David Owens, Extension Entomologist, owensd@udel.edu
Alfalfa
Begin scouting alfalfa regrowth for potato leafhopper. There is a dynamic threshold table in our recommendations guide. Using it, thresholds can be significantly different depending on plant height and value of hay. The table can be found here: https://www.udel.edu/content/dam/udelImages/canr/pdfs/extension/sustainable-agriculture/pest-management/Insect_Control_in_Alfalfa_-2023.pdf.
Soybeans
Vegetative stage POST herbicide applications are beginning to go out. It is very tempting for many producers to tank-mix a pyrethroid with the herbicide. We have evaluated this timing on more than a dozen cooperator farmer fields using large strip trials over the last three years, funded in part by Northeast SARE and USDA-NIFA. Only on one occasion was this application justifiable due to reduced defoliator levels 3 weeks after application. Yields were not impacted by this application, and neither were reproductive stage pest populations (stink bugs and corn earworm). Soybeans have an incredible ability to tolerate heavy defoliation and thus this application is not advised. If in doubt, scout. If defoliators are present at high enough levels to make this application justifiable, heavy defoliation greater than 40% will be observed. You may see some significant looking defoliation on the upper most leaves, but you have to look at the entire canopy.
Sorghum
If sorghum is being planted now or later on, it should be scouted once it enters reproductive stages for sugarcane aphid and corn earworm. Aphids are sporadic but significant yield reducers. We have done sorghum variety trials the last two years funded in part through USDA-NIFA EIP grant. Virginia Tech’s Dr. Maria Balota also wrote a sorghum pest management article a few years ago for Crop and Soils Magazine. She generously shared the article with me. If you want either or both resources (variety trial results or Article), email me at owensd@udel.edu.