How to Manage Pests
Identification:
Key to Aphids Commonly Found in San Joaquin Valley Alfalfa and Cotton
Note: This key includes only the aphid species that
are most commonly found in alfalfa and cotton in California's San Joaquin
Valley. If you are unable to identify an aphid using this key, see
your local Cooperative Extension
farm advisor for assistance.
Aphids may be difficult to identify as they attack California alfalfa and
cotton.
The alfalfa aphids, pea aphid (Acyrthosiphon pisum (Harris))
and blue alfalfa aphid (A. kondoi Shinji), are similar in
appearance. Recently, the cowpea aphid, Aphis craccivora Koch,
has become a pest of alfalfa and has been found colonizing cotton in California’s
San Joaquin Valley. The cowpea aphid on cotton is easily confused
with cotton aphid, A. gossypii Glover, at certain times of
the year.
Since economic thresholds have been developed for individual species, proper
aphid management requires accurate identification.
Use this key to identify an aphid. While aphids appear to be very
simple insects, they are really very complex, both in their biology and their
morphology. As with other insects, external morphological features are used
to identify individuals to the species level.
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This drawing of a typical aphid shows a number
of morphological features important in identification.
- Look at an aphid through a 10x hand lens to see the important
characters that distinguish the aphids included in this key.
- On each page of the key, click on the box that best matches
the character of the aphid you’re trying to identify.
Begin the Key
Additional reading
Acknowledgments
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