Cotton row spacing for boll weevil management in low-input production systems

Authors: PAIM, ELCIO ANTONIO - University Of Brasilia; DIAS, ANTONIO MACEDO - University Of Brasilia; Showler, Allan; CAMPOS, KAROLAYNE LOPES - University Of Brasilia; SANTOS, PATRICIA - University Of Brasilia; GRILO, PEDRO PAULO - Universite De Montreal; TORRES, JORGE BRAS - Federal Rural University Of Pernambuco; BASTOS, CRISTINA - University Of Brasilia

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 3/16/2021
Citation: Paim, E., Dias, A., Showler, A., Campos, K., Santos, P., Grilo, P., Torres, J., Bastos, C. 2021. Cotton row spacing for boll weevil management in low-input production systems. Crop Protection Journal. 145. https://doi.org/10.1016/j.cropro.2021.105614.
DOI: https://doi.org/10.1016/j.cropro.2021.105614

Interpretive Summary: Despite being an important commodity, < 2% of the cotton cultivated area in Brazil is considered to be “low-input”. A major reason for this relatively small area is infestation by boll weevils which are usually controlled using conventional insecticides. Cotton grown in low-input and conventional systems of Brazil lack an integrated pest management strategy. We hypothesized that the certain row spacings will act as a preventive cultural practice driving boll weevil infestations, lint production and fiber quality. We assessed the effects of three row spacings: 0.5 m (narrow), 0.75 m (conventional), and 1.0 m (wide) on boll weevil infestation levels, during two field trial seasons. In both seasons, plants were surveyed for 23 successive weeks and fallen structures were collected for 16-21 weeks. Boll weevil-infested and non-infested reproductive structures, numbers of boll weevils, and yield parameters were assessed. Fallen structures were examined to assess weevil emergence. The narrow row spacing was the least effective, and the conventional and wide spacings delayed boll weevil control interventions and resulted in fewer boll weevil-injured reproductive structures early in the season, and produced lower numbers of adult boll weevils without altering the quantity and improving the quality of lint. This is the first study to demonstrate the effect of row spacing on boll weevil infestations and inflicted injury in low-input systems. The results can also be applied to conventional cotton production systems. Further, we showed that it is possible to obtain economically viable yields in low-input areas even under relatively high boll weevil pressure.

Technical Abstract: Despite being an important commodity, < 2% of the cotton cultivated area in Brazil is considered to be “low-input”. A major reason for this relatively small area is infestation by boll weevils, Anthonomus grandis grandis Boheman, which are usually controlled using conventional chemically-based insecticides. Cotton grown in low-input and conventional systems of Brazil lack an integrated pest management strategy. We hypothesized that the alteration in row spacing would act as a preventive cultural practice driving BW infestation, lint production and fiber quality, justifying its adoption. We assessed the effects of three row spacings: 0.5 m (narrow), 0.75 m (conventional), and 1.0 m (wide) on boll weevil infestation levels, during two seasons field trials. In both seasons, plants were surveyed for 23 successive weeks and fallen structures were collected for 16-21 weeks. BW-infested and non-infested reproductive structures, number of BW, and yield parameters were assessed. Fallen structures were kept for 21 days to assess BW emergence. The narrow row spacing was the least effective, and the conventional and wide spacings delayed boll weevil control interventions and resulted in fewer boll weevil-injured reproductive structures early in the season, and produced lower numbers of adult boll weevils without altering the quantity and improving the quality of lint. This is the first study to demonstrate the effect of row spacing on boll weevil infestations and inflicted injury in low-input systems. The results can also be applied to conventional cotton production systems. Further, we showed that it is possible to obtain economically viable yields in low-input areas even under relatively high boll weevil pressure.