Isolation and Characterization of Microsatellite Markers for Soybean Looper (Lepidoptera: Noctuidae).

We constructed 13 microsatellite markers for Chrysodeixis includens (Walker), a serious crop pest in the Americas. All SSR (Simple Sequence Repeat) markers were polymorphic, with no evidence of linkage disequilibrium between any loci in any population. The total number of alleles per locus ranged from 5 for L3, L9, and L11 to 26 for L6; the mean number of alleles per locus in three populations of C. includens ranged from 2.33 for L3 to 14.67 for L6. Hardy-Weinberg equilibrium (HWE) deviation was not observed in four loci for at least one population (L3, L5, L9, L10). Markers L6, L7, L8, L10, L11, L12, and L13 showed a frequency of null alleles > 0.2 for at least one population. STRUCTURE and F-statistics revealed low population structure among the populations (FST = 0.013) and a high degree of inbreeding (FIS = 0.658). The SSR markers developed here will be useful in future studies on the ecology, demography, host dynamics, and gene flow of C. includens. This information is essential to understand the recent status of C. includens as a key pest in South America.

Beyond selectivity: are behavioral avoidance and hormesis likely causes of pyrethroid-induced outbreaks of the southern red mite Oligonychus ilicis?

Secondary pest outbreak is a counterintuitive ecological backlash of pesticide use in agriculture that takes place with the increase in abundance of a non-targeted pest species after pesticide application against a targeted pest species. Although the phenomenon was well recognized, its alternative causes are seldom considered. Outbreaks of the southern red mite Oligonychus ilicis are frequently reported in Brazilian coffee farms after the application of pyrethroid insecticides against the coffee leaf miner Leucoptera coffeella. Selectivity favoring the red mite against its main predatory mites is generally assumed as the outbreak cause, but this theory has never been tested. Here, we assessed the toxicity (and thus the selectivity) of deltamethrin against both mite species: the southern red mite and its phytoseid predator Amblyseius herbicolus. Additionally, behavioral avoidance and deltamethrin-induced hormesis were also tested as potential causes of red mite outbreak using free-choice behavioral walking bioassays with the predatory mite and life-table experiments with both mite species, respectively. Lethal toxicity bioassays indicated that the predatory mite was slightly more susceptible than its prey (1.5×), but in more robust demographic bioassays, the predator was three times more tolerant to deltamethrin than its prey, indicating that predator susceptibility to deltamethrin is not a cause of the reported outbreaks. The predator did not exhibit behavioral avoidance to deltamethrin; however insecticide-induced hormesis in the red mite led to its high population increase under low doses, which was not observed for the predatory mite. Therefore, deltamethrin-induced hormesis is a likely cause of the reported red mite outbreaks.

Insecticide survival and behavioral avoidance in the lacewings Chrysoperla externa and Ceraeochrysa cubana.

Insecticide impact on non-target species, such as insect predators and parasitoids, is an ever-growing concern in agriculture and recent studies have been shifting focus from lethal to sub-lethal effects since they may prevail in field conditions, although more difficult to assess. Synthetic insecticides are the main concern, but the recent spread of biopesticide use in agriculture draws attention, particularly the main botanical insecticide currently in use - azadirachtin. Here we assessed the lethal and behavioral sub-lethal response of predatory larvae of the lacewing species Chrysoperla externa and Ceraeochrysa cubana to two frequently used synthetic insecticides, malathion and permethrin, and to the bioinsecticide azadirachtin. The recommended field concentration of the synthetic insecticides led to low survival time of lacewing larvae from both species, in contrast with azadirachtin. However, all three compounds led to 100% mortality of the lacewing larvae from both species. Insecticide repellence (i.e., avoidance without contact) was similar for both synthetic insecticides in both species, but azadirachtin was a stronger repellent for C. externa, but not C. cubana. In addition, insecticide irritability (i.e., avoidance after contact) occurred in both lacewing species to all three insecticides tested. The notion that natural compounds are safer than synthetic compounds to non-target species is refuted in the present study, which also detected significant irritability to all of the insecticides regardless of their origin, and species-specific repellence elicited particularly by azadirachtin. Therefore, bioinsecticides should not be exempted from risk assessment, and non-target sub-lethal effects should not be neglected when considering potential insecticide use in agriculture.