Pink Bollworm Scouting Guide
Guide A-219
Shane T. Ball, Extension Agronomy SpecialistLloyd M. English, Extension Entomolgoy Specialist
College of Agriculture and Home Economics New Mexico State University
This publication is scheduled to be updated and reissued 3/04.Regular scouting of cotton fields allows producers to treat pink bollworm infestations before serious damage is done. Determining when to spray for pink bollworm is a crucial decision for producers. Proper scouting methods and timely insecticide applications at economic threshold levels will maximize pink bollworm control and allow maximum results from beneficial insects and spiders.
Growth Stage: Crop Emergence to Early Squaring (pinhead- to match-head-sized squares)
Between crop emergence and early squaring, 50 to 80% of pink bollworm moths emerge and die before cotton is available for food. Pheromone traps inspected between planting and pinhead squaring monitor only the number of suicidal moths in the field area. However, from pinhead to match-head squaring, the number of moths caught in the traps provides good advance notice of potential pink bollworm infestation.
Pheromone mating disruption treatments should be applied as soon as moths appear in the traps. Subsequent treatments may be necessary if indicated by the trap catches. The last treatment should be completed before the cotton is one third grown (about 1/4 inch in diameter), which will allow beneficial insects and spiders to reestablish before early bloom.
Growth Stage: Early Squaring to Defoliation
Rosetted bloom counts are used to determine field infestation levels in areas where adult moths have been captured. However, the only reliable way to determine pink bollworm infestation is to sample bolls. Treatment thresholds are expressed in terms of the percentage of infested bolls.
The treatment threshold in New Mexico is 10 to 15 percent infested bolls for upland cotton and 5 to 10 percent for Pima cotton during the first six weeks after flowering (boll set). These thresholds are useful only if a large number of susceptible bolls are present. Generally, a single treatment should be sufficient, but new bolls should be checked weekly. If the percent infested is greater than the threshold, a second treatment is warranted.
When sampling upland cotton, choose bolls between 14 and 21 days after flowering. This is when they are most susceptible to pink bollworm. Bolls at this stage are fully grown but have only partially developed lint. The bolls feel slightly spongy when squeezed. Pima bolls are most susceptible to pink bollworm from 14 to 35 days after flowering.
For standard sampling, select 25 bolls from each quarter of the field (100 total). Pick one or two bolls from each plant, staying away from plants near field edges and rank cotton.
Cut the bolls open and check each lock for larvae, warts, or mines where the larvae have entered. Young larvae are hard to see because they are nearly the same color as the lint, except for their brown heads.
Don't count the boll as infested unless you find the larvae, even if you find a wart or tunnel in one lock. It is important to find the larvae while they are small so insecticide treatments will effectively control adult moths in the early generations, preventing high infestations.
References
Allen, Charles T. 1994. Pink bollworm management in Texas. The Texas A&M University System, Texas Agricultural Extension Service. Bulletin B-1511. 7pp.
Allen, Charles T., Emory P. Boring III, James F. Leser, and Thomas W. Fuchs, 1995. Management of cotton insects in the High Plains, Rolling Plains, and Trans Pecos Areas of Texas. The Texas A&M University System, Texas Agricultural Extension Service. Bulletin B-1209, 13pp.
Ward, Charles R. 1994(a). Cotton insect management suggestions for 1994-1995. New Mexico State University, Cooperative Extension Service. Handbook 10-A. 18pp.
Ward, Charles R. 1994(b). Insecticides for use with cotton insect management suggestions for 1994-1995. New Mexico State University, Cooperative Extension Service. Handbook 10-B. 16pp.
New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department of Agriculture cooperating.
Reprinted March 1999
Electronic Distribution March 1999