It is also important to record any parasitized or diseased larvae of each species. If the number of healthy worms exceeds 5-6 larvae per sweep and defoliation is obvious then controls may be needed. If harvest time is near, haying will destroy most of the larvae and save the time and expense for chemical control. A key to the common defoliators found on alfalfa in Oklahoma is provided below. Nutrient deficiency and pH problems.
Many studies indicate that alfalfa can be reestablished successfully following alfalfa.
Most reports of problems with autotoxicity are from greenhouse and field studies where top growth of alfalfa was incorporated into the soil and alfalfa replanted immediately. Assuming little foliage was plowed under due to a thin stand, the importance of autotoxicity would be reduced greatly. Under some circumstances good producers can have success with alfalfa following alfalfa immediately with special attention. Deep moldboard plowing can assist with removing many of the insects and pathogens from the area where seedlings will grow. Rotation to other crops allows more time to address these problems.