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Wheat midge, Sitodiplosis mosellana Géhin, is an invasive pest of wheat, Triticum aestivum L. (Poaceae) throughout Canada and the United States. The applicability of available monitoring tools, including sex-pheromone baited traps, yellow sticky cards, and soil core sample surveys, in the northern-most agroecosystem of its invasive range has not been assessed. In this study, the attraction of male wheat midge to two Delta traps (green and orange) baited with one of three pheromone lures (a flex lure and two red septa lures from different sources) were compared. The efficacy of three yellow sticky cards (7 × 12 cm, 14 × 18 cm, and 14 × 18 cm rolled into a cylinder) for capture of male and female midge was assessed. Larvae were extracted from wheat heads sampled at the same sites to determine relationships with earlier adult trap capture. More male adult midges were captured in pheromone-baited traps with a greater surface area and in traps baited with the Scotts flex lure than the Great Lakes IPM septa lure, which had higher and more variable pheromone release rates. The smaller yellow sticky cards captured more male and female midges than the larger yellow sticky cards, regardless of shape. The number of female midges captured on yellow sticky cards predicted the number of larvae in wheat heads. The number of male midges captured in pheromone-baited traps did not predict larval density. Relationships were found between the number of overwintering cocoons recovered in soil core samples and emerging midges the following spring.

The Asphondylia prosopidis Cockrell complex with its fungal associate produces four distinct bud galls on honey mesquite (Prosopis glandulosa). They are considered as potential biological control agents to reduce seed production of invasive mesquites. Previous studies suggest that the complex may consist of more than one gall midge species or biotype. Therefore, before conducting host specificity tests, it is essential to understand the relationships among the gall midges in the complex. Each gall type was collected from sympatric regions in Arizona, New Mexico, and Texas for four years. Here we show that midges producing each gall type were clearly separated based on phylogenetic analysis using DNA sequences in the cytochrome oxidase subunit I region. Furthermore, we confirmed that morphological differences between pupae from each gall type were discernible, although variable, using a scanning electron microscope. Based on these differences, we suggest that the A. prosopidis complex consists of four different gall midge species, three of which are cryptic species. Among them, Asphondylia species producing a barrel gall type and A. prosopidis producing the original gall type are potential biological control agents of P. glandulosa because they are multivoltine species with four to five generations per year that complete their annual life cycle exclusively on flower buds of mesquite.

Fern-insect interactions have not received the same attention as angiosperm-insect interactions have. It has even been stated that ferns may have very few interactions with animals because of their lack of flowers, fruits, and seeds. Consequently, for many decades fern-insect interactions have been overlooked and underestimated, especially for highly developed interactions such as those with gall-formers. The present work aims to review the galls of ferns and lycophytes worldwide, to provide an updated checklist including unpublished data and to estimate the global gall diversity of ferns and lycophytes. We recorded 93 host species, belonging to 41 genera. Galls were found in 20 fern families and one lycophyte family (Selaginellaceae). Most galls occur within the more derived ferns of the order Polypodiales, especially the fern families Polypodiaceae (21 host species), Dryopteridaceae (14 host species) and Athyriaceae (11 host species). Thirty-eight of the 133 gall morphotypes were induced by mites and 95 by insects of six orders (Coleoptera, Diptera, Hymenoptera, Lepidoptera, Thysanoptera, and Hemiptera). Among the insects, Cecidomyiidae (Diptera) caused most of the galls (35 morphotypes). So far, most galls have been reported from the Neotropical region (40 spp.) and Oriental region (28 spp.).

A new gall midge, Asphondylia nepetae sp. n. Viggiani (Diptera: Cecidomyiidae), causing flower gall on Clinopodium nepeta (L.) Kuntze (Lamiaceae), is described from Europe. The morphological characteristics of adult, larvae, and pupa are described and illustrated. Molecular approach (by sequencing 28S-D2, ITS2, and COI) confirmed that A. nepetae is a distinct species. The development of the gall is always associated with the presence of the fungus Botryosphaeria dothidea (Moug.: Fr.) Ces. and De Not. (Botryosphaeriales: Botryosphaeriaceae). The new species can complete several generations per year, on the flowers of the same host plant and its adults emerge from late spring to autumn. Pupae overwinter inside peculiar flower galls in a state of quiescence. The impact of the pest is highly variable with a percentage of flowers infested that ranged between 3 and 57.5% in the sampled years. Insect mortality was, at least in part, due to parasitoids that attack the young stages of the midge. Among them, the dominant species was Sigmophora brevicornis (Panzer) (Chalcidoidea: Eulophidae). © The Author(s) 2018.

Gall-inducing insects are known for altering source-sink relationships within plants. Changes in photosynthesis may contribute to this phenomenon. We investigated photosynthetic responses in wheat [Triticum aestivum L. (Poaceae: Triticeae)] seedlings attacked by the Hessian fly [Mayetiola destructor (Say) (Diptera: Cecidomyiidae], which uses a salivary effector-based strategy to induce a gall nutritive tissue in susceptible plants. Resistant plants have surveillance systems mediated by products of Resistance (R) genes. Detection of a specific salivary effector triggers downstream responses that result in a resistance that kills neonate larvae. A 2 × 2 factorial design was used to study maximum leaf photosynthetic assimilation and stomatal conductance rates. The plant treatments were-resistant or susceptible wheat lines expressing or not expressing the H13 resistance gene. The insect treatments were-no attack (control) or attack by larvae killed by H13 gene-mediated resistance. Photosynthesis was measured for the second and third leaves of the seedling, the latter being the only leaf directly attacked by larvae. We predicted effector-based attack would trigger increases in photosynthetic rates in susceptible but not resistant plants. For susceptible plants, attack was associated with increases (relative to controls) in photosynthesis for the third but not the second leaf. For resistant plants, attack was associated with increases in photosynthesis for both the second and third leaves. Mechanisms underlying the increases appeared to differ. Resistant plants exhibited responses suggesting altered source-sink relationships. Susceptible plants exhibited responses suggesting a mechanism other than altered source-sink relationships, possibly changes in water relations that contributed to increased stomatal conductance.

Understanding the mechanisms by which plants tolerate herbivory is important in the study of insect-plant interactions. In cranberry, current season growth has been identified as the main source of photosynthate for the developing fruits. Feeding injury by larvae of cranberry tipworm, Dasineura oxycoccana Johnson, disrupts the apical growth of cranberry shoots or uprights, but does not impact fruit output. To study the effects of experimentally depleting photosynthate available from sources other than the current season growth on fruit output, we girdled tipworm-injured uprights. This technique enabled us to estimate the contribution of current season growth in supplying photosynthate to developing fruits in tipworm-injured uprights. The mean fruit weight declined by >55% in those tipworm-injured uprights that were limited to photosynthate from only the current season growth (girdled uprights). The result was consistent between two phenologically different cultivars of cranberry, one a native selection from wild cranberry stands (‘Howes’) and the other a hybrid (‘Stevens’). In addition, fruit weight was positively correlated to current season leaf area in the girdled uprights only. These results strongly suggest that physiological integration among the different sources of photosynthate plays a key role in the tolerance of tipworm feeding injury for fruit output in cranberry.

Monitoring of Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae), populations is important for targeted management methods. Also, effectiveness of monitoring efforts is critical to surveillance efforts in regions of the world without this pest. Current Hessian fly monitoring traps rely purely on a single attractant, the female sex pheromone, which is ineffective for monitoring females in the population. Our objective was to examine another attractant targeting vision of both males and females. To do this, we evaluated emitted light of various wavelengths and intensities produced by light-emitting diodes (LEDs). Hessian flies were released in the center of a four-leaf clover-shaped arena, which contained an LED within each collection cup at the apex of each of the four cloverleaves. Initially, we examined a range of colors, including red, amber, green, and blue, with wavelengths of 624, 590, 527, and 472 nm, respectively. Both sexes of Hessian fly preferred green LEDs; therefore, we examined specific wavelengths within the green spectrum (502, 525, and 565 nm), and varied light intensities (4, 8, 12, and 16 W/m2). Specifically, females preferred wavelengths in the lower region of the green spectrum (502 and 525 nm), and both sexes preferred high intensity light (16 W/m2). This is the first report of Hessian fly attraction to select emitted wavelengths and intensities from LEDs under controlled conditions. Leveraging these results into new trap designs will add a second sensory modality to the existing trap; however, future studies are needed to assess attraction to LED traps under field conditions.

Gall midges (Diptera: Cecidomyiidae) damage mango by feeding on flowers and fruit tissues, inducing galls on leaves, and providing inoculums of anthracnose. Dasineura amaramanjarae Grover and Procontarinia mangiferae (Felt), two gall midges that damage flowers in all mango-growing areas of the world, have recently been recorded in Pakistan, and studies were conducted in 2011 and 2012 on the within-tree and orchard distribution patterns and cultivar preference of both species in Pakistan at one location (Rahim Yar Khan). Both gall midge species were found on all mango cultivars examined (Chaunsa, Fajri, Dusehri, Surkha, Sindhri, and Anwar Ratul), with the most damage occurring to Surkha and Dusehri. Research on midge distribution patterns in different parts of mango orchards (central, southern, northern, eastern, and western sides) showed these species to be found in all areas, with the greatest numbers in the central and southern regions. In addition, both species were most abundant on the lower parts of the mango tree canopy.

Blueberry gall midge, Dasineura oxycoccana (Johnson), is a key pest of blueberries in Florida. As a larva, this insect feeds in developing flower and leaf buds. Management of D. oxycoccana relies principally on chemical insecticides; however, efficacy is limited because D. oxycoccana is sheltered within the plant during most of its life cycle. Natural enemies, particularly parasitoids, may play an important role in regulating D. oxycoccana populations. To determine the seasonal dynamics and parasitism rates of eulophid and platygastrid wasps parasitizing D. oxycoccana larvae, we sampled D. oxycoccana larvae by collecting infested blueberry leaf buds from a minimally-managed farm in north central Florida. Midge larvae were examined under a microscope to determine parasitism status of host instars. Parasitism rates ranged from 25 to 40% over the 3-yr study. Percent parasitization was significantly higher in third instars than first or second instars. Midge larvae in the centers of leaf buds were significantly less likely to be parasitized than larvae in outer layers of leaf buds. Thirty-seven percent of midge larvae had been parasitized multiple times, suggesting these parasitoids do not discriminate between parasitized and unparasitized hosts. Implications for pesticide use in relation to the conservation of natural enemies and management of D. oxycoccana populations are discussed.

For animals that lay eggs, a longstanding question is, why do females choose particular oviposition sites? For insects that lay eggs on plants there are three hypotheses: maximizing suitable habitat for juveniles, maximizing female lifespan, and maximizing egg survival. We investigated the function of the oviposition-site choice behavior of a gall midge, the Hessian fly, Mayetiola destructor (Say). In spite of living less than a day and having hundreds of eggs, the ovipositing female is choosy about the placement of eggs. Choosiness makes sense. The tiny gall-making neonate larva has limited movement and strict requirements for colonization. We examined whether offspring benefit from the Hessian fly female's preference for the plant's youngest leaf. To do this we restricted the female's access to the first, second, or third leaf of a seedling (wheat Triticum aestivum L.) plant. Being placed on older leaves did not impact egg survival or larval survival during migration to attack sites at the base of the plant, but did have negative impacts on egg-to-adult survival (reduced by 48%) and reproductive potential (reduced by 30-45%). These negative impacts appear to come from larvae having to search harder to find the limited number of reactive plant cells that can be reprogrammed to form the gall nutritive tissue. We propose that the ability of larvae to find these reactive cells in spite of being placed on an older leaf is important because it creates leeway for female behavior to evolve in the face of other selection pressures, e.g., attack by egg parasitoids.

The seasonal development of the swede midge Contarinia nasturtii Kieffer was studied in Quebec in 2004 and 2005 using pheromone traps, emergence cages, and visual inspection in relation to degree-day accumulations (DD7.2°C). Peak emergence of overwintering adults occurred between 344 and 731 DD7.2°C (second half of June) during both seasons. The swede midge had three to four overlapping generations in Quebec based on adult captures in pheromone traps and abundance of larvae in the field. The level of infestation was higher in late transplants than in early transplants, with cauliflower and broccoli being more susceptible to damage than white or red cabbage under high pest population.

Insect herbivory can negatively or positively affect plant performance. We examined how a stem gall midge Rabdophaga rigidae affects the survival, growth, and bud production of current year shoots of the willow Salix eriocarpa. In mid-May, the gall midge initiates stem galls on the apical regions of shoots. The following spring, galled shoots had thicker basal diameters and more lateral shoots than ungalled shoots. Although galled shoots were on average 1.6 times longer than ungalled shoots, there were no significant differences in shoot length or in the numbers of reproductive, vegetative, and dormant buds per shoot. However, the subsequent survival of galled shoots was significantly higher than that of ungalled shoots, probably because of the thicker basal diameter. This increased shoot survival resulted in approximately two times greater reproductive, vegetative, and dormant bud production on galled shoots compared with ungalled shoots in the following spring. These results suggest that the willow regrowth induced by galling can lead to an increase in bud production through increased shoot survival.

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7°C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower (≈1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. T...

Climate variability is expected to have an influence on the population of Hessian fly, Mayetiola destructor Say (Diptera: Cecidomyiidae), a serious insect pest of winter wheat in the southeastern United States. This study had two objectives: 1) to examine the effects of El Nino-Southern Oscillation (ENSO) on Hessian fly infestation and 2) to develop a weather-based Hessian fly infestation model for wheat yield loss prediction. At least 20 years of Hessian fly infestation and wheat yield records from two locations in South Georgia were used for this study. The yearly values of infestation were separated by ENSO phase and tested to assess the infestation differences across ENSO phases. Each year, yield losses from infestation were calculated by subtracting the yields of resistant varieties from those of susceptible ones. The yield losses were then separated by ENSO phase and tested. Multiple regression analyses were conducted to identify the contribution of monthly weather variables and changes in wheat acreage to Hessian fly infestation. Results showed that Hessian fly infestation and yield losses were greatest during the La Nina and least during the El Nino phase. The weather conditions that significantly increased the risk for infestation were those of the August-February period. The risk of infestation was higher during August-September under wetter, cooler conditions and during October-February under drier, warmer conditions. These findings could help wheat growers reduce the risk of infestation in the years that are expected to have more infestation through the adoption of necessary mitigation measures before the crop season.

The sunsower midge, Contarinia schulzi Gagne ´ (Diptera: Cecidomyiidae), is a pest of cultivated sunsower (Helianthus annuus L.). Larval feeding can cause damage and yield loss to the sunsower head. Adult emergence is extended and larvae are well protected in the sunsower recep- tacle, making chemical control methods difÞcult and expensive. Sunsower midge enter sunsower Þelds at the edges but Þeldwide distributions occur, although the dynamics are not fully understood. Two commercial Þelds in 1999 and one Þeld in 2000 were systematically sampled by dividing each Þeld into Þxed sample points. Mean egg and larval densities from each sample point were used to describe sunsower midge populations. The sunsower heads at each sample point were also assessed for damage. Maps of sunsower midge population density, cumulative density, and sunsower head damage ratings were estimated with kriging interpolation. Maps were estimated several times during Þrst generation sunsower midge infestation. Field edges that were initially populated continued to be areas of infestation throughout the sampling period. Damage ratings were related to population densities when infestations were high. In 2000, we tested the larval hatching rate from different-sized egg masses with regression to determine an estimation technique for combining numbers of eggs and larvae.

“Bottom-up” factors strongly influenced the spatial and temporal pattern of survival of Asphondylia atriplicis Townsend (Diptera: Cecidomyiidae) on Atriplex canescens (Pursh) Nutall (Chenopodiaceae) at three locations in Phoenix, AZ. In contrast, “top-down” effects of natural enemies did not influence the pattern of A. atriplicis mortality. A. atriplicis induces a fleshy, multilocular, rounded stem-gall near the apical meristems of A. canescens. A. atriplicis survival increased as gall size increased, and as the depth of larva in the gall increased. Larval mortality from unknown factors on A. atriplicis decreased with gall size, but the overall interval parasitism rate did not change significantly with gall size. The interval parasitism rate for the eurytomid parasitoid group with the shortest ovipositor was negatively correlated with gall size, but interval parasitism by all other parasitoids was not influenced by gall size. Gall size was strongly influenced by the bottom-up forces of environmental and plant heterogeneity. Gall size varied among seasons, sites, and plants. Larval survival and gall-size covaried in each season and site and among plants.

Oviposition preferences of a herbivore, the wheat midge Sitodiplosis mosellana (Gehin) (Diptera: Cecidomyiidae), on wheat were investigated in relation to two hypotheses: female preferences are adapted to offspring performance; plants may evolve independent defenses that both deter oviposition and reduce offspring performance. Variation in egg density and larval performance were measured for three plant genotypes: a preferred, susceptible wheat; a less preferred, susceptible wheat; a less preferred wheat defended against larval feeding. Oviposition peaked 10–11 d after emergence of the inflorescences and then declined sharply on all three wheat genotypes, although the inflorescences of the genotypes developed at different rates. On the preferred, susceptible wheat, larval performance was high for oviposition that occurred until pollination and low later. On a less preferred wheat, larval performance was high when eggs were laid before or after pollination. On a defended wheat, larval performance was always low. Oviposition preference was associated with larval performance that varied with plant developmental stage, but imperfectly, possibly because females do not detect cues for seed development. Females deposited eggs further from larval feeding sites when ovipositing on less preferred wheats, regardless of whether larval performance on the wheat was high or low. A low preference in combination with a shift in oviposition site supports the hypothesis that some wheats have evolved a defense that deters oviposition. This defense against oviposition is independent of a defense that reduces larval performance, which causes an apparent failure in the expected preference-performance relationship.

The Australian tree Melaleuca quinquenervia (Cavanilles) Blake is an invasive weed in wetland systems of Florida. A biological control program targeting M. quinquenervia has resulted in the release of the gall forming midge Lophodiplosis trifida Gagné (Diptera: Cecidomyiidae). Populations of the introduced herbivore readily established at all 24 release sites across the weed's range in Florida, and there was no evidence that founding colony size (100, 2,000, or 6,000 adults) influenced herbivore establishment or local population growth rates. Landscape level spread of L. trifida from release sites averaged nearly 6 km/yr, ranging as high as 14.4 km/yr. Prerelease host range testing predicted that L. trifida oviposits indiscriminately on test plant species but does not complete development on any of the test species, including congeners present in Florida. To test the predictability of these host range tests, L. trifida was released in a common garden consisting of 18 test plant species that were interplanted with M. quinquenervia. Plant species postulated to be at risk experienced no gall development by L. trifida while intermingled M. quinquenervia trees supported 704.8 (± 158.5) galls per plant. Historically, many introduced Cecidomyiidae have limited effect on plant performance of target weeds because of recruitment of native parasitoids that disrupt biological control efficacy. In contrast to this trend, there has been no evidence to date that parasitoids are exploiting L. trifida in Florida.

The backpropagation algorithm in artificial neural networks was used to forecast dynamic data of a forest pest population of the pine needle gall midge, Thecodiplosis japonensis Uchida et Inouye, a serious pest in pine trees in northeast Asia. Data for changes in population density were sequentially given as input, whereas densities of subsequent samplings were provided as matching target data for training of the network. Convergence was reached, generally after 20,000 iterations with learning coefficients of 0.5–0.8. When new input data were given to the trained network, recognition was possible and population density at the subsequent sampling time could be predicted.

Eggs and neonate larvae of the aphidophagous midge Aphidoletes aphidimyza Rondani are vulnerable to intraguild predation and starvation. The role of A. aphidimyza females in selecting suitable oviposition sites for offspring survival and development was investigated in the laboratory on potato. Oviposition preference, measured as the number of eggs laid in different microhabitats, increased with density of the potato aphid, Macrosiphum euphorbiae (Thomas), and plant pubescence. However, midge females do not discriminate between plants colonized by the coccinellid predator Coleomegilla maculata lengi Timberlake and those that are not. A. aphidimyza egg survival in the presence of C. macula larvae and adults was higher in sites characterized by a high density of trichomes than in other microhabitats. The selection of pubescent leaves infested with aphids by ovipositing females reflects both the food dependence and predation risk constraints of immature midges.

The life history and host specificity of Rhopalomyia n. sp., a multivoltine gall former and potential agent for the biological control of scentless chamomile [Tripleurospermum perforatum (Merat) Lainz, Asteraceae], was investigated at field sites in Eastern Austria and under seminatural conditions in Switzerland from 1995 to 1997. Rhopalomyia n.sp. produced 4 generations per year in Switzerland and induced galls in different meristematic tissues of T. perforatum, including the apical meristems of rosettes and bolting plants, leaf axils, buds, and flowers. Galls formed in axillary buds or flowers were usually single-chambered, whereas the majority of galls induced in apical meristems consisted of several chambers (up to 80), each containing 1 larva. Gall volume increased with the number of chambers per gall. The gall midge was attacked by 1 parasitoid species (Aprostocetus n. sp.) in the field. The probability of parasitoid attack was higher in multichambered galls than in single-chambered galls, whereas percentage parasitism per gall was either unaffected by gall size or declined with an increasing number of chambers per gall. Gall midge females contained on average 92.5 eggs, of which 20-96% were laid, depending on temperature. Females in culture produced an average of 61 offspring, and the gall midge population increased up to 150-fold during 2 generations. A threshold temperature of 7.02 degrees C was calculated, and 478.5 DD were necessary to complete development from egg to adult. A total of 51 plant species and varieties in 6 tribes in the family Asteraceae were offered in no-choice and multiple-choice oviposition and development tests under seminatural conditions. Development to adult was restricted to the genus Tripleurospermum, and T. perforatum was the preferred host plant in all tests. Rhopalomyia n. sp. is a multivoltine species with the potential for rapid population increase. Its ability to induce galls on all plant stages, especially to attack the rosettes of scentless chamomile in late summer and early spring, should supplement the effect of 2 univoltine weevil species already released. Permission for field release of Rhopalomyia n. sp. in North America was granted in October 1998.

Asphondylia flocossa Hawkins (Diptera: Cecidomyiidae) and its associated community of natural enemies were sampled in galls on Atriplex polycarpa (Torrey) Watson (Chenopodiacedae) at 3 locations north of Phoenix, AZ, between October 1994 and March 1995. Galls collected in the autumn had dramatically smaller diameters and shorter trichomes than galls collected in the spring. Asphondylia flocossa were more likely to emerge from larger than average galls with a thick trichome layer in both the autumn and winter samples. The different species of natural enemies each emerged from galls with different characteristics. There was significant variation among taxa of natural enemies for both gall diameter and trichome depth in both the spring and autumn samples. The community of natural enemies also varied significantly among populations and more markedly between seasons. Both Asphondylia flocossa and Rileya tegularis Gahan (Hymenoptera: Eurytomidae) were much more abundant in spring samples than in autumn samples. In contrast, Torymus cappilaceus (Huber) (Hymenoptera: Torymidae) and an undescribed species of Galeopsomyia (Hymenoptera: Eulophidae) were abundant in the autumn samples but almost non-existent in the spring samples. The first 2 species tended to emerge from relatively large galls while the latter 2 species tended to emerge from small galls. Torymus umbilicatus (Gahan) (Hymenoptera: Torymidae) was the only parasitoid abundant in samples from both seasons. This species emerged from galls with the widest range of diameters and trichome depths of any species, both within and between seasons. The feeding biology of the individual species coupled with seasonal and temporal covariation in gall morphology makes natural enemy control of gall size unlikely. The data is consistent with the hypothesis that gall morphology influences insect community composition.

The pattern of attack of a leaf galling Contarinia sp. (Diptera: Cecidomyiidae) on its host plant Bauhinia hrevipes Vogel (Leguminosae) was studied in southeastern Brazil for 2 yr to test the plant vigor hypothesis, which predicts that attack will be centered on the most vigorous (longer) shoots. Most attacks by the leaf galling herbivore occurred on the longest shoots, although these represented the smallest proportion of the available shoot population. Virtually all (100%) of the longest shoots were attacked in 1993 and 1994. Variation in shoot length explained 70% of the variation in the number of galls per shoot in 1993 and 78% in 1994, supporting the plant vigor hypothesis. Nevertheless, no relationship was found between female preference for longer, more vigorous shoots and larval performance. Progeny of females that attacked the longest shoots did not experience higher success than progeny raised on shorter shoots. The hypersensitive reaction of the hosts to galling was observed easily as a brown circular spot around the oviposition site. This reaction to gall initiation was the major mortality factor, killing 90.3%of the galls in 1993 and 95.2%in 1994, hence leaving few gallers to natural enemies such as parasites, predators, and pathogens. Overall, only 4.7% of the galls produced adults in 1993 and 6.7% in 1994.

The movement of ovipositing female Hessian flies, Mayetiola destructor (Say), was investigated using 2 different field release techniques. The 1st technique (experiment 1) indirectly measured female movement between patches of wheat, Triticum aestivum L., by recording the spatial distribution of resulting larval infestations. Females laid eggs in wheat patches at all distances (1-27 m) from the release patch. The 2nd technique (experiments 2 and 3) directly measured movement of adult females and involved release of females into circular plant arrays of either host (wheat) or nonhost oat, Avena sativum L., and their recapture at different times after and at different distances from release. Recapture percentages decreased from 78 to 15% as the duration between release and recapture increased and were lower in the nonhost (oat) compared with host (wheat) arrays. The greater recapture of females from host arrays than from nonhost arrays indicate that females disperse at a greater rate through arrays of nonhost plants. Mathematical models were used to explore dispersal patterns of females in host and nonhost arrays over time. Simple random diffusion models did not describe the data adequately because a proportion of the released individuals dispersed farther than was predicted. An alternative model incorporating these faster dispersing individuals is proposed. Dispersal of females in field arrays supported predictions made from previous experiments in which female movement was quantified in smaller arrays in a greenhouse.

The influence of wind velocity on the behavior of ovipositing female Hessian flies, Mayetiola destructor (Say), was examined in a wind tunnel. Females exposed to wind speeds ranging from 0 to 2.0 m/s, tended to stay for longer on wheat, Triticum aestivum L., plants when the wind speeds experienced were higher, than when they were lower. However, although flight departing from plants was suppressed at higher wind speeds, on-plant behavior was not suppressed under these conditions. Thus, females that stayed longer on plants because of higher wind speeds laid more eggs per visit than females at lower wind speeds. Flight direction upon leaving a host plant was also influenced by wind. As winds increased >0.9 m/s, females no longer exhibited flights to upwind groups of wheat plants and were more likely to land in downwind groups of plants or to be blown out the end of the wind tunnel. When groups of females were released into host plant patches in low (0.1 m/s) or high (0.7 or 1.2 m/s) wind speeds, females in higher winds laid most of their eggs in the patches they were released into and in patches downwind of release patches. Alternatively, females in low winds laid eggs in upwind as well as downwind patches. In this experiment, the total number of eggs laid during the test period was greater in lower versus higher winds. The effects of the above responses to the reproductive biology of Hessian flies are discussed.

We investigated the effects of plant density, plant diversity, and light availability on susceptibility of saplings of Stryphnodendron microstachyum Poeppig & Endlicher to attack by herbivores and pathogens in the lowlands of northeastern Costa Rica. Seedlings of S. microstachyum were planted at either low or high density. High density stands were planted in 2 environments with 2 plant diversities within each environment : monocultures in abandoned pastures (=sun) and in 5-yr-old secondary forest (=shade), or polycultures in which S. microstachyum was planted with 4 other species also in sun and shade. Low density stands consisted of isolated individuals in 4 types of sites (abandoned pasture, secondary forest understory, primary forest understory, and primary forest light gap). Numbers of galls (Diptera : Cecidomyiidae), larvae (Lepidoptera : Noctuidae : Euclystis), and fungal spots (Melanconiales : Pestalotia) were greater in the high density stand than in low density stands, and greater in the shade than in sun. We found no differences in infection between monocultures and polycultures at high density, nor did we find Euclystis larvae or Cecidomyiidae galls in low density stands. Numbers of fungal spots per leaf and density of galls were greater on larger plants. These data suggest that higher plant densities increase the probability of attack by herbivorous insects and leaf pathogens, and that plantations of tropical native tree species in partial shade, as a means of reforestation, run the risk of outbreaks of normally rare plant enemies. Furthermore, the observed positive relation between plant size and attack suggests that plantations of this tree species will become more susceptible to pest outbreaks as the trees mature.

Gravid females of Rhopalomyia solidaginis Lw. oviposit on the vegetative shoot buds of Solidago altissima L., and their emerging larvae induce the development of conspicuous, rosette galls with varying numbers of larval chambers per gall. Most galls have only one larval chamber, whereas some have 2-12 chambers. These differences in the number of larval chambers per gall result in variability in the dimensions of galls. Gall populations from several old fields of central Pennsylvania were harvested to assess the morphometric relationships within galls of various numbers of larval chambers, energy allocation pattern among gall components, and host-plant energy allocation to the galls. We found that the normal stem diameter, a measure of host-plant vigor, is a predictor of gallmaker performance. Also, gall sizes likely vary because the gall midges differ in their ability to induce galls but primarily because of variation in the number of larvae per gall and in the quality of different host genotypes. We also found that the strong relationship between the number of larval chambers and the gall stem diameter indicated the stimulation of the goldenrod genotype to create a strong resource base for accommodating the gall. However, our results suggest the possibility of competition among siblings (when the gall houses multiple larvae) for host-plant resources. Our energy estimates reinforce the role of host-plant quality in determining the gall quality.

The blueberry gall midge, Dasineura oxycoccana Johnson, is a serious pest of rabbiteye blueberries in Florida, Georgia, and Mississippi, and a potential pest of southern and northern highbush blueberries. Its damage has been observed with increasing frequency in highbush blueberry plantings in the Great Lakes region, including in Wisconsin and in Michigan. Unlike in rabbiteye blueberry plantings, where blueberry gall midge primarily damages flowering buds, it is found to damage only the vegetative shoots of northern highbush blueberry. In this study, farms throughout Michigan were surveyed for the presence of blueberry gall midge and it was found in 43 of 46 sampled farms in 11 counties. From 2009-2011, several monitoring techniques, including yellow sticky traps, emergence traps, observational sampling, and vegetative shoot dissections were used to determine the ecology of this species in blueberry fields in southwest Michigan. Emergence traps were most useful in early detection of blueberry gall midge in April, and observational sampling for damage symptoms and vegetative shoot dissections revealed multiple population peaks throughout July and August. Infestation was detected in vegetative shoot tips in all parts of the bushes, with initial infestation greatest at the base of bushes. Degree day accumulations until first midge detection and peak infestation suggest some potential for predicting key events in the pest's phenology. This information about the distribution and timing of infestation will be useful in developing management strategies for blueberry gall midge infestation.

The dispersion pattern of Contarinia sorghicola Coquillet was explored by analyzing the distribution of captures along transects in grain sorghum plots. Adhesive traps at different distances from the edges of the plots were used to intercept dispersing midges. Mortality rates were determined experimentally. A passive diffusion model was fitted to the distribution of captures and the diffusion coefficient estimated. The passive diffusion model gave a good approximation to the spatial distribution of midges dispersing in sorghum plots. The estimated diffusion coefficient suggests that females disperses at a rate of 90 m2/h in sorghum plots. The model is used to predict the spatio-temporal distribution of midges dispersing inward from the edges of plots and identify areas susceptible to midge attack.

The larvae of Asphondylia rudbeckiaeconspicua Osten Sacken develop in ovoid chambers in polythalamous summer galls on the flower heads and apical meristems of Rudbeckia laciniata L. (Asteraceae). Three wasps are known to parasitize the gallmaker; Rileya americana Girault, Torymus sp. near asteridis , and T. advenus O.S. In the current study we addressed three questions. Are gallmakers that occupy deep gall chambers less likely to be parasitized than those in shallow gall chambers? Does chamber depth vary with the number of chambers? And finally, does larval survival vary with the number of larvae per gall? At the three populations studied, unparasitized gallmakers occupied the deepest chambers, followed by R. americana , then by Torymus spp. Mean chamber depth increased with the number of chambers per gall at all sites, which raised the possibility that individual vulnerability to parasitoid attack could vary with the number of gallmates through the group effect on chamber depth. In one population, the rate of parasitism by Torymus spp. was highest in galls with an intermediate number of hosts. Thus, survivorship for the gallmaker at this site can be explained by the responses of Torymus spp. to the number of chambers per gall. Patterns of parasitism for Rileya were marginally related to chamber number in another population.

Dispersion patterns of eggs, larvae, and adults of Prodiplosis longifila Gagne were determined for lime orchards in Dade County, Florida, during 1987 and 1989. Dispersion indices generated by Taylor's power law and Iwao's patchiness regression were compared. Taylor's power law provided a better description of variance-mean relationships for eggs, larvae, and adults than did Iwao's patchiness regression. All insect stages exhibited aggregated patterns of spatial distribution ( b > 1.4). Sample size requirements for fixed levels of precision were determined for eggs and larvae using estimated variance–mean relationships obtained from Taylor's power law regressions. Color sticky traps placed on the tree canopy provided a more efficient method of sampling P. longifila populations than ground emergence traps and collection of larval samples.

Cytological analysis of wheat infested by the Hessian fly, Mayetiola destructor (Say), indicated that on susceptible plants, virulent larvae (biotype L, virulent to resistance genes H3,5,6,7/8) caused a generalized increase in cuticular-membrane permeability of cells in the lower leaf sheath. On resistant plants, feeding by avirulent larvae (biotype GP, no genes for virulence) resulted in localized responses. This suggests that plant responses limited the ability of avirulent larvae to elicit generalized changes in cell permeability. Analyses of plant protein patterns by polyacrylamide gel electrophoresis and immunoblots indicated that separate changes in protein metabolism occurred in susceptible versus resistant wheat in association with Hessian fly infestation. In susceptible wheat, ribulose-l,5-bisphosphate carboxylase (Rubisco) increased in the lower leaf sheath in association with infestation. In resistant wheat (cv. Caldwell, H6 gene for resistance), proteins of low molecular weight appeared in the lower leaf sheath in association with infestation by avirulent larvae. Protein changes associated with infestation were not elicited by physical wounding of plants. Protein changes detected in resistant wheat infested by avirulent larvae (biotype GP) did not appear when the plants were infested with virulent larvae (biotype L). Results support the hypothesis that hypersensitivity is the phenotypic basis of resistance in the Hessian fly-wheat interaction and involves “recognition” of an avirulence gene product or process.

Many insect herbivores can only use hosts during a specific phenological stage, i.e., a phenological window. Previous studies have primarily examined the effects of these windows on insect herbivores, but relatively little is known about the mechanisms controlling the phenological windows. In most gall insect systems, phenological windows have been attributed to the short duration of physiologically active plant tissues that induce gall formation (reactive plant tissue). In the fruit gall midge, Asphondylia aucubae Yukawa and Ohsaki, and the host plant (i.e., Aucuba japonica) system, the disappearance of reactive plant tissue closes the phenological window, but its presence does not define the opening of the window. The hard endocarp of the fruit covers most potential oviposition sites just before the midge emergence season, but decreases in proportional cover during the emergence season. We experimentally manipulated the timing of oviposition relative to fruit development. Midges that emerged earliest and attacked fruits during their earliest developmental stages were unable to oviposit because of intact, hard endocarps, whereas their counterparts that emerged later could oviposit more readily through cracks in the endocarp. We noted possible oviposition avoidance behavior and the necessity of more frequent (repeated) ovipositor insertions to intensively stimulate the decreased reactive tissues during the latter half of the emergence season. Overall, our results indicated that the fragmentation of the defensive, hard endocarp of the host plant defines the opening of the phenological window in this plant-herbivore system.

Discussions and simulation models have been used by others to develop strategies for deploying genes in wheat ( Triticum spp. ) for resistance to the Hessian fly, Mayetiola destructor (Say). Effects of deploying genes one at a time in sequence and redeploying a gene after a 10-yr absence from the commercial crop in Indiana during 1955–1989 are presented. Three genes, H3, H6 , and H5 , were deployed in 1955, 1962, and 1971, respectively, and H6 was redeployed in 1981. A reduction in infestation levels of Hessian fly occurred for 6–8 yr after each deployment. Redeployment of H6 , after a 10-yr absence in commercial use, was highly effective. Other methods of deploying resistance genes in conjunction with cultural practices should be considered for control of Hessian fly. When considering the pyramiding of genes for resistance, one must evaluate the time required to develop new productive cultivars. Efficient methods to determine that all of the pyramided genes are present in a line are important for the successful use of pyramided genes. Wheat cultivars are seldom grown for more than 8–10 yr, but the same pyramided genes might be used in subsequent cultivars.

In the northern part of its range in North America, the Hessian fly, Mayetiola destructor (Say), has one generation each year and overwinters in diapause. In the southern part of its range, it may have six generations each year, and does not overwinter in diapause; however, its summer development is interrupted by an aestival period. Between these two extremes, the number of generations varies with geographical location and prevailing climatic conditions, and the species usually diapauses and aestivates each year. Laboratory aestivation can be induced by high temperatures (daily thermocycles ranging from 17 to 36°C), and terminated by exposure to four or more consecutive days at 21.1°C. Diapause was terminated at 21.1°C in about the same number of days of exposure to daylengths of 8:16 or 16:8 (L:D), suggesting that photoperiod is less important than temperature. Extremely high Indiana temperatures during the summer of 1988 induced a more intense aestivation, and its termination was delayed in the field. Many eggs were laid on wheat that fall after the Hessian fly-free date, and a very mild winter followed, resulting in the largest spring fly infestation recorded in the last 24 yr. A large percentage of aestival puparia submerged under water for weekly intervals up to seven weeks delayed pupating by the duration of time that they were submerged, suggesting that a higher titer of oxygen might be necessary to break aestivation.

Susceptible ‘Newton’ and resistant ‘Abe’ winter wheat ( Triticum aestivum L. em Thell.) were infested with larvae of biotype E Hessian fly, Mayetiola destructor (Say). Plants and crowns of infested ‘Newton’ weighed less, were shorter, had fewer tillers, and had significantly less soluble carbohydrates than the control plants. Only the plant height of infested resistant ‘Abe’ was significantly reduced. This finding was unexpected because avirulent larvae have never been shown to affect the growth of a resistant host. In ‘Newton,’ only the quantity of sucrose differed between treatments, being significantly greater in the infested than the control plants, although there was a trend for the control plants to have more fructan and less sucrose, glucose, and fructose than the treated plants. No differences were noted in soluble carbohydrates between infested and control ‘Abe.’ Ancymidol, a plant growth retardant, stunted both wheat cultivars but did not alter resistance in ‘Abe.’ Gibberellic acid (GA3) reversed ancymidol-induced growth inhibition but did not reverse Hessian fly stunting in ‘Newton.’ Therefore, stunting of wheat by the Hessian fly and ancymidol treatments appear to involve different biochemical pathways.

Spurgia esulae Gagne (= Bayeria capitigena Bremi of Solinas & Pecora), a multivoltine gall midge recorded on Euphorbia esula in Italy, was selected as a candidate for the biological control of leafy spurge ( Euphorbia esula L. “complex”) in North America. Its potential host range was studied in 1982 at Rome, Italy, and in 1984 at Albany, Calif., using populations associated with Euphorbia esula from San Rossore near Pisa, Italy. Of 56 plant species or varieties in 22 families tested at the Rome laboratory, the midge oviposited and completed its life cycle only on plants in the genus Euphorbia (subgenus Esula ). In the tests conducted in Rome, complete development occurred on five populations of North American leafy spurge (from Montana, Nebraska, North Dakota, Oregon, and Saskatchewan) and on European E. peplus L., E. cyparissias L., E. myrsinites L., E. characias L., E. serrulata Thuillier, and on E. lathyris L. from Chico and Castro Valley, Calif. Of 12 native North American Euphorbia species tested at Albany in 1984, four species in the subgenus Esula ( E. incisa Engelmann, E. palmeri Engelmann, E. robusta (Engelmann) Small, and E. spathulata De Lamarck) supported the complete development of S. esulae . The restricted host range suggested use of this midge as a biological control agent against leafy spurge in North America. Releases of S. esulae were made in Montana in 1985 and in North Dakota in 1986; this species became established in both states.

Experiments were conducted to determine the effect of Hessian fly, Mayetiola destructor (Say), larval feeding on one susceptible and two resistant wheat, Triticum aestivum L. em Thell., cultivars. The stem number, plant and crown weights, and soluble crown carbohydrates were measured in susceptible ‘Monon’ (with the H3 gene) and resistant ‘Abe’ (H5 gene) and ‘Caldwell’ (H6 gene) wheat infested with biotype E Hessian fly larvae. All plant variables were significantly different between infested and control ‘Monon’ wheat, and no significant difference in plant variables was detected in the resistant wheats 4 wk after infestation. Of the four carbohydrates analyzed, only fructan in ‘Monon,’ and fructose in ‘Abe’ differed significantly between the two treatments. These data support the use of resistant genes in plants to control the Hessian fly, in that essentially no damage was observed in the resistant wheat, whereas susceptible ‘Monon’ was damaged severely.

Carabid predators of the wheat midge, Sitodiplosis mosellana (Gehin), in northeastern Saskatchewan were determined by immunoelectro-osmophoresis. Fourteen carabid species in the genera Agonum, Amara, Bembidion , and Pterostichus were identified as having fed on wheat midge larvae in the field. Adult Bembidion quadrimaculatum L., Bembidion obscurellum Motschulsky, Agonum placidum Say, and Pterostichus corvus LeConte killed 9, 15, 43, and 48 midge larvae per beetle per day, respectively, in laboratory studies without alternative prey. Estimates of daily predation in the field for all carabid species combined ranged from

The cecidomyiid midge Rhopalomyta california Felt is native to California where its larvae develop in terminal galls on Baccharis pilularis DC. Galls are usually multichambered and can contain >50 larvae per gall (one larva per chamber). Regression analyses involving >3,500 galls collected on 21 sample dates at two field sites in northern California revealed that average percentage of survival (larva to adult) of R. california was either independent of, or directly related to, gall size (chambers per gall). No inverse density dependence was detected, suggesting that any intraspecific competition that may have occurred in larger galls did not reduce midge survival. This was confirmed in laboratory studies. The apparent inability of the midge's primary parasites to fully exploit host larvae in larger galls also may enhance midge survival in these galls. Under laboratory conditions, however, the mean number of eggs per female was significantly reduced in females that developed in larger galls, suggesting that intraspecific competition among larvae occurred. These patterns, if observed on B. halimifolia L., could influence the effectiveness of R. californica as a biological-control agent for this weed in Australia and elsewhere. It is suggested that response to intraspecific competition be included in preintroductory evaluation of candidate agents in biological control of weeds.

The duration of feeding and relative amounts consumed by Hessian fly, Mayetiola destructor (Say), larvae on resistant and susceptible seedling wheat plants labeled with [35S]L-methionine was investigated. Plants were labeled over 48-h periods from initial infestation to 8 d after infestation, and the uptake of 35S by larvae determined. With the H3 and H5 genes for resistance, the uptake of 35S by larvae was significantly less than on susceptible controls, and suggested that the larvae were unable to initiate or maintain sustained feeding on the resistant plants. With the H6 gene for resistance, uptake of 35S by larvae during the first 48 h was not significantly different from that on susceptible controls, but then declined between 48 and 96 h. These data indicate that with the H6 gene, larvae fed actively for the first 48 h after infesting the plants, then ceased their feeding between 48 and 96 h. All larvae on resistant plants were alive 48 h after infesting plants and approximately 60% were alive 96 h after infesting resistant plants. All larvae on resistant plants were dead by 144 h after infestation. Results are discussed in the context of possible mechanisms of action for the resistance genes investigated.

The effects of several plant characters on the oviposition behavior of Hessian flies were investigated by presenting mated females with various combinations of chemical, color, and tactile cues in choice bioassays. When applied to filter paper, one plant equivalent (PE) of a chloroform extract of wheat leaves stimulated 438 times more egglaying than chloroform controls. One PE of oats extract stimulated 10 times more egglaying than chloroform controls. Wheat extracts stimulated 12 times more egglaying than oats extracts. Doseresponse tests using wheat extracts showed that females were stimulated to oviposit at concentrations as low as 0.01 PE; they laid more eggs as dosage increased. Higher dosages of oats extract (1.0 PE) were required to elicit significantly more oviposition than occurred on chloroform controls. In separate tests with and without wheat extract, females laid more eggs on yellow, green, and orange papers than on blue and red papers. Choice tests using green and grey filter paper strips indicated that egglaying responses were stimulated primarily by hue rather than intensity of colors. Tactile cues associated with venation of grass leaves were mimicked by making parallel grooves (“veins”) down the long axis of wax-covered filter paper. In tests without wheat extract, females laid 28 times more eggs on the veined surface than on the smooth surface. With wheat extract present, the veined surface elicited only two times more egglaying than the smooth surface. Vertical grooves received four times more eggs than horizontal grooves. In a test using a factorial treatment design with chemical, color, and tactile cues either absent or present, females laid the most eggs on the treatment that combined all three cues. Removal of chemical cues caused a significantly larger reduction in egglaying (93%) than did the removal of either tactile or color cues (70%)

To identify adaptive strategies of gall-inducing cecidomyiids, we studied the life history traits of Pseudasphondylia rokuharensis (Diptera: Cecidomyiidae), a univoltine species inducing fruit galls on a deciduous shrub, Viburnum dilatatum. Although univoltine gall midges that are associated with trees or shrubs are usually difficult to rear from immature stages under artificial conditions, we successfully reared P. rokuharensis from first instar to adult. Mature larvae entered diapause in autumn, and the diapause terminated after low temperature treatment (4 mo of incubation at 5 degrees C). The adults emerged within a shorter period of time than those without low temperature treatment. Thus, the diapause provides better synchronization of adult emergence in the spring. Because adults live for only a few days, this synchronization improves the chances of adults finding a mate. This is the first report on the mechanism of larval diapause termination for univoltine and tree- or shrub-associated gall midges. The numbers of days needed for adults to emerge under laboratory conditions after low temperature incubation were significantly different between two different localities. This result might suggest the possible existence of ecoclines in their life history parameters.