A novel use of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) as inoculative agent of baculoviruses.

BACKGROUND: Alphabaculoviruses are Lepidoptera-specific virulent pathogens that infect numerous pests, including the Spodoptera complex. Due to their low environmental persistence, the traditional use of Alphabaculoviruses as bioinsecticides consist in high-rate spray applications with repeated treatments. Several abiotic and biotic factors can foster its dispersion, promoting their persistence in the agroecosystem. Amongst biotic factors, predatory arthropods can disperse the viruses by excretion after preying on infected individuals. Therefore, this study focused on promoting predator's ingestion of nucleopolyhedrovirus (NPV)-treated diets, and the later exposition of the insect host to leaf surfaces contaminated with predator excreta. The virus-host-predator system studied was Spodoptera littoralis nucleopolyhedrovirus (SpliNPV), Spodoptera littoralis (Boisduval) and Nesidiocoris tenuis (Reuter). The infective potential of N. tenuis feces and the retention time of SpliNPV were assessed under laboratory conditions after feeding on treated diets (sucrose solution and Ephestia kuehniella eggs). RESULTS: Mortality of S. littoralis larvae was lower via N. tenuis excretion than in positive control (spray application) in the first infection cycle, together with a delay in host death. In the second infection cycle, both SpliNPV-treated diets triggered 100% mortality. Both diets allowed the transmission of SpliNPV, with a faster excretion via sucrose solution compared to E. kuehniella eggs. SpliNPV remained in N. tenuis digestive tract and was viable after excretion at least for 9 days for both diets. CONCLUSIONS: This study demonstrated the potential of the predator N. tenuis as inoculative agent of baculoviruses, representing a new alternative that, along with inundative applications, might contribute to improve pest management strategies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Comparison of the Parasitization of Chelonus inanitus L. (Hymenoptera: Braconidae) in Two Spodoptera Pests and Evaluation of the Procedure for Its Production.

Chelonus inanitus (L.) is an egg-larval parasitoid of noctuids Spodoptera exigua (Hübner) and S. littoralis (Boisduval), whose mass rearing or real potential has not been targeted yet. To improve the rearing in the factitious host Ephestia kuehniella Zeller, we investigated the influence of host age and number of females parasitizing simultaneously on the overall rearing success, the influence of host age on the life cycle, and the influence of host species on the parasitoid body size. The proportion of emerging C. inanitus was higher from young host eggs, but more females emerged from mature eggs. Under high parasitoid competition, we observed a reduction in non-parasitized hosts without reducing parasitoid emergence. The parasitoid life cycle was longer in females, but the mismatch between sexes was smaller in mature eggs. The parasitoid size was smaller in the factitious host than in the natural hosts. Under semi-field conditions, we investigated the competition among parasitoid females on the overall parasitism success. The reproductive parasitism was more successful in S. exigua than in S. littoralis, and the maximum emergence was reached with three and four females, respectively. The control of S. littoralis may be attributed to the high developmental mortality, a non-reproductive parasitism that is often underestimated.

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

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.

The Role of Annual Flowering Plant Strips on a Melon Crop in Central Spain. Influence on Pollinators and Crop.

Planting flower strips adjacent to crops is among the habitat-management practices employed to offer alternative floral resources to pollinators. However, more information is needed to understand their potential spill-over of pollinators on nearby insect-pollinated crops. Over the course of two consecutive years, the suitability of a flower mixture of 10 herbaceous plants for pollinators was evaluated on a weekly basis, in a randomized block design of two melon plots (10 × 10 m2) with or without 1 m-wide flower strips. Floral coverage and pollinator visits to the plant species, as well as pollinator visits and the yield and quality of the crop, were assessed. Additionally, the selected mixture was tested for 1 year in a commercial field in order to ascertain how far the flower strip could influence visitors in the crop. The most suitable species for a flower strip in central Spain based on their attractiveness, floral coverage and staggered blossom were Coriandrum sativum L., Diplotaxis virgata L., Borago officinalis L. and Calendula officinalis L. The flower strip can act as either pollinator competitor or facilitator to the crop, depending on their floral coverage and/or the predominant species during the crop bloom period. The concurrence of blooming of the rewarding plant C. officinalis with the melon crop should be avoided in our area. In the commercial field, the bee visitation rate in the melon flowers decreased with the distance to the flower strip. No influence of the specific flower strip evaluated on crop productivity or quality was found.

Compatibility of early natural enemy introductions in commercial pepper and tomato greenhouses with repeated pesticide applications.

Successful integrated pest management in protected crops implies an evaluation of the compatibility of pesticides and natural enemies (NE), as control strategies that only rely on one tactic can fail when pest populations exceed NE activity or pests become resistant to pesticides. Nowadays in Almería (Spain), growers release NE prior to transplanting or early in the crop cycle to favor their settlement before pest arrival because this improves biocontrol efficacy, although it extends pesticide exposure periods. The purpose of this research was to evaluate the compatibility of two applications of pesticides with key NE in 2-year trials inside tomato and sweet pepper commercial greenhouses: Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), Orius laevigatus (Say) (Hemiptera: Anthocoridae) and Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae). In tomato, flubendiamide and chlorantraniliprole (IOBC category 1) were compatible with N. tenuis, but chlorpyrifos-methyl and spinosad (IOBC categories 2-3), which effectively reduced Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) density, compromised its predatory activity. In sweet pepper, chlorantraniliprole (IOBC category 1) was the only pesticide compatible with O. laevigatus while chlorantraniliprole, emamectin benzoate, spirotetramat and pymetrozine were harmless (IOBC category 1) to Amblyseius swirskii, and sulfoxaflor slightly harmful (IOBC category 2) to this phytoseiid predator.

Impact of Feeding on Contaminated Prey on the Life Parameters of Nesidiocoris Tenuis (Hemiptera: Miridae) Adults.

Insecticide selectivity to natural enemies is an important concern in integrated pest management programs. Although there is a wide range of information concerning pesticide lethal and sublethal effects on contaminated surfaces, little is known when the route of exposure occurs at a trophic level. This study evaluates this route of pesticide intake on the omnivorous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) for the first time. Under laboratory conditions, prey treated with six insecticides (flubendiamide, spirotetramat, deltamethrin, flonicamid, metaflumizone, and sulfoxaflor) were offered to N. tenuis adults for 3 days. Mortality (24, 48, and 72 h after treatment), offspring production (third until eighth day) and longevity were documented. Metaflumizone and sulfoxaflor were classified as moderately harmful products because although the percentage of mortality was only 28 and 36%, respectively, both products caused a severe decrease in offspring production and longevity. Flonicamid and flubendiamide were classified as slightly harmful products; although they did not have a lethal effect, sublethal impact was important on the parameters studied. Spirotetramat and deltamethrin were insecticides categorized as harmless. This information could be useful for selecting the most appropriate insecticides to control pests in tomato crops in which N. tenuis is a relevant biological control agent.

Residual Acute Toxicity of Some Modern Insecticides Toward Two Mirid Predators of Tomato Pests.

The successful integration of chemical and biological control strategies for crop pests depends on a thorough evaluation of the effects of pesticides on the natural enemies of pests. A case-by-case review is difficult to achieve because of the many combinations of pests, natural enemies, and crops that need to be tested. Within this framework, we tested and compared seven insecticides representative of four different modes of action (MoAs) groups on closely related predators (Miridae): flubendiamide, spirotetramat, metaflumizone, and sulfoxaflor on Nesidiocoris tenuis Reuter and flubendiamide, spiromesifen, indoxacarb, and imidacloprid on Macrolophus basicornis (Stal). We follow the standardized methodology of the International Organization for Biological Control, a sequential testing exposure scheme. The lethal effect of each insecticide was evaluated in adults after three days of contact with treated surfaces in the laboratory, extended laboratory, and semifield tests (inert substrate, tomato leaves, and tomato plant as the treated surface, respectively). Flubendiamide, spiromesifen, and spirotetramat were classified as harmless (class 1), metaflumizone was slightly harmful (class 2) but persistent, indoxacarb was harmless (class 1), and sulfoxaflor and imidacloprid were toxic (class 4) and exhibited a long residual activity. Our results suggest similarities in the acute toxicities of insecticides from the same MoA group on related species of natural enemies.

Lethal and sublethal toxicity of fipronil and imidacloprid on Psyttalia concolor (Hymenoptera: Braconidae).

Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) is a koinobiont endoparasitoid of several species of tephritid (Diptera) larvae, such as Bactrocera oleae (Gmelin) and Ceratitis capitata (Wiedemann). Here, we report on the effects of imidacloprid and fipronil on P. concolor females, when different routes of exposure were evaluated: residual contact (cover and bait sprays) and via treatment of host species. Moreover, the persistence of the bait formulated compound also was studied. For each experiment, lethal (mortality) and sublethal effects (parasitization rate or longevity) were studied. Fipronil produced 100% mortality irrespective of exposure route, and it was very persistent, because 34-d-old residues still produced this high mortality rate, being as toxic or even more toxic than the reference product dimethoate. Toxicity of imidacloprid depends on the mode of exposure, although always remained less toxic than dimethoate. Imidacloprid caused high mortality or sublethal effect to the progeny in cover sprays and when applied via treated host, being harmless in bait sprays application. In conclusion, our results suggest that fipronil should not be used in the field when the parasitoid is present. On the contrary, although imidacloprid is physiologically active against females of P. concolor, ecological selectivity may result through the use of bait treatment.