Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Cucumbers
Continue to scout all fields for cucumber beetles and aphids.
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. With recent hot weather, we have started to find economic levels of spider mites in a number of fields. As a general guideline, a treatment should be considered when you find 20-30% of the plants infested with 1-2 mites per leaf. Acramite (one application only), Agri-Mek, bifenthrin, Danitol, and Oberon are labeled on melons for mite control. Zeal was also labeled this year for spider mite control on melons but it can not be applied by air (one application only). Also, it is considered ovicidal/larvacidal but will not control adult populations. Be sure to check all labels for rates, precautions and restrictions, especially as they apply to pollinators.
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 7-10 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 (in state: 1-800-345-7544; out of state: 302-831-8851) or visiting our website at (http://ag.udel.edu/extension/IPM/traps/latestblt.html). You will also need to consider a treatment for pepper maggot. We have also found the first beet armyworm hatching egg mass so be sure to watch for this insect, which can quickly cause defoliation.
Potatoes
Continue to scout fields for Colorado potato beetle (CPB), corn borers (ECB), aphids and leafhoppers. 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 ½. It should also be noted that we did receive a 24c (specific local need) label for the use of Coragen on potatoes for Colorado potato beetle control. Please refer to the label for use directions and restrictions (http://www.cdms.net/LDat/ld8KF004.pdf).
Snap Beans
Continue to scout for leafhopper and thrips activity in seedling stage beans. As a general guideline, once corn borer catches reach 2 per night, fresh market and processing snap beans in the bud to pin stages should be sprayed for corn borer. Sprays will be needed at the bud and pin stages on processing beans. Acephate can be used at the bud and pin stages on processing beans but remember it has a 14-day wait until harvest. Additional sprays may 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 (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html). Once pins are present on fresh market snap beans and corn borer trap catches are above 2 per night, a 7-10 day schedule should be maintained for corn borer control.
Sweet Corn
Continue to sample seedling stage fields for cutworms and flea beetles. You should also sample all fields from the whorl through pre-tassel stage for corn borers and corn earworms. The first silk sprays will be needed for corn earworm as soon as ear shanks are visible. Be sure to check both blacklight and pheromone trap catches for silk spray schedules since the spray schedules can quickly change. Trap catches are generally updated on Tuesday and Friday mornings (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/silkspraythresh.html). You can also call the Crop Pest Hotline (in state: 1-800-345-7544; out of state: 302-831-8851). Be sure to watch for the first fall armyworm larvae in whorl stage sweet corn – we anticipate seeing them any day and they may already be here. A treatment should be considered 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.