Anthonomus grandis It is widely known as the boll weevil. It is the main pest of cotton crops in Brazil.
Crops attacked
The main crop attacked by the boll weevil is cotton (gossypium spp.).
The insect has a great capacity for adaptation and can use other plants, such as cultivated fruits (banana, papaya and mango), as food during the off-season.
Biology
The boll weevil's life cycle goes through four stages: egg, larva, pupa and adult.
Females lay eggs inside flower buds and bolls of the cotton plant, protecting them with a waxy substance.
Larval development occurs within plant structures, protecting them from natural enemies and insecticides.
The complete cycle lasts around 21 to 30 days, depending on weather conditions.
The larval stage lasts approximately 3 to 4 days, followed by a pupal stage of 3 to 5 days.
The average longevity of adults varies from 37 to 42 days, and females have a high oviposition capacity, laying up to 150 eggs during their lifetime.
During the off-season, the boll weevil may enter a state of quiescence, reducing its metabolic activity to survive in the absence of adequate food.
Furthermore, it is capable of using alternative food resources, such as pollen from other host plants present in cerrado and caatinga areas.
Ecology
The cotton boll weevil is a nocturnal insect, with a high dispersal capacity and adaptation to environmental conditions.
During the harvest, adults migrate to crops attracted by pheromones released by cotton plants.
After the end of the crop cycle, the weevil abandons the crop and disperses to refuge areas, such as native vegetation and crop residues.
The weevil presents an adaptive strategy known as "bet-hedging", which consists of distributing the population between strategies of searching for food and shelter, reducing the risk of local extinction.
The species also demonstrates a strong dependence on cotton for reproduction, being unable to develop completely on other plants.
Damage
The boll weevil causes direct damage by feeding and laying eggs in the reproductive structures of cotton, resulting in the loss of bolls and reduced productivity.
Small populations can multiply rapidly, resulting in significant economic losses.
Control
Management strategies include:
- Cultural: destruction of cultural remains, sanitary vacuum and elimination of volunteer plants.
- Chemical: use of insecticides with localized or total area application. Rotation of molecules is essential to avoid resistance.
- Biological: use of parasitoids and entomopathogenic fungi, although the mass production of these agents still faces challenges.
- Monitoring: Pheromone traps help in early detection and planning of control actions.
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