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Understanding reproductive systems of rare plants is critical for conservation efforts. Lakela’s Mint, Dicerandra immaculata Lakela var. immaculata, is an endangered plant endemic to an approximately 4.8-km long area in Florida, USA. We used an experimental garden and three populations of Lakela’s Mint to determine: (1) what is the breeding system (autonomous, asexual, self-fertile, cross-fertile) and are insects necessary for reproduction; (2) which native and nonnative insect species visit flowers and is the frequency of visits to a plant influenced by its height; (3) does the number of flowers visited within a plant by individual insects differ among native and nonnative insect species and due to plant height; and (4) is seed output influenced by plant height? Our results indicate that the breeding system of Lakela’s Mint was facultative outcrossing. Insect-pollinated flowers produced more seeds than flowers that reproduced autonomously or asexually. The honey bee Apis mellifera L., a nonnative species, was the most frequent visitor to plants and visited more flowers within plants than native pollinators, but its behavior was not influenced by plant height. Native pollinators such as Bombus impatiens Cresson were attracted more frequently to shorter plants, but visited fewer flowers than on taller plants. Despite having fewer total and pollinated flowers, shorter plants had a higher output of intact seeds than taller plants, which could be due to differences in efficiency between native and nonnative pollinators or other factors. Our results add insight into factors influencing seed output and interactions between pollinators and rare plants.

BACKGROUND The leafminer, Phyllocnistis citrella Stainton, reproduces on leaf flush during winter. Deployment of pheromone during winter could suppress moth populations in spring and summer more than a spring application alone. We tested the primary pheromone component of P. citrella, (Z,Z,E)-7,11,13-hexadecatrienal, released gradually over several months from elastomeric dispensers in a citrus grove in 6.4 ha main plots in winter and/or 3.2 ha subplots in spring (834 mg triene ha−1) and evaluated moth catch and leaf mining. RESULTS After winter treatment, dispensers provided >85% disruption of male moth catch in traps for 37 weeks, and after spring treatment they provided >92% disruption for 26 weeks, but there was only a 12% reduction in leaf infestation in spring. Two applications were no better than only a single application in spring. Disruption of moth catch was weaker in treated plots where traps were placed high (3.1 m) rather than low (1.6 m) in the tree canopy. CONCLUSION Dispensers provided effective and persistent disruption of male catch in pheromone-baited monitoring traps but were minimally effective in reducing leaf infestation by P. citrella. Winter application of pheromone did not reduce leaf mining in spring compared with spring application alone. Tops of trees may have provided a refuge for mating. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Recent efforts to disrupt mating of the leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), a global pest of citrus, have focused on the use of SPLAT™ (ISCA Technologies), a flowable wax emulsion intended to serve as a slow-release matrix for pheromones. Early success with this approach was overshadowed by the expense and difficulty of application, and variation in wax component chemistry that contributed to reduced longevity of pheromone emission in the field. Solid elastomer dispensers (DCEPT CLM™, ISCA Technologies, Inc.) loaded with a 3:1 blend of ( Z,Z,E)7,11,13-hexadecatrienal and (Z,Z)-7,11-hexadecadienal, the major components of the P. citrella sex pheromone, provided disruption of trap catch in commercial citrus orchards for periods exceeding 30 wk. The triene component alone worked as well as or better than the 3:1 blend. The height of dispensers placed by hand in the tree canopy had a significant effect on trap shutdown. Dispensers placed low (0.6 m) in the canopy resulted in a reduction of trap shutdown in the upper third (>3 m) of the canopy suggesting that the net movement of pheromone molecules was downward during the period of active moth flight. Although moth flight appeared equivalent among the heights tested, placement of dispensers higher in the canopy appears more effective given this downward movement of pheromone plumes. These studies suggest that season-long trap catch disruption can be attained in citrus with a single application of a hand-applied dispenser.

Male Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) were captured in pheromone- baited traps in pastureland 1.2 km west of an infested citrus grove. Capture of males was correlated with northeast wind blowing from the groves, which suggests males were transported passively on wind currents from groves before orienting to pheromone traps. Female P. citrella located and oviposited on 75% of sentinel citrus plants placed 1.2 km west of the groves by 6 weeks. Movement of this species as far as 1.2 km suggests that groves treated with pheromone components for mating disruption will be vulnerable to damage caused by mated females arriving from neighboring groves within 1.2 km. Treated groves may be particularly susceptible to influx of moths carried on wind. Machos del minador de hojas Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae) fueron capturados en trampas de feromonas en pastizales hasta 1.2 kilometros al oeste de un huerto de citricos. El numero de los machos capturados en el pastizal disminuyo con el aumento de distancia de los huertos. La captura de machos fue correlacionada con un viento del noreste que soplo desde los huertos. Esto sugiere que los machos fueron transportados pasivamente por las corrientes de viento de los huertos antes de navegar en contra el viento hacia las trampas de feromonas. Las plantas de citricos centinales colocadas 1.2 kilometros al oeste de los huertos se infesto en 6 semanas. Estos datos sugieren que la eficacia de perturbacion sexual en P. citrella puede ser dependiente de la escala, con mejores resultados donde se trata en areas mas grandes. View this article in BioOne

We collected a native North American species, Phyllocnistis insignis (FreyB Sapindales: Rutaceae) groves at 4 sites in southeastern Florida during 2012. Phyllocnistis insignis moths were found in pheromone-baited traps year round with a peak flight in May. In trials designed to evaluate mating disruption of P. citrella, application of triene (SPLAT CLM™) disrupted trap catch of P. insignis during a 9 week period following treatment in spring (825 mg triene/ha), but not winter (750 mg triene/ha). In a second experiment, application of triene (837 mg/ha) and a 3:1 blend of triene and diene (840 mg triene + 280 mg diene/ha, respectively) loaded onto rubber dispensers disrupted catch of male P. insignis during a 12 week period following treatment of 0.14 ha plots. Also, application of a 3:1 blend of triene and diene (764 mg + 253 mg/ha, respectively) formulated in SPLAT CLM disrupted trap catch of male P. insignis during a 4 week period following treatment in a 66 ha plot. In a third experiment, application of blend (837 mg triene + 278 mg diene/ha) reduced the incidence of trap catch to zero during a 16 week period following treatment of 0.87 ha plots. These data suggest that efforts to disrupt mating of P. citrella influence non-target populations of the congeneric leafminer species, P. insignis. View this article in BioOne

Susceptibility of the armyworm, Mythimna unipuncta (Haworth), to infection by a baculovirus (NPV) isolated from a Kentucky armyworm population was compared on two suspected progenitors of tall fescue, Festuca mairei and Festuca arundinacea subsp. fenas , with spiny leaf margins intact or removed to test whether leaf spines abrade or puncture the peritrophic matrix (PM) and facilitate passage of virions to infection sites in midgut tissue. PCR amplification and sequencing of selected genes from the virus and phylogenetic inference from aligned sequences were carried out to identify and classify the virus. Edge spines had no effect on percentage infection or days to death of newly molted 5th instars fed spiny- or smooth-edged F. mairei leaf blades for 24 h before and after droplet feeding doses of 10 8 or 10 9 OBs ml −1 . Fifth instars fed spiny- or smooth-edged grass blades had similarly undamaged PMs when viewed by scanning electron microscope. Fourth instars fed virus-treated F. arundinacea subsp. fenas leaf blades with spiny edges intact or removed did not differ in proportion infected or days to death. The food bolus moves in a liquid medium within the PM, and frass dissections showed that edge spines were often located inside a food bolus separated from the PM by non-spiny plant material rather than contiguous with the PM; therefore, friction of edge spines with the PM may have been low. These results suggest that armyworms will not be less susceptible to baculovirus infection when feeding on tall fescue cultivars with smooth leaf edges planted for improved livestock performance compared with those feeding on standard spiny-edged cultivars. We believe this to be the first study to investigate the effects of a natural physical structure on disruption of the PM and infection by a baculovirus.

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.

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.

The leafminer, Phyllocnistis citrella Stainton, reproduces on leaf flush during winter. Deployment of pheromone during winter could suppress moth populations in spring and summer more than a spring application alone. We tested the primary pheromone component of P. citrella, (Z,Z,E)-7,11,13-hexadecatrienal, released gradually over several months from elastomeric dispensers in a citrus grove in 6.4 ha main plots in winter and/or 3.2 ha subplots in spring (834 mg triene ha(-1) ) and evaluated moth catch and leaf mining.After winter treatment, dispensers provided85% disruption of male moth catch in traps for 37 weeks, and after spring treatment they provided92% disruption for 26 weeks, but there was only a 12% reduction in leaf infestation in spring. Two applications were no better than only a single application in spring. Disruption of moth catch was weaker in treated plots where traps were placed high (3.1 m) rather than low (1.6 m) in the tree canopy.Dispensers provided effective and persistent disruption of male catch in pheromone-baited monitoring traps but were minimally effective in reducing leaf infestation by P. citrella. Winter application of pheromone did not reduce leaf mining in spring compared with spring application alone. Tops of trees may have provided a refuge for mating. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

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.

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.