Biological control is an efficient pest control method but there are still limitations that are hindering its wider adoption. Genetic improvement of biological control agents (BCAs) can help to overcome these constraints, but the choice of key attributes for better performance that need to be selected is still an open question. Several characteristics have been suggested but the harsh reality is that selective breeding of BCAs has received a lot of attention but resulted in very little progress. Identifying the appropriate traits to be prioritized may be the first step to reverse this situation. In our opinion, the best way is to look at the factors limiting the performance of key BCAs, especially generalist predators (pesticide compatibility, prey-density dependence, non-suitable crops, and extreme environmental conditions), and according to these challenges, to choose the attributes that would allow BCAs to overcome those limitations. The benefits of selection for higher resistance to toxins, whether artificially applied (pesticides) or plant produced (plant defenses); increased fitness when feeding on non-prey food (supplemented or plant-derived); and better adaptation to extreme temperature and humidity are discussed. In conclusion, genetic improvement of BCAs can bring about new opportunities to biocontrol industry and users to enhance biocontrol resilience.

Imidacloprid and thiamethoxam are neonicotinoids that have been tested in several Orius species, including Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), but not the variability in their effect among Orius populations of a single species. In this study, the variation in susceptibility to imidacloprid and thiamethoxam in 30 Mediterranean wild populations and four commercial populations of O. laevigatus was investigated in the laboratory using a standard dip bioassay method. Lethal concentration values (LC 50 ) and the mortality of adults at the maximum field rate (MFR) were calculated. The range of LC 50 of thiamethoxam was from 0.7 to 5.9 mg l À1 , an 8.4-fold variability, obtaining mortality at MFR (100 mg l À1 ) of >89.1% in all populations. The baseline obtained a value of 2.1 mg l À1 , which is very low compared to the MFR. For imidacloprid, the LC 50 varied from 7.7 to 94.7 mg l À1 (12.3-fold variability). Mortalities at the MFR (150 mg l À1 ) were 57.7-99.2%, that is, more variable than for thiamethoxam. The LC 50 value of the baseline was 48.7 mg l À1 , also low compared to the MFR. This variation was exploited to select two populations resistant to thiamethoxam and imidacloprid, respectively. Artificial selection for on average 40 cycles significantly increased the resistance to thiamethoxam (LC 50 = 149.1 mg l À1 ) and imidacloprid (LC 50 = 309.9 mg l À1 ). Mortalities at the MFR in the thiamethoxam-and imidacloprid-resistant populations were 44.5 and 36.9%, respectively. These results demonstrate that resistance can be enhanced in biocontrol agents by artificial selection under laboratory conditions, starting with populations showing no or very low tolerance. Our neonicotinoid-resistant populations might enhance the wider adoption of biological control by allowing punctual or hotspot applications of neonicotinoids to control several main and secondary pests.

No abstract

BACKGROUND Insecticide resistance in the natural enemies of pest species is a very desirable trait. It allows better integration of biological control with the synthetic and natural compounds applied to manage certain pests, especially secondary pest outbreaks. Insecticide resistance in predatory insects has been documented for lady beetles and lacewings, but intriguingly no cases of field‐evolved resistance have been noted in any heteropteran predator. In this work, we first explored the variation in susceptibility to pyrethroids in wild and commercial populations of Orius laevigatus (Fieber). Second, we exploited this genetic variation to artificially select a strain of O. laevigatus resistant to pyrethroids. RESULTS We found significant variation [median lethal dose (LC50) 1.6–77.0 mg L−1] in susceptibility to pyrethroids in wild populations of the heteropteran predator O. laevigatus, with a baseline LC50 value of 14.6 mg L−1. We successfully selected a strain of O. laevigatus highly resistant to pyrethroids (LC50 = 1059.9 mg L−1). In addition, such resistance was expressed in every instar, particularly in the last nymphal stages, increasing the resilience of the whole population present in the crop facing pyrethroid application. CONCLUSION The level of resistance achieved may be sufficient to allow survival of adults and nymphs of O. laevigatus exposed to the maximum field rate of several pyrethroids and natural pyrethrins, widely used to control a number of pests in organic and integrated pest management crops. Therefore, this strain resistant to pyrethrins and pyrethroids would improve the resilience of biocontrol protocols, which is an urgent requirement for wider adoption of biological control. © 2021 Society of Chemical Industry

No abstract