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

Abstract

Natural enemies are exposed to insecticide sprays for herbivorous species and may evolve field resistance to insecticides. Natural enemies selected for resistance in the field, however, are welcome for pest control. The susceptibility of 20 populations of Eriopis connexa from various crop ecosystems to λ-cyhalothrin was tested. Three bioassays were conducted: (i) topical treatment with lethal dose (LD)50 previously determined for populations considered standard for susceptibility (LD50S) and for resistance (LD50R) to λ-cyhalothrin at technical grade; (ii) dose-mortality assay to calculate the LD for populations exhibiting significant survival to the LD50R; and (iii) determination of survival when exposed to dried residues at field rates. Among the 20 tested populations, seven populations did not survive or survival rates were lower than 10% when treated with LD50R; three populations survived >20%, but lower than 50%; while ten populations exhibited equal or greater survival rates compared with the 50% expected survival for the LD50R. Thus, these ten populations were subjected to dose-mortality response, and the LD50 values varied from 0.046 to 5.44 µg a.i./insect with resistance ratio of 8.52- to 884.08-folds. Adults from these ten populations that were ranked as resistant according to the LD50R exhibited survival from 44.5 to 100% exposed to the lowest and from 38.8 to 100% exposed to the highest field rates of λ-cyhalothrin, respectively. Otherwise, the remaining ten populations ranked as susceptible according to the LD50R showed survival from 3.3 to 56% exposed to the lowest and from 0 to 17.7% exposed to the highest field rates of λ-cyhalothrin, respectively. Therefore, 50% of the tested E. connexa populations exhibited field-evolved resistance to λ-cyhalothrin and the use of a discriminatory LD50 for resistance matched the survival obtained when exposed to the insecticide field rates.

Selection for resistance to pyrethroids in the predator Orius laevigatus

“…However, among predatory insects, lady beetles and lacewings are the most reported, with no cases of field‐evolved resistance in any heteropteran predator 7 . Naturally occurring predators in field crops, such as lady beetles and lacewings, are historically exposed to insecticides, resulting in resistant populations in crop fields with high insecticide use, but not in organic crops or those with little dependency on insecticides 15–19 . In addition, some lady beetle species, such as Eriopis connexa and Hippodamia convergens , have been reported to evolve resistance, whereas others equally exposed to insecticides, such as Cycloneda sanguinea , have not 17 .…”

“…Selection for resistance to pyrethroids has been carried out in other BCAs, such as lady beetles and lacewings 16,19,36 . However, those selections departed from populations collected in crop fields already exhibiting field‐evolved resistance.…”

“…However, O. laevigatus , like most natural enemies, is very susceptible to natural pyrethrins and their synthetic analogues, the pyrethroids 11–14 . These compounds are used widely in organic and IPM crops to cope with several pests, hampering the establishment and reproduction of BCAs 15–19 . Therefore, selection of O. laevigatus strains resistant to pyrethrins and pyrethroids would improve the robustness of biocontrol protocols, which is an urgent requirement for the wider adoption of biological control 3,6,19,20 …”

“…Although not as widespread a phenomenon as in pest species, insecticide resistance has been reported for a number of BCAs, such as predatory mites, insect predators and parasitoids (see Bielza 2016 for a recent revision 7 ). Lady beetles and lacewings are the predatory insects with most documented cases of field‐evolved and laboratory‐selected insecticide resistance 15–19 . However, there are no reported cases of field‐evolved resistance in any heteropteran predator, 7 despite their wide release in protected vegetable crops.…”

Inheritance of polygenic but stable pyriproxyfen resistance in a bio‐control agent Chrysoperla carnea (Neuroptera: Chrysopidae): cross‐resistance and realized heritability

“…Genetic improvement plans have provided an opportunity to control insect pests effectively. Numerous beneficial arthropods are reported to have improved climatic tolerance, 25 increased fitness, 26 increased predation 18 and insecticide resistance 20,21,27,28 . Insecticide‐resistant natural enemies can be of high importance in cropping systems where insecticides are used with priority 19 .…”