Survival and preference of cotton boll weevil adults for alternative food sources

Abstract

Plants that have potential as alternative food source (floral nectar, pollen and plant tissues) to the boll weevil during the intercropping season were evaluated considering the prevalent conditions of Cerrado in the Central Brazil. Initially, we tested the nutritional adequacy for the survival of the insect of flower resource (pollen and nectar) provided by eight plant species (fennel, mexican sunflower, castor bean, okra, hibiscus, sorghum, pigeonpea and sunn hemp). Subsequently, we tested if the resources provided by the selected plants continued to be exploited by the boll weevil in the presence of cotton plant, its main food source average longevity of boll weevil adults was significantly longer when they were fed on hibiscus' flowers (166.6 ± 74.4) and okra flowers (34.7 ± 28.9) than when they fed on flowers of other six species. Subsequently, the preference of the boll weevil in the use of resources was compared between okra or hibiscus and cotton plants, in dual choice experiments. Boll weevils preferred plants of the three species in the reproductive stages than those in vegetative stages. Although the cotton plant in the reproductive stage was the most preferred plant of all, boll weevils preferred flowering okra and hibiscus than cotton at the vegetative stage.Keywords: Anthonomus grandis, Malvacea, okra, hibiscus. Sobrevivência e preferência para exploração de recursos de adultos do bicudo do algodoeiro ResumoPlantas que podem ser uma fonte potencial de recursos alimentares (néctar floral, pólen e tecidos vegetais) para o bicudo do algodoeiro durante a entressafra foram avaliadas, considerando as condições ambientais prevalentes na região de Cerrado do Brasil Central. Primeiro, testamos a adequação nutricional dos recursos (pólen e néctar) fornecidos por oito espécies de plantas (erva-doce, margaridão, mamona, quiabo, hibisco, sorgo, feijão guandu e crotalária) como único recurso alimentar para a sobrevivência do inseto. Posteriormente, nós avaliamos se os recursos fornecidos pelas plantas selecionadas continuaram a serem explorados pelo bicudo na presença do algodoeiro, seu recurso alimentar principal. A longevidade média do bicudo do algodoeiro foi significativamente maior quando eles foram alimentados com flores de hibisco (166,6 ± 74,4) e quiabo (34,7 ± 28,9) do que quando alimentados com flores das outras seis espécies. Em seguida, a preferência do bicudo no uso de recursos foi comparada contrastando o quiabo e o hibisco com o algodão, em experimentos de dupla escolha. Os bicudos preferiram as plantas das três espécies na fase reprodutiva em relação àquelas em estádios vegetativos. Embora a preferência por plantas de algodão na fase reprodutiva tenha sido maior, os bicudos preferiram plantas em floração de quiabo e hibisco quando estas foram contrastadas com o algodão na fase vegetativa.

Survival pattern of the boll weevil during cotton fallow in Midwestern Brazil

“…In the Distrito Federal and in the state of Goiás, nearly all boll weevils at the end of the crop did not remain protected within the dry bolls for more than 50 days, but probably left in search of shelter and food in the surrounding areas (Figure 3). This result reinforces the importance of destroying cotton stalks for boll weevil management, since, at any time, adults who have left the structures are able to colonize the regrowth of cotton plants after harvest (Paula et al, 2013;Ribeiro et al, 2015).…”

“…The development of larvae in bolls generates larger adults with greater lipid reserves (Rolim, 2014), which may favor survival during the cotton fallow period. The boll weevils from the bolls at the end of the crop cycle allocated energy to survive in detriment of developing their reproductive system (Paula et al, 2013). This pattern is associated with the phenology of the cotton plant and may be considered the main adaptive strategy of the boll weevil to overcome fallow periods in Midwestern Brazil.…”

“…2017 DOI: 10.1590/S0100-204X2017000300002 50 days for males and females, respectively). Pimenta et al (2016) also assessed the nutritional suitability of alternative plants for adult boll weevils, which showed a preference for flowering okra and hibiscus over cotton in its vegetative stage. According to Ribeiro et al (2010), pollen from different plant species found in remnants of Cerrado vegetation is used by adult boll weevils during the intercrop period.…”

“…During the fallow period, when cotton plant residues are completely removed, according to legislation, in the Distrito Federal and in the state of Goiás, boll weevils are found around the cotton fields, mainly in facultative reproductive dormancy, especially the females (Paula et al, 2013). However, the physiological reduction in reproduction does not keep boll weevils from moving and searching for food to survive until the cotton fields have been planted again and squares begin to form (Jones et al, 1992;Hardee et al, 1999;Showler & Abrigo, 2007;Ribeiro et al, 2010;Macêdo et al, 2015).…”

“…A similar behavior has also been observed for boll weevils in the temperate and subtropical regions of North America (Showler, 2003(Showler, , 2006. In the tropics and subtropics, males and females go into reproductive dormancy (Spurgeon & Raulston, 2006;Paula et al, 2013), but remain active throughout the year (Guerra et al, 1982;Macêdo et al, 2015) due to alternative foods that can sustain them in the absence of cotton (Hardee et al, 1999;Ribeiro et al, 2010).…”