By Robert Wright and Jeff Bradshaw et.al
Several species of aphids may occur in Nebraska alfalfa. We have received a report of high numbers of spotted alfalfa in one field in the Scottsbluff, Nebraska area seen at first cutting. There are four aphids commonly seen in Nebraska alfalfa — pea aphid, spotted alfalfa, blue alfalfa aphid and cowpea aphid. They differ in their seasonal occurrence and damage potential.
A recent article by Iowa State University Extension Entomologist Erin Hodgson summarizes life cycles and identification of these four aphids.
Spray Thresholds for Aphids in Alfalfa*| Alfalfa growth stage | Pea aphid/Cowpea aphid | Blue alfalfa aphid/Spotted alfalfa aphid |
|---|
| Seedling | 5 per stem | 1 per stem |
| <10" | 40 per stem | 10 per stem |
| 10-20" | 75 per stem | 30 per stem |
| >20" | 100 per stem | 50/100 per stem |
*Resource: http://www.ipm.ucdavis.edu/PMG/r1300211.html
Insecticide options for Nebraska alfalfa can be found in 2022 Guide for Weed, Disease, And Insect Management, Nebraska Extension Circular 130.
Nebraska Extension Educator Nathan Mueller reported seeing potato leafhoppers in Gage County on June 15. Potato leafhoppers have the potential to injure alfalfa in Nebraska every year. They don't overwinter in Nebraska but rather are brought in on southerly winds. Generally, they are a second and third cutting pest. If you have not yet started to scout for potato leafhopper, now would be a good time to begin.
Potato leafhopper. (Photo by Jim Kalisch)
These small (1/8 inch long), bright green, wedge-shaped insects may cause severe damage to alfalfa. This feeding results in a distinctive yellow or purple triangle shape at the leaf tip. First year, spring planted alfalfa fields are particularly attractive to and vulnerable to potato leafhoppers, as are fields planted last year. In older fields, these insects are usually a problem on second and third cuttings.
For treatment guidelines and control options, see this CropWatch article.
Source : unl.edu