Insects Impacting Cotton During Bloom

Controlling insects has long been a priority for cotton growers. The use of thresholds and insecticides has helped to change the face of cotton production. Two other forces — boll weevil eradication and transgenic varieties — have also changed the industry.

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The use of varieties containing Genuity® Bollgard II® cotton offers growers enhanced protection from Lepidopterous pests — helping protect the bolls by controlling most leaf- and boll-feeding worm species (i.e. tobacco budworm, pink bollworm and cotton bollworm). Using Genuity Bollgard II cotton can provide greater yield protection. The advanced dual-gene system of Genuity Bollgard II cotton allows a wider spectrum of worm control with fewer sprays. Decreasing the number of insect sprays can conserve beneficial insect populations and reduce flaring of other pest infestations, such as aphids and spider mites.

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Identifying problem caterpillars — The number of eggs and newly hatched larvae do indicate pressure, yet they do not necessarily indicate that control measures are needed. Because caterpillars are susceptible to Genuity Bollgard II cotton, and must feed for a short time prior to being controlled by the B.t. toxin, it is more important to monitor young larvae than egg lay. Identifying escapes is complicated, but most authorities agree that larva of 1/4 inch in length that appear healthy have good chances of survival.

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Modified whole plant search — Inspecting the terminal squares and blooms is suggested in scouting for worms on cotton with Genuity Bollgard II cotton technology. The nodes above and below the white bloom are the primary target area for scouting since most surviving bollworm larvae feed on pollen from newly bloomed bolls. This leads to larval survival being closely associated with newly bloomed bolls and bloom tags. In addition to that area, all bolls beneath this area should be scouted outwardly for fall armyworm bract etching.

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Aphids

TOBACCO BUDWORM

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Damage: Holes in the bloom base. Circular holes in the bolls with frass (excrement) present.Tunneling in termina

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Cutworms

PINK BOLLWORM

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Damage: Rosetted petals. Holes through boll, carpel walls and seed

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Armyworms

COTTON BOLLWORM

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Damage: Holes in the bloom base. Circular holes in the bolls with frass (excrement) present. Tunneling in terminal

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Cabbage Looper

BEET ARMYWORMS

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Damage: Holes in the bloom base. Circular holes in the bolls with frass (excrement) present. Skeletonized leaves

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Plant Bugs

PLANT BUGS

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Damage: Blooms are disfigured, twisted and coarse. Small depressions in bolls

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Beet Armyworm

FALL ARMYWORM

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Damage: Holes in the bloom base. Circular holes in the bolls with frass (excrement) present. Tunneling in terminal

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Thrips

BOLL WEEVIL

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Damage: Soft, dark area on boll with cream colored grub inside boll

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Cotton Bollworm, Tobacco Budworm, Pink Bollworm — Heliothine pests are the target of Genuity Bollgard II cotton technology. Worm populations can be present from early bloom through late season, with the strongest generations coming during boll fill, the most damaging time of the year. Bollgard technology was first judged solely on its efficacy during this period, using the transgenic varieties as a risk management tool. However, seasons during which budworm and bollworm populations are low have indicated that the in-plant protection also provides economic benefit while populations are below normal threshold levels.

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Genuity Bollgard II cotton has varying efficacy against worms other than the ones mentioned on the previous page. Use state guidelines or consultant recommendations for monitoring and control of insect pests that are not controlled.

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Other Cotton Insect Pests — Plant bugs and boll weevils can cause serious yield loss during early bloom. Thus, it is critical that they are monitored and controlled when necessary. In addition to normal field scouting, monitoring percent retention of bolls in the top five first positions can be a valuable tool in the management of plant bugs.

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This article is from the Cotton Management Guide, a publication with year-round advice on managing high-yielding cotton. Download the Deltapine Cotton Management Guide now or sign up for new content to be delivered to your email each month.​