How to Manage Pests

UC Pest Management Guidelines

Cotton

Cotton Aphid

Scientific Name: Aphis gossypii

(Reviewed 5/13, updated 5/13)

In this Guideline:


DESCRIPTION OF THE PEST

Cotton aphid is the most common aphid on cotton in California and it can be present at any time during the growing season. Cotton aphid is highly variable in body size and color, and adults may be winged or wingless. Nymphs and adults of wingless cotton aphids vary in color from yellow to green to nearly black. The darker forms tend to be substantially larger. Nymphs that are developing into winged adults look very different from the nymphs developing into wingless adults: they bear small welts or protuberances on their bodies and may be covered with a coat of dusty-appearing whitish wax. Their body color is often greenish blue, or amber and blue.

Damage

The different forms of the cotton aphid differ in their ability to cause population outbreaks and plant damage, therefore it is important to be aware not only of the number of aphids present, but also of their color form. The small yellow aphids develop slowly from newborn nymph to adult and do not produce many offspring; thus, their populations rarely increase rapidly. The larger, darker aphids (green and black) are quite different; they develop more rapidly, produce many more offspring in a rapid burst, and can generate rapid population growth rates.

Additionally, damage caused by cotton aphid varies seasonally with the growth stage of the plant.

Presquaring (Early Season)

Heavy populations on seedling cotton can cause crinkling and cupping of leaves leaves, failing to expand, defoliation, and a severe stunting of seedling growth. In addition, honeydew contamination on leaves may make the leaves appear wet and shiny. Cotton appears to be able to compensate fully for early season damage as long as the aphid feeding ceases.

Squaring and Boll Production (Mid-season)

Low aphid numbers (<25/leaf) on mid-season cotton often do not generate any obvious damage symptoms. High aphid numbers (>50/leaf) create the same symptoms as observed on seedling cotton (cupped, crinkled leaves, honeydew accumulations, sooty mold, and in extreme cases, limited defoliation). High aphid numbers at this time can decrease the size of bolls, stunt plant growth, and may increase square and boll shedding.

From the Opening of the First Boll until Harvest (Late Season)

The cotton crop is most sensitive to cotton aphid damage at this time because honeydew can contaminate the exposed cotton lint, creating "sticky cotton". Aphid populations as low as 5/leaf can result in honeydew deposition on lint.

Management

Generally, cotton aphid populations on seedling cotton plants (presquare) in most regions of the western United States are not considered a pest problem. However, some areas have consistently severe and prolonged problems with early season aphids. Growers in these areas may need to adopt a more aggressive approach to monitoring and controlling these pests, especially when their fields have a history of early season aphids persisting into the period when squares are produced and yield losses can occur.

Biological Control

During the pre-squaring period of the crop, natural control of aphids is generally strong. The parasitic wasp Lysiphlebus testaceipes and a group of aphid predators (including the lady beetles Hippodamia convergens and Coccinella novemnotata franciscana and the predatory larvae of syrphid flies) are important natural enemies.

During the period of square and boll production and continuing until harvest, parasitic wasps and coccinelid beetles may still be present, especially if aphids reach extremely high densities, but in most fields they are rare. The most common aphid natural enemies at this time are minute pirate bugs (Orius tristicolor), bigeyed bugs (Geocoris spp.), damsel bugs (Nabis spp.), a complex of green lacewings (Chrysoperla and Chrysopa spp.), and a fungus (Entomophthora sp.). Although these natural enemies do provide some control, they generally are not able to strongly suppress aphid populations, or cause strong suppression only after severe damage has occurred to the plant.

Augmentative releases of predatory green lacewings generally are not effective. Natural densities of lacewing eggs are often quite high, making it prohibitively expensive to achieve meaningful increases in egg densities through releases. Furthermore, lacewing larvae are generalist predators and will feed on (cannibalize) other green lacewings, reducing the effectiveness of augmentive releases to suppress aphids.

Cultural Control

Higher cotton aphid numbers consistently develop on late-planted cotton (late April to early May) when compared to early-planted cotton (early April). Additionally, aphids prefer cotton plants that are well watered and highly fertilized. Thus avoid excessive or poorly scheduled nitrogen applications that stimulate growth later in the cropping season.

Cultivar selection also appears to influence aphid population growth. Pima cultivars appear to be more susceptible to aphid infestations and associated damage. Within the Acala cotton cultivars, hairy-leaf varieties, which comprise the majority of the market, are more susceptible to aphids than are smooth-leaf varieties.

Organically Acceptable Methods

Cultural and biological controls and sprays of insecticidal soap, oils, and azadirachtin are acceptable for use on organically grown cotton.

Resistance

Chemical management of cotton aphid can be extremely erratic and unpredictable. Part of the problem is that cotton aphid has developed resistance to many chemical classes, including organochlorine, organophosphate, carbamate, and pyrethroid insecticides. In addition, these broad-spectrum pesticides kill the natural enemies of the cotton aphid. Another resistance concern is with the neo-nicotinoid insecticides. Repeated applications of any neonicotinoids can result in resistance to all neo-nicotinoids.

To manage resistance, follow the basic principles of IPM: (1) spray only when pests reach economic thresholds; (2) start with the most selective pesticides and avoid pyrethroids early in the season in order to preserve natural enemies; (3) save the broad-spectrum pesticides for mid- to late-season aphid outbreaks; and (4) rotate insecticides that have a different mode of action group number if you have to spray more than once. The following table summarizes these insecticide resistance guidelines.

Insecticide Resistance Management Guidelines for Cotton Aphids.
Insecticide Class Mode of Action1 Seedling Cotton Squaring to Boll Crack2 Boll Opening to Harvest2
Organophosphate (OP) 1B Least disruptive OPs: Dibrom, MSR3, Thimet (at planting) MSR (if not used previously), Lorsban3, or Dibrom Lorsban (if not used previously) in combination with Curacron or insecticides in other chemical classes
Carbamate 1A at planting sidedress Lannate
Neonicotinoid 4A Gaucho (seed treatment)
Cruiser (seed treatment)
Provado (if not used previously), Centric, Assail Assail
Unknown 9C   Carbine  
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
2 Tank mixes of insecticides from two different classes may improve aphid control and may help control other arthropod pests that may be present during this period.
3 Applicable for lower aphid densities and ground application; consider tank mixes with Provado for high densities or for aerial application.
4 If significant aphid population is present, may need to apply an insecticide over-the-top during the period when aldicarb is being activated.
5 There are several products available and restrictions may be different between them. Check the label and contact Agricultural Commissioner if uncertain about any local restrictions.
Monitoring and Treatment Decisions

in some areas along the eastern edge of the southern San Joaquin Valley (especially eastern Tulare County) early season aphids can be a persistent problem. If early season populations have a history of being severe, a seed treatment may be warranted; otherwise, seed treatments are not usually applied for cotton aphid control.

Because research has shown that cotton aphids can be stimulated by pyrethroids and increase in numbers, be sure to carefully monitor for aphids following application of pyrethroid insecticides.

The critical time for monitoring aphids is from crop emergence through preharvest. To improve the efficiency of your monitoring program, combine sampling of aphids with monitoring for other pests. From crop emergence to seedling growth, sample aphids, mites, and thrips together as described in MONITORING SPIDER MITES, APHIDS, AND THRIPS. From early squaring through boll development, combine sampling for aphids with monitoring for mites and whitefly as described in MONITORING SPIDER MITES, APHIDS, AND WHITEFLY. From first open boll to preharvest, combine sampling for aphids with whitefly monitoring as described in MONITORING APHIDS AND WHITEFLY. Monitoring forms are available on the online version of this guideline.

Make insecticide applications only when the cotton aphid population exceeds the economic threshold. Terminate the crop as early as feasible, using the nodes above cracked boll (NACB) method described in MONITORING PLANT GROWTH.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, also consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. ACETAMIPRID
  (Assail 70WP) 0.6–1.1 oz 12 28
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate–Long NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: A neonicotinoid. Apply mid- to late season.
 
B. FLONICAMID
  (Carbine 50WG) 1.7–2.8 oz 12 30
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 9C
 
C. IMIDACLOPRID
  (Provado 1.6F) 3.75 fl oz 12 14
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: A neonicotinoid. Foliar application. Do not exceed 0.31 lb a.i./acre/season.
 
D. THIAMETHOXAM
  (Centric 40 WG) 2 oz 12 21
  SELECTIVITY: High
  PERSISTENCE: Pest: ModerateNE:2 Short
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: A neonicotinoid. Apply mid- to late season.
 
E. PYMETROZINE
  (Fulfill) 2.75 oz 12 21
  SELECTIVITY: High
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 9B
  COMMENTS: Offers some suppression of whiteflies.
 
F. ALDICARB* 14 lb 48 90
  SELECTIVITY: High
  PERSISTENCE: Pest: Long NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: A carbamate. Apply at first squaring. Sidedress granules 8–16 inches to one side of the plant row, 2–6 inches deep. Follow immediately with irrigation to activate material. Do not graze or feed trash to livestock. Do not make more than 1 application at planting and one postemergence application per crop. Observations indicate that lepidopterous pest problems may occur following treatment. Apply between March 1 and Sept. 1 only.
 
G. CHLORPYRIFOS*
  (Lorsban Advanced) 1–2 pt 24 14
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Moderate NE:2 Short
  RESISTANCE: in some cotton aphid populations.
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: An organophosphate. Ground or air application. Gives only moderate control of aphid populations before plant squaring, but effectively controls mid- and late season infestations. Do not allow livestock to graze on treated fields. Do not feed trash or treated forage to livestock. Avoid drift and tailwater runoff into surface waters.
 
H. OXYDEMETON-METHYL*
  (MSR Spray Concentrate) 1.5–2 pt 7 days 14
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Short NE:2 Short
  RESISTANCE: in some cotton aphid populations.
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: An organophosphate. Do not apply more than once a season.
 
I. PROPHENOFOS*
  (Curacron 8E) 0.5 pt 48–72 14
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: An organophosphate. Ground or air application. Tank mixing may affect the selectivity and persistence of this material.
 
J. OXAMYL*
  (Vydate C-LV) 12.7–34 fl oz 48 14
  SELECTIVITY: Low
  PERSISTENCE: Pest: Moderate NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: A carbamate. Apply in sufficient refined vegetable oil (minimum 3 pt/acre) or in sufficient water to obtain thorough coverage.
 
K. NALED
  (Dibrom 8E) 1 pt 48 See comments
  SELECTIVITY: Low
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: An organophosphate. Do not apply after first bolls open. Tank mixing may affect the selectivity and persistence of this material. Do not apply more than 5 pt/acre/season.
 
The following three materials are organically acceptable foliar sprays.
 
L. INSECTICIDAL SOAP#
  (M-Pede) 2.5 oz/gal 12 0
  SELECTIVITY: Low
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION: A contact insecticide with smothering and barrier effects.
  COMMENTS: Spray to wet all infested plant surfaces and repeat treatments at weekly to biweekly intervals. Rotate sprays to avoid more than three consecutive sprays of this material.
 
M. NARROW RANGE OIL#
  (TriTek, etc.) 1–2 gal/
100 gal water
4 0
  SELECTIVITY: Low
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Works by suffocating eggs, nymphs, and adults. Requires total spray coverage.
 
N. AZADIRACHTIN#
  (Neemix 4.5) 0.25–1 pt 4 0
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: un
  COMMENTS: in an organically certified crop, restrictions apply regarding the use of this material.
 
SEED TREATMENTS (not usually required for cotton aphid)
 
A. IMIDACLOPRID
  (Gaucho 600 F) 6.4 oz/
50 lb bag of seed
12 0
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Long NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: A neonicotinoid. Seed treatment. May stimulate buildup of spider mites.
 
B. THIAMETHOXAM
  (Cruiser 5FS) Label rates 12 0
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate–Long NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 4A
  COMMENTS: A neonicotinoid. Do not apply another neonicotinoid within 45 days of planting seed treated with Cruiser 5FS.
 
** Mix with sufficient water to provide complete coverage.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically produced cotton.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
2 NE = natural enemies

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

Insects and Mites

  • 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
Acknowledgment for contributions to Insects and Mites:
  • E. E. Grafton-Cardwell, Kearney Agricultural Research and Extension Center, Parlier
  • N. C. Toscano, Entomology, UC Riverside

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