Fitness Advantage in Heterozygous Ladybird Beetle Eriopis connexa (Germar) Resistant to Lambda-Cyhalothrin

Abstract

The pyrethroid lambda-cyhalothrin is widely recommended for use against defoliators in crop ecosystems, but this broad-spectrum insecticide lacks efficacy against aphids; thus, key aphid predators such as the ladybird beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae) must be preserved. Given that populations of E. connexa recently identified as resistant to lambda-cyhalothrin show potential of integrating chemical and biological control in crop ecosystems, a historical goal of integrated pest management. In the present study, the resistance maintenance over F1, F2, and F3 progenies from crossing resistant (R) and susceptible (S) E. connexa populations that might be expected after releasing R predator in the crop field and the F1 offspring performance when the R population is crossed with the S population are evaluated. The offspring performance is determined for F1 progenies from crossing the R population at F40- and F45-reared generations in the laboratory with the S population at F38- and F1-reared generations in the laboratory. The mortality rate in the heterozygous F1 progeny is low and similar to the rate for the R population (<5%), but it is about 75% in F2 and F3 progenies from crossing R and S populations. Fecundity and longevity of the heterozygous F1 progeny are significantly greater compared to the R population. These results suggest that when R population beetles are released and mating with S population residents, their field offspring retains the resistance phenotype with the advantages of greater egg production and longer survival compared to the parental R population.

Field-evolved resistance to λ-cyhalothrin in the lady beetleEriopis connexa

“…However, the release or natural presence of the resistant population in the field, even when crossing with wild susceptible individuals, produce F1 offspring, which are also resistant due to the autosomal mode of resistance inheritance to λ-cyhalothrin (Rodrigues et al ., 2013 a ). These offspring also present enhanced biological performance due to reduced adaptive cost in the F1 offspring (Lira et al ., 2016). Therefore, it may be feasible to conserve the resistant trait or rear the resistant population to be released into restricted sites, such as protected crops in greenhouses, or specific sites, such as those composed of vegetable crops that are simultaneously infested by aphids and defoliators.…”

Heterosis and reselection for pyrethroid resistance trait maintenance in the lady beetle Eriopis connexa (Germar)

“…Surviving insects in treatments (i) and (ii) were collected and reared to establish the subsequent descendant generations (F1 to F4) that were used for experiments. A total of four generations was used as this is the time needed for the loss of resistance by crossing R × S individuals (Lira et al, 2016). Additionally, a four generations cycle is similar to that which would be attained during E. connexa phenology in row crop agroecosystems.…”

“…In E. connexa , this cost in fecundity and longevity can be reduced in descendants through the crossing of resistant and susceptible individuals, which results in heterosis or outbreeding enhancement. This phenomenon is a type of hybrid vigour (Lira et al, 2016).…”

“…The maintenance of the resistant phenotype in the population after a field release of resistant individuals, may vary depending on factors, such as: (i) the adaptive cost that lambda‐cyhalothrin resistance imposes on resistant phenotypes (McKenzie & Batterham, 1994), (ii) the dominance of resistance genes in the population (Georghiou & Taylor, 1977), (iii) the presence and intensity of selection pressure (Crow, 1957; Georghiou & Taylor, 1977) and (iv) rates of immigration of susceptible individuals into populations and subsequent mating with resistant phenotypes (Dunley & Croft, 1992). However, the absence of selection pressure and the continuous mating between resistant and susceptible individuals can contribute to a rapid reduction in E. connexa resistant phenotypes (Lira et al, 2016; Rodrigues et al, 2020). In the absence of selection pressure and mating with susceptible individuals, the ratio of resistant is reduced by ≈50% after four generations (Rodrigues et al, 2020).…”

“…The resistance of E. connexa to lambda-cyhalothrin is possible due to an increased esterase enzymatic profile (Rodrigues et al, 2014(Rodrigues et al, , 2020. In turn, it generates a fitness cost, with resistant beetles having reduced reproductive potential and reduced longevity when compared to susceptible individuals (D' Ávila et al, 2018;Ferreira et al, 2013;Lira et al, 2016;Santos et al, 2016). Other insects such as Aphis gossypii (Glover) expressed longer pre-reproductive period and low reproductive rate (Zhang et al, 2020).…”