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Extension Entomology

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Alfalfa Update

By — Dr. Jeff Whitworth, Dr. Holly Schwarting

Alfalfa continues to be problematic in NC Kansas.  There seems to be many fields of good alfalfa, apparently treated in an effective manner from both an insecticide and a timing standpoint, and not affected by the freezing temperatures earlier this spring.  Many of these fields have been, or are being, swathed.  However, there are some fields that have had, or are having, a difficult time overcoming the combination of alfalfa weevil larval feeding, early season dry conditions, and the early spring freezing temperatures.  In all fields, the early season warmth sped up alfalfa weevil development and feeding, then the cooler temperatures slowed it back down.  Alfalfa weevil larvae were 1st detected in NC Kansas in early March.  Small, 1st instar larvae are still being detected in some fields.

AW larvae 13

Some larvae pupated and developed into adults as long as three weeks ago, and they are still in the alfalfa fields.  So, NC Kansas still has a significant number of adults.  Treating for adult alfalfa weevils is rarely effective, but swathing within 7-10 days should help manage both larvae and adults without an insecticide application.

AW adult

Adult potato leafhoppers have also been noted in alfalfa fields.  These usually migrate into Kansas between the 2nd and 3rd cuttings, so they are about a month early this year. Leafhopper adult (2)

Sugarcane Aphids

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Sugarcane aphids are also still causing much concern throughout KS.  Dr. Bob Bowling, Extension Entomologist TAMU, has conducted research on these aphids for a couple of years in Texas and answered a couple of the most common questions about this aphid.  According to Dr. Bowling, these aphids will not infest corn or wheat, only plants in the sorghum family, i.e., sorghum, Johnsongrass, shattercane, etc.  They are a tropical or sub-tropical insect so probably will not overwinter in KS, or even continue to thrive and increase in numbers as the weather becomes cooler with lower humidity.  Also, and maybe most importantly, the honeydew breaks down within a few days after the colony is gone (or at least is no longer producing honeydew).  The products registered in Kansas for treating these aphids (Transform and Sivanto) both seemed to provide good control in the TAMU efficacy trials when used with at least 15 gal./acre of water (carrier).

sugarcane aphid colony

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