Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Squash Bugs in Cucurbits (including melons)
At this same time last season, Jerry Brust from the University of Maryland did a nice article for the Weekly Crop Update titled Squash Bugs in Pumpkins. Be sure to follow this link for good pictures of the adult, egg masses and damage. It appears that this season we are again seeing squash bugs in cucurbits. Some consultants are reporting what they feel are higher levels of squash bugs in watermelon fields compared to past seasons. In past years we have seen this pest cause problems in squash and pumpkins and it appears that they could be causing damage in some watermelon fields.
Ruth Hazzard of the University of Massachusetts Vegetable Extension Program has written a fact sheet about squash bugs in vine crops which includes information on which crops are affected, plant damage and the life cycle of the squash bug. Be sure to follow this link for more detailed information: http://www.umassvegetable.org/soil_crop_pest_mgt/insect_mgt/squash_bug.html.
The following are a few key points from this fact sheet:
● “Squash bugs are most attracted to Hubbard squash, summer squash, pumpkins, watermelons, muskmelons, cucumbers, and butternut squash in decreasing order. Because of low attraction and low survival rate, squash bugs do not usually become a pest on cucumber, watermelon, butternut squash and muskmelon.”
● “Squash bug feeding can cause wilting in leaves, stems, and vines that are beyond the feeding site. The injury may appear as light-colored areas that later turn brown and die, symptoms that resemble bacterial wilt.” It is important to remember, there are a number of factors that can cause wilting in cucurbits – including a number of diseases – so a correct diagnosis is critical.
● Although squash bugs may also vector Cucurbit Yellow Vine Disease (CYVD) caused by the bacterium Serratia marcescens, this disease has not been detected in our region. There is a link in this fact sheet to an article from the University of Connecticut on cucurbit yellow vine disease http://www.hort.uconn.edu/ipm/veg/htms/cucrbinct.htm.
● “In late summer and fall, large nymphs and new squash bug adults can also damage the fruit of fall vine crops.”
Cucumbers
Continue to scout all fields for cucumber beetles and aphids. Since fresh market cucumbers are susceptible to bacterial wilt, treatments should be applied before beetles feed extensively on cotyledons and first true leaves. Although pickling cucumbers have a tolerance to wilt, a treatment may still be needed for machine-harvested pickling cucumbers when 5% of plants are infested with beetles and/or plants are showing fresh feeding injury.
Melons
At this time, cucumber beetles can still be found in high levels. In addition, economic levels of spider mites are being found in a few fields. The threshold for mites is 20-30% infested crowns with 1-2 mites per leaf. Acramite, Agri-Mek, bifenthrin, Danitol, and Oberon are labeled on melons for mite control. Zeal is also labeled for ground application only. 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 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 should also continue to check fields for aphids. A treatment may be needed prior to fruit set, if you find 1-2 aphids per leaf for at least 2 consecutive weeks and beneficial activity is low.
Potatoes
Continue to scout fields for Colorado potato beetle (CPB), corn borers (ECB) and leafhoppers. Low levels of the first aphids have also been found.
Snap Beans
Continue to sample all seedling stage fields for leafhopper and thrips activity. Both insects can be found in seedling stage fields. 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. After the pin stage, sprays are based on trap catches 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. Since trap catches can change quickly, be sure to check our website for the most recent trap catches and information on how to make a treatment decision in processing snap beans using trap catches (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html).
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. Both species can be found feeding in whorls and tassels of sweet corn. A treatment should be applied if 15% of the plants are infested with larvae. 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 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).