Some of the insects that may infest sorghum are the Southwestern corn borer, Lesser stalk borer, corn leaf aphid, greenbug, sorghum midge, corn earworm, fall armyworm, stink bugs, cutworms, flea beetles and spider mites. Chemical treatment may not be warranted for most of these insects unless the damage is severe. Severe insect damage is most common when sorghum is planted late or following a corn or sorghum crop. Leaf feeders such as the corn earworm and fall armyworm generally do not cause economic damage. The Southwestern corn borer, by contrast, can cause economic damage and the crop should be monitored carefully for this insect. This pest feeds in the leaf whorls and causes a shothole appearance to the leaves when they unfold. After feeding on the leaves, the larvae move down the plant and bore into the stalk where the real damage occurs. Tunneling in the stalk by this pest, especially by the second and succeeding generations, weakens the stalk and may cause lodging. Southwestern corn borer should be chemically controlled when 25% of the whorls are infested. Cultural practices that may be helpful for control of this pest include avoid planting after corn or sorghum, planting early-maturing hybrids, sowing the crop early, planting over a short period of time over an area-wide basis to avoid population build-up, maintaining strong stalks through proper plant population and irrigation and fertilizer practices, and surface tillage at harvest to break the stalks and expose the larvae to cool winter temperatures and desiccation. The lesser stalk borer may be a problem when planting in June or July after wheat or barley. Application of an insecticide or flooding of young plants may control this insect. Greenbug can be damaging since it injects toxins into the plant. Nutrient or water stress can lead to buildup of greenbugs. Chemical treatment after heading is not recommended. Sorghum midge is a gnat-like insect whose larvae feed on the developing seed. Early planting helps avoid high populations of this insect. Cutworms are most likely to be a problem if sorghum follows small grain, corn, sorghum, or spring vegetable crops. The larvae of this insect feed at night just above the soil surface by cutting off young plants or chewing holes in the stems of older plants, then seek cover during the day in the soil or debris. Spider mites feed mostly on the lower surface of leaves, and, as populations increase, individual mites are barely visible Soil Test Nitrate ppm NO3 -N Approximate Nitrogen Fertilizer Rate lbs N/acre 0-10 150-200 10-20 100-150 20-50 30-100 Above 50 0-30 Table 2. Estimated seasonal nitrogen fertilizer rates for grain sorghum based on pre-plant soil nitrogen levels. These guidelines have not been verified for grain sorghum grown in Arizona. The University of Arizona Cooperative Extension 3 without magnification although their fine webbing will be evident. The infestation is usually observed on the edges of the field