Joanne Whalen, Extension IPM Specialist;jwhalen@udel.edu
Lima Beans
We are starting to find spider mites, especially in dry land fields. Controls are only effective if treatments are applied before populations explode. In addition to dimethoate, Hero (zeta-cypermethrin + bifenthrin) and bifenthrin , Acramite (bifenazate) is also labeled on lima beans for spider mite control. Be sure to check the labels for rates and restrictions, including the minimum gallons per acre for ground and aerial application.
http://www.cdms.net/LDat/ld4TA029.pdf
http://www.cdms.net/LDat/ld72P041.pdf
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. Be sure to read all labels carefully for rates and restrictions since some materials, especially miticides are restricted to only one application as well as ground application only.
Peppers
As soon as the first flowers can be found, be sure to consider a corn borer treatment. Depending on local corn borer trap catches, sprays should be applied on a 7 to 10-day schedule once pepper fruit is ¼ – ½ inch in diameter. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (302-831-8851) or visit our website at http://agdev.anr.udel.edu/trap/trap.php. At this time, you will also need to consider a treatment for pepper maggot.
Potatoes
Continue to scout fields for Colorado potato beetle, leafhoppers, and aphids. We are seeing an increase in leafhopper populations and low levels of aphids can be found. Controls will be needed for green peach aphids if you find 2 aphids per leaf during bloom and 4 aphids per leaf post bloom. This threshold increases to 10 per leaf at 2 weeks from vine death/kill. If melon aphids are found, the threshold should be reduced by half.
Snap Beans
Continue to sample all seedling stage fields for leafhopper and thrips activity. As a general guideline, once corn borer catches reach 2 per night, fresh market and processing snap beans should be sprayed for corn borer. Once pins are present on fresh market snap beans and corn borer trap catches are above 2 per night, a 7 to 10-day schedule should be maintained for corn borer control. On processing snap beans, sprays will be needed at the bud and pin stages. Depending on trap catches of corn borer and corn worm, additional sprays may also be needed after the pin spray on processing beans. Since trap catches can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans after bloom. After the pin spray on processing beans, the spray schedule will be determined by a combination of both moth catches and field scouting.
http://agdev.anr.udel.edu/trap/trap.php
Sweet Corn
The first silk sprays will be needed for ear feeders as soon as ear shanks are visible. Be sure to check both blacklight and pheromone trap catches since the spray schedules can quickly change. Trap catches are generally updated on our website (http://agdev.anr.udel.edu/trap/trap.php) and the Crop Pest Hotline (302-831-8851) by Tuesday and Friday mornings. Information on how to use the trap catch information in combination with field scouting can be found at http://extension.udel.edu/ag/insect-management/insect-trapping-program/action-thresholds-for-silk-stage-sweet-corn/. In addition to corn borer and corn earworm, you will also need to start scouting whorl stage corn for fall armyworm larvae. A treatment should be considered for whorl feeders when 12-15% of the plants are infested. Since fall armyworm feeds deep in the whorls, sprays should be directed into the whorls and multiple applications are often needed to achieve control.