from dietary mixing with nutrient-rich flower tissues and favor them during foraging. We tested that "Floral Affinity Hypothesis" with Popillia japonica, a day-active ruteline scarab that feeds intermittently throughout its adult life on multiple plant species. In field tests with six species of flowering hosts, far more landings occurred on flowers than on foliage for all plants except Hibiscus syriacus which bears flowers along the main stem rather than terminally. Trials with elevated plants showed that height of the floral display contributes to beetles' landing on flowers. Flower petals generally were preferred over leaves in laboratory choice tests. Nitrogen and water content were comparable or higher in foliage than in petals, but plant sugars were much higher in petals. Longevity and fecundity of beetles provided single-plant diets of Hibiscus, Rosa x hybrida, or Trifolium flowers for 3 weeks were as high, or higher, than for beetles fed foliage of Tilia cordata, a highly suitable resource. As expected, rotating flowers or Tilia foliage with marginally suitable Quercus palustris foliage enhanced those parameters relative to a diet of Quercus alone, but beetles provided high-quality Tilia foliage also benefitted from dietary mixing with flowers. Nearly all past dietary mixing studies concerned immature insects, for which growth rate is paramount. Opportunistic florivory by adult beetles represents a type of dietary mixing wherein the premium may be calorie-rich food for fueling flight muscles, with ensuing reproductive benefits.

Juan G. (Rod) Rodriguez passed away peacefully on 28 October 2014, surrounded by his loving family in Lexington, Kentucky. He was born on 23 December 1920 in Espanola, New Mexico, the oldest of seven children. He graduated from Santa Fe High School and received a Bachelor of Science from New Mexico State University in 1943, and a M.S. (1946) and Ph.D. from Ohio State University in 1949. He was a Professor of Entomology at the University of Kentucky from 1949 until his retirement in 1989. After graduating from New Mexico State University, where he was active in the ROTC, Rod was inducted into the United States Army in the fall of 1943. He had obtained a civilian pilot's license while in college and initially trained as a pilot, intending to join the Army Air Corps. He was then placed into the 422nd Infantry Regiment, …

Adult Japanese beetles, Popillia japonica Newman (Coleoptera: Scarabaeidae), tend to aggregate and feed most heavily in the upper canopy of host plants, defoliating them from the top down. We examined characteristics of linden (Tilia cordata L.) foliage from different canopy zones and tested two hypotheses that might account for vertical stratification of feeding by this vagile, polyphagous folivore. In the field, P. japonica caused 4-12 times more damage to upper canopy leaves in full sunlight than to lower canopy leaves in sun or shade. However, this within-tree pattern apparently cannot be explained by differences in nutritional parameters (protein, water, and sugar content) or "defensive" properties (toughness, tannins) of leaves. Furthermore, beetles did not discriminate between foliage from different canopy zones in laboratory choice tests, nor were fecundity or longevity higher for beetles fed upper canopy, sun-exposed leaves. Clonal grape plants suspended from vertical posts in the field at 3.65, 1.83 or 0 m above ground showed a top-down defoliation pattern identical to that seen in linden trees. This suggests that the height of foliage per se strongly affects initial orientation and attack by P. japonica. Recent related studies have shown that both sexes of P. japonica are strongly attracted to host volatiles induced by feeding of conspecific beetles. We suggest that Japanese beetles begin to feed in the upper canopy for reasons unrelated to host nutritional variation (e.g., behavioral thermoregulation, visual orientation to the host silhouette), and that top-down defoliation follows as additional beetles are attracted to feeding-induced volatiles acting as aggregation kairomones.

The Japanese beetle is a polyphagous insect that typically aggregates on preferred host plants in the field. We studied the response of Japanese beetles to artificial damage, fresh feeding damage, and overnight feeding damage to test the hypothesis that beetles are attracted to feeding-induced volatiles. Crabapple leaves that had been damaged overnight by Japanese beetles or fall webworms attracted significantly more Japanese beetles than did undamaged leaves. Artificially damaged leaves or leaves freshly damaged by Japanese beetles, however, were not significantly more attractive than undamaged leaves. Leaves that had been damaged overnight by Japanese beetles or fall webworms produced a complex mixture of aliphatic compounds, phenylpropanoid-derived compounds, and terpenoids. In comparison, artificially damaged leaves or leaves with fresh Japanese beetle feeding damage generated a less complex blend of volatiles, mainly consisting of green-leaf odors. Feeding-induced odors may facilitate host location and/or mate finding by the Japanese beetle.

Females of the scarabaeid beetleCyclocephala lurida produce a volatile sex pheromone which attracts conspecific males. Field experiments demonstrated that larvae of both sexes also emit volatile chemicals that stimulate similar responses in adult males, including attempts by the attracted males to mate with the nonreproductive immature stage. Significantly more adult males were caught in traps baited with conspecific male or female larvae or adult females than in blank control traps. Hexane extracts of both male and female grubs were at least as effective as live larvae in trapping male adults, demonstrating that the behavioral responses are mediated by volatile chemicals. Sensory and behavioral responses of males to sex pheromones emitted by adult females are part of the functional communication system. However, their response to grubs is not functional, because grubs are normally temporally and spatially inaccessible to mate-seeking males. In theory, the evolution of a communication system is problematic because it requires the development of a signal in one sex and the sensory and behavioral attributes to respond to that signal in the other sex. The ontogeny of sex pheromone communication inC. lurida suggests a partial solution to this evolutionary problem. We propose that this sex pheromone communication system is probably derived from noncommunicative volatile chemicals that are lost in adult males and retained by adult females.

Phytomyza ilicicola (Diptera: Agromyzidae), a univoltine specialist leafminer, typically reaches higher population densities on cultivated host planted in sunny, urban sites than it does on native trees in the forest understory. I tested the hypothesis that environmental factors, more specifically differences in light intensity and soil fertility, are responsible for this observed pattern, either by affecting leaf morphology or nutritional quality, or indirectly through early leaf abscission. Clonal trees were planted at a common site and experimentally shaded and fertilized for 14 months before being exposed to oviposition by adult flies. Differences in leaf thickness, nitrogen and water status, and in the abundance, developmental rate, survival, pupal weights and abscission-related mortality of leafminers were compared among trees. Leaves from experimentally shaded trees were larger and thinner, with only two palisade cell layers as compared to three to four layers in leaves from unshaded trees. Crystals, probably of calcium oxalate, are abundant in the abaxial cell layer, and it was hypothesized that these might set mechanical constraints on larvae feeding within shaded leaves. However, there was little or no difference in leafminer abundance, developmental rate, survival to pupation, area of finished mines, or pupal weight between shaded and unshaded trees. Leafminers compensated for feeding within thinner, shaded leaves by consuming portions of the abaxial and adaxial palisade layers and leaving a thinner roof on the mine. Furthermore, there was no difference in thickness between leaves with successful or aborted mines in either shade or sun. Leaves from fertilized trees contained 37% higher total nitrogen than those from unfertilized control trees. Fertilization did not significantly affect leafminer abundance, developmental rate, mine area or pupal weight, but survival to pupation was slightly lower on fertilized trees. Abscission-related mortality of P. ilicicola was much higher in full sun than for shaded trees, opposite of what would be predicted if early abscission per se were a primary determinant of relative abundance between habitats. These results indicate that structural constraints on leafminer larvae within shaded leaves, differences in leaf nitrogen related to soil fertility, and/or differential mortality resulting from early leaf abscission are probably not the proximate causes of density variation of this leafminer between woods and urban habitats.

The twolined chestnut borer, Agrilus bilineatus (Weber) (Coleoptera: Buprestidae), attacks oaks (Quercus spp.) that have been weakened by prior environmental or biotic stress. Our earlier work showed that trees with relatively low winter starch reserves are more likely to be attacked by A. bilineatus the following summer. We hypothesized that such trees may have less energy available for defense (Callus formation and allelo-chemical synthesis) in tissues wounded by borer larvae. However, wounding experiments showed little or no relationship between winter or summer carbohydrate reserves, callus formation, radial growth, or concentrations of tannins and phenolics in wounded or nonwounded phloem tissues. Trees with relatively low winter carbohydrate reserves were again found to be attractive to adult A. bilineatus, although not all low starch trees were attacked or successfully colonized by borers. There was a trend for carpenterworm larvae, Prinoxystus robiniae (Lepidoptera: Cossidae), a generalist bark and wood borer, to be more successful in establishing galleries on low starch trees. Carpenterworms gained significantly more weight when fed phloem from trees attractive to A. bilineatus. Oaks that attracted large numbers of A. bilineatus or that were successfully colonized by the borer produced significantly less callus than did non-attacked trees when experimentally wounded at about the time of Agrilus egg hatch. Callus formation may limit the establishment of small larvae that feed slowly in the cambial region. These results indicate that current theory regarding relationships between increased tree stress and decreased allocation of energy reserves to radial growth and defense against phloem borers may be an oversimplification. We suggest that tree growth and the defensive response of phloem tissues may be limited more by the rate of carbohydrate utilization or by changes in source-sink relationships than by storage levels. Callus formation and synthesis of allelochemicals in wounded phloem may be under the same control as cambial activation, which is mediated by plant growth regulators and can be influenced by environmental conditions.