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Tobacco Budworm
Classification and Description: The tobacco budworm, Heliothis virescens (Lepidoptera: Noctuidae), is a common pest in cotton. This insect has complete metamorphosis, and it is the larval (caterpillar) stage that can potentially injure cotton. Egg and larval stages of this insect are very similar in appearance to bollworm, and these insects are often considered collectively (as a complex) in cotton. Adult moths are about ¾ of an inch long with a wing span of 1 - 1 ½ inches wide. The forewings are yellowish to olive-colored with three slanted, darker lines. These slanted lines make three “chevrons” across the forewings.
Hosts, Life History and Distribution: Tobacco budworm larvae feed on a variety of wild and cultivated plants, although its host range is not as wide as the bollworm and it is rarely found in corn. It is found throughout Tennessee. The pupa is the overwintering stage and is found in the soil. In Tennessee, infestations in cotton vary greatly from year to year. Larval development is nearly identical to bollworm, and three generations are possible in cotton.
Pest Status and Injury: The tobacco budworm typically does little damage to cotton grown in Tennessee because of the wide adoption of Bt cotton, to which it is highly susceptible. However, it is still a significant pest because of insect control costs associated with the use of Bt cotton. The damage it causes to non-Bt cotton is very similar to that of bollworm, feeding on squares, blooms and bolls. Injury to flowering cotton is more common and of greater economic concern. Injured fruiting structures often shed, and large bolls that are damaged will typically rot. As with bollworm damage, outbreaks of tobacco budworm are sometimes associated with previous insecticide applications that have reduced populations of natural enemies.
Management Considerations and Thresholds: Cotton bolls become progressively less susceptible to injury as they mature. Bolls greater than 18-20 days in age (about 350 DD60’s) are generally safe from attack except from larger caterpillars. Consequently, insecticide applications for this pest can typically be terminated about 350-400 DD60’s past cutout, or NAWF5. Because tobacco budworm is highly resistant to pyrethroid insecticides, it is extremely important to determine if tobacco budworms are present in non-Bt cotton fields when making an insecticide selection. Several methods can be used to help distinguish between tobacco budworm and bollworm infestations. Unless resistance develops, infestations in Bt cotton can be assumed to be bollworm.
Treatment thresholds in non-Bt cotton are: eight larvae per 100 plants prior to bloom, or four larvae per 100 plants after first bloom. Treating for eggs alone is generally not recommended unless counts are unusually high. Nevertheless, it is extremely important that insecticides be timed to control small larva (< ¼ inch in length) and hatching eggs. Currently recommended insecticides and rates are available in the Insect Control Recommendations for Field Crops (PB1768).
Print-Ready PDF Publication (Tobacco Budworm W031)