Formação de carimãs e sobrevivência do bicudo do algodoeiro em cultivares de algodão

Abstract

O objetivo do trabalho foi estimar a formação de carimãs em diferentes cultivares de algodoeiro e a sobrevivência dos bicudos no interior dessas estruturas vegetais. A formação de carimãs foi estimada nas cultivares de algodão FM 975 WS, FM 944 GL, FM 982 GL e FM 910. Maçãs secas (carimãs) de cada cultivar foram coletadas em 20 pontos amostrais em uma área de dois hectares. Os carimãs coletados foram transportados para o laboratório e dissecados para contagem dos bicudos adultos no seu interior. A sobrevivência de adultos do bicudo foi avaliada por meio da coleta de 750 carimãs da cultivar FM 910, dissecando-se posteriormente 50 carimãs a cada 15 dias, a partir da data de coleta até 210 dias, quantificando-se adultos vivos e mortos. Os adultos foram alimentados com botões florais de Hibiscus sp. até a morte. Os resultados demonstraram que a formação de maçãs secas que não se abrem (carimãs) varia com o tipo de cultivar de algodão escolhida para plantio. A grande maioria da população de bicudos aprisionados nos lóculos dos carimãs não sobrevive por longo período de tempo, embora uma porção bastante reduzida dessa população seja capaz de sobreviver e emergir dessas estruturas por mais de cinco meses.

Cotton harvest aid products can favour the formation of structures that protect Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae) from insecticide application

“…Thereby, the use of defoliants with a larger propensity to form dry bolls may favour the survival of boll weevils throughout the off‐season, because inside the dry bolls, the boll weevil is protected from the action of insecticides used at the end of the crop cycle, as our results suggest. Several studies have reported the boll weevil capacity to survive throughout the off‐season inside dry bolls (do Vale et al, 2021; Greenberg, Showler, et al, 2004; Macêdo, 2014; Pires et al, 2017; Ribeiro et al, 2020; Showler, 2007; Summy et al, 1993). Furthermore, the defoliants, when compared with the control, did not increase boll weevil mortality.…”

“…These results corroborate the importance of learning the effects of applying the proper defoliants, since they may affect the infestation of pests such as the boll weevils (Greenberg et al, 2007; Leon et al, 2020; Raper et al, 2021; Ribeiro et al, 2015). Research efforts have sought to identify factors or develop strategies to reduce the formation of dry bolls, aimed at a lower final number of dry bolls and boll weevils that survive inside these structures throughout the off‐season, which may reduce the number of individuals that may infest the next cotton crop (do Vale et al, 2021; Ferrari et al, 2012; Mailhot et al, 2007; Osekre et al, 2009; Praça, 2007; Ribeiro et al, 2020; Srivastava et al, 2010), and our results can contribute to the development of these control strategies.…”

Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae) induces the formation of shelter structures in cotton plants

“…Therefore, inadequate boll weevil management in the current crop, which can increase the number of dry boll and individuals of this insect, puts the next cotton crop at risk. This increases the need to keep populations of this pest small through control methods and by mitigating the formation of dry boll with adequate nitrogen fertilization and choosing cultivars less favorable to their formation (Ferrari et al 2012, Ribeiro et al 2020, do Vale et al 2021. Weevil survival in these structures during the off-season, can be reduced with methods such as destroying cotton stumps and post-harvest soil preparation practices (Greenberg et al 2004a, Ribeiro et al 2015.…”

Dry bolls and their association withAnthonomus grandis grandisBoheman (Coleoptera: Curculionidae) survival through cotton fallow periods

“…A boll weevil was considered dead if it did not move when the rostrum or abdomen were lightly pressed with tweezers. Hibiscus flower buds were used because they are known to be rich sources of pollen and nectar, belong to the same family as cotton, and are often used in the boll weevil survival tests (Pimenta et al 2016;Pires et al 2017;Ribeiro et al 2020).…”

“…The pest mainly uses cotton fruiting bodies (buds and bolls) in which to lay eggs (Gabriel 2002;Showler 2007;Azambuja and Degrande 2014;Bélot et al 2016) and has a series of strategies to remain in the environment when cotton plants are absent (Summy et al 1993;Showler and Scott 2004;Showler 2006Showler , 2007. In tropical regions, these strategies often consist of using alternative food resources (Cuadrado and Garralla 2000;Showler and Scott 2004;Ribeiro et al 2010;Macêdo et al 2015) or remaining inside dry cotton bolls (Guerra et al 1984;Summy et al 1993;Greenberg et al 2004;Showler 2006;Ribeiro et al 2015Ribeiro et al , 2020Pires et al 2017). Inside dry bolls, boll weevils are protected from the heat and desiccation that occurs on the soil surface, from pesticide applications, and from natural enemies (Summy et al 1993;Greenberg et al 2004;Showler and Scott 2004;Macêdo 2014), allowing them to survive to infest the next cotton crop (Summy et al 1993;Greenberg et al 2004;Showler 2007;Pires et al 2017).…”