Number Of Natural Enemies Research Articles

Dual effects of additional food supply and threshold control on the dynamics of a Leslie–Gower model with pest herd behavior

Bemisia tabaci is a major agricultural pest and recognized by the United Nations Food and Agriculture Organization (FAO) as the second largest pest in the world. This paper aims to study the management of Bemisia tabaci from theoretical aspects. Firstly, considering the omnivorous nature of natural enemy species and pest herd behavior, a Leslie–Gower type pest-natural enemy model with additional food supply and non-differentiable rational uptake function is put forward, and the effects of additional food supply and aggregation efficiency on the dynamical behavior of the system are analyzed. Secondly, for the slowness of pest control by natural enemy species, a threshold control strategy is adopted to prevent the spread of Bemisia tabaci by spraying a certain intensity of insecticides and releasing a certain number of natural enemies. The complex dynamics of the system induced by the threshold control are discussed such as the existence of predator-extinction periodic solution, the existence and stability of coexisting order-1 periodic solution. Thirdly, from the perspective of cost control, an optimization problem is constructed based on the existence of the order-1 periodic solution, and the optimal control threshold, control strength and control frequency are determined. At last, to illustrate the theoretical results more intuitively, the numerical simulations in MATLAB program are presented to illustrate the effectiveness and practical significance of the control measures. The results of this study provide a reference for the scientific and reasonable management of Bemisia tabaci and is helpful to realize the sustainable development of agricultural production.

How plant composition in margins influences the assemblage of pests and predators and its effect on biocontrol in melon fields

Many agricultural landscapes offer few resources for maintaining natural enemy populations and floral plantings have frequently been adopted to enhance biological pest control in crops. However, restored margins may harbour both pests and natural enemies. The aim was to compare the abundance of pests and natural enemies in three types of margins (unmanaged, sown herbaceous floral strips and shrubby hedgerows) as well as in adjacent melon fields. Besides, yield was compared among melon fields as way of testing the effect of the type of margin on biocontrol. The research was carried out during 2 years in twelve melon fields from four different locations in southern Spain. Arthropods were sampled periodically in margins and melon fields by visual inspections and Berlese extraction. Hedgerow and floral strips hosted higher numbers of both pests and predators than unmanaged margins. Besides, hedgerows had a similar or higher number of natural enemies than floral strips but lower number of pests. In just a few occasions, the type of margin had a significant effect on the abundance of pests and natural enemies in melon fields, but rarely there was consistency between the two growing seasons. No differences were found in yield. We hypothesised that the lack of association in the abundances of pests and natural enemies between margins and melon fields could be attributed to the overriding effects of the landscape and/or the internal population dynamics of arthropods in melon fields. Overall, shrubby hedgerows are more recommended than herbaceous floral strips.

Spatial and temporal distribution of Scirtothrips dorsalis (Thysanoptera: Thripidae) and their natural enemies in Florida strawberry fields.

Given the recent invasion of Scirtothrips dorsalis Hood in North America, there is limited information regarding their distribution and population dynamics in cultivated small fruit crops. Therefore, we investigated the spatial and temporal distribution of S. dorsalis and their natural enemies in commercially produced strawberry fields in Florida. During 2 consecutive strawberry production seasons, 4 and 6 geographically separated strawberry fields were sampled and were divided into grids with 30-40 sampling points per field. At each sampling point, 4-5 leaf and flower samples were collected, and sticky traps were deployed. We quantified the occurrence of S. dorsalis as well as potential natural enemies, including Orius spp., Geocoris spp., and other predators such as long-legged flies. During both years, most of the S. dorsalis and natural enemies were found on field borders, and counts progressively diminished further into the interiors of plots and away from field edges. Cluster and outlier analysis revealed that S. dorsalis formed statistically significant clusters and that these "hot spots" remained in the same general locations throughout the season. There was a strong relationship between the occurrence of natural enemies and the presence of S. dorsalis, but the number of natural enemies was generally low compared to S. dorsalis. Our results indicate that targeting field borders for chemical control or planting strawberries away from natural areas containing potential alternative hosts for thrips may be an effective strategy for reducing agricultural inputs; however, future field assessments are needed to determine if these methods could replace the treatment of entire fields.

IMPLEMENTATION OF INTEGRATED PEST CONTROL THROUGH REFUGIA PLANTS IN RICE PLANTS (Oryza sativa L.)

The use of natural enemies to control pests is a natural way that is safe for humans and the environment. One way this can be done is by conservation of natural enemies. Conservation is generally carried out through habitat management, namely by planting flowering plants that function as a source of feed, hosts (alternative prey, refuge) for natural enemies of pests. Refugia is a cultivated plant and has the potential to support natural enemy habitats ((both predators and parasites). The research method is experimental, namely comparing land that uses refugia plants and land that does not use refugia plants (conventional). This research was carried out on rice cultivation owned by farmers in Kangenan Village, Pademawu District, Pamekasan Regency. The study lasted for approximately 3 (three) months starting from April -June 2023. Data analysis using t-test by comparing the number of pests on land planted with reugia and conventional land.The results showed that the average number of locust pests on refugia land was 1.542857 and on conventional land 2.057143, the average number of walang sangit pests was 1.25714286 and conventional land was 2.05714286, the average number of caterpillar pests was 1.228571 and on conventional land was 1.885714.While the number of natural enemies of dragonflies on refugia land was 2.69 and on conventional land was 2.49. Based on the results of T tests on refugia and conventional land, locust pest Tstar 3.378975544 was obtained greater than Tcritical one1 1.782287548 , Tstar caterpillar pest 3.189526128 greater than Tcritical one 1.782287548, Tstar pest walang sangit 2.172198564 greater than Tcritical one 1.782287548 means that refugia plants can affect pests on rice plants because of the presence of refugia plants on the edge of the field as a temporary shelter for natural enemies.

Lablab (Lablab purpureus L.) genotypes and field margin vegetation influence bean aphids and their natural enemies.

Lablab (Lablab purpureus L.) is an important food and livestock feed legume that can also enhance soil fertility. However, its production is limited by insect pests, notably the black bean aphid (Aphis fabae). The present field study was conducted to determine the difference in the contribution of lablab genotypes and natural field margin vegetation (FMV) to the abundance and diversity of natural enemies and the damage, incidence, and abundance of bean aphids. Eighteen lablab genotypes were planted in the presence or absence of FMV in a randomized complete block design experiment replicated four times. Data on aphid abundance, incidence, and severity of damage were collected at four growth stages of the crop. Lablab genotypes significantly influenced aphid incidence, suggesting some level of tolerance to aphid colonization. Findings showed that lablab genotypes were a significant influence on natural enemy species richness with no statistical difference for abundance and natural enemy species diversity. However, the genotypes did not vary significantly in their influence on the number of aphid natural enemies. FMV was associated with low bean aphid damage. Overall, the presence or absence of FMV did not influence the number of natural enemies caught on the crop. This concurs with recent work that shows a similar number of natural enemies with field margin plants but may reflect the reduced number of pest insects. Cropping seasons influenced aphid abundance and damage severity, with the populations developing at the early stages of lablab development and decreasing as the crop advanced. This pattern was similar both in the presence or absence of FMV. The findings of this study highlight the important contribution of crop genotype together with the presence of field margin species in the regulation of aphids and their natural enemies in lablab.

Abundance, diversity and richness of natural enemies of the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), in Zambia.

The fall armyworm (FAW), Spodoptera frugiperda, an invasive pest originating from the Americas is a serious pest threatening cereal production and food security in Zambia. We studied the prevalence and abundance of natural enemies of FAW in three Agroecological regions (AERs I, II, and III) to identify those that could potentially serve as bio-control agents. Sampling of FAW parasitoids and predators was done along trunk roads at intervals of 10 km. Molecular sequence analysis and morphological characterization were used to identify natural enemies. Over 11 species of FAW natural enemies, including egg, egg-larval, and larval parasitoids, and predators, were identified in Zambia. The mean number of natural enemies and species richness was higher in AER I and IIa. Consequently, egg parasitism was highest in those two regions, at 24.5% and 12.2%, respectively. Larvae parasitism was highest in AER I (4.8%) and AER III (1.9), although no significant differences were observed. The most abundant and widely distributed parasitoid was Drino sp. (Diptera: Tachinidae), while Rhynocoris segmentarius (Germar) (Hemiptera: Reduviidae) and Belanogaster sp. (Hymenoptera: Vespidae) were the most prevalent predators. Our study reveals the presence of two natural enemies belonging to the genus Tiphia and Micromeriella, uncommon to FAW. Significant differences in the number of parasitoids were observed in polycropping, with the highest recovery of 12 ± 10% from maize + cowpeas + pumpkin and watermelon mixed cropping. The higher the rainfall, the lower the number of natural enemies recorded. Variations in rainfall patterns which affect FAW availability, cropping systems and the three AERs may explain natural enemies' species diversity in Zambia. The information provided in this study can aid the development of a national biological control programme for sustainable management of fall armyworm.

Efficacy of entomopathogenic fungi, nematodes and spinetoram combinations for integrated management of Thrips tabaci.

Two consecutive field trials using a blend of entomopathogens in combination with a new chemistry insecticide were conducted to determine treatment effects on onion thrips (Thrips tabaci Lindeman) populations, crop damage, plant development, crop yield and impact on natural enemies. Products were tested in an onion cropping system and included the insect pathogenic fungus Beauveria bassiana (isolate WG-11), an entomopathogenic nematode Heterorhabditis bacteriophora (strain VS) and the new-chemistry chemical insecticide spinetoram. In all treatments, a significant decrease in thrips per plant population was detected in both trials. Overall, dual application of entomopathogens and insecticide was more effective than singly applied treatments. The lowest number of thrips larvae (1.96 and 3.85) and adults (0.00 and 0.00) were recorded when treated with dual application of B. bassiana and spinetoram at 7 days post application (DPA) after the second spray application in 2017and 2018, respectively. Damage on onion plants was considerably decreased in all treatments relative to the control. The lowest damage was observed on onion plants treated with B. bassiana + spinetoram at 7 DPA after the second spray application during both years. A significant decrease in the number of natural enemies (beetles, spiders, mites, lacewings, ants and bugs) on onion plants was recorded during both years. Insect pathogens when applied alone and in combination with each other considerably protected arthropod natural enemies compared to insecticide application applied alone. Significant increase in plant agronomic traits was observed compared to the control. Among all the treatments, B. bassiana + spinetoram produced maximum leaf length, leaf weight, total leaves, neck diameter, bulb diameter, number of rings per bulb, bulb weight, dry matter and plant yield following the 2017and 2018 applications, respectively. The findings of the study reveal the potential of using insect pathogens and insecticide for control of T. tabaci. However, combinations containing spinetoram are harmful to nontarget organisms, whereas biological control agents help in protecting biodiversity in onion agroecosystems. © 2023 Society of Chemical Industry.

Arthropods on grapes benefit more from fungicide reduction than from organic farming.

Pesticides are considered main contributors to global arthropod declines and therefore may decrease the provision of ecosystem services such as natural pest control. Organic farming and cultivating pest- and disease-resistant varieties can allow pesticide applications and their impacts on nontarget organisms and the environment to be reduced. We investigated the effects of organic versus conventional management and fungus-resistant versus susceptible wine grape varieties on arthropod biodiversity and pest control of grape berry moths in 32 vineyards in the Palatinate region, Germany. Hazard quotients of applied pesticides were calculated for each vineyard. The cultivation of fungus-resistant varieties led to significantly reduced hazard quotients and in turn enhanced abundances of natural enemies, particularly theridiid and philodromid spiders. Unexpectedly, organic management resulted in higher hazard quotients than conventional management and reduced numbers of natural enemies, particularly earwigs. Pest predation rates showed no significant differences between grape varieties or management types. Widespread benefits of organic management on arthropod biodiversity found in other crops were absent in our viticultural study region. This is likely due to the dominant role of fungal diseases in viticulture, which requires high numbers of fungicide treatments under both conventional and organic viticulture. Thus, fungicide reduction through the cultivation of fungus-resistant grape varieties is one key element to fostering the abundance of arthropods in general and beneficial arthropods in particular. Beyond vineyards, this is potentially relevant in numerous other crop types. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of Distance from Wetland Borders on Hymenopteran Wasps and Spider Abundance in Maize-soybean Cropping System

The non-crop habitats within agroecosystems are important resources for ecological and biological insect pest management. Diversified cropping systems are known to influence pests populations, however, how neighboring habitats to the agricultural fields affect insect pest natural enemies population dynamics is not clear. This study focused on understanding the influence of wetland borders on Hymenoptera wasps and predatory spider prevalence in a maize-soybean intercrop system. The Hymenoptera wasps and spiders population estimates were carried out in twelve farmers’ fields stratified within 0-300 and 500-1100 meters from the wetland borders. Data were collected once a week starting one week from the emergence of maize and soybean plants until post-flower growth of the two crops. Results showed crop fields within 0-300 meters from the wetland borders had significantly higher numbers of wasps and spiders, while crop fields set up at 500-1100 meters from the wetland borders, the population of Hymenoptera wasps and spiders was significantly reduced. The findings of this study indicate that stable habitats such as wetland borders harbour higher numbers of natural enemies of crop pests and crop fields at close proximity benefit from quick migration of natural enemies from the pool in stable habitats. These findings can be used to design field architectures such as field margins or borders that can support insect pest natural enemies survival and migration into crop fields.

Salibu Rice Cultivation in Tungro Endemis Region

Salibu is modified ratoon rice which has advantages in economic and time-saving. Tungro disease is one of probable handicap for salibu to be controlled in their endemic area. Rice virus tungro disease is caused by Rice Tungro Bacilliform Virus (RTBV) and Rice Tungro Spherical Virus (RTSV) which are transmitted by leafhopper. The research goals are to know the growth of leafhopper population and the spread of the tungro disease in salibu and conventional rice farming system as well as their effect on yield. The research was conducted in split plot experiment and designed in a randomized block design. The main plot were 1) salibu system and 2) conventional system (non-salibu). The subplots were varieties 1) TN1 (sensitive variety), 2) Ciherang (commonly used by the farmer), and 3) Inpari 36 (tungro new resistant variety). The results revealed that the tungro attack rate, dry milled grain yield, and 1000 dry grain weight were significantly higher in conventional cultivation than salibu (P < 0.05). The number of leafhopper populations tended to be higher in salibu system than in conventional system. The number of natural enemies did not show a particular pattern related to green leafhopper's presence. The Shannon Wiener diversity index for natural enemies ranged from low to medium. Regarding to the results, salibu system is not recommended yet in the tungro endemic areas. Keywords: Salibu, rice tungro virus disease, green leafhopper, natural enemies

Attraction of leaf hopper, Amrasca biguttulla biguttulla, and whitefly, Bemisia tabaci, toward natural essential oils in cotton

Abstract Leaf hopper, Amrasca biguttula biguttula, and whitefly, Bemisia tabaci are the most economical sucking pests of cotton (Gossypium spp.) causing stunting, shortening of internodes and transmitting plant pathogenic viruses. The management of these pests is primarily based on application of synthetic pesticides, which not only triggers resistance to insecticide molecules but also contributes to environmental pollution. We aimed to study the attraction of A. biguttula and B. tabaci toward six natural essential oils (NEOs) viz., sandalwood, basil, grapefruit, rose, clove and mint oils using yellow sticky traps under field conditions. The results showed that traps treated with sandalwood and basil oils attract significant numbers of A. biguttula and B. tabaci as compared to the other traps during the seasons 2016-2017 and 2017-2018. Further, the Attractive Index (AI) of sandalwood and basil oils to these pests were significantly higher (i.e., >1). In addition, the traps treated with sandalwood and basil oils caught relatively lower numbers of natural enemies. The GC-MS analysis specified the presence of vital attractive volatile compounds, viz., santalene, funebrene and pentadecane in sandalwood; and linalool, β-farnesene, caryophyllene and methyl eugenol in basil oil. Based on the results obtained it can be concluded that application of sandalwood and basil oils increased the attracting efficacy of sticky traps for the management of A. biguttula and B. tabaci in cotton.

Revisiting implementation of multiple natural enemies in pest management

A major goal of biological control is the reduction and/or eradication of pests using various natural enemies, in particular, via deliberate infection of the target species by parasites. To enhance the biological control, a promising strategy seems to implement a multi-enemy assemblage rather than a single control agent. Although a large body of theoretical studies exists on co-infections in epidemiology and ecology, there is still a big gap in modelling outcomes of multi-enemy biological control. Here we theoretically investigate how the efficiency of biological control of a pest depends on the number of natural enemies used. We implement a combination of eco-epidemiological modelling and the Adaptive Dynamics game theory framework. We found that a progressive addition of parasite species increases the evolutionarily stable virulence of each parasite, and thus enhances the mortality of the target pest. However, using multiple enemies may have only a marginal effect on the success of biological control, or can even be counter-productive when the number of enemies is excessive. We found the possibility of evolutionary suicide, where one or several parasite species go extinct over the course of evolution. Finally, we demonstrate an interesting scenario of coexistence of multiple parasites at the edge of extinction.

Preliminary studies on the parasitism rate of larval parasitoids of the diamondback moth (Plutella xylostella) L. (Lepidoptera: Plutellidae) in the Ashanti region of Ghana

The diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) is the most important pest of the brassicas worldwide. Over the years, management of this pest has largely relied on conventional insecticides, with well-documented negative impacts. Biological control using indigenous natural enemies is a promising way to manage the pest while reducing the use of synthetic insecticides. However, due to the negative impact of synthetic insecticides on beneficial insects, the number of natural enemies in the agroecosystem is often below the levels that may have significant pest reduction. Here, we assessed the range and parasitism rates of the larval parasitoids of P. xylostella in the Ashanti Region of Ghana. On the whole, one hymenopteran endo-parasitoid species, Cotesia plutellae, was identified in the P. xylostella larval samples. In all, the percentage of field parasitism of P. xylostella larvae ranged between 11% and 23%. Given the percentage of parasitism in this preliminary study, we are of the view that there is potential in relying on endemic parasitoids to biologically manage P. xylostella if conditions in agroecology are improved to encourage the survival of these beneficial insects.

Microbes, Dodonaea viscosa and Chlorantraniliprole as Components of Helicoverpa armigera IPM Program: A Three Region Open-Field Study

Field trials were conducted on the efficacy of different control options against Helicoverpa armigera on tomato. We evaluated and compared pest control, safety to natural enemies, crop yield and economics of application for various treatments including: a mycoinsecticide based on Beauveria bassiana; a baculovirus, H. armigera nucleopolyhedrovirus (HaNPV); a plant extract from Dodonaea viscosa; and the insecticide chlorantraniliprole (Coragen®). Trial sites were located in the Bahawalpur, Faisalabad and Rawalpindi regions in Punjab, Pakistan. A combined application of HaNPV + chlorantraniliprole was better than all other treatments in reducing pest larval populations and fruit damage, and in increasing crop yield. The least effective control was with D. viscosa, but plots treated with this plant extract also had the greatest number of natural enemies. Treatment with HaNPV + chlorantraniliprole resulted in the fewest natural enemies at all observation times and in all field sites, but the highest yields, varying from 42.8–46.6 tons ha−1, and the highest cost:benefit ratios of 1:1.74–1:1.81. Our findings suggest that a combined application of a specific microbial agent and an insecticide effectively controls H. armigera, increases tomato yield, reduces costs and maximizes economic returns. This open-field study concludes that all of the microorganisms and other treatments have the potential to combat H. armigera populations and could be used in successful integrated pest management programs.

Plant Diversification with Biopesticide Application in the Production of Cucumber (Cucumis sativus Linn.) under Carmen, Davao del Norte Conditions

The cucumber is one of the most important vegetable crops in the world regarding its nutrient composition and uses. However, this crop is also very susceptible to pest infestations that lead to significant yield loss. Therefore, this study was designed to investigate the effects of intercropping as a pest management approach in cucumbers. Results revealed that intercropping Zinnia flower with oriental herbal nutrient application significantly reduces the incidence of many important pests such as aphids, whiteflies, and cucurbit leaf beetles. On the other hand, intercropping the Zinnia flower plus the application of OHN was also found to increase the number of natural enemies in cucumber, such as parasitoids and ladybird beetles. It is therefore concluded that intercropping flowers in tandem with biopesticide can be a promising pest management strategy to minimize the dependence on synthetic insecticides. Further research must be carried out in this line of study to gain more insights and provide more scientific evidence supporting intercropping as a very important strategy and component in pest management programs. Keywords : Arthropod diversity, habitat modification, intercropping, pest management, vegetable crop

Optimizing control of flea beetles through ecological engineering of vegetable agroecosystem in Kashmir

Ecological engineering is a concept of habitat manipulation to reduce dependence on insecticides. It is the intentional involvement of plant communities and insectary plants in managed landscapes influencing natural enemies survival. These natural enemies lead to reduction in pest population in environmentally acceptable production practices. Field experiments were conducted during 2019 and 2020 to evaluate impact of ecological engineering on the flea beetles, P. striolata and A. himensis and their natural enemies on brinjal crop. Three treatments with different plant species were worked out for pest management study. Results showed that Treatment I caused maximum increase in mean number of natural enemies (1.11/ 10 plants) which in turn brought maximum mean pest reduction. Treatment II caused second maximum increase in mean number of natural enemies (0.92/ 10 plants). Treatment III caused minimum increase in mean number of natural enemies (0.68/ 10 plants). The diversity of predators was documented in different treatments. Simpson’s diversity index, Shannon-Weiner index and Evenness index were found higher in Treatment I followed by Treatment II and Treatment III. The maximum mean % increase of natural enemies in main crop over control (250.52 %) with maximum mean % reduction of target pest (63.46 %) was observed in Treatment I. The mean % increase of natural enemies in main crop over control (167.44 %) with mean % reduction of target pest (54.41 %) was observed in Treatment II. The mean % increase of natural enemies in main crop over control (20.97%) with mean % reduction of target pest (48.88%) was observed in Treatment III.

Field margins and botanical insecticides enhance Lablab purpureus yield by reducing aphid pests and supporting natural enemies.

Botanical insecticides offer an environmentally benign insect pest management option for field crops with reduced impacts on natural enemies of pests and pollinators while botanically rich field margins can augment their abundance. Here, we evaluated the non‐target effects on natural enemies and pest control efficacy on bean aphids in Lablab of three neem‐ and pyrethrum‐based botanical insecticides (Pyerin75EC®, Nimbecidine® and Pyeneem 20EC®) and determine the influence of florally rich field margin vegetation on the recovery of beneficial insects after treatment. The botanical insecticides were applied at the early and late vegetative growth stages. Data were collected on aphids (abundance, damage severity and percent incidence) and natural enemy (abundance) both at pre‐spraying and post‐spraying alongside Lablab bean yield. The efficacy of botanical insecticides was similar to a synthetic pesticide control and reduced aphid abundance by 88% compared with the untreated control. However, the number of natural enemies was 34% higher in botanical insecticide‐treated plots than in plots treated with synthetic insecticide indicating that plant‐based treatments were less harmful to beneficial insects. The presence of field margin vegetation increased further the number of parasitic wasps and tachinid flies by 16% and 20%, respectively. This indicated that non‐crop habitats can enhance recovery in beneficial insect populations and that botanical insecticides integrate effectively with conservation biological control strategies. Higher grain yields of 2.55–3.04 and 2.95–3.23 t/ha were recorded for both botanical insecticide and synthetic insecticide in the presence of florally enhanced field margins in consecutive cropping seasons. Overall, these data demonstrated that commercial botanical insecticides together with florally rich field margins offer an integrated, environmentally benign and sustainable alternative to synthetic insecticides for insect pest management and increased productivity of the orphan crop legume, Lablab.

Efficacy of stored indigenous predatory mite Phytoseiulus persimilis against Tetranychus urticae red form on eggplant under greenhouse conditions

Cold storage is the most prevalent method to obtain sufficient number of natural enemies after mass rearing. In this study efficacy of stored indigenous Phytoseiulus persimilis Athias-Henriot against Tetrancyhus urticae red form on eggplant under greenhouse conditions were assessed after determining best storage conditions for the predatory mite stored at 5 and 10 oC with >98% RH conditions. Treatments in the greenhouse experiments consisted of T. urticae release (control), P. persimilis release stored at 5 oC for 15-day and unstored P. persimilis releases in 2014. In 2015, P. persimilis release stored at the same temperature for 30-day was made along with a control and unstored P. persimilis release. P. persimilis survival was 100% after 5.5 weeks at 5 oC, and was 75% at 10 oC for the same storage period. No significant difference was observed between the total mean numbers of T. urticae mixed stages in unstored and stored predatory mite release treatments for 15-day-stored predatory mites. On the contrary, a significant difference was detected among the T. urticae densities in all three treatments on some sampling dates at 30-day-stored predatory mite released treatments. The results showed that P. persimilis demonstrated great effectiveness on suppressing the T. urticae red form, and 15-day-stored indigenous strains of P. persimilis could be successfully used in the biological control of T. urticae in greenhouse-grown eggplant when compared to 30-day-stored P. persimilis.

Pesticide Regime Can Negate the Positive Influence of Native Vegetation Donor Habitat on Natural Enemy Abundance in Adjacent Crop Fields

The benefits of non-crop vegetation to conservation biological control of insect pests in adjacent crops have often been demonstrated. Other studies have established that pesticide use can negatively impact natural enemies; but little is known about the outcomes from providing non-crop vegetation in systems with pesticide use. Here we conducted a natural experiment, sampling arthropods from within a set of four fields with varying pesticide use intensities that were otherwise similar and had perennial native vegetation adjacent to a single edge. Bayesian network analysis was applied to model the entire data set, then sensitivity analysis of numbers of arthropods captured in pitfall traps and sticky traps revealed that the overall effect of pesticide toxicity was large. Numbers of multiple arthropod taxa were especially strongly reduced in fields with pesticide regimes that had greater calculated toxicity scores. The effects on natural enemy numbers of the presence of adjacent perennial native vegetation was weaker than the effect of pesticide regime for all taxa except for Staphilinidae, for which it was equivalent. The benefit to in-crop numbers of natural enemies from the adjacent vegetation was strongest for ground active Araneae, Formicidae, and Dermaptera. Descriptive statistical analysis of the spatial distribution in the least heavily sprayed field suggested that the native vegetation was donor habitat for in-crop natural enemies, especially Hymenoptera, Dermaptera, and Formicidae, with numbers elevated close to the native vegetation, an effect that was apparent for around 100 m. Conservation of invertebrates in agricultural landscapes, including efforts to promote natural enemies for conservation biological control, are strongly impeded by “real world” pesticide regimes that include frequent applications and toxic compounds. Landscape features such as perennial native woody vegetation are potentially important refuges for a wide range of natural enemy taxa. The donor habitat effect of such refuges can elevate in-crop densities of these important ecosystem service providers over a scale of around 100 m, implying scope to enhance the strength of biological control in large fields (around 4 ha) by use of entirely wooded margins provided pesticide use is moderated.

Plant Extracts as Potential Acaricides for the Management of Red Spider Mite, Oligonychus coffeae Nietner (Acarina: Tetranychidae), in the Tea Ecosystem: An Eco-Friendly Strategy

The effects of the application of aqueous extracts of a selection of five traditional plants (Murraya paniculata, Cassia tora, Amphineuron opulentum, Tithonia diversifolia, andCassia alata) were compared with that of synthetic acaricide in reducing the population of red spider mite (Oligonychus coffeae), a major tea pest, alongside their impact on natural enemies and green leaf yield. Analysis of large-scale field trials showed that all the five plants extract treatments resulted in similar yield; this was analogous to the application of synthetic acaricide. A reduction in the pest population was observed to be on par with the synthetic acaricide, with a higher number of natural enemies treated using the pesticide-plant-treated plot in comparison to the synthetic acaricide-treated plot, which indicated pesticidal plants had a lower impact on natural enemies. A phytotoxicity study on tea leaves indicated that aqueous extracts of selected plants are non-phytotoxic and do not impart any taint to the prepared tea samples. Therefore, the present investigation outlines how plant extracts used as a botanical pesticide display toxicity against red spider mite on tea plants without harming the beneficial insects, increasing the yield and avoiding any lethal consequence for the tea plants or consumers.