As you prepare to fill your high tunnels and greenhouses or even field plots, take a close peek at the weeds in your area. There can be some sneaky pests that have overwintered on the plant material in and around your farm. In high tunnels in particular, I have recently found overwintering populations of two spotted spider mites and a variety of aphid species. Before you put those tender little transplants into these environments, be sure to get rid of the straggling weeds and insects. Remove the plant material, move it away from your growing space, and allow some down time before you move the new crops in. Aphids and mites can not survive without living plant material. They will not overwinter in the soil, they need to be feeding on active growing plant material.
Happy growing season!
Figure 1. Bird cherry oat aphid and two spotted spider mites overwintering on weeds.
Figure 2. An aphid that has been parasitized by a wasp. The wasp will emerge from the swollen body.
Figure 3. Two spotted sider mite adults and eggs.
Figure 4. A snapshot of the weeds hosting these and other insects in the high tunnel.
Figure 5. Henbit infested with aphids and a syrphid fly larvae (predator). Photo by John Obermeyer.