Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Coragen
The new label has been posted to CDMS. Please refer to the link for crops labeled, rates and use restrictions (http://www.cdms.net/LDat/ld8KF000.pdf).
Cabbage
Continue to scout for diamondback and imported cabbageworm larvae. Economic levels of diamondback larvae can be found. A treatment should be applied when 5% of the plants are infested and before larvae move to the hearts of the plants.
Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. Economic levels of aphids can be found, so be sure to check plants as soon as they are set in the field. In general, cucumber beetle levels have been low. However, as temperatures increase be sure to watch carefully for an increase in populations.
Peppers
Fields should be sampled for thrips and corn borers. On young plants, corn borer larvae can bore into the stems and petioles. In areas where peppers are isolated or corn is growing slowly, moths are often attracted to young pepper plants. Therefore, you should watch for corn borer moths laying eggs in all fields. As a general guideline, treatment may be needed if there is no corn in the area or you are using rye strips as windbreaks. You should also look for egg masses. At this time of year, thrips can damage peppers by vectoring tomato spotted wilt virus and by causing direct plant damage. Although there are no available thresholds, a treatment may be needed if you see populations increasing.
Potatoes
Be sure to watch for an increase in Colorado potato beetle adult activity and egg laying. We have found the first egg masses and larvae will be present as soon as temperatures start to increase. A treatment should be considered for adults when you find 25 beetles per 50 plants and defoliation has reached the 10% level. Once larvae are detected, the threshold is 4 small larvae per plant or 1.5 large larvae per plant. We are starting to see an increase in corn borer activity and the earliest planted fields will be attractive to egg laying moths (http://ag.udel.edu/extension/IPM/traps/latestblt.html). A corn borer spray may be needed 3-5 days after an increase in trap catches or when we reach 700-degree days (base 50). If you are scouting for infested terminals, the first treatment should be applied when 10% (fresh market) or 20-25% (processing) of the terminals are infested with small larvae.
Snap Beans
All seedling stage fields should be scouted for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by 1/3. Also be sure to watch for damage from bean leaf beetle. Damage appears as circular holes in leaves and in some cases significant defoliation has occurred. As a general guideline, a treatment should be considered if defoliation exceeds 20% prebloom.
Sweet Corn
Continue to sample for cutworms and flea beetles. As a general guideline, treatments should be applied if you find 3% cut plants or 10% leaf feeding. In order to get an accurate estimate of flea beetle populations, fields should be scouted mid-day when beetles are active. A treatment will be needed if 5% of the plants are infested with beetles. Watch for small corn borer larvae in the whorls of the earliest planted fields. A treatment should be applied if 15% of the plants are infested.