David Owens, Extension Entomologist, firstname.lastname@example.org
Continue scouting for early signs of asparagus beetle activity and egg lay. Earlier this week, I spent some time looking for them and it took a while, but I did find an adult beetle. Asparagus beetles will stick their cylindrical dark eggs at a 90 angle to the stem. Minnesota scouting recommendations suggest to sample 20 plants in each of 5 locations for at least 100 spears/plants. Thresholds are 2% of spears with eggs, 5-10% of plants with adults, and 50-75% of plants with larvae.
Continue monitoring transplants for mites and for aphids. Melon aphids occasionally get drawn into greenhouses and can build up to very high numbers prior to transplanting in fields. Look for leaves that curl or cup downwards and for sticky specks on trays from their honeydew excretions. Heavily impacted plants, if not treated, can have a hard time catching up. For spider mites, check weeds that might be growing along the edge of the greenhouse and any weeds coming up underneath of the tables. Look for small stippling on new leaves.
Reports of aphid activity in spinach have come in this week. The good news is we have a lot of modes of action that are not harmful against biological control agents. The bad news is that parasitic wasps tend to destroy the aphid larvae, glue the aphid down on the leaf, and change its color from green to straw brown. Labeled materials include the 4A, 4C, and 4D ‘neonicotinoids and neonicotinoid-like’. This is followed by several group 9 materials (PQZ, Fulfill, Versys). Diamides and Torac are also labeled and performed well in last year’s cabbage aphid trial. If a pyrethroid is used, please note that it will kill biological control agents, not all of which glue the aphid down like parasitic wasps.
Begin scouting for worms. Cabbage whites have been active several weeks now and are ovipositing into various Cole crops. Early thresholds are pretty high, between 20-30%. Other Lep pests are active but in very low numbers. Be sure to get good coverage on plants, spreader sticker type adjuvants are helpful to get good deposition on the waxy leaves. If you use Radiant or a diamide like Coragen, Harvanta, or Exirel, do not use a sticker. These products try to get into the leaf tissue while a sticker tries to keep it on the leaf surface.