Adult
Identification & Incidence: Migrating PLH populations become established on Ohio alfalfa during the 2nd cutting and may reduce yields until late August. Foliar injury is indicated by yellowing of foliage, termed hopperburn, and plants are stunted. Critical periods of injury occur from late 2nd cutting to early 4th cutting.
Adult
Nymph
Sampling: Prediction
of PLH injury depends on detection of abundant PLH presence prior to onset of
foliar injury. Sweep net sampling is most effective method.
Economic Threshold: Potential for economic injury exists when number of
PLH per 10 sweeps exceeds height of stand expressed in inches. Threshold may
be increased during periods of vigorous growth or decreased during periods of
stand stress. Presence of PLH nymphs in abundance indicates high potential for
injury.
Action thresholds for control of PLH
| Alfalfa Tolerance for Stress | |||
|---|---|---|---|
| Stand Ht | Low | Medium | High |
| Inches | Action Threshold of PLH/10 Sweeps | ||
| 6 | 3 | 6 | 9 |
| 10 | 5 | 10 | 15 |
| 16 | 8 | 16 | 24 |
| 20+ | 10 | 20 | 30 |
Management Options: Timely harvests will reduce PLH population development and impact. New seedings are especially vulnerable and should be monitored closely. The use of PLH resistant alfalfa is an alternative to the use of foliar treatments, although these cultivars should be watched closely during the establishment year for possible damage. See chart for insecticides labeled for PLH.