How to Manage Pests

UC Pest Management Guidelines

HOW TO SAMPLE

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 5^th 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 (example form—86 KB, PDF).

• 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 (3^rd or 4^th 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.

TREATMENT THRESHOLDS

• Spider mites: 30-50% of leaves show mite presence.
• 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 to 75 aphids per fifth main stem node leaf.
• 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.

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

IMPORTANT LINKS

• Photos of spider mites, aphids, and whitefly
• Spider mite, aphid, and whitefly monitoring form (86 KB, PDF)

PUBLICATION

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444
General Information
L. D. Godfrey, Entomology, UC Davis
P. B. Goodell, UC IPM Program, Kearney Agricultural Center, Parlier
E. T. Natwick, UC Cooperative Extension, Imperial Co.
D. R. Haviland, UC IPM Program, Kern Co.

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