AgWatch

Alfalfa Will Be Attractive

LEXINGTON, KY.
    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.
   Typically, the potato leafhopper is a key pest during this time of year. Damage is easy to overlook because the appearance of wedge-shaped yellow areas at leaf tips may be the first indication that they are present. The potential for damage is greatest on spring seeded stands; then established fields that have not been cut for over 35 days. This amount of time gives leafhoppers a chance to build in numbers.
   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.
   Foliage loss to grasshoppers presents a threat as they move into fields to chew on alfalfa foliage and stems. Adults can fly in from some distance away; the wingless nymphs can hop in from nearby fields. Also, grasshoppers should be abundant because the bacteria and fungi that normally provide natural control are not very effective under hot, dry conditions. Watch for feeding damage along field margins.
   A number of 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 winter-hardiness of alfalfa.
   Finally, there are blister beetles. Large numbers of blister beetles 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 and blister beetles tend to clump together in masses. Their feeding damage is not an issue but contamination of alfalfa with blister beetles is a serious health threat for horses that consume them.
   Check with your local cooperative extension office for more information on blister beetles in alfalfa.
   The potential for damaging insects in alfalfa is greater than normal this year. Check it regularly to catch problems early. Δ
 DR. LEE TOWNSEND: Entomologist, University of Kentucky

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