Jasmonic acid and salicylic acid induced defensive response in wine grapes against Drosophila suzukii (Diptera: Drosophilidae).

To better understand the elicitor induced defense in wine grapes against Drosophila suzukii (Matsumura), two varieties, Pinot Noir and Chardonnay, were sprayed with jasmonic acid (JA) and salicylic acid (SA). Total phenols, total flavonoids, total tannins and total soluble sugars were quantified. Oviposition preference by D. suzukii in response to JA and SA applications were also studied. Behavioral response of D. suzukii to various sugars was recorded. The effect of flavonoids (gallic acid, catechin, quercetin at 100 and 500 ppm) on mortality of D. suzukii was also studied in CAFE assay. Our results showed that JA and SA application significantly affected phenol, flavonoid and tannin contents of grapes. Reduced injury was observed in treated plants; this reduction was more pronounced in Chardonnay than Pinot Noir. The number of eggs laid by D. suzukii females was lower in JA and SA-treated plants; this reduction was more pronounced under no-choice conditions than under choice conditions. In prandial behavior, sucrose solution (5%), glucose solution (5%), fructose solution (5%), sucrose (5%) + yeast (5%) solutions and yeast solutions (5%) showed higher attraction of D. suzukii females compared to control treatments. Among flavonoids, catechin (100 ppm) showed higher mortality of D. suzukii than rest of the treatments. The results of this study can be used for developing management strategies of D. suzukii in wine grapes and related crops.

Dendrochronology reveals different effects among host tree species from feeding by Lycorma delicatula (White).

The spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), was first detected in the United States in Berks County, Pennsylvania, in 2014. Native to China, this phloem-feeding planthopper threatens agricultural, ornamental, nursery, and timber industries in its invaded range through quarantine restrictions on shipments, as well as impacts on plants themselves. The long-term impacts of L. delicatula feeding on tree species have not been well studied in North America. Using standard dendrochronological methods on cores taken from trees with differing levels of L. delicatula infestation and systemic insecticidal control, we quantified the impact of L. delicatula feeding on the annual growth of four tree species in Pennsylvania: Ailanthus altissima, Juglans nigra, Liriodendron tulipifera, and Acer rubrum. The results suggest that L. delicatula feeding is associated with the diminished growth of A. altissima, but no change was observed in any other tree species tested. The results also suggest that systemic insecticides mitigate the impact of L. delicatula feeding on A. altissima growth.

Development of rearing methodology for the invasive Spotted Lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae).

Lycorma delicatula, White (Hemiptera: Fulgoridae), spotted lanternfly, is a univoltine, phloem-feeding, polyphagous and invasive insect in the USA. Although a primary host for this species is Ailanthus altissima, tree of heaven, L. delicatula also feeds on a wide range of hosts important to the USA including cultivated grapevines. Due to the need for classical or augmentative biological control programs to reduce impacts of L. delicatula across invaded areas, we developed a laboratory-based rearing protocol for this invasive species. Here, we evaluated the use of A. altissima apical meristems, epicormic shoots, and fresh foliage cut from A. altissima as a food source for rearing newly hatched L. delicatula. On these sources of plant material <20% of L. delicatula developed into adults and no oviposition occurred. However, when young, potted A. altissima trees were used as a food source, >50% of L. delicatula nymphs developed to the adult stage under natural daylengths and temperatures ranging from 20-25°C. The addition of wild grapevine, Vitis riparia, did not increase survivorship or reduce development time. To elicit mating and oviposition, adults were provided with A. altissima logs as an oviposition substrate and maintained under shortened daylengths and reduced nighttime temperatures (12L:12D and 24°C:13°C). This resulted in 2.12 egg masses deposited per female, which was 4× more than when adults were maintained in standard rearing conditions (16L:8D and 25°C). Based on these experiments, we present a protocol for reliably rearing L. delicatula under laboratory and/or greenhouse conditions.

Phenology of Lycorma delicatula (Hemiptera: Fulgoridae) in Virginia, USA.

The spotted lanternfly, Lycorma delicatula (White), is an invasive planthopper that was first discovered in North America in Berks County, Pennsylvania in 2014. Currently, L. delicatula has spread to eight additional states and threatens agricultural, ornamental, and timber commodities throughout the United States. The timing of insect life events is very important in the development of pest management tools and strategies. In 2019 and 2020, L. delicatula phenology was successfully documented in Winchester, Virginia using weekly 5-min observational surveys at established monitoring plots. Each year, L. delicatula were active in the environment from May to November with initial detections of first, second, third, fourth, and adults occurring in May, May, June, June, and July, respectively. Cumulative average growing degree days were also calculated for the onset of each L. delicatula life stage using local weather data and a lower developmental threshold of 10°C. First-instar L. delicatula were initially observed at 135 and 111.5, adults at 835 and 887, and egg masses at 1673.5 and 1611.5 in 2019 and 2020, respectively. Combined, these data can be used by growers and land managers to facilitate timing of effective pest management strategies.

Spatio-Temporal Model for Predicting Spring Hatch of the Spotted Lanternfly (Hemiptera: Fulgoridae).

The effect of temperature on the rate of spotted lanternfly, Lycorma delicatula (White) (Hemiptera: Fulgoridae), egg development was investigated for a population in Pennsylvania. Mean developmental duration (days ± SE) for egg hatch was evaluated at five constant temperatures of 19.9, 24.2, 25.1, 26.7, and 30°C using egg masses laid during the fall of 2018 and collected in 2019 from Berks Co., Pennsylvania. Base temperature thresholds for egg development were estimated using intercept and slope parameters by fitting a linear relationship between average temperature and developmental rate for the Pennsylvania study, two Korean studies, and the combined data sets. The base threshold estimates were then used to calculate seasonal accumulated degree-days (ADD) and construct logistic equations for predicting cumulative proportion of hatch in the spring. The fitted logistic prediction equations were then graphed against the egg hatch observations from field sites in Pennsylvania (2017) and Virginia (2019). When base temperature estimates from the three studies and combined studies were used to calculate ADD, the logistic models predicted similar timing for seasonal egg hatch. Because the slopes and intercepts for these four data sets were not statistically different, a base temperature threshold of 10.4°C derived from the combined model is a good estimate for computing ADD to predict spotted lanternfly spring emergence across a spatio-temporal scale. The combined model was linked with open source weather database and mapping programs to provide spatiotemporal prediction maps to aid pest surveillance and management efforts for spotted lanternfly.

Development of Behaviorally Based Monitoring and Biosurveillance Tools for the Invasive Spotted Lanternfly (Hemiptera: Fulgoridae).

The spotted lanternfly, Lycorma delicatula White, is an invasive planthopper (Hemiptera: Fulgoridae) that was first detected in the United States in Berks County, PA, in 2014, and has since spread in the mid-Atlantic region. This phloem-feeding pest has a broad host range, including economically important crops such as grape where their feeding causes dieback of infested plants. Monitoring the presence and abundance of L. delicatula is of utmost importance to develop pest management approaches. Current monitoring practices include sticky bands deployed on tree trunks, sometimes paired with commercially available methyl salicylate lures. A drawback associated with sticky bands is the high numbers of nontarget captures. Here, we developed traps for L. delicatula based on a circle trap originally designed for weevils. These traps are comprised of a screen funnel that wraps around the trunk of a tree and guides individuals walking up the trunk into a collection device. In 2018 and 2019, we compared circle trap designs with sticky bands in Pennsylvania and Virginia. In both years, circle trap designs yielded captures that were equivalent to or exceeded captures of L. delicatula on sticky bands. Nontarget captures were significantly lower for circle traps compared with sticky bands. Presence of a methyl salicylate lure in association with traps deployed on host trees or vertical tree-mimicking posts did not increase L. delicatula captures compared with unbaited traps. Circle traps, modified using vinyl screen and a larger collection device, present an alternative to the current approach with reduced nontarget capture for monitoring L. delicatula.

Effects of Interspecific Larval Competition on Developmental Parameters in Nutrient Sources Between Drosophila suzukii (Diptera: Drosophilidae) and Zaprionus indianus.

Two invasive drosophilids, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and Zaprionus indianus (Gupta) (Diptera: Drosophilidae) are expanding their geographic distribution and cohabiting grape production in the Mid-Atlantic. The ecological and economic impact of these two species within vineyards is currently unknown. Zaprionus indianus was presumably not capable of ovipositing directly into grapes because they lack a serrated ovipositor and may use D. suzukii oviposition punctures for depositing their own eggs. Therefore, an interspecific larval competition assay was performed at varying larval densities using commercial medium and four commonly grown wine grapes in Virginia to investigate the impact Z. indianus larvae may have on the mortality and developmental parameters of D. suzukii larvae. Zaprionus indianus did not affect D. suzukii mortality or development parameters even at high interspecific densities when reared in commercial medium, but it did cause higher D. suzukii mortality within grapes. Mortality was also influenced by the variety of grape in which the larvae were reared, with smaller grapes having the highest D. suzukii mortality. Presence of Z. indianus also increased development time to pupariation and adult emergence for most interspecific competition levels compared with the intraspecific D. suzukii controls. Pupal volume was marginally affected at the highest interspecific larval densities. This laboratory study suggests that competition from Z. indianus and grape variety can limit D. suzukii numbers, and the implications on D. suzukii pest management be further verified in the field.

Brown Rice Vinegar as an Olfactory Field Attractant for Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in Cherimoya in Maui, Hawaii, with Implications for Attractant Specificity between Species and Estimation of Relative Abundance.

Drosophila suzukii (Matsumura) is an agricultural pest that has been observed co-infesting soft-skinned fruits with Zaprionus indianus Gupta. The characterization of olfactory preferences by species is a necessary step towards the development of species-specific attractants. Five olfactory attractants were used to survey the populations of two invasive drosophilids in cherimoya in Maui, Hawaii. The attractants used were apple cider vinegar (ACV), brown rice vinegar (BRV), red wine (RW), apple cider vinegar and red wine (ACV+RW; 60/40), and brown rice vinegar and red wine (BRV+RW; 60/40). For D. suzukii, BRV+RW resulted in more captures than BRV, ACV, and RW, while ACV+RW resulted in more captures than ACV. No differences were observed between BRV+RW and ACV+RW. BRV had greater specificity in attracting D. suzukii compared to ACV, ACV+RW, and RW. For Z. indianus, no significant differences were observed in either the mean captures or specificity for any attractant used. Collectively, these findings demonstrate that (1) BRV and BRV+RW are effective field attractants and (2) D. suzukii has unique olfactory preferences compared to non-target drosophilids, while (3) Z. indianus' preferences do not appear to vary from non-target drosophilids, and (4) the accuracy of relative abundance is impacted by the specificity of the attractants.

Drosophila suzukii (Diptera: Drosophilidae) Oviposition and Adult Emergence in Six Wine Grape Varieties Grown in Virginia.

Drosophila suzukii (Matsumura) is a pest of small fruits and grapes in the United States and in its home range of Japan. Physiological and morphological laboratory testing was performed on six commonly grown wine grape varieties in Virginia. Skin thickness, penetration force, and ºBrix were analyzed to determine ovipositional preferences. Experiments were performed for three consecutive years from grapes collected at one Virginia vineyard. More eggs were laid in intact Viognier grapes than any other variety. Oviposition into intact grapes was not affected by skin thickness or ºBrix; however, oviposition increased when penetration force decreased. An ovipositional choice test determined no varietal preferences. Survivorship from egg to adulthood using uninjured and injured grapes was also assessed to determine varietal suitability as D. suzukii hosts, with more flies emerging from injured grapes than uninjured. However, D. suzukii adults did emerge from intact grapes and at higher percentages than previously recorded in other wine grape studies. All varieties had eggs oviposited into them when injured. Determining the time at which each grape variety became susceptible to oviposition was determined using a D. suzukii bioassay spanning 12 wk using grapes from the green pea stage until ripe. Susceptibility to D. suzukii oviposition was based upon ripening period and penetration force. Early ripening varieties may be more susceptible to D. suzukii oviposition in the field with later maturing, harder fleshed-varieties which may escape D. suzukii oviposition.

Host plant preference of harlequin bug (Hemiptera: Pentatomidae), and evaluation of a trap cropping strategy for its control in collard.

Harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae), is a piercing-sucking pest of cole crops, causing cosmetic damage in low populations, while heavy pest pressure can kill plants or entire fields. Field studies were conducted to evaluate a trap crop for control of harlequin bug in collard. Field-cage choice tests found that potential trap crop plant species, mustard (Brassica juncea 'Southern Giant Curled'), rapeseed (B. napus 'Athena'), rapini (B. rapa), and arugula (Eruca satica) attracted more harlequin bugs than collard (B. oleracea 'Champion') and a nonbrassica control, bean (Phaseolus vulgaris'Bronco'). Mustard was the most consistently selected by harlequin bug over collard in choice tests, and was found to be an effective trap crop for reducing feeding injury on collard at two experimental sites. Augmentation of the mustard trap crop with a systemic, neonicotinoid insecticide provided no added control of harlequin bug for the 10 wk duration in the spring season.

Analysis of Wolbachia strains associated with Conotrachelus nenuphar (Coleoptera: Curculionidae) in the Eastern United States.

We studied the distribution patterns of Wolbachia infection associated with plum curculio strains in eight states of the eastern United States. The presence of the Wolbachia-specific gene wsp identified infections of this endosymbiont in 97.8% of the 93 samples tested. Three distinct Wolbachia strains were identified. The strains wCne1 (593 bp) and wCne2 (593 bp) were 97% identical, and their sequences were both 84% identical with wCne3 (590 bp). BLASTN searches through GenBank showed strong similarities between the wsp sequences of the three strains compared with Wolbachia sequenced from other hosts. Degree of similarity with sequences in other Wolbachia strains is discussed. Polymerase chain reaction-restriction fragment length polymorphism was used for superinfection detection. Of 93 samples, 15 (16.1%), 21 (22.6%), 19 (20.4%), and 36 (38.7%) samples were infected by wCne1, wCne2, wCne1 + 2, and wCne3, respectively. Only two (2.2%) samples had no infection. The wCne3 strain was always present as a single infection. Wolbachia strains approximate the distribution of plum curculio strains: northern strain infected with wCne1 and wCne2 strains in supergroup B, and southern strain infected with wCne3 strain in supergroup A, with the mid-Atlantic region as the convergence area. Based on haplotype distribution of plum curculio mitochondrial cytochrome oxidase I, there was a closer relation of the mid-southern plum curculio clade to the far-southern clade than to the northern clade. However, Wolbachia symbionts in mid-southern plum curculio are more closely related to those in northern plum curculio than to those in far-southern plum curculio. The relationship of Wolbachia infection with reproductive incompatibility between plum curculio populations was also discussed.

Evaluation of reproductive compatibility of interstrain matings among plum curculio populations in the eastern United States.

Reproductive compatibility of interstrain matings in plum curculio, Conotrachelus nenuphar (Herbst), was studied during the summers of 2004 and 2006. There was a unidirectional incompatibility in the cross-matings along a rough north to south transect of the range of plum curculio (4 x 4 two-factorial design). There was significantly lower fertility in West Virginia males mated with New York and Virginia females (40 and 29%, respectively), and Florida males had a significantly lower fertility with Virginia and West Virginia females (46 and 37%, respectively), but Florida females were compatible with males of all four populations. Three northern populations were compatible with each other in all cross-mating combinations (New York, Massachusetts, and New Jersey; 3 x 3 two-factorial design). There was a unidirectional reproductive incompatibility in the combination of New Jersey males with Florida females (47%) and a bi-directional incompatibility between Florida and West Virginia reciprocal cross-mating (26 and 21%, respectively). The pattern of the reproductive incompatibility among geographic populations could help us to distinguish plum curculio strains and to clarify their strain distribution range to enrich our knowledge on their population ecology and biosystematics.

Host plant choice experiments of Colorado potato beetle (Coleoptera: Chrysomelidae) in Virginia.

Field and laboratory-choice experiments were conducted to understand aspects of host plant orientation by the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), in Virginia. In laboratory bioassays, L. decemlineata oriented to volatiles emitted by potato, Solanum tuberosum L., foliage over both tomato, Lycopersicon esculentum L., and eggplant, Solanum melongena L., foliage, and eggplant over tomato foliage, all of which had been mechanically damaged. Field choice tests revealed more L. decemlineata adults, larvae, and egg masses on eggplant than on tomato. In other experiments, counts of live L. decemlineata on untreated paired plants and counts of dead beetles on imidacloprid-treated plants did not differ between potato and eggplant. L. decemlineata was significantly attracted to eggplant over both tomato and pepper. To determine whether feeding adults affected orientation to host plants, an imidacloprid-treated eggplant or potato plant was paired with an untreated eggplant or potato plant covered in a mesh bag containing two adult male beetles. Significantly more adults were attracted to eggplant with feeding male beetles paired with another eggplant than any other treatment combination. These results indicate that the presence of male L. decemlineata on plants affects host plant orientation and suggests that the male-produced aggregation pheromone may be involved.