Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Asparagus
Continue to scout for asparagus beetle adults and eggs. Feeding by beetles can disfigure spears. Depending on the market, the presence of eggs on the spears can make them unmarketable. As a general guideline, a treatment is recommended if 2% of the spears are infested with eggs or if 5% of the plants are infested with adults. In addition, in recent years multiple applications are often needed to control this insect pest and avoid damage, so early detection is important.
Melons
Be sure to scout all melons for aphids, cucumber beetles, and spider mites. The first cucumber beetles are starting to be found in the earliest planted cantaloupe fields. As soon as we get a few consecutive days of warm, sunny weather, populations can explode, so be sure to scout carefully since damage occurs quickly. Since beetles can continue to re-infest fields as well as hide under the plastic, multiple applications are often needed to achieve control.
Snap Beans
Be sure sample all seedling stage fields 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 one third. We are also seeing bean leaf beetle damage in early planted fields so be sure to watch for adult beetles. Damage appears as circular holes in leaves and significant defoliation can quickly occur. 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.