Reducing boll weevil populations by clipping terminal buds and removing abscised fruiting bodies

Abstract

Cotton pests damaging fruiting bodies (squares and young bolls) are difficult to control and their damage results in direct yield loss. Small growers, with low technological inputs, represent a large portion of cotton growers worldwide comprising more than 76 countries; they rely mainly on cultural practices to counteract pest attack in their crops. Boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), oviposition involves puncturing cotton squares and young bolls, causing abscission. We examined the impact on boll weevil population of collecting abscised cotton fruiting bodies and clipping plant terminals at 50% boll maturation in the field during two cotton‐growing seasons and under field cage conditions. Greatest numbers of damaged squares occurred ca. 117 days after planting and clipped plants resulted in reduction of abscised structures and adult boll weevils compared with non‐clipped plants, irrespective of cotton variety. Damaged young bolls were found ca. 128 days after planting in 2009 and 2011, but clipping had no effect. Numbers of boll weevils found in plants of the varieties BRS 201 and BRS Rubi (both in 2009) and BRS Rubi (in 2011) were, respectively, 13‐, 17‐, and 20‐fold greater when clipping plus collecting abscised fruiting bodies were not practiced. Furthermore, the average percentage of the boll weevil parasitoid Bracon vulgaris Ashmead (Hymenoptera: Braconidae) emerging from abscised and collected structures was similar between clipped and non‐clipped plant terminals in both seasons. Clipping plant terminals did not result in yield reduction and reduced adult boll weevil production. Collecting abscised reproductive structures, clipping plant terminals, and using both practices together reduced boll weevil populations by as much as 63, 57, and 79%, respectively, in cage trials. Thus, these practices cause significant impact on boll weevil populations and are feasible of adoption, especially for smallholder cotton growers.

Boll weevil within season and off-season activity monitored using a pheromone-and-glue reusable tube trap

“…In fact, in two out of three surveyed years in our study, the average number of boll weevils captured per GGT was higher during the intercropping periods. These results may be explained by the fact that in the Semiarid, despite the long dry season, cotton plants continue to hold some green tips hosting pest species supporting off-season weevil population (Neves et al, 2010;2013b). However, there was a switch to high mean numbers of weevils captured during the cropping season 2010, likely due to the high density of weevils present during the previous intercropping period 2009/2010 (Table 1).…”

Parasitoides do bicudo Anthonomus grandis e predadores residentes em algodoeiro pulverizado com caulim

“…Desta forma, oferecendo uma opção racional e de baixo custo para o cultivo do algodoeiro no sistema de agricultura familiar e orgânico, preconizado para o Semiárido Nordestino (NEVES; TORRES; VIVAN, 2009 NEVES;TORRES, SILVA, 2010;NEVES et al, 2013).…”

Interaction ofAnthonomus grandisand cotton genotypes: biological and behavioral responses

“…Therefore, we continued our experiments using only VOCs released by plants in the reproductive stage. However, it should be noted that in the absence of the preferred structures (flowers and squares), the boll weevil can feed on leaves and plant tips (Gilliand & McCoy, ), as well as developing bolls (Neves et al., ).…”

“…It is able to disperse long distances searching for the host plant or refuge areas. Cotton fields are colonized by boll weevils predominantly during squaring-flowering stages (Neff & Vanderzant, 1963;Smith et al, 1965) and weevil oviposition induces abscission of these structures 5-8 days later (White & Rummel, 1978;Showler, 2008;Neves et al, 2013), resulting in direct yield loss. Several studies have shown that VOCs play important roles in the attraction of the weevils to cotton plants (White & Rummel, 1978;Dickens, 1984Dickens, , 1989Dickens, , 1990Magalhães et al, 2012).…”