First Report Using a Native Lacewing Species to Control Tuta absoluta: From Laboratory Trials to Field Assessment

Testing the Effects of Prey Type on the Life History and Population-Level Parameters of Chrysoperla externa (Neuroptera: Chrysopidae)

Green lacewings are valuable predators, utilized in augmentative biological control against various agricultural pests. However, further studies are required to comprehend the performance of these predators when consuming natural prey. We investigated the capacity of Chrysoperla externa (Hagen) to utilize the following three distinct prey types: the pupae of the coffee leaf miner Leucoptera coffeella (Guérin-Mèneville & Perrottet), the eggs of the sugarcane borer Diatraea saccharalis (F.), and the eggs of the Mediterranean flour moth Ephestia kuehniella (Zeller). The first two of these species are naturally occurring prey found in field crops, while the last serves as a factitious prey species for the mass rearing of natural enemies. We hypothesized that the type of prey would differentially affect the life history and population-level parameters of C. externa. Laboratory experiments were conducted to compare the pre-imaginal survival and developmental times, adult longevity and reproduction, and population growth of C. externa when larvae were provided with each of the three prey items. Results indicated that C. externa utilized the two natural prey items, L. coffeella pupae and D. saccharalis eggs, for its development, reproduction, and population growth. However, larvae developed significantly faster and females exhibited higher reproductive parameters, including fecundity and daily oviposition, when consuming the factitious prey, E. kuehniella eggs. This resulted in a higher intrinsic rate of population increase, as well as shorter times for the population to double in size. Understanding the population dynamics of C. externa when consuming different prey items is crucial for optimizing their utilization in augmentative biological control programs.

A review on biology and possible management strategies of tomato leaf miner, Tuta absoluta (Meyrick), Lepidoptera: Gelechiidae in Nepal

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), Tomato Leaf Miner (TLM) moth, is one of the notorious oligophagous pests of solanaceous crops that mines primarily on mesophyll of leaves as well bore tomato fruits. In Nepal, T. absoluta, the pest that has a potential to create loss up to 100%, was detected in 2016 in a commercial tomato farm at Kathmandu. So, the farmers and researchers must heed for effective management contrivance to improve the yield of tomato in Nepal. The devastating nature of T. absoluta causes its unusual proliferation so that it needs dire study of its host range, potential damage and sustainable management strategies. We discussed the data and information on T. absoluta available in several research papers comprehensively and provided succinct information on occurrence of T. absoluta in the world, its biology, life cycle, host plants, yield loss due to T. absoluta and several novel control tactics which helps farmers, researchers, policy makers to sustainably rise the tomato production in Nepal as well as in global context to attain food security. Sustainable pest management strategies such as Integrated Pests Management (IPM) approaches incorporating and prioritizing biological control methods with usage of chemical pesticides with less toxic active ingredient can be encouraged to the farmers for controlling the pests sustainably.

DNA screening of Drosophila suzukii predators in berry field orchards shows new predatory taxonomical groups

Drosophila suzukii (spotted wing drosophila, SWD) is a pandemic quarantine pest that attacks mostly red fruits. The high number of life cycles per year, its ability to rapidly invade and spread across new habitats, and highly polyphagous nature, makes this a particularly aggressive invasive species, for which efficient control methods are currently lacking. The use of native natural predators is particularly promising to anchor sustainable and efficient measures to control SWD. While several field studies have suggested the presence of potential predatory species in infested orchards, only a few confirmed the presence of SWD DNA in predators' gut content. Here, we use a DNA-based approach to identify SWD predators among the arthropod diversity in South Europe, by examining the gut content of potential predator specimens collected in SWD-infested berry fields in North Portugal. These specimens were morphologically identified to the family/order, and their gut content was screened for the presence of SWD DNA using PCR. New SWD predatory taxonomical groups were identified, as Opiliones and Hemerobiidae, in addition to known SWD predators, such as Hemerobiidae, Chrysopidae, Miridae, Carabidae, Formicidae and Araneae. Additionally, the presence of a spider family, Uloboridae, in the orchards was recorded for the first time, posing this family as another SWD-candidate predator. This study sets important bases to further investigate the potential large-scale use of some of these confirmed predator taxa for SWD control in South Europe.

Anatomy and histology of the alimentary canal of larvae and adults of Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae)

The larvae of the lacewing Chrysoperla externa are important predators with the potential to be used in the biological control in agriculture. Although some studies provide important data on the gut morphology in lacewings, they are limited to few species. This study describes the anatomy and histology of the alimentary canal in the predatory larvae and herbivorous adult of C. externa. In larvae, the crop is the larger part of the foregut and it is connected to the midgut by the stomodeal valve. The midgut is an enlarged sac-like organ. At the mid-hindgut transition, there are eight Malpighian tubules. The hindgut is a non-functional vestigial region in the larvae. In adults, the crop has a diverticulum associated with large tracheal trunks, a conic proventriculus with sclerotized lips followed by an elongated tubular midgut. Histological analyses of larval and adult midgut show the presence of a single-layered epithelium with columnar cells with well-developed brush border, nests of regenerative cells, and a peritrophic matrix lining the midgut lumen. The hindgut in adults has an epithelium with cubic cells lined by a thin cuticular intima and rectal pads in the rectum. These data are discussed in comparison with the digestive tract in other Chrysopidae.

Morphology of the male and female reproductive tracts of virgin and mated Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae)

Predatory insects have reproductive organs rich in complex changes that may be responsible for the success of their population growth. The species Chrysoperla externa is a predator used in biological control programs in Latin America. However, there is no morphological data about the morphology of the reproductive tract in this insect. This study describes the morphology of the reproductive organs of virgin and mated C. externa male and female. The male has a pair of testes yellow in color and five pairs of accessory glands closely associated with the seminal vesicles. The testis follicles are twisted filled with cysts in different developmental stages. The pair of ovaries in the females shows asymmetry with 9-11 ovarioles per ovary with oocytes in different developmental stages and a spherical spermatheca. Virgin and mated males have no differences in the size of the testes, seminal vesicle, and accessory glands. C. externa females show morphological changes in the reproductive tract according to sexual maturation, which is triggered by mating. The ovary activation occurs after female mating. The ovaries are of merotistic polytrophic type. The spermathecal reservoir is lined by a flattened epithelium with a thin cuticular intima and associated with well-developed muscles. It is concluded that the reproductive tract of C. externa is similar in virgin and mated males and females. Egg production is activated only after mating and the development of reproductive tract structures is faster in mated females.

The Role of Chrysoperla carnea (Steph.) (Neuroptera: Chrysopidae) as a Potential Dispersive Agent of Noctuid Baculoviruses

Simple Summary

Baculoviruses (BV) infect several lepidopteran pests of economic importance, such as the beet armyworm Spodoptera exigua. The joint use of microbiological and macrobiological strategies may improve the efficacy of control. Laboratory bioassays were developed to evaluate the interactions between two BVs: the multiple nucleopolyhedroviruses of S. exigua (SeMNPV) and Autographa californica (AcMNPV), and the predator Chrysoperla carnea. The excretion products of the predator’s larvae (drops) and adults (meconia) were microscopically examined after the ingestion of BV-infected S. exigua larvae. For both types of excreta and BVs, viral occlusion bodies (OBs) (resistance forms) were observed. These OBs were infective to healthy S. exigua larvae when applied in water suspension and in direct deposition. The virulence of meconia was higher in suspensions (higher viral load), while larval drops were more virulent in direct application due to their liquid nature and their easiness of consumption. The fitness of C. carnea was slightly affected by the consumption of both BV-infected prey. No preference was shown between healthy and BV-infected S. exigua, and both were preferred vs. the aphid Macrosiphum euphorbiae. Our findings present C. carnea, and particularly its larvae, as a promissory candidate for BV dispersion in the field.

Abstract

Baculoviruses (BV) are highly effective against lepidopteran pests of economic importance such as Spodoptera exigua. The combined use of entomopathogens and macrobiological control agents requires the study of their relationships. Laboratory bioassays were developed to evaluate the interactions between the multiple nucleopolyhedroviruses of S. exigua (SeMNPV) and Autographa californica (AcMNPV), and the predator Chrysoperla carnea. The microscopic examination of predator’s excreta (larval drops and meconia) after the ingestion of BV-infected S. exigua revealed the presence of viral occlusion bodies (OBs). The reinfection of S. exigua larvae with BVs-contaminated excreta by using OBs water suspensions or by direct application both yielded high mortality values but different speed-of-kill results. Meconia killed before in suspensions due to their higher viral load and larval excretion drops did so in direct application due to their liquid nature and their easiness of consumption. The prey-mediated ingestion of SeMNPV and AcMNPV triggered slight effects in C. carnea, which were probably derived from the food nutritional quality. Chrysoperla carnea larvae did not discriminate between healthy and BV-infected S. exigua, while a preference was shown for S. exigua (healthy or infected) vs. Macrosiphum euphorbiae. Our findings present C. carnea, and particularly its larvae, as a promissory candidate for BV dispersion in the field.