Infestation of Anthonomus grandis grandis (Coleoptera: Curculionidae) contributes to forming shelter structures in cotton plants

Abstract

Herbivorous arthropods can induce their host to form structures where they shelter during unfavourable periods. The boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), can spend the off-season inside cotton plant structures, known as dry bolls, protected from pesticides, natural enemies and heat and desiccation on the soil surface, thereby increasing its survival and preserving its reproductive capacity. However, the relationship between the boll weevil and dry boll formation is not fully understood and requires further study. The formation and external and internal characteristics of dry bolls on cotton plants infested with different densities of boll weevils, and the emergence and survival of this insect from these structures, were evaluated. Compared with non-infested control plants, plants infested with boll weevil formed almost twice as many dry bolls, which were 2.3 times heavier and with a diameter 1.7 times larger than those on non-infested plants. Boll weevil infestation reduces the number of bolls and commercial mass of fibre + seeds, reducing productivity and increasing cotton harvest contaminants. However, dry bolls on non-infested plants demonstrate that other factors are involved in their formation.