Bollgard Cotton and Resistance of Tobacco Budworm (Lepidoptera: Noctuidae) to Conventional Insecticides in Southern Tamaulipas, Mexico

Abstract

Insecticide susceptibility in tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), was determined for 8 yr (1991-2001) with larvae sampled from cotton in southern Tamaulipas, Mexico. Before 1996, when Bollgard cotton expressing the Cry1A(c) delta-endotoxin was introduced into the region, two important patterns were documented. The first was economically significant increases in resistance to certain insecticide groups. The second was occurrence of virtually complete control failures in the field during 1994 and 1995. The largest resistance changes were recorded for the type II pyrethroids cypermethrin and deltamethrin. These products are the most widely used products in the region. Resistance ratios for these products increased up to > 100-fold from 1991 to 1995. After 1996, the resistance levels declined. These findings did not occur with other products of scant use (e.g., permethrin, profenofos, and endosulfan) or low tobacco budworm efficacy coupled to a high use pattern (e.g., methyl parathion). This clear trend toward reversal of resistance to type II pyrethroids can be understood, in part, with respect to two factors: 1) the high adoption rate of transgenic cotton in the region, from 31.2% in the beginning (1996) to approximately 90% in 1998; this has considerably curbed the use of synthetic insecticides, with the attending loss of selection pressure on this pest; and 2) the potential immigration to the region of susceptible tobacco budworms from cultivated and wild suitable hosts as well as from transgenic cotton might have influenced the pest population as a whole. The influence of transgenic cotton on southern Tamaulipas can be more clearly seen by the drastic reduction of insecticide use to control this important pest. Now tobacco budworms in this region are susceptible to type II pyrethroids. Two effective and fundamentally different pest management tools are now available to cotton growers in southern Tamaulipas: transgenic cotton, coupled with careful use of pyrethroids, offers the possibility of sustainable and profitable cotton production.

Bacillus thuringiensis Vip3Aa Toxin Resistance in Heliothis virescens (Lepidoptera: Noctuidae)

“…The expected mortality, Y(x), for the backcross progeny at concentration x is calculated as Y(x) ϭ 0.50 (WRS ϩ WRR), where WRS and WRR are the mortality values of the presumed RS (F 1 ) and RR (resistant parental line, Vip-Sel) genotypes at concentration x, respectively (59,60). The 2 test for goodness of fit between the backcross and expected mortality was calculated as described by Sokal and Rohlf (61) as 2 ϭ (F 1 -pn) 2 /pqn, where F 1 is the observed number of dead larvae in the backcross generation at concentration x, p is the expected proportion of dead larvae calculated as Y(x), n is the number of backcross progeny exposed to concentration x, and q ϭ 1 -p. The 2 value is compared with the 2 distribution with 1 degree of freedom, and if P is Ͻ0.05, the null hypothesis of monogenic resistance is rejected (59,60). The genetic variation within Vip-Unsel, Vip-Sel, F 1 reciprocal crosses, backcrosses, and F 2 crosses was determined using the analysis of variance (ANOVA) to test for significant variation in mortality among families produced by the single-pair crosses.…”

Potential of antranilic diamides applied in seeds of soybeans with and without cry1ac protein for Helicoverpa armigera caterpillar control

“…This insecticidal protein has also been shown to be efficacious in controlling H. virescens larvae in soybean and cotton (Terán-Vargas, 2005;Bortolotto et al, 2014). In soybean, even in more developed plants (withseed pods), the concentration of the insecticidal protein is sufficient to control H. virescens larvae (Bernardi et al, 2013;Bortolotto et al, 2014) (Table 5).…”

Heliothis virescens and Bt cotton in the United States

“…It has primarily been cotton, on which intensive selection pressure with synthetic insecticides 20,21 forced TBW to develop high levels of resistance to all kinds of pesticides in different places of the Western Hemisphere. [22][23][24] In the US, this pest at one time or another had developed different degrees of tolerance to all the chemicals that have been used against it in significant quantities. 20,22,23,[25][26][27] One group of synthetic insecticides after another has shown to be no match for the capacity of this pest to rapidly acquire resistance.…”

“…Before this point, employing the best control measures, the bollworm complex together with the boll weevil [Anthonomus grandis (Boheman)] were causing at least 15-20% yield losses on cotton. A report of the use of Bt-cotton 24 illustrates how this technology can have an impact on IRM and the control of this pest. Before Bt-cotton was available in northeastern Mexico, TBW in several places with the aid of pheromone-baited traps and by field evaluations.…”