Pectinophora gossypiella (Saunders)
Common name: Pink bollworm
Geographical distribution: The pink bollworm is of south-Asian origin, and has spread to all regions where cotton is cultivated (CIE Map #13, 1990 revised).
Host plants: Cotton and other members of the family Malvaceae, especially Hibiscus spp.
Morphology: The adult moth is brown-grey, its forewings bear transverse dark stripes, the hindwings are silvery and the body is about 0.6-0.8 cm in length. The fully grown larva is pink, about 1.0-1.2 mm long, with a black head and segmental protuberances that bear small setae.
Life cycle: Adults fly at night, placing their eggs (about 500/female), singly or in small groups, all over the cotton plant, preferring the buds and flowers. The larvae penetrate into buds, flowers, squares and especially bolls wherein they develop in a few weeks, boring an exit hole at maturation. In summer development is continuous, a generation requiring about 4-7 weeks. Towards autumn the larvae enter a prepupal diapause, remaining in this state during winter, either hidden in the soil, within unpicked bolls or inside stored seeds. Some larvae have a prolonged (for as long as 30 months) diapause. They pupate in the spring, the emerging adults initiating the first generation, most of whose members die due to the lack of suitable host plants. The surviving females lay eggs on adventitious or bi-annual cotton, and their descendants form the second, more harmful pest generation.
Economic importance: The pink bollworm is a major pest of cotton. Early in the spring the newly-emerged larvae penetrate into buds and flowers, while later in the season they attack the bolls as they become available. A single larva] can destroy several buds and flowers as well as 2-3 bolls, eating the seeds and spoiling the lint. Total damage may reach 20-50% of the yield. In the Middle East the bollworm is of special importance in Israel, Syria and Turkey.
Monitoring: Trap-monitoring with “gossyplure”, an artificial pheromone formulation, is initiated as soon as the cotton plants emerge, and no later than at the formation of the first squares. In Israel, traps (each placed within a “sampling unit” of 10 acres) are arranged along the eastern border of the field. This is because the adults are mostly active at night, when winds blow from the east. The traps should be positioned above the plants’ apices, and raised as they grow. Trapping of 8 insects/night through the main flowering period requires an immediate chemical treatment, whereas during boll maturation the trigger for a spray rises to 12 insects per night.
Cultural control: Threshing and thoroughly burying all plant remains after cotton picking is recommended for pink bollworm control. Adventitious cotton plants growing around commercial fields and any harvested cotton remains lying by roadsides should also be destroyed. Other cultural methods include killing the larvae within seeds or lint bales by heating to about 60ºC. Mass trapping with long-lived pheromone traps has been used to control the pink bollworm in Brazil. Early-fruiting cotton cultivars are being tried as trap crops for the pest, as are sprays of kaolin dust films. The latter are more effective if applied along with pyrethroids.
Chemical control: Organophosphates were used in the past to control the pest, whereas pyrethroids are more common now. The pesticides should be applied as soon as the bollworm is found in the pheromone traps, because the chemicals do not affect the pest after it had penetrated into the boll.
Genetically modified cotton: The use of modified Bt cotton, which expresses toxins from Bacillus thuringiensis (Bt), has reduced the need for pesticides and may enable the long-term suppression of the pink bollworm. Such suppression is now threatened by pest strains that show resistance to Bt cotton.
Biological control: Only few natural enemies of the pink bollworm are known, and none seem to have any controlling effect.
Attique, M.R., Ahmad, Z., Mohyuddin, A.I. and Ahmad, M.M. 2004. Oviposition site preference of Pectinophora gossypiella (Lepidoptera: Gelechiidae) on cotton and its effects on boll development. Crop Protection 23: 287-292.
Carriere, Y. (and 6 co-authors). 2003. Long-term regional suppression of pink bollworm by Bacillus thuringiensis on cotton. Proceedings of the National Academy of Sciences of the United States of America 100: 1519-1523.
Mafra-Neto, A. and Habib, M. 1996. Evidence that mass trapping suppresses pink bollworm populations in cotton fields. Entomologia Experimentalis et Applicata 81: 315-323.
Pierce, J.B., Ellington, J.J., Kirk, C.E. and Carrillo, T. 2002. Plant population, planting date and cotton variety impact on early squaring and development of a trap crop for pink bollworm (Lepidoptera: Noctuidae). Journal of Entomological Science 37: 219-226.
Sachs, Y. 1998. Recommendations for the Control of Cotton Pests. Cotton Production Board of Israel (in Hebrew).
Sisterson, M. S., Liu, Y. B., Kerns, D. L. and Tabashnik, B. E. 2003. Effects of kaolin particle film on oviposition, larval mining, and infestation of cotton by pink bollworm (Lepidoptera: Gelechiidae) Journal of Economic Entomology 96: 805–810.
L. Unlu, L. and Bilgic, A. 2004. The effects of the infestation ratio of spiny bollworm (Earias insulana) and pink bollworm (Pectinophora gossypiella) on cotton yield grown in semi-arid region of Turkey. Journal of Applied Entomology 128: 652-657.