Location: Southeast Watershed Research
2023 Annual Report
Accomplishments
1. Parasitism and predation of natural and sentinel stink bug egg masses. Stink bugs, including the invasive brown marmorated stink bug (BMSB) and native southern green stink bug (SGSB), are agricultural pests that feed on crops. Monitoring predation and parasitism of stink bug egg masses furthers our understanding of potential biological control tactics. However, best practices for laboratory and field assessments of parasitism and predation of egg masses require further attention. Thus, potential differences in predation and parasitism between sentinel (lab-reared) and naturally occurring BMSB and SGSB egg masses were studied in soybean. In 2018 and 2019, BMSB natural egg masses had higher parasitism and lower predation compared to sentinel egg masses in soybean. In a paired field test in 2020 and 2021, there was no difference in parasitism between BMSB natural and sentinel eggs, but much higher incidence of parasitism was detected in natural SGSB egg masses than sentinel eggs. In conclusion, both collecting natural egg masses and deploying refrigerated egg masses may be the best methodology for field assessment of parasitism of stink bug egg masses; however, if natural egg masses are not easily available, deploying sentinel eggs is a good alternative.
2. Seasonal density and natural mortality of stink bugs in field crops. Stink bugs, including the invasive brown marmorated stink bug (BMSB) and native southern green stink bug (SGSB), are pests that damage a variety of agricultural crops. At a study site in the southeastern US, the density of stink bug species and patterns of parasitism and predation on corn, cotton, and soybean and host trees in an adjacent woodline were studied. We assessed parasitism and predation of naturally-laid egg masses in crops and sentinel egg masses in host trees were assessed. Pheromone-baited stink traps were used to determine BMSB seasonal development. Overall, BMSB and SGSB were the dominant bugs observed. Adult BMSB were first detected each year on trees, followed by corn, and then cotton and soybean, suggesting that trees served as a source of BMSB dispersing into crops. For BMSB, more nymphs were captured in soybean than in corn or cotton. For SGSB, more adults were captured in corn and cotton than in soybean, and more nymphs were captured in corn during 2019 and 2021 than in 2020. Percentage parasitism of SGSB egg masses (74.2%) was higher than BMSB egg masses (54.3%). Accordingly, conservation biological control can enhance parasitism of native stink bugs and BMSB in field crop agroecosystems.
3. Incidence of bird predation on the brown marmorated stink bug. In agroecosystems, the brown marmorated stink bug (BMSB) is a pest that causes significant economic losses to a variety of crops every year. Chemical-based insect control and management practices are common but face immense pressure to respond to rapidly evolving pest populations. Insect feeding birds may provide a means of sustainable, non-chemical management of insect pests. In forest margins surrounding peach, pecan, and mixed peach-pecan orchards, 278 fecal samples were examined from 19 bird species for presence of BMSB to determine whether birds eat this pest. Overall, we found evidence that three bird species, including the Northern cardinal, tufted titmouse, and Carolina wren, consume BMSB. Because birds are members of the broader food web network, future studies will be conducted to more fully understand avian pest control services for stink bugs in agroecosystems.
4. Effect of ultraviolet radiation (UVC) on whitefly eggs. The silverleaf whitefly is a pest in agriculture crops and can spread plant diseases in those crops. Currently, the common way to control this pest is to apply chemical insecticides. However, this whitefly is becoming resistant to many of the chemical insecticides used to control them. A nonchemical control option is needed to reduce the need for chemical insecticides. Ultraviolet radiation (UV) is nonvisible radiation with wavelengths ranging from 100 nm to 400 nm. UVC, wavelengths 100 nm to 280 nm, can kill insects and cause their eggs not to hatch. An exposure UVC for 4 different times from 15 to 90 seconds at either 29 or 12 inches resulted in a reduction of egg hatching compared to untreated eggs. If these results can be duplicated in the field, a non-chemical control option would be available to farmers to manage and slow insecticide resistance in their fields. The general public will also benefit from fewer chemicals being applied in the environment.
5. Use of prohexadione calcium and postemergence herbicide tank-mixtures in peanut. When grown in excess, peanut vines have the potential for fostering disease under the canopy and can become damaged during mid-to-late season pesticide applications. The use of a plant growth regulator in peanut can reduce vine growth and increase yield, with the potential of increasing overall net return. With input costs significantly increased, the use of tank-mixtures can alleviate the costs and loss of time from sequential applications. Given the recent interest and recommendation of applying a plant growth regulator (PGR) to peanut, this study is designed to determine the effect of tank-mixing prohexadione calcium with commonly used postemergence herbicides on peanut injury and weed control. The field study focused on determining the level of visual injury and overall impact to peanut yield from PGR and postemergence herbicide tank-mixtures while the greenhouse study focused on identifying species-specific levels of weed control. Preliminary results showed that PGR and herbicide tank-mixtures could be applied postemergence without reducing yield. Greenhouse results showed varying levels of control depending on the specific species, so future research includes adding an additional run of this study to ensure the trends are accurately described.
6. Repeated applications of organic herbicides in peanut. Management of weeds in organic peanut requires a system approach that typically relies on cultural and mechanical control methods rather than chemical control. There are an extremely limited number of organic herbicides available for use that allows producers to maintain their organic certification and most still need to be evaluated for their effectiveness in runner-type peanut. This study was conducted to determine if repeated applications of organic herbicides would provide economical weed control without reducing yield. In conjunction with the field studies, greenhouse studies are being conducted to evaluate the level of weed control achieved on various common and troublesome species. Preliminary results showed that small and large seeded runner-type peanut can recover quickly from phytotoxic burn. There were inconsistent trends in pod yield among the repeated herbicide applications. The high input prices of these products and repeated applications warrants further evaluation of how to best utilize these products in runner-type peanut.
Review Publications
Grabarczyk, E.E., Mizell, R.F., Northfield, T.D., Greene, J.K., Cottrell, T.E., Tillman, P.G., Anderson, P.C., Riddle, C.T., Hunter, W.B. 2023. Spatiotemporal distribution of the glassy-winged sharpshooter, Homalodisca vitripennis (Hemiptera: Cicdellidae) in a southeastern agroecosystem. Florida Entomologist. 105(4):280-286. https://doi.org/10.1653/024.105.0403.
Tillman, P.G., Kesheimer, K.A., Hirsch, K., Grabarczyk, E.E. 2023. Assessment of development, parasitism, and predation of Hoalyomorpha halys (Hemiptera: Pentatomidae) in sassafras (Lauraceae) in southeastern US agroecosystems. Florida Entomologist. 106(1):16-21. https://doi.org/10.1653/024.106.0103.
Tillman, P.G., Grabarczyk, E.E., Balusu, R., Kesheimer, K., Blaauw, B., Sial, A., Vinson, E., Cottrell, T.E. 2023. Predation and parasitism of naturally occurring and sentinel stink bug egg masses of halyomorpha halys (Stal) and nezara viridula (L.) (hemiptera: pentatomidae) in various southeastern habitats. Journal of Insect Science. 23(2):1-12. https://doi.org/10.1093/jisesa/iead012.
Cottrell, T.E., Tillman, P.G., Grabarczyk, E.E., Toews, M., Sial, A., Sriyanka, L. 2023. Habitat and vertical stratification affect capture of stink bugs (Hemiptera: Pentatomidae) and biological control of the invasive brown marmorated stink bug. Environmental Entomology. 20:1-3. https://doi.org/10.1093/ee/nvad061.
Grabarczyk, E.E., Cottrell, T.E., Schmidt, J.M., Tillman, P.G. 2023. Low incidence of avian predation on the brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae) in southeastern orchard systems. Insects. 14:595. https://doi.org/10.3390/insects14070595.
