 Hello, my name's Jan Knodl. I'm the Extension Entomologist for North Dakota State University. This video is about scouting for spider mites and field corn. Spider mites are a very tiny arthropod found on the underside of the leaf. They feed on the corn plant with piercing sucking mouth parts. They feed on the plant sap. When you're ready to go out and scout, you start in the field edge to determine if spider mites are present. Look for the stippling on the leaves and or discoloration. Here you can see the mite infestation is fairly severe. You can see the yellowing and the necrosis of the plant tissue. In a severe situation, the leaves will go brown and you'll have leaf loss. If you turn the leaf over, you can see some gray area along the midrib and this is actually webbing of the spider mites. Damage typically occurs near tasseling or later in the growing season. As with soybeans, spider mites infest corn plants from the bottom upwards. The management goal is to keep damage from reaching the leaf ear. Easy technique for looking for spider mites is to use a white sheet of paper and take the leaves that you suspect having spider mites and tap them to dislodge the spider mites and then look at the sheet of paper for mites that may be moving around. After you check the field edge and you found spider mites, you want to continue to check the rest of the field by sampling 20 sites and a couple plants per site and walking a U pattern through the field. Try to determine how far the mites have moved into the field. In some situations, you may be able to get by with only spraying the field edges. Under hot, droughty conditions, the spider mites can move and reproduce faster, so the whole field may need spraying. The goal of preventing spider mite economic loss is to prevent the spider mites from reaching the leaves near the ear, prevent the stippling from getting up to that leaf. So in general, the threshold is when it's in the lower quarter to third of the plant is when you see stipplings would be an action threshold. A more detailed threshold has been developed by Texas A&M University. It takes into account the market value of the corn percent infested leaves per plant and percent total leaf area damage and the control cost per acre. Corn is susceptible to spider mite damage from tasseling through the hard-dough stage. When corn has reached the hard-dough stage, it is no longer susceptible. For a two-spotted spider mite control in corn, there are several insecticides and miticides recommended. We have the organophosphate insecticide dimethylate active ingredient and also the only pyrethroid a registered active ingredient by fendthrin. Trade names are tundra and discipline. We don't recommend using other active ingredients of pyrethroid insecticides because pyrethroid insecticides are known to flare spider populations. The two miticides registered in corn are comite and oberon. They are used primarily in the southern states due to the severity of mite problems in corn. Go back to the field and re-scout about five to seven days after treatment. The reason why is because the spider mite eggs are not controlled with insecticides. The eggs will hatch usually in about five days. Check to see if those young nymphs that hatch from the eggs are increasing in population. If so, you may need to re-treat with a second application. Thanks for joining me today and learning how to scout for spider mites in field corn. Please see the Extension Entomology website for more information.