Cotton is the most important cash crop of Pakistan.Cotton and cotton made products contribute 51% of total exports of Pakistan. Cotton crop occupies largest area as compared to other crops which opens opportunities for domestic employment and contributes a lot in the local economy.
Cotton feeds the largest (Textile) industry of Pakistan and earns highest export revenues. Apart from the lint, cotton seed contributes 80 percent of the national oilseed production leaving behind a valuable cottonseed meal as byproduct to feed animals.
Cotton is a strong pillar of the national economy but there is a huge rom to improve which demands better strategies and best available resources. Seed quality, availability and application of fertilizers, disease management, insect pest control, and post-harvest management are the factors to increase productivity.
Cotton grows under hot warm climatic conditions which is very suitable for insect pests. Insect pests cause a huge lost in the yield and damages the quality of the lint. In Pakistan, white fly, jassids, thrips, mites, mealybug (sucking pests) and bollworms (chewing pests) are common cotton pests.
Among four different bollworms (American bollworm, spotted bollworm, army bollworm, pink bollworm), pink bollworm (PBW) is the major threat and causes huge yield loss.
PBW is an endoparasite that penetrates in flowers ovary and young bolls. Infected flowers fail to open and twisted into rosette form. Petals of flowers stick to each other due to the saliva secreted by PBW. Infected cotton bolls fail to open completely which make the picking difficult and causes discoloration of the lint.
It also infects the seeds and reduces the oil production of the seed. The larvae emerge at the time when crop is full of flowers and bolls. It is very important to control PBW at early stages, once the larvae enter flowers and bolls it is very difficult to control.
Pink bollworm life cycle
Eggs: Eggs are white in colour when first laid bu turn to orange, a black dot (larval head capsule) appears before hatching. Eggs hatch in about three to four days. Eggs measure about 0.5 mm long and 0.25 mm wide. A female PBW lay 100-250 eggs either on back side of the leaves or in the flowers.
Larvae: Mature larvae are 10-12 mm long and have broad horizontal bands of red/pink colour. Young larvae are tiny, white in colour with darkbrown head upto second instars. It becomes pinkish in third and fourthinstar. Larval period lasts for about 10-14 days.
Pupae: The pupa is light brown and approximately 7 mm long. The pupal period is 7-10 days long.
Adult: Adults are small, grayish brown, inconspicuous moths. The wing tips are conspicuously fringed. There is a time period of 2-3 days after emergence during which the female mates and prepares to lay eggs. Pre-oviposition period is about ten days. Adults may live for one to two months. The moths are about 7-10 mm with a wing span of 15-20 mm.
Integrated Pest Management
Following are common management practices for PBW control:
- Deep ploughing after harvesting of last picking.
- Cleanup of green bolls is critical to limit PBW survival. Ideally, greenbolls should be burned.
- Do not leave green bolls piled on turn rows since this allows strong PBW overwintering survival. Ifgreen bolls cannot be burned or ginned, it is best to graze the animals after last picking which can reduce PBW populations.
- Horizontal stacking of cotton sticks will be help full for PBW management.
The first generation in the spring emerges from diapausing (resting) caterpillars sheltered in bolls or seeds left in cotton fields and other areas, or within cocoons in the soil.
Pink bollworm development is dependent on temperature and moisture conditions that stimulate the caterpillar to enter the pupal stage. Moth emergence begins in early to late March and continues into July, with the peak in April and early May.
Female moths lay their eggs within 10 days after emergence. During most years, 60-80% of the moths emerges and die before squaring cotton is available for infestation. This is known as “suicide emergence” and is the basis for community-wide planting dates as a management practice.
- Exposure of seeds for 20 min at 48.9 C
- Plucking of rosette flowers and buried them deep into the soil.
- Use of pesticides against PBW above ETL is recommended.
Pink Boll Worm were effectively controlled by Rogas and Apanteles spp. Chelonusblackburni was effective as uni-parental egg-larval parasite. Apantelesangaleti was effective parasitoid of PBW. Trichogramma evinces efficiently parasitized PBW eggs under field condition.
Use of sex pheromones
The female of Pink Boll Worm secretes pheromone for mating. Artificially such pheromones are to be filled in plastic capsule and use as traps. Theses traps attracts male moth and they got capture into these traps. To control Pink Boll Worm, four sex pheromone traps per acre are enough. These traps should install after the sowing of cotton at the height of 3 feet. Mating disruption technique can also be used by using PB ropes.
For the management of pink bollworm using PB Rope L @ 100 dispensers/acre applied at pin square stage of cotton proved to be promising option in endemically infested areas. These installed ropes secrete pheromones to confuse the male even leading to death of male moths. Depletion of male moths in the environment results in reduction of laying fertile eggs and thus brings down larval infestation and crop damage.
- Avoid mixing of two or more insecticides / tank mixing.
- Repeated application of same insecticide should be avoided.
- Use neem based formulations.
- Alternate with various chemical groups (Cyclodine, Organophosphates, Carbamates,
- Pyrethroids and insect growth regulator).
- Recommended sprays against PBW are Lambda cyhalothrin 2.5 EC @ 330 ml per acre or Triazophos 40 EC @ 100ml per acre or Gamma cyhalothrin 60 CS @ 100