How to Manage Pests
UC Pest Management Guidelines
(Reviewed 11/06, updated 9/07)
In this Guideline:
Using the procedures below, take weekly stem samples for blue
alfalfa aphids, pea aphids, cowpea aphids, and natural enemies during stand
establishment and in spring- and fall-established stands. Sample for cowpea
aphids, spotted alfalfa aphids and natural enemies in summer-established
stands. Natural enemies can quickly reduce aphid infestations. As aphid
threshold populations are approached, check every 2 to 3 days to determine if
natural enemies and disease cause the population numbers to decrease.
See monitoring form with detailed
treatment threshold information.
HOW TO SAMPLE (View photos of aphids)
Randomly choose 5 stems from each of 4 areas per field,
noting if the average plant height is less than 10 inches, 10 to 20 inches, or
more than 20 inches.
Bend each stem sample over a white pan and tap;
dislodged aphids will fall in. The stem can also be shaken into a sweep net if
a pan is not available.
Take sweep net samples (see SAMPLING WITH A SWEEP NET) for lady beetle
adults and larvae, fungal-killed aphids, parasitized aphid mummies, and the
presence of other predators such as syrphid flies and lacewing larvae. Natural enemies can
quickly reduce the aphid population.
Record results on a monitoring form. A treatment may be
warranted if natural enemies fail to keep the aphid population in check.
PROCEDURE AND TREATMENT THRESHOLD
||Stand establishment and established stands (spring and fall)
||Established stands (summer)
||blue alfalfa, pea aphids, cowpea aphid, and natural enemies
||cowpea aphid, spotted alfalfa aphid, and natural enemies
|When to start
||February during stand establishment
||Early summer (June for spotted alfalfa aphid)
||If both blue alfalfa and pea aphid species are present, use the blue
alfalfa aphid treatment thresholds.
No thresholds are established for aphids on seedling alfalfa.
|If only spotted alfalfa aphids are present and reach treatment
thresholds, be sure to sweep and compare spotted alfalfa aphids and lady beetles according to the following "Treatment Thresholds" table.
|If natural enemies are present
||Check the field every 2 to 3 days to see if the aphid population declines. If it does, insecticides may not be necessary.
||Plants less than
||Plants more than
||After last fall cutting
|Blue alfalfa aphid
|Spotted alfalfa aphid
UC IPM Pest Management Guidelines:
UC ANR Publication
- C. G. Summers, Entomology, Kearney Agricultural Center, Parlier
- P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
Top of page