David Owens, Extension Entomologist, owensd@udel.edu
Cucurbits
Scout for striped cucumber beetle on any planted cucurbit – cantaloupe, cucumber, watermelon, and summer squash. They have been spotted in watermelon planted last week and in high tunnel cucumbers. Of those, watermelon is the least attractive when planted side by side. All besides watermelon are susceptible to bacterial wilt. Seeds treated with a neonicotinoid treatment such as Farmore FI400 should provide 14 days of control. When male cucumber beetles find a cucurbit, they release an aggregation pheromone that brings in more beetles, both male and female. This means that large areas of fields might not have many beetles while smaller areas have intense populations. They overwinter in wooded areas and ditch banks; I focus my scouting on field edges nearest those habitats. If a field can be separated into zones, you may only need to treat certain zones rather than an entire field. If injecting an insecticide into drip lines, look for a table with rates per 1,000 row feet of drip tape and given drip tape intervals. Some products do not include these tables, but the amount can be calculated easily. If, for example, someone were to put Admire Pro in drip lines at 10.0 fl oz/acre, you need to know how many row feet of drip tape you have. Lets divide 43,560 by bed center spacing (most watermelon are 7 feet apart) = 6,222 row fee; 10.0 fl oz should be injected into those 6,223 row feet. Another way to look at it is by dividing the total area by 43560. Let’s say I have 3 beds 50 feet long. 7 beds x 7 feet x 200 feet = 0.225 acres x 10.0 fl oz and those beds should receive 2.25 fl oz of Admire. The last several years we have conducted drip trials on overwintered beetles, comparing Admire Pro and Platinum. In two of four years, we have counted more dead beetles underneath Platinum treated plants and for a longer period of time than Admire treated plants. Please note that tray drench treatments are not labeled for striped cucumber beetle.
Legumes
Snap beans planted into tilled fields should have an insecticide seed treatment. The first generation seedcorn maggot flight is underway. If your seed does not have an insecticide on it, consider planting either no-till or later in the month when air temperatures are warmer which favors snap bean growth.
Potato
Colorado potato beetles continue to move into potato fields. Thresholds are 50 adults and small larvae per 50 stems across the field. Adults are laying eggs, and a small plot of potatoes at the research farm has hit threshold with larvae.
Eggplant and Tomato
Scout for flea beetles! Flea beetles can cause significant damage to young eggplant. Pyrethroids, neonics, Verimark, Torac, and Entrust are all labeld for flea beetles. Thresholds are 1-2 per transplant. Tomatoes may also be heavily fed upon but are generally much more tolerant of flea beetles.
Cole Crops
Please note that pyrethroids will not control diamondback moth caterpillars. Diamondback larvae are too small to eat through an entire leaf, they usually leave window-paned areas where the upper leaf surface remains intact, turning to a light brown color. Scout also for harlequin bug. The best materials for harlequin bug include pyrethroids, neonicotinoids, and if small nymphs are present, Neonics will not disrupt the natural enemies that target our worm pests.