10 MIN READ

Early-Season Insects in Cotton

April 13, 2022

  • Insects can slow early-season cotton growth, reduce stands, delay fruit set, all of which may lead to loss of yield potential.

  • Scouting is necessary to find, identify, and determine population levels of early-season insects that may damage cotton.

  • Growers should use both preventative and responsive integrated pest management tactics to reduce the risk of economic injury because of early-season insects that may exceed economic injury levels.

Early-season insects may be a pest of cotton in all agronomic conditions but can be more prevalent in weedy fields with a history of insect damage. Additionally, increased risk of early season insect injury may occur under reduced tillage systems, fields with uncontrolled weedy borders, and/or a crop that is under stress. Insect damage can be manifested by curled leaves, chlorosis (yellowing), leaning or wilting seedlings, and injury to the terminal bud. Intensive and comprehensive crop scouting is the major tool farmers have to identify insect injury quickly allowing time to implement control tactics if insect populations exceed the treatment threshold.


Management tactics

Weed control. Some weeds are alternative hosts for insects attacking cotton, so reducing weed populations three to four weeks prior to planting helps reduce insect populations prior to seedling emergence.

Tillage. Reducing the previous crop residue in which some insect pests can reside, weed destruction, and direct exposure of insect pests are some of the benefits of tillage in managing early season insect pests.

Seed treatments. Insecticide seed treatments can help reduce damage to young seedlings by early-season insects, including thrips and aphids.

Insecticide applications. Insecticides can be applied in-furrow at planting or as a foliar spray in-season. Insect pressure can vary by year and by field; therefore, insecticide application should be based on scouting observations, and not by a pre-determined schedule. Apply during the most susceptible stage of insect development and be mindful of preventing resistance.

Scouting. Effective cotton insect control relies on frequent and thorough scouting. Fields should be scouted every 4 to 5 days with enough time spent in the field to accurately assess insect populations and stages. The objective is to avoid unnecessary insecticide applications and time applications correctly. Allot time for additional field checks to account for possible increased insect pressure.

Beneficial agents. Lady beetles, spiders, minute spider bugs, parasitic wasps, and insect fungal diseases help control inspect pests. It is important to identify these beneficials correctly in the field and understand what insect pests they help to reduce to avoid unnecessary insecticide application.

Economic thresholds. Economic thresholds are the point at which insect density requires action to prevent economic loss. It is important to apply insecticides based on scouting and threshold levels to reduce costs and loss of beneficial insects. Thresholds can vary for several reasons including insect species, crop development stage, yield potential, treatment cost, market price, secondary pests, and other considerations. Use local thresholds recommended by state extension specialists along with on-farm considerations.


Identification and Damage Symptoms of Early-season Cotton Insects1,2

Click on the insect to learn more
Wireworms.
Figure 1. Wireworms. Picture courtesy of Frank Peairs, Colorado State University, Bugwood.org

WATCH: Planting Until Emergence

  • Subterranean, dark brown with tough exoskeleton and three pairs of legs and well-defined head.

  • Feed on seed and germinating seedling, under high populations, plant may never emerge.

  • Missing plants.

  • Injury more common in fields after sod or small grains, weedy fallow fields, and those with reduced tillage.

  • No rescue treatment options



IM
Figure 2. Thrips injury in cotton.

WATCH: Emergence to 4 Leaf

  • Yellow to brown, gray or black, tiny (~1/8-inch long), narrow wings.

  • Feed on underside of cotyledons first, then terminal bud. Cotton terminal bud slow to develop, extending damage time and slowing growth. Injury more severe when plant is under additional stress

  • Curled, gnarled leaves.

  • Presence of immatures may indicate at-plant insecticide not active.

  • Thrips infestation is impacted by tillage when weeds are destroyed, adults can move to emerging cotton

  • Recently, a prediction model for thrips attacking cotton has been developed and can be found at https://products.climate.ncsu.edu/ag/cottontip/


Cutworm
Figure 3. Cutworm. Picture courtesy of Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org.

WATCH: Seedling to open boll

  • Black cutworm: gray to brown, greasy; Variegated cutworm: mottled yellow and brown, smooth; Granulate cutworm: gray, dull.

  • Seedlings cut at or below soil surface.

  • May be leaning or wilting, with several plants in a row affected.

  • Destroy weeds at least 4 weeks prior to planting to reduce risk of injury by cutworms, if planting prior to weed destruction, consider a band application over row.

  • Maintain a minimum stand of one plant per row foot to maintain yield potential.



IM
Figure 4. Aphids. Picture courtesy of Ronald Smith, Auburn University, Bugwood.org.

WATCH: Seedling to open boll

  • Pear shaped, light yellow to dark green, two cornicles on abdomen, winged or wingless.
  • Found on undersides of leaves, stems, terminals, sometimes fruit.
  • Produce sticky “honeydew”, can cause leaves to curl, turn yellow and shed.
  • Beneficial insects as well as fungus can help control. Infected aphids appear grey and downy.

IM
Figure 5. Plant bug. Picture courtesy of Russ Ottens, University of Georgia, Bugwood.org

  • Tarnished plant bug illustrated in Figure 5.
  • Feed on seedling terminal bud, leaves, stems.
  • Can be a major economic pest during early square formation when adults feed on flower buds. Overall, the ultimate impact of early season injury is a delay in crop maturity.
  • Risk increases when cotton is close to other crop hosts, such as corn.

IM
Figure 6. Fleahopper. James Smith, Mississippi State University, Bugwood.org

WATCH: Squaring

  • Pale green, 1/8-inch long (Figure 6).
  • More often a pest of Texas and Oklahoma, but periodically a problem in New Mexico and the Midsouth.
  • During blooming, fleahopper control is rarely justified
  • Damaged squares die and turn brown, resulting in a “blasted” appearance resulting in square drop
  • Pinhead squares are most susceptible.

IM
Figure 7. Older spider mite damage. Photo courtesy of John C. Frenh, Sr.

WATCH: Squaring to harvest

  • Tiny (barely visible) arthropods with eight legs.
  • Feed on undersides of leaves and plant sap, causing discoloration (Figure 7).
  • More common during periods of dry weather.
  • Severe infestations can cause defoliation and boll shed.

Sources

1Allen, K., Luttrell, R., Sappington, T., Hesler, L., and Papiernik, S. 2018. Frequency and abundance of selected early-season insect pests of cotton. Journal of Integrated Pest Management, Volume 20. 1–11 pp.

2Knutson, A. 2018. Cotton Fleahopper. Texas A & M University Extension. https://extensionentomology.tamu.edu/insects/cotton-fleahopper/


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