Turning a Pest into a Natural Enemy: Removing Earwigs from Stone Fruit and Releasing Them in Pome Fruit Enhances Pest Control

The European earwig Forficula auricularia (L.) (Dermaptera: Forficulidae) is an omnivorous insect that is considered a minor pest of stone fruit and a key predator of pests in pome fruit orchards. In many pome fruit orchards, earwigs are absent or in low abundance due to broad-spectrum spray programs and the slow recolonization rate of earwigs. Orchards in transition to organic or "selective" conventional programs often struggle to achieve effective levels of biological control, and thus, may benefit from inoculating earwigs to expedite their re-establishment. In a two-year study, we evaluated the potential for mass trapping earwigs from stone fruit using rolled cardboard traps to reduce fruit damage and provide earwigs for augmentation in pome fruit. We also tested whether a single mass release or five releases (on alternating weeks) of the same total number of earwigs in apples and pears reduced pests relative to plots where no releases occurred. Mass trapping did not decrease earwig abundance or substantially reduce fruit damage in stone fruit orchards. However, trapping was an efficient method for providing earwigs for augmentation. Earwig abundances were only increased in orchards where earwigs were previously low or absent; however, multiple orchards with varying prior levels of earwigs exhibited reductions in key pests (woolly apple aphid and pear psylla). For some other pests evaluated, plots with mass releases of earwigs had a slight trend in overall lower pest density when compared with control plots. A strategy for moving earwigs out of stone fruit orchards and into pome fruit orchards could be an effective method for augmenting orchard predator populations.

Meta-Analysis of Herbicide Non-Target Effects on Pest Natural Enemies

A critical component of integrated pest management is minimizing disruption of biological control by reducing the use of pesticides with significant non-target effects on natural enemies. Insecticide non-target effects testing for natural enemies has become increasingly common, but research examining the non-target effects of herbicides on natural enemies is scarce, and recommendations regarding herbicide selectivity are non-existent. We used meta-analysis to summarize laboratory bioassays testing non-target effects of herbicides on arthropod natural enemies and identify patterns in taxon susceptibility and active ingredient toxicity. Data were extracted from 78 papers representing 801 total observations. Herbicides increased natural enemy mortality and decreased longevity, reproduction, and predation. Mesostigmatan mites and hemipterans were the most sensitive to herbicides, and spiders, neuropterans, and hymenopterans were the least sensitive. Mortality was higher in juvenile predators versus parasitoids but did not differ between adults; parasitoid juveniles are likely better protected within the host. In terms of acute mortality, metribuzin, glufosinate, and oxyfluorfen were the most harmful herbicides. Only nicosulfuron, rimsulfuron, pendimethalin, phenmedipham, atrazine, and urea did not increase natural enemy mortality. The large effect size of glufosinate is particularly concerning, as it is the most likely replacement herbicide for glyphosate in many crops. Many active ingredients remain under-studied. Our analysis indicates that herbicides have a strong potential to disrupt biological control in cropping systems.

Two in one: the neotropical mirid predator Macrolophus basicornis increases pest control by feeding on plants

BACKGROUND

Plant defenses activated by European zoophytophagous predators trigger behavioral responses in arthropods, benefiting pest management. However, repellence or attraction of pests and beneficial insects seems to be species-specific. In the neotropical region, the mirid predator Macrolophus basicornis has proved to be a promising biological control agent of important tomato pests; nevertheless, the benefits of its phytophagous behavior have never been explored. Therefore, we investigated if M. basicornis phytophagy activates tomato plant defenses and the consequences for herbivores and natural enemies.

RESULTS

Regardless of the induction period of M. basicornis on tomato plants, Tuta absoluta females showed no preference for the odors emitted by induced or control plants. However, Tuta absoluta oviposited less on plants induced by M. basicornis for 72 h than on control plants. In contrast, induced plants repelled Bemisia tabaci females, and the number of eggs laid was reduced. Although females of Trichogramma pretiosum showed no preference between mirid-induced or control plants, we observed high attraction of the parasitoid Encarsia inaron and conspecifics to plants induced by M. basicornis. While the mirid-induced plants down-regulated the expression of genes involving the salicylic acid (SA) pathway over time, the genes related to the jasmonic acid (JA) pathway were up-regulated, increasing emissions of fatty-acid derivatives and terpenes, which might have influenced the arthropods' host/prey choices.

CONCLUSION

Based on both the molecular and behavioral findings, our results indicated that in addition to predation, M. basicornis benefits tomato plant resistance indirectly through its phytophagy. This study is a starting point to pave the way for a novel and sustainable pest-management strategy in the neotropical region. © 2022 Society of Chemical Industry.

Estimating intrinsic growth rates of arthropods from partial life tables using predatory mites as examples

The intrinsic rate of natural increase of a population (r_m) has been in focus as a key parameter in entomology and acarology. It is considered especially important in studies of predators that are potential biological control agents of fast-growing pests such as mites, whiteflies and thrips. Life-table experiments under controlled laboratory conditions are standard procedures to estimate r_m. However, such experiments are often time consuming and may critically depend on the precise assessment of the developmental time and the fecundity rate early in the reproductive phase. Using selected studies of predatory mites with suitable life-table data, we investigated whether and how measurements of growth rates can be simplified. We propose a new method for estimating r_m from partial life tables, in which the researcher can choose a level of precision based on a stand-in measure of relative error. Based on this choice, the procedure helps the researcher to decide when a life-table experiment can be terminated. Depending on the chosen precision, significant amounts of experimental time can be saved without seriously compromising the reliability of the estimated growth parameter.