How to Manage Pests

UC Pest Management Guidelines


Monitoring Spider Mites, Aphids, and Whitefly (Early Squaring to Boll Development)

(Reviewed 5/13, updated 5/13)

In this Guideline:


Take a combined sample for spider mites, aphids, and whitefly at least once a week from early squaring through boll development. Beginning at least 50 paces into the field, choose a sample plant at random and select the 5th mainstem node leaf from the terminal. Using a hand lens, turn the leaf over and check for insects and mites on the underside (these are called leaf-turns). (Record monitoring results)

Aphids Count and record number and color (yellow or black).
Spider mites Note the presence or absence—no need to count.
Whitefly adults If 3 or more are found, count the leaf as infested
Whitefly nymphs Place a quarter-sized ring between the central and left-side main veins and check for presence or absence of large nymphs (3rd or 4th instar).

Repeat these leaf-turn samples on 10 plants in this area of the field, walking at least 20 paces between sample plants. Then move to another area, repeating the procedure in a total of 4 areas of the field. Be sure to check the edges of the field for whiteflies migrating in. Also check for natural enemies of aphids, mites, and whiteflies including western flower thrips, western predatory mites, bigeyed bugs, minute pirate bugs, lacewing larvae, syrphid fly larvae, lady beetles, as well as parasitized aphids and whiteflies.


(See specific pest sections for more details on thresholds and treatment options.)

Aphids Between first square and open boll when populations are persisting or building over a 5- to 7-day period, the treatment threshold is 50 aphids per fifth main stem node leaf.
Spider mites 30% of leaves show mite presence.
Whitefly adults 40% leaves with at least 3 adults.
If using insect growth regulators (IGRs), nymphs must also be present to justify treatment. If high numbers of adults are at field edges, but no nymphs, an edge treatment with a non-IGR may be required.
Whitefly nymphs 40% leaves infested with large nymphs.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

General Information

  • L. D. Godfrey, Entomology, UC Davis
  • P. B. Goodell, UC IPM Program and Kearney Agricultural Research and Extension Center, Parlier
  • E. T. Natwick, UC Cooperative Extension - Desert Research and Extension Center, Imperial County
  • D.R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
  • V. M. Barlow, UC Cooperative Extension, Riverside County and UC IPM Program

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