Mortality of the cotton boll weevil in drip and sprinkler irrigated cotton crops.

R.F Faustino,J.R Pereira,C.A.D Silva,A.I.A Pereira,J.C Zanuncio

doi:10.1590/1519-6984.248154

Abstract

The cotton boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is a key cotton crop pest in Brazil. Adverse climatic factors, such as high temperatures and low soil moisture, dehydrate oviposited cotton squares (bud flowers) on the ground and cause high mortality of its offspring within these plant structures. The objective of this research was to evaluate the mortality of the cotton boll weevil in drip and sprinkler irrigated cotton crops. The experimental design was in randomized blocks with two treatments: drip (T1) and sprinkler (T2, control) irrigated cotton crops with sixteen replications. Each parcel had one emergence cage, installed between two cotton rows per irrigation system, with 37 cotton squares with opened oviposition punctures and yellowish bracts, to capture adult cotton boll weevils. The average number of boll weevils that emerged from the cotton squares and the causes of mortality at different development stages were determined per treatment. Third-generation life tables of the boll weevil were prepared using the natural mortality data in drip and sprinkler irrigation treatments and plus actual, apparent and indispensable mortality rates and the lethality of each mortality cause. We conclude that the application of water directly to the root zone of the plants in a targeted manner, using the drip irrigation system, can cause high mortality of the cotton boll weevil immature stages inside cotton squares fallen on the ground. This is because the cotton squares fallen on the drier and hotter soil between the rows of drip-irrigated cotton dehydrates causing the boll weevils to die. This is important because it can reduce its population density of the pest and, consequently, the number of applications of chemical insecticides for its control. Thus, contributing to increase the viability of cotton production, mainly in areas of the Brazilian semiarid region where the cotton is cultivated in organic system.

Highlights

Brazil is one of the largest cotton producers in the world, with an estimated cultivated area of 1.1 million hectares (IBGE, 2020) mainly in the Cerrado Biome with rainfed conditions (Ferreira et al, 2020)
A total of 527.0 mm of water was supplied during the phenological cycle of the cotton culture by the sprinkler and drip irrigation systems, twice a week according to the capacity of soil water retention and the crop evapotranspiration
The number of adult cotton boll weevil (CBW) emerged from the cotton squares was higher in the sprinkler (0.35 ± 0.11) and lower (0.00 ± 0.00) in the drip treatment per emergency cage (F1.15 = 9, 00; P

Summary

Introduction

Brazil is one of the largest cotton producers in the world, with an estimated cultivated area of 1.1 million hectares (IBGE, 2020) mainly in the Cerrado Biome with rainfed conditions (Ferreira et al, 2020). This culture is expanding with areas irrigated, mainly small properties in the semi-arid region of the Northeast Brazil (Bezerra et al, 2015). For example, keeps the soil dry and warm between the rows of cultivated plants, which can harm insects that need environments with mild temperatures and high humidity to develop and reproduce (Amini et al, 2012; Rendon and Walton, 2019). The high volumes of drip irrigation in vines can increase lateseason leafhopper populations (Daane and Williams, 2003)

Objectives

Methods

Results