–by Dr. Jeff Whitworth
Alfalfa should probably still be monitored for pests. Every alfalfa field sampled throughout south central and north central Kansas from 8-13 October had significant infestations of potato leafhoppers (see fig 1). The treatment threshold for potato leafhoppers is variable as the economics of hay production is so dynamic depending upon the end use of the hay. However, potato leafhoppers can stress alfalfa in 2 ways–removing plant fluids due to their feeding with the simultaneous injection of a toxin (see fig 2 of “hopper burn”). These two factors may stress alfalfa at any time of the year, but especially this time of year (especially during this dry period) because it may hamper the plant’s ability to prepare for overwintering. One positive note, however, all potato leafhoppers observed in the last 10 days were adults; so hopefully, they will be migrating out of Kansas for overwintering sites in the southern U.S. All fields sampled had not been swathed, so if they are cut soon this should also help eliminate any leafhopper problems.
Figure 1. Potato Leafhoppers (Cayden Wyckoff)
Figure 2. “Hopper Burn on alfalfa (Cayden Wyckoff)