Continue to watch for insects in alfalfa as drought continues, advises University of Kentucky Extension entomologist Lee Townsend.
“Alfalfa, with its long tap root, will be able to stay greener and more succulent long after most everything else has dried, so it will attract a lot of insects that feed either on insects or a wide range of plants,” he says.
Check for potato leafhopper, as damage is easy to overlook. The first sign the pest is present will likely be wedge-shaped yellow areas at leaf tips. The potential for damage is greatest on spring-seeded stands, then on established fields that have not been cut for more than 35 days, giving leafhoppers a chance to build in number.
A lot of other sap-feeding insects, such as tarnished plant bugs, will move to alfalfa. “Generally, they are not an issue, but large numbers of sap feeders can speed up wilting of stressed plants,” Townsend says.
Expect alfalfa foliage and stem loss from grasshoppers, because adults can fly in from some distance away and the wingless nymphs can hop in from nearby fields. They should be abundant because the bacteria and fungi that normally provide natural control aren’t very effective under hot, dry conditions. Watch for feeding damage along field margins.
Many caterpillars, including the green cloverworm and alfalfa caterpillar, are in alfalfa every summer. “With poor growing conditions and limited food choices, they may combine with grasshoppers to cause reduced yield and winterhardiness of alfalfa,” he says.
Finally, be wary of blister beetles. Large numbers are rare in Kentucky alfalfa, but this is the time of year when they are active and alfalfa may be the best food choice they have now. As with grasshoppers, infestations begin along field edges. The beetles tend to clump together in masses, and they’re a serious health threat for horses that consume them.
For more on blister beetles, read “Blister-Beetle Outbreak Draws Texas Hay Warning.”