Spatio‐temporal distribution of Anthonomus grandis grandis Boh. in tropical cotton fields

Abstract

BACKGROUND: Knowledge of the spatio-temporal distribution of pests is important for the development of accurate management approaches. The boll weevil, Anthonomus grandis grandis Boh., is a deleterious cotton, Gossypium hirsutum L., pest in the western hemisphere. The spread of boll weevils across cotton fields remains poorly understood. We assessed the dispersal pattern of adult weevils through cotton fields cultivated in a tropical area during dry and wet seasons using geostatistics for the number of adults and infested reproductive structures (buds, bolls and total). RESULTS: Adult weevils and infested reproductive structures increased across both seasons despite the prevailing climatic variables. In both seasons, boll weevil adults and infested reproductive structures followed an aggregated distribution. The distances over which samples maintained spatial dependence varied from 0.7 to 43.4 m in the dry season and from 6.0 to 614.4 m in the wet season. Boll weevil infestations started at field borders and the infested reproductive structures (oviposition and/or feeding punctured) were greater than the adults regardless of cotton growth stage.CONCLUSION: Sampling for boll weevils in cotton fields should start at the field borders and focus on total infested reproductive structures (buds + bolls) and as cotton plants develop, sampling should focus on the field as a whole. Distances among samples will vary from 6 to 470 m. Thus, despite the cotton phenological stage or growing season, monitoring of boll weevil should be done by sampling total infested reproductive structures with a minimum distance of 6 m among samples.

Monitoring cotton squares with opened and/or yellowed bracts to determine the need and efficency of chemical control against the cotton boll weevil

“…Twenty plants were randomly sampled per parcel every five days. Free-living BW adults were not included in the sampling because their numbers were low and without representative damage to the cotton plants (Oliveira et al, 2022).…”

“…This increases the availability of cotton squares for BW female oviposition as the cotton plants mature (Greenberg et al, 2003(Greenberg et al, , 2005. Thus, the infestation of reproductive structures should increase until the 'cutout' (end of cotton square production), if insecticide spraying is not carried out to control BW (Showler, 2006;Oliveira et al, 2022). This explains why the mean numbers of cotton squares with oviposition punctures were similar in the last two evaluations between treatments sprayed systematically and weekly with malathion or from the economic damage threshold of 5% and 10% of cotton squares, respectively, with opened and/or yellowed bracts and oviposition punctures.…”

“…BW management depends on evaluating the spatial and temporal distribution of populations of this insect with periodic sampling to define chemical insecticide applications (Oliveira et al, 2022). However, BW terrestrial sampling by manipulating and observing a medium-sized cotton square (4-6 mm in diameter) in the upper third of the plant crown with feeding and/or oviposition punctures made by this insect is expensive and inefficient over large areas (Luttrell et al, 2015;Severtson et al, 2016;Neves et al, 2018).…”

Selection of entomopathogenic fungi to control stink bugs and cotton boll weevil1

“…Insecticide sprays are the main control tool used by producers to reduce the insect population. When no control strategy is adopted, outbreaks of boll weevils from the beginning of flowering until the cut-out (end of square production) can cause significant losses, even reaching 100 % (Abrapa 2018, Oliveira et al 2022). Until just over 10 years ago, such losses ranged between 51 and 74 million dollars in Brazilian crops (Oliveira et al 2013).…”

Mpp23Aa/Xpp37Aa Insecticidal Proteins from Bacillus thuringiensis (Bacillales: Bacillaceae) Are Highly Toxic to Anthonomus grandis (Coleoptera: Curculionidae) Larvae

“…These applications can be performed weekly until the insect is no longer detected. Consequently, the field may receive as many as 25 applications in a single growing season, boosting expenses regarding agricultural inputs, and negatively affecting the environment and entomofauna [ 7 , 8 , 9 ]. However, the low effectiveness of the available synthetic agents has contributed to inefficient control measures, an increase in the insect population, and its genetic diversity.…”