CHECK NEW STANDS FOR INSECT PROBLEMS

All alfalfa fields, especially new ones, should be checked in the fall for several possible insect pests. Cutworms or armyworms can be present in both new and established alfalfa. Problems are frequently observed with fall armyworms, webworms, cutworms, and aphids during the fall.  

Problems of this nature should be thoroughly monitored, especially in new stands of alfalfa. Producers can do their own pest scouting, they can hire someone to do it for them, or they can ask pesticide applicators to help. A combination of all three methods is likely the best.  

Two cutworms per square foot or 1-2 spotted alfalfa aphids per stem, can devastate a new stand of alfalfa, and even with good glasses they cannot be seen from the pickup or the coffee shop. Like it or not, you have to get down on your hands and knees to check new stands for these problems. Don't rely on a glance from the pickup truck to make these important decisions.  

Carefully inspect the undersides of leaves for aphids and the soil's surface for evidence of cutworm presence (look for little mounds of soil). If large (1 ½") caterpillars (worms) are found near these mounds, then the insect is about to pupate and controls are unnecessary. If many (more than three per square foot) small larvae are found then chemical controls are needed.  

When checking for aphids in new stands of alfalfa, do not attempt to use a sweep net, since young plants may be damaged and young stands cannot be adequately checked in this manner. Keep in mind, that even established stands can only tolerate about 10 spotted aphids per stem if the growth is less than 10 inches tall. As previously mentioned, new stands can only tolerate 1-2 spotted aphids per stem. It is rare to find this many spotted aphids on resistant varieties, but look anyway. You may find blue alfalfa aphids, for which genetic control is not nearly as good.  

If chemical control is necessary, Lorsban^® or the permethrin products (Pounce^® or Ambush^®) should do an excellent job. Remember the material you choose is only as good as the application. Therefore, apply at least 2 gallons of water per acre by air or 10 gallons of water per acre by ground. Do not apply insecticides when temperatures are below 50^oF and/or wind velocity exceeds 8-10 mph.