Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. 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, Oberon, and Zeal (one application only; ground application only) are labeled on melons for mite control. Be sure to check all labels for rates, precautions and restrictions, especially as they apply to pollinators. Just a few comments about our newer miticides:
Oberon is considered active against all life stages including eggs (juvenile stages are often more susceptible than adults). It has surface and translaminar activity. See link for technical bulletin for more information (http://www.bayercropwest.com/=file:District-Literature/11170437173294490a02022173973622/doc).
Zeal is described as predominately an ovicide/larvacide. Adult mites will not be controlled so initial activity may appear slow, although eggs laid by treated mites will not be viable (sterilizes the adults). In evaluations in other states, it has been highly effective and long lasting, but results may not be apparent for one week – so do not evaluate control soon after treatment. In a recent evaluation on melons, it appears to have provided good control but we will continue to evaluate this study and keep you updated. It has both contact and translaminar activity. See the following link for more information (http://www.plantmanagementnetwork.org/pub/php/news/2005/zeal/). As a reminder, this material cannot be applied by air.
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 (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. Be sure to watch carefully for beet armyworm larvae since they can quickly defoliate plants.
Potatoes
Continue to scout fields for Colorado potato beetle (CPB), 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 half.
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 data 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 to 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. 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.