Kaolin and copper-based products applications: ecotoxicology on four natural enemies

Testing the Single and Combined Effect of Kaolin and Spinosad against Bactrocera oleae and Its Natural Antagonist Insects in an Organic Olive Grove

The presence and infestation level of Bactrocera oleae was monitored in an organic olive orchard divided into differently treated parcels with kaolin (K), spinosad (S) and with kaolin and spinosad (K + S) in alternate rows. The treatments did not seem to affect olive fruit fly population dynamics, while statistically significant protective effects were recorded against total and harmful infestation, but not against the active one. Eventually, neither kaolin nor spinosad were shown to have a particular detrimental effect against naturally occurring B. oleae parasitoids.

Side Effects of Kaolin and Bunch-Zone Leaf Removal on Generalist Predators in Vineyards

In vineyards, kaolin application and bunch-zone leaf removal (LR) were effective in the control of leafhoppers and Lobesia botrana, but their side effects on generalist predators are still poorly understood. In north-eastern Italian vineyards, the impact of kaolin and LR on species and functional diversity of spiders, as well as the abundance of spiders and generalist predatory insects, was assessed in one vineyard for two consecutive years and in two vineyards for one year. The ecological indices of the spider community were never influenced by kaolin and only in one case were they influenced by LR. At the spider family level, kaolin reduced the abundance of Araneidae, Oxypidae and Salticidae, but only in single cases. In single cases, kaolin reduced the amount of Orius sp. anthocorids and increased that of Scymninae coccinellids, whereas LR increased the amount of Aeolothrips sp. The moderate use of kaolin and the application of LR had negligible and inconsistent impacts on generalist predatory arthropods in vineyards and were therefore, compatible with IPM strategies.

Collection and Processing of Behavioural Data of the Olive Fruit Fly, Bactrocera oleae, When Exposed to Olive Twigs Treated with Different Commercial Products

The need for the development of sustainable control methods of herbivorous insects implies that new molecules are proposed on the market. Among the different effects the new products may have on the target species, the alteration of insect oviposition behaviour might be considered. At the scope, parallel simple behavioural assays can be conducted in arena. Freely available software can be used to track observed events, but they often need intensive customization to the specific experimental design. Hence, integrating such software with, e.g., R environment, can provide a much more effective protocol development for data collection and analysis. Here we present a dataset and protocol for processing data of the oviposition behaviour of the olive fruit fly, Bactrocera oleae, when exposed to olive twigs treated with different commercial products. Treatments were rock powder, propolis, a mixture of rock powder and propolis, copper oxychloride, copper sulphate, and water as the experimental control. JWatcher was used to simultaneously collect data from 12 arena assays and ad-hoc developed R code was used to process raw data for data analyses. The procedure described here is novel and represents a valuable and transferable protocol to analyse observational events in B. oleae, as well as other biological systems.

Field and Laboratory Efficacy of Low-Impact Commercial Products in Preventing Olive Fruit Fly, Bactrocera oleae, Infestation

Simple Summary

The adoption of sustainable methods for herbivore pest control has become mandatory in Europe, with the EU directive 128/09. Since then, stringent evaluation protocols have been applied to insecticides and several molecules (that are suspected to be unsafe for the environment or human health) have been banned. Hence, the evaluation of sustainable methods, e.g., preventive tools based on the manipulation of pest behaviour, must be considered. Using field and laboratory assays, we tested the efficacy of different products in preventing infestation of a key pest of olive orchards, the olive fruit fly Bactrocera oleae. Our findings may be useful for the development of control strategies in integrated pest management (IPM) and organic agriculture.

Abstract

The olive fruit fly, Bactrocera oleae, is the key pest of olive trees in several areas of the world. Given the need for the development of sustainable control methods, preventive tools, based on the manipulation of pest behaviour, must be considered. Here, under field and laboratory conditions, we tested the efficacy of different products in preventing B. oleae infestation. A field trial was conducted, from July to November 2020, in an olive orchard located in Central Italy. A table olive variety was selected and sprayed with rock powder, propolis, the mixture of both, copper oxychloride, or water (control). All treatments, except propolis, caused a reduction of B. oleae oviposition in olives, compared to the control. The mixture allowed the strongest reduction of fly infestation throughout the season, suggesting a synergistic effect. Behavioural no-choice assays were conducted to better understand the effects of treatments on B. oleae females. Compared to the control, females showed a lower preference for the central area of an arena containing an olive twig bearing two olive fruits, fully developed, but still green, treated with rock powder, plus propolis mixture. For all treatments, B. oleae showed lower oviposition events, suggesting deterrence to oviposition. Our results indicate that the tested products may have value against B. oleae, within integrated pest management (IPM) and organic agriculture.

Effect of Sustainable Preharvest and Postharvest Techniques on Quality and Storability of High-Acidity ‘Reinette du Canada’ Apple

Consumers are more disposed towards paying price premiums for sustainable food products. This fact is especially important for products with a PDO (Protected Designation of Origin) label, such as the high-acidity apple cultivar ‘Reinette du Canada’. However, ‘Reinette du Canada’ apple fruit is affected by two of the main post-harvest disorders in apple cultivars, bitter pit and senescent breakdown. As a means to achieve sustainable production of this high-quality apple cultivar, the effect of a sustainable preharvest technique, summer pruning, in combination with a zero-residue postharvest treatment allowed in organic farming on calcium-related disorders and quality in global terms in this PDO-labelled apple cultivar was assessed during storage. The combination of the two sustainable practices was an effective tool in diminishing senescent breakdown from 43% to 17% and to decrease bitter pit incidence by up to 21% (from 36% to 15%) throughout storage, especially in fruit with high susceptibility to this disorder during storage. Moreover, the overall acceptability was kept high (values of more than 3 on a 5-point scale) when applying this environment-friendly sustainable horticulture practice, which will not only reduce the synthetic pesticide input in the apple agroecosystem, but also contribute to producing fruit with zero residues.

Side effects of a mixture of essential oils on Psyttalia concolor

Integrated Pest Management programs do not always prioritize natural enemies when selecting control methods; too often these important pest reducing agents are negatively affected by the action of other methods in agroecosystems. The aim of this research was to evaluate side effects of a bioinsecticide, developed from the mixture of cedar (Cedrus atlantica), eucalyptus (Corymbia citriodora) and lemon grass (Cymbopogon citratus) essential oils (EOs), in a ratio of 1:1:1, on Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) which is a parasitoid of some pests of the Tephritidae family, as Ceratitis capitata. The LD₅₀ of the EOs mixture for C. capitata females was 3.09 µl/g, whereas the LD₅₀ for P. concolor females was 20.45 µl/g which suggests the natural enemy is more tolerant to the EOs mixture. P. concolor parasitized L3 larvae of C. capitata through a voile treated with the mixture of EOs at 1.8% without causing any deleterious effects neither on the percentage of attacked hosts nor on the emergence rate, whereas at the highest concentration tested, 4.8%, decreased both parameters during the 2 first days after treatment. Semi-field assays showed that mixture of EOs was harmless to P. concolor when released 4 h after treatment whereas killed 55 ± 3.9% males and 37.5 ± 1.6% females of C. capitata. The mixture of EOs used jointly with lambda-cyhalothrin or kaolin, both compounds applied against C. capitata in conventional and organic farming, respectively, did not increase the toxicity and/or persistence against the pest.

Ecotoxicity of neonicotinoids and diamides on population growth performance of Zygogramma bicolorata (Coleoptera: Chrysomelidae)

Relative ecotoxicity of approved neonicotinoids (i.e. imidacloprid, clothianidin, acetamiprid, thiacloprid, thiamethoxam and dinotefuran) and diamides (i.e. chlorantraniliprole, cyantraniliprole and flubendiamide) was examined on population growth parameters of Zygogramma bicolorata Pallister on parthenium under laboratory conditions at 27 ± 1 °C, 65 ± 5% relative humidity and 10 L : 14D photoperiod. The dose of all tested insecticides in the bioassay procedure was within a minimum range of their recommended field rate. In acute toxicity trial, imidacloprid caused highest rate of mortality in treated adults of Z. bicolorata, however, it was lowest in flubendiamide treatment followed by cyantraniliprole and chlorantraniliprole. Further, based on toxicity coefficient (E) value in acute toxicity trial, all were classified as harmful (H) and diamides were classified as moderately harmful (MH) as per IOBC classification. Moreover, chronic toxicity trials were carried out through life table response experiments (LTREs) in the F₁ progeny of acute toxicity experienced group. Prolonged development with the highest mortality was evident in as compared to diamides. Furthermore, population growth parameters i.e. potential fecundity (Pf), natality rate (m_x), intrinsic rate of increase (r_m), net reproductive rate (R₀) and finite rate of increase (λ) was greatly reduced in Z. bicolorata treated with neonicotinoids as compared with diamides. However, mean generation time (T_c), corrected generation time (τ) and the doubling time (DT) was prolonged in neonicotinoids followed by diamides. Furthermore, proportion of females was greatly reduced (0.43-0.48 females) in neonicotinoids as comparison to diamides (0.53-0.55 females) and control (0.67 females). On the basis of ecotoxicity trials, the tested neonicotinoids were highly toxic to Z. bicolorata than diamides. Therefore, diamide insecticides could be used with Z. bicolorata, however, for validation experimentation need to be done under natural field conditions.

Side Effects of Kaolin and Bunch-Zone Leaf Removal on Predatory Mite Populations (Acari: Phytoseiidae) Occurring in Vineyards

The effects of kaolin and bunch-zone leaf removal on populations of predatory mites Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten were assessed in the context of four trials (2015-2016) carried out against Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) in vineyards located in north-eastern Italy. Laboratory experiments were performed to evaluate the effects of kaolin on the survival and fecundity of K. aberrans and T. pyri populations originating from the same grape-growing area. In field trials, kaolin caused a gradual decrease in population density levels of both phytoseiid species (with the maximum reduction ranging from 49 to 91%) with a complete population recovery in the next spring. In laboratory experiments, kaolin was moderately harmful to both species, reducing their fecundity significantly (around 60%). Bunch-zone leaf removal determined lower phytoseiid populations in all trials, but this effect was significant only for K. aberrans in one of them. A limited use of kaolin and the adoption of bunch-zone leaf removal did not irreversibly affect phytoseiid populations in vineyards and thus can be considered compatible with IPM strategies.

Non-target toxicity of synthetic insecticides on the biological performance and population growth of Bracon hebetor Say

Bracon hebetor Say (Hymenoptera: Braconidae) is an important biological control agent of various species of order Lepidoptera and extensively used in biological control program worldwide. Present study evaluated the lethal and sublethal effects of insecticides on B. hebetor using demographic and population growth parameters. Doses of all the tested insecticides were within a maximum range of their recommended field dosages and adults were treated using residual glass vials method. For control experiments adults were treated with distilled water. Among the tested insecticides, the survivorship of various stages of B. hebetor was considerably prolonged on cyantraniliprole followed by chlorantraniliprole and shortest on chlorpyrifos and profenofos treated group. Total immature development time was prolonged in chlorpyrifos and profenofos treated group. Population growth parameters like intrinsic rate of natural increase (r_m), net reproductive rate (R₀), finite rate of increase (λ) and mean generation time (T_c) were considerably reduced in B. hebetor groups treated with chlorpyrifos and profenofos. However, B. hebetor groups treated with chlorantraniliprole and cyantraniliprole showed a little or no much difference in population growth parameters when compared with untreated group. It was also observed that chlorpyrifos and profenofos modified the sex ratio, thereby female emergence get reduced. On the basis of present findings it can be concluded that all tested insecticides caused considerable ecotoxic effects on B. hebetor compared to control. However, comparisons among the tested insecticides on the basis of IOBC criteria showed that chlorantraniliprol and cyntraniliprol was less toxic as compared to other insecticides tested on this biological control agent.

Efficacy and Mode of Action of Kaolin in the Control of Empoasca vitis and Zygina rhamni (Hemiptera: Cicadellidae) in Vineyards

During 2015, the influence of kaolin applications and bunch-zone leaf removal on the grapevine leafhoppers, Empoasca vitis (Göthe) and Zygina rhamni Ferrari, and their egg parasitoids (Anagrus spp.) was tested in four vineyards of northeastern Italy. The mode of action of kaolin on E. vitis nymphs was also investigated in the laboratory. In the treated plots, kaolin was applied at a rate of 2% w/v on two occasions separated by 5-6 d. In two vineyards, it was applied either on the whole canopy or the bunch zone at the beginning of the E. vitis second generation (preventive criterion), and in the other two vineyards, it was applied to the whole canopy at the peak of the E. vitis third generation (curative criterion). Both the preventive and curative kaolin applications caused a significant decrease in the populations of E. vitis and Z. rhamni nymphs. The effect of the preventive applications was persistent and was associated with reduced E. vitis leaf symptoms. Kaolin did not influence the activity of Anagrus spp. Bunch-zone leaf removal did not affect leafhopper populations. Laboratory experiments showed that inhibition of feeding was the main mode of action through which kaolin affected nymph populations. Based on these outcomes, kaolin could be a valuable alternative to synthetic insecticides in controlling grapevine leafhoppers.

Copper and Zinc Tolerance in Bacteria Isolated from Fresh Produce

The continued agricultural exposure of bacteria to metals such as copper and zinc may result in an increased copper tolerance through the food chain. The aim of this study was to determine the Cu and Zn tolerance of bacteria from fresh produce (cucumber, zucchini, green pepper, tomato, lettuce, vegetable salad, broccoli, cabbage, carrot, green onion, onion, and mango). Isolates (506 aerobic mesophiles) from 12 different food produce products were tested for growth in a range of Cu and Zn concentrations. Selected isolates were identified using 16S rDNA sequencing, and the presence of metal resistance genes was studied using PCR amplification. More than 50% of the isolates had MICs for copper sulfate greater than 16 mM, and more than 40% had MICs greater than 4 mM for zinc chloride. Isolates with high levels of tolerance to Cu and Zn were detected in all the produce products investigated. A selection of 51 isolates with high MICs for both Cu and Zn were identified as belonging to the genera Pseudomonas (28), Enterobacter (7), Serratia (4), Leclercia (1), Bacillus (10), and Paenibacillus (1). A study of the genetic determinants of resistance in the selected gram-negative isolates revealed a high incidence of genes from the pco multicopper oxidase cluster, from the sil cluster involved in Cu and silver resistance, and from the chromate resistance gene chrB. A high percentage carried both pco and sil. The results suggest that Cu and Zn tolerance, as well as metal resistance genes, is widespread in bacteria from fresh produce.

Effects of Kaolin on Lobesia botrana (Lepidoptera: Tortricidae) and Its Compatibility With the Natural Enemy, Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae)

Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) is an important grapevine pest in Europe recently encountered in America. Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae) is amongst the most effective parasitoids for Lepidopteran species. Studies to evaluate the effect of kaolin, an inert, nontoxic mineral, on oviposition, egg hatch, and neonate mortality of these species were carried out. Efficacy on L. botrana neonate larvae, oviposition, and egg hatch was evaluated. Effects of kaolin on parasitism and emergence of T. cacoeciae from L. botrana and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs were also evaluated. Lobesia botrana egg hatch and oviposition rates were reduced, and neonate larvae mortality was significantly greater in kaolin-treated arenas and when included in synthetic neonate larvae diet. Kaolin had no effect on T. cacoeciae parasitism in both hosts. There was only a slight but statistically insignificant effect on T. cacoeciae progeny emergence from L. botrana eggs and no effect from E. kuehniella. The results involving reductions in L. botrana oviposition and egg hatch and increase in larval mortality with kaolin suggest this compound may contribute to reduction in population densities and can be considered in rational integrated pest management strategies for L. botrana. Due to the laboratory results presented on parasitoid emergence, even though field bioassays would give a more exhaustive evaluation, it appears kaolin can be compatible with T. cacoeciae in L. botrana management.

Effects of kaolin particle films on the life span of an orb-weaver spider

Araniella cucurbitina (Araneae: Araneidae) is a widespread orb-weaver spider commonly found in agroecosystems. Mineral particle films such as kaolin, due to their protective or anti-feeding action, can represent an alternative to pesticides, especially in organic farming systems, but little is known about its effects on A. cucurbitina. Therefore, we tested the effect of kaolin sprays on the life span of A. cucurbitina under laboratory conditions. Four treatments were tested encompassing different exposure routes. Thus, kaolin sprays were applied on (i) the surface, (ii) the prey (fly), (iii) the spider and (iv) both spider & prey. A control group was tested with water in each treatment. Results showed that sprays of kaolin significantly affected the survival of A. curcubitina when applications were done on the surface and on both spider & prey registering a reduction of 48% and 56%, respectively. Spiders in control obtained higher probability of reaching alive at the end of the assay than those treated with kaolin. Differences observed can be explained by the feeding behavior of the species and may depend on the consumption of the web by the spider and the ratio spider/fly for body size.

Evaluation of a push-pull strategy for the management of Frankliniella bispinosa (Thysanoptera: Thripidae) in bell peppers

A push-pull strategy for managing the anthophilous Frankliniella bispinosa (Morgan) in pepper and increasing conservation biological control was evaluated. Push components of ultraviolet (UV)-reflective mulch and foliar applications of kaolin and the pull component of sunflower companion plants were evaluated in replicated field experiments in 2011 and 2012. Adult F. bispinosa rapidly colonized and reproduced in the peppers and sunflowers during early flowering, but populations declined later, as numbers of the predatory Orius insidiosus (Say) and Orius pumilio (Champion) increased in both hosts. Numbers of F. bispinosa were reduced by kaolin during early pepper flowering. Thrips numbers were increased on some of the later sample dates, apparently due to reduced predation that resulted from negative effects of kaolin and UV-reflective mulch on Orius populations. Numbers of thrips increased in peppers with companion plants during the first week of flowering each year, followed by declines in thrips numbers during the next 2 wk in 2011. There was little effect each year of the companion plants on the numbers of Orius in the pepper flowers. There was one date in 2011 and no dates in 2012 in which UV-reflective mulch or kaolin acted in concert with the presence of the companion plants to reduce thrips numbers in the main crop of pepper. Yield effects were not attributed to thrips damage. We conclude that sunflower companion plants did not act additively or synergistically with kaolin or UV-reflective mulch to reduce thrips and increase Orius populations in pepper.

Do biopesticides affect the demographic traits of a parasitoid wasp and its biocontrol services through sublethal effects?

Pesticide risk assessments are usually based on short-term acute toxicity tests, while longer-term population dynamic related traits, critical to the success of biological control and Integrated Pest Management (IPM) programs, are often overlooked. This is increasingly important with respect to new biopesticides that frequently cause no short-term acute effects, but that can induce multiple physiological and behavioral sublethal effects, leading to a decrease in population growth and ecosystem services. In this study we assessed the lethal and sublethal effects of six biopesticides [abamectin, azadirachtin, Bacillus thuringiensis, borax plus citrus oil (Prev-Am®), emamectin benzoate, and spinosad], used in tomato crops to control the invasive pest Tuta absoluta (Lepidoptera: Gelechiidae), on adults and pupae of the parasitoid Bracon nigricans (Hymenoptera: Braconidae). Data on female survival and production of female offspring were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinosad caused 100% and 80% mortality in exposed adults (even 10 d after the treatment) and pupae, respectively. Although most of the biopesticides had low levels of acute toxicity, multiple sublethal effects were observed. The biocontrol activity of both females that survived 1-h and 10-d old residues, and females that emerged from topically treated pupae was significantly affected by the application of the neurotoxic insecticides emamectin benzoate and abamectin. Furthermore, very low B. nigricans demographic growth indices were estimated for these two insecticides, indicating potential local extinction of the wasp populations. Among the tested products, Bt proved to be the safest for B. nigricans adults and pupae. Our findings emphasize that acute toxicity assessment alone cannot fully predict the actual impact of pesticides on non-target parasitoids. Thus, sublethal effects related to the species specific life-history variables must be carefully considered in order to assess pesticide risks and to incorporate new pesticides, including biopesticides, into IPM programmes.