Sobrevivência e potencial reprodutivo de adultos do bicudo previamente alimentados com fontes alimentares alternativas

Abstract

The ecological success of the cotton boll weevil is related to its high capacity to survive for long periods feeding on alternative food sources in the absence of its main reproductive host, however, there is no information about this feeding on their living conditions and reproductive capacity. The objective of this work was to determine the survival and reproductive potential of adults of the cotton boll weevil previously fed with alternative food sources. Three experiments were carried out. The first aimed to determine the impact of prolonged feeding of the cotton boll weevil with alternative food sources on its survival and reproduction. In general, the survival curves of adult boll weevils fed with cotton squares or banana endocarp remained similar over time, with a trajectory of moderate, mild and accentuated fall, respectively, in the period of 0-50 days, 51-100 days and from 101-129 days. However, adult boll weevils fed with orange endocarp, showed a consistent and moderate drop up to 80 days, decreasing sharply from this period until the death of the last survivor at 108 days. The highest number of cotton squares with punctures of feeding and oviposition were observed for boll weevils previously fed with cotton squares and the smallest for those previously fed with banana and orange endocarps. The highest egg viability was observed for boll weevil females previously fed with cotton squares at 30 and 60 days of age and the lowest for those previously fed with orange. At 90 days of age, only females fed with cotton squares deposited viable eggs, the others previously fed with orange and banana deposited non-viable eggs. In the second experiment, the morphology and morphometry of the boll weevil reproductive organs were evaluated after prolonged feeding with alternative food sources. Up to 30 and 60 days of age, 80-90% of boll weevil males and females fed with alternative food sources had their reproductive organs morphologically suitable for reproduction after having access to a diet that stimulates reproduction (cotton squares). At 90 days, however, only a small proportion of boll weevil males and females fed on cotton squares had their reproductive organs morphologically suitable for reproduction. Boll weevil females fed on cotton squares had the largest ovariole length and oocyte width, and those fed banana and orange endocarps the smallest. Likewise, the largest area and diameter of the testis were observed for male boll weevils fed on cotton squares and the smallest for those fed on banana and orange endocarps. A third experiment was carried out to determine the influence of the diet consumed by boll weevil females and males on their process of sexual selection and mating. It was observed that 41.7% and 58.3% of the 90-day-old boll weevil females fed with cotton squares and banana endocarp chose males fed with cotton squares and banana, respectively. All banana-fed females chose cotton squares-fed males, but none of them laid viable eggs. Among males fed with cotton squares, 100% of them chose females fed with cotton squares. On the other hand, 66.7% and 33.3% of males fed on banana chose females fed on cotton squares or banana, respectively. This study indicates that female boll weevils fed for prolonged periods with alternative food sources are not able to reverse the atrophy of their reproductive organs after 90 days of age. This indicates the need for cotton growers to carry out the correct destruction of the cotton crop residues and to respect the sanitary void during the off-season of this crop so that boll weevils do not have access to the cotton squares before 90 days.