Seasonal activity of spotted lanternfly (Hemiptera: Fulgoridae), in Southeast Pennsylvania.

The spotted lanternfly, Lycorma delicatula (White, 1845), is an invasive species in the United States. This pest causes damage to vineyards and has the potential to negatively affect other crops and industries. Information describing the seasonal timing of life stages can improve its management. In 2019 and 2020, spotted lanternfly seasonal activity was followed weekly from spring egg hatch to the first hard freeze. Weighted mean timing of activity for each nymphal instar, early adults, late adults, total adults, and egg mass deposition are presented for 2019 and 2020 on Acer rubrum and 2020 on Ailanthus altissima. Logistic equations describing the percentage completion of each activity period on these hosts were fitted using a start date of 1 January to calculate accumulated degree days (ADD). For the adult and egg mass deposition periods, we additionally used a biofix of the date adults were first observed to calculate ADD. ADD from 1 January adequately estimated the timing of nymphal instars but ADD from observation of the first adult better estimated the timing of adult activity and egg mass deposition. Late adult activity and egg mass deposition periods appeared to be influenced by another environmental cue, such as day length. Maps of season-long ADD show that spotted lanternflies are unlikely to reach adulthood in colder regions of the northeast United States, and therefore may not establish there. We also report a strong seasonal trend in sex ratio on A. rubrum, where the population shifted from over 80% male to over 80% female in October.

Efficacy and nontarget effects of broadcast treatments to manage spotted lanternfly (Hemiptera: Fulgoridae) nymphs.

Management to control the spotted lanternfly, Lycorma delicatula (White), would ideally achieve managers' goals while limiting impacts on nontarget organisms. In a large-scale field study with 45 plots at least 711 m2, we tested foliar applications of dinotefuran and 2 formulations of Beauveria bassiana (Balsamo) Vuillemin, each applied from the ground and separately by helicopter. Applications targeted early instar nymphs. For both application methods, a single treatment with dinotefuran significantly reduced L. delicatula numbers, as measured by catch on sticky bands (91% reduction by air and 84% reduction by ground 19 days after application) and by timed counts (89% reduction by air and 72% reduction by ground 17 days after application). None of the B. bassiana treatments significantly reduced L. delicatula numbers, even after 3 applications. Beauveria bassiana infection in field-collected nymphs ranged from 0.4% to 39.7%, with higher mortality and infection among nymphs collected from ground application plots. Beauveria bassiana conidia did not persist for long on foliage which probably contributed to low population reduction. Nontarget effects were not observed among arthropods captured in blue vane flight intercept traps, San Jose Scale pheromone sticky traps or pitfall traps, but power analysis revealed that small reductions of less than 40% may not be detected despite extensive sampling of 48,804 specimens. These results demonstrate that dinotefuran can markedly reduce local abundance of L. delicatula with little apparent effect on nontarget insects when applied shortly after hatch, and that aerial applications can match or exceed the effectiveness of applications from the ground.

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.

Fidelity and Timing of Spotted Lanternfly (Hemiptera: Fulgoridae) Attack Patterns on Ornamental Trees in the Suburban Landscape.

Invasive herbivores can have dramatic impacts in new environments by altering landscape composition, displacing natives, and causing plant decline and mortality. One of the most recent invasive insects in the United States, the spotted lanternfly (Lycorma delicatula), has the potential to cause substantial economic and environmental impacts in agriculture and forestry. Spotted lanternfly exhibits a broad host range, yet reports of late-season movement from the surrounding landscapes onto select tree species in suburban environments have been reported. In this study, we aimed to evaluate the fidelity of spotted lanternfly attack on specific, individual trees within the same species during this movement period. In 2018 and 2019, we observed that individual red (Acer rubrum L. [Sapindales: Sapindaceae]) and silver maple (Acer saccharinum L. [Sapindales: Sapindaceae]) trees were preferentially attacked over other nearby trees of the same species. Foliar elemental composition was a good predictor of spotted lanternfly attack numbers, indicating that individual variation in nutrients may influence spotted lanternfly attraction to and/or retention on maple trees. Our data also confirm reports of late-season movement from surrounding landscapes throughout autumn. Collectively, our results show that spotted lanternfly exhibits some fidelity to particular trees in the landscape during this movement period. While other potential mechanisms also contribute to host plant selection by spotted lanternfly, our data show that host nutritional profiles influence spotted lanternfly infestation of suburban trees at the landscape scale. Our data establish that late-season infestations of suburban trees by spotted lanternfly occurred and that variation in host quality should be further considered in the management of this invasive insect pest.

A Method for a Long-Term Marking of Spotted Lanternfly (Hemiptera: Fulgoridae) Using a Stable Isotope of Nitrogen.

Developing a lifelong marking method for Lycorma delicatula (White, 1845) is crucial to investigate ecological processes. Here we validate a marking method using stable isotope enrichment (15N) of host plants to track spotted lanternfly (SLF), an invasive species causing economic damage on grapes, hardwood forest and landscape tree species. To validate this method, we first determined the isotope dosage to be sprayed on the host plants and subsequently detected in SLF. Second, we examined whether 15N mark remains detectable from the nymphal to adult stage. We demonstrated that two stable isotope dosages applied to the host plants were assimilated by the insect and equally detectable in the exoskeleton, wings, and mature eggs ready to be oviposited. This safe and reliable method can be used to examine fundamental processes of the biology and ecology of SLF that range from dietary resources and resource allocation to food-web structure and dispersal patterns.

Can a specialist parasitoid, Macrocentrus cingulum (Hymenoptera: Braconidae), influence the ecotype structure of its preferred host Ostrinia nubilalis (Lepidoptera: Crambidae)?

Synchronization between a parasitoid and its preferred host is an essential strategy for successful biological control. Two ecotypes of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) in North America are distinguished by their voltinism. In this study, the differential impact of a specialist parasitoid, Macrocentrus cingulum Brischke (Hymenoptera: Braconidae), on the univoltine and multivoltine populations of O. nubilalis is investigated. Four years of field and laboratory study suggested that M. cingulum emergence was synchronized with the spring emergence of the multivoltine ecotypes of O. nubilalis in Pennsylvania. Univoltine populations experienced minimal parasitism from M. cingulum. Field-collected data suggested that the postdiapause multivoltine O. nubilalis field population was male biased, whereas the univoltine population was female biased. M. cingulum-parasitized postdiapause O. nubilalis larvae were significantly heavier than the male and nonparasitized female larvae. Sex ratio differences observed in overwintered O. nubilalis populations in the presence or absence of M. cingulum parasitism suggested preferential parasitism between male and female O. nubilalis larvae. Correlation between the larger parasitized O. nubilalis larval host and the number of adult parasitoids emerging per host suggested a potential evolutionary advantage to parasitizing female or larger hosts.

Use of spectral vegetation indices derived from airborne hyperspectral imagery for detection of European corn borer infestation in Iowa corn plots.

Eleven spectral vegetation indices that emphasize foliar plant pigments were calculated using airborne hyperspectral imagery and evaluated in 2004 and 2005 for their ability to detect experimental plots of corn manually inoculated with Ostrinia nubilalis (Hübner) neonate larvae. Manual inoculations were timed to simulate infestation of corn, Zea mays L., by first and second flights of adult O. nubilalis. The ability of spectral vegetation indices to detect O. nubilalis-inoculated plots improved as the growing season progressed, with multiple spectral vegetation indices able to identify infested plots in late August and early September. Our findings also indicate that for detecting O. nubilalis-related plant stress in corn, spectral vegetation indices targeting carotenoid and anthocyanin pigments are not as effective as those targeting chlorophyll. Analysis of image data suggests that feeding and stem boring by O. nubilalis larvae may increase the rate of plant senescence causing detectable differences in plant biomass and vigor when compared with control plots. Further, we identified an approximate time frame of 5-6 wk postinoculation, when spectral differences of manually inoculated "second" generation O. nubilalis plots seem to peak.

Female European corn borer (Lepidoptera: Crambidae) ovarian developmental stages: their association with oviposition and use in a classification system.

Reproductive development of female European corn borer, Ostrinia nubilalis (Hübner), was investigated and a classification system proposed. Females collected in a blacklight trap during 1982 and 1983 were dissected and their reproductive system examined. Female reproductive systems were divided into six stages based on ovum development within the ovarioles, ovum depletion, ovariole appearance, and fat body color and shape. The female reproductive systems were also staged on the basis of spermatophore appearance. The time necessary to classify a female is also reported. Based on the classification system, the relationship between female age and stage of ovarian development was quantified under three temperature regimes. Females were found to experience a 3- to 5-d preoviposition period before initiation of egg deposition under optimal temperature conditions. This delay between adult emergence and initiation of egg laying corresponded with more advanced ovarian developmental stages collected in blacklight traps and indicates that actively ovipositing females are primarily being collected in blacklight traps.

Infestation of European corn borer (Lepidoptera: Crambidae) in sweet corn as predicted by time of oviposition.

Oviposition by European corn borer, Ostrinia nubilalis Hübn, was examined in relation to sweet corn development from 1994 to 1996, and related to harvest infestation levels. Stepwise multiple regression and linear regression showed that 79-87% of the variability of larvae per ear or proportion of ears infested at harvest was explained by the number of egg masses laid from about anthesis to brown silk stages. The analyses indicated three periods of oviposition with differing implications to harvest infestation level: (1) eggs laid from 784-337 degree-days (DD) before harvest (before green tassel) had very low correlation to harvest infestation; (2) eggs laid from 336-169 DD before harvest (green tassel to green silk) were highly correlated with harvest infestation; and (3) eggs laid during the last 168 DD of sweet corn development (green silk to harvest) had low to moderate correlation with harvest infestation. The 336-169 DD period corresponded to the anthesis to brown silk growth stages, which was approximately 14-21 d long, and would be the likely period for optimum chemical control. The results of this study are compared with existing recommendations from the midwestern and northeastern U.S., and potential explanations for the patterns observed are discussed.

Biotechnology and the European corn borer: measuring historical farmer perceptions and adoption of transgenic Bt corn as a pest management strategy.

A 3-yr, multi-state survey of farmers who had planted transgenic Bacillus thuringiensis (Bt) corn was conducted to evaluate perceptions of Bt corn performance and its utility as a management option for European corn borer, Ostrinia nubilalis (Hübner). A questionnaire was sent to farmers in Illinois, Iowa, Kansas, Minnesota, Nebraska, and Pennsylvania who had grown Bt corn during the growing seasons of 1996, 1997, or 1998. There were 7,427 usable questionnaires returned with the following response percentages: 1996 (42.1%), 1997 (35.0%), and 1998 (22.6%). Adoption rates, based on percentage of acreage planted to Bt corn, increased dramatically from 1996 (10.5%) to 1998 (40.7%). The states growing the highest percentage of Bt corn were Minnesota, Iowa, and then Nebraska However, Illinois, was adopting Bt corn at the fastest rate. Historical use of insecticides did not influence the adoption of Bt corn. In addition, of those farmers who used insecticides to control European corn borer, the percentage that decreased their use of insecticides nearly doubled from 13.2% (1996) to 26.0% (1998) over this 3-yr period. The primary reason farmers planted Bt corn was to eliminate the yield loss caused by European corn borer. Scouting for European corn borers decreased from 91% (scouting 2.2 times a year) in 1996 to 75% (scouting 1.8 times a year) in 1998. The percentage of farmers not scouting for European corn borers increased from 9.6% (1996) to 25% (1998). Most farmers believed yields of Bt hybrids were either similar to or greater than the yields of non-Bt hybrids. Minnesota farmers perceived the greatest yield advantages. Farmers are becoming more aware of insect resistance management guidelines; however, they also clearly show preferences for having the flexibility to use different spatial plantings of Bt and non-Bt corn. Finally, after having planted Bt corn and obtained excellent control of European corn borer, most farmers believed that this insect had been causing more yield loss than they previously had suspected in their non-Bt corn. The data represented here provide an historical foundation for how transgenic Bt corn was used by farmers during the first 3 yr of commercial availability, their initial perceptions on the performance of this technology, and their attitudes regarding management of the European corn borer.