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Alabama Cotton: What Pests to Watch for and When

Ernst Undesser
By Ann Chambliss, Alabama Cooperative Extension March 14, 2017

Alabama Cotton: What Pests to Watch for and When

THRIPS

Thrips may delay maturity if heavy damage occurs at the 1 to 5th true leaf stage. Use seed treatments or insecticide applied in-furrow at planting. Make foliar spray when the first true leaf is just emerging if cotton is planted before May 10 and the minimum nighttime temperature is below 65⁰ F.

 

PLANT BUGS

Monitor cotton for pinhead square set when squaring begins (about 6th true leaf). Continue checking pinhead square set until about first bloom. During this same time period use sweep net (can be purchased for about $75 from Gempler’s,  www.Gempler’s.com) to sample for adults. Spray for adults if 5-8 per 100 row feet (33 sweeps) are found.

PLANT BUGS

After first bloom check for immature plant bugs (small, green with long antenna) with a drop cloth spread between two rows. Beat plants briskly to dislodge immatures from inside of the square bracts. Spray at threshold of one immature per row foot. Continue surveys for about 3-4 weeks.

APHIDS          

Only treat when over 50% of the plants have aphid clustering under leaves, honeydew is present, and cotton is under drought stress.

ESCAPE BOLLWORMS   

For about 10-14 days, beginning July 20 in Central Alabama monitor squares and white blooms for small bollworm larvae.  Move this date 10 days earlier for South Alabama and 10 days later for North Alabama.

If the field has not been sprayed multiple times for plant bugs, fire ants will also be searching white blooms for these small larvae. Spray pyrethroid at a high labelled rate if 5 to 10 or more larvae about quarter inch in length are found per 100 plants.

You may look at fewer than 100 plants but express the number on a 100 percent basis. Tobacco budworms do not escape genetic cotton, therefore, even large bollworms can be controlled unless they are already imbedded in a boll.

STINK BUGS

Begin looking for stinkbug damage on field borders (first 5-10 rows) about the third week of bloom. This would be about July 20 in an average plant date year. Pull 10-25 bolls that are the size of a quarter in diameter and still soft to the touch. This boll would be about 10-12 days old.

If you find internal damage on the border, search further into the field and collect more bolls.  Treat border and/or the entire field when 10% of these bolls have internal damage from stinkbugs. Damage will appear as warts in the boll wall or dark areas around the seed.

Continue scouting for stinkbugs until the top bolls you hope to harvest are about 25 days old and hard. Scout for 5-6 weeks beginning the third week of bloom.

SPIDER MITES      

Observe for the presence of spider mites underneath leaves. Mites will move when the leaf is pulled, inverted, and the mites are exposed to the sun. Treat when mites are detected over much of the field and the weather outlook for the next 7-10 days is hot and dry.

Mites do not reproduce or spread as fast when weather conditions are not favorable.  Rainfall does not kill mites, they just do not reproduce and spread as rapidly.


Source: : https://sites.aces.edu/group/commhort/blog/Lists/Posts/Post.aspx?ID=367

Ernst Undesser
By Ann Chambliss, Alabama Cooperative Extension March 14, 2017