Cotton Pink Bollworm: Identification & Management Guide (2026)
คำตอบรวดเร็ว
Pink bollworm larvae feed inside cotton bolls where sprays can't reach them, so timing matters more than product choice — scout with pheromone traps from squaring onward and treat at the first sign of rosette flowers (a diagnostic symptom) or moth threshold, before larvae enter bolls. In regions with confirmed Bt-resistant pink bollworm populations, Bt cotton alone is no longer sufficient; integrate pheromone mating disruption, refuge crops, and timely insecticide application. Destroy crop residue and unopened bolls immediately after the final harvest to break the pest's carryover between seasons.
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Egg and early larval stage
Tiny, flattened, oval eggs (barely visible without magnification) laid singly or in small groups on squares, flower buds, and young bolls. Newly hatched larvae are pale with a dark head and immediately begin boring into the boll or square — from this point, the larva is inside plant tissue and effectively protected from foliar sprays.
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Rosette flower (diagnostic symptom)
Larval feeding inside a flower bud before it opens causes the petals to stick together, preventing normal flower opening — the flower opens in a distorted, twisted 'rosette' shape instead of normally. This is one of the most reliable field-scouting indicators of active pink bollworm infestation, visible before boll damage becomes apparent.
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Boll damage
Larvae feed inside developing bolls on the seeds and surrounding lint, often webbing seeds together with silk and frass (excrement). Infested bolls may show small, dark entry holes, and premature or irregular boll opening. Pink-colored larvae (the source of the common name) are visible if the boll is opened and examined. Lint quality and yield are both reduced by feeding damage and staining.
วิธีรักษา
Pheromone mating disruption
Deploy synthetic pink bollworm sex pheromone dispensers throughout the field at label-recommended density, which confuses male moths and disrupts their ability to locate females for mating, reducing the number of fertile eggs laid. Most effective as an area-wide, season-long strategy rather than a rescue treatment.
จังหวะเวลา: Install at or before squaring stage, before the pest population builds, and maintain through the season per product label.
Pheromone trap monitoring for threshold-based decisions
Deploy pheromone traps at recommended density starting at squaring to monitor moth activity and time other interventions. Rather than spraying on a calendar schedule, use trap catch thresholds (per local extension guidelines) combined with rosette flower counts to decide when intervention is actually needed.
จังหวะเวลา: From squaring stage through harvest; check traps at least weekly.
Timely destruction of crop residue after final harvest
Immediately after the last harvest pick, destroy stalks (shredding or plowing under), remove and destroy unopened bolls, and manage ginning waste to eliminate overwintering larvae. This single practice, done consistently across a growing region, significantly reduces the following season's starting population.
จังหวะเวลา: Immediately after final harvest — delay allows surviving larvae to enter diapause and successfully overwinter.
Remove and destroy rosette flowers and infested bolls during scouting
Hand-removing and destroying visibly infested rosette flowers and damaged bolls during regular field walks physically removes developing larvae before they complete development and emerge as breeding moths.
จังหวะเวลา: During weekly scouting from squaring through boll development.
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Insect growth regulator (e.g., novaluron) at early infestation
Pyrethroid or other contact/systemic insecticide for confirmed high populations
เหมาะสำหรับ: การเกษตรขนาดใหญ่ การระบาดรุนแรง
Plant non-Bt refuge crops as required/recommended
Refuge planting (non-Bt cotton or other host crops planted alongside Bt cotton) is designed to maintain a population of Bt-susceptible moths that dilute resistance genes when they interbreed with any resistant survivors, slowing the spread of Bt resistance. Follow regional refuge requirements exactly — refuge programs only work at high compliance rates across a growing region.
Rotate away from cotton where feasible
Breaking continuous cotton cultivation with a non-host rotation crop for at least one season reduces the carryover population available to infest the next cotton crop, complementing residue destruction.
Coordinate residue destruction and pheromone programs area-wide
Pink bollworm moths can fly between neighboring fields, so individual-farm control measures are far less effective than coordinated, area-wide residue destruction and pheromone trapping/mating disruption across a whole growing region.
Avoid extending the growing season unnecessarily
Late-maturing or extended-season cotton provides more time for pink bollworm generations to build up. Following recommended regional planting and harvest windows limits the number of pest generations the crop is exposed to.
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อุณหภูมิ
Most active development between 25-32°C; development slows significantly below 15°C, and larvae enter diapause (dormancy) in response to shortening day length and cooling temperatures in autumn
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ความชื้น
Moderate humidity favors moth activity and egg survival; extreme dry heat can reduce egg viability somewhat, though this is a secondary factor compared to host plant availability and stage
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ปริมาณน้ำฝน
Rainfall has limited direct effect since larvae feed inside protected plant tissue for most of their development, unlike foliage-feeding pests more directly affected by rain washing them off
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ฤดูกาล
Population builds through the season from squaring onward, typically peaking mid-to-late season as multiple overlapping generations accumulate; overwintering larvae in residue restart the cycle the following season
สำหรับเกษตรกรCotton
Pink bollworm is fundamentally different from most cotton pests because the larvae spend almost their entire feeding period protected inside the boll, which means insecticide timing is everything — a spray applied even a few days after larvae have entered bolls will have little effect on those individuals. This is why pheromone trap monitoring and rosette flower scouting for early intervention matter more for pink bollworm than for many other pests, and why area-wide coordination (refuge compliance, synchronized residue destruction) has a much bigger impact than any single farmer's individual actions. In regions with confirmed Bt resistance, growers should not assume Bt cotton alone provides adequate control and should budget for an integrated program combining monitoring, targeted insecticide timing, and end-of-season residue destruction as standard practice, not just a response to visible damage.
เกษตรกรยังถามอีกว่า
Why doesn't my Bt cotton control pink bollworm anymore?
In several major cotton-growing regions, pink bollworm populations have developed genetic resistance to the Cry1Ac and Cry2Ab Bt toxins used in most commercial Bt cotton varieties, through a combination of resistance allele selection over successive generations and, in some cases, inadequate refuge compliance regionally. Where resistance is confirmed or suspected, Bt trait should be treated as one layer of protection within an integrated program, not a standalone solution.
What exactly is a 'rosette flower' and why does it matter?
A rosette flower is a cotton flower that fails to open normally because a pink bollworm larva feeding inside the unopened bud has caused the petals to stick together, resulting in a twisted, bunched appearance instead of a normal open flower. It's one of the earliest visible field symptoms of infestation — checking for rosette flowers during scouting can flag a developing problem before any boll damage is visible.
Is it worth destroying crop residue if my neighbors don't do the same?
Individual residue destruction still reduces your own field's overwintering population and is worth doing, but pink bollworm moths can fly between fields, so the full benefit is much greater when residue destruction and other management practices are coordinated across a growing area. Talking with neighboring growers or through a local farmer cooperative/extension program about area-wide coordination often produces a bigger impact than any single farm acting alone.
Can pheromone traps alone control pink bollworm without any insecticide?
Pheromone-based mating disruption can significantly reduce mating success and population growth, and works especially well combined with other tactics, but is generally not recommended as a sole control method in fields with already-high pink bollworm pressure — it's most effective as a preventive, area-wide strategy that reduces (not necessarily eliminates) the need for insecticide, rather than a complete replacement for it in high-pressure situations.
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