Biological Pest Management Research Articles

Volatile Profiling of Fifteen Willow Species and Hybrids and Their Responses to Giant Willow Aphid Infestation

The giant willow aphid (Tuberolachnus salignus) is a large stem-feeding insect which forms dense colonies on infested plants. Since T. salignus is a new invasive species in New Zealand, we have a poor understanding of the plant chemical responses to aphid infestation. This study aimed to characterize the volatile organic compounds (VOCs) emissions of fifteen different willow species and hybrids growing in New Zealand, and to evaluate changes in response to T. salignus attack in a field trial. Volatiles were collected using a headspace sampling technique and analysed using gas chromatography-mass spectrometry (GC-MS). We found high variability in the volatile profiles of different species and hybrids, with (Z)-3-hexenyl acetate and (E)-β-ocimene being the only common components to all blends. Taxonomically related plants showed an overlapping pattern of VOC emission, and there seemed to be a clear separation between shrub and tree willows. Responses to aphid infestation were variable, with only four species/hybrids showing changes in their total VOC emission, or that of at least one class of VOCs. A weak positive correlation between aphid population estimates and VOC emissions suggests that responses are species-specific and not infestation-dependent. These results reveal useful information about the interaction between T. salignus and its potential host plants for biological control and pest management purposes.

Using the organic system plan template as a policy lever for improving biodiversity on US organic farms

In the USA, conservation and monitoring of biodiversity on organic farms have been poorly enforced, leading to the suggestion of explicitly addressing biodiversity through the organic system plan. We use primary data to examine the efficacy of this approach. We find that that farmers reporting using no-till farming, cover crops, and buffer strips observed improved or maintained levels of pollinator and wild animal biodiversity on their farms. Those using biological pest management observed higher or constant levels of pollinators on their farms. Inclusion of questions about biodiversity on the certifier-provided template, used to guide development of the organic system plan, was determined to be positively and significantly related to the predicted probability of observing higher or constant levels of pollinator and wild animal biodiversity on their farms.

Effect of gamma irradiation and subsequent cold storage on the development and predatory potential of seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera; Coccinellidae) larvae

Seven spot ladybird beetle, (Coccinella septempunctata) is a widely distributed natural enemy of soft-bodied insect pests especially aphids worldwide. Both the adult and larvae of this coccinellid beetle are voracious feeders and serve as a commercially available biological control agent around the globe. Different techniques are adopted to enhance the mass rearing and storage of this natural enemy by taking advantage of its natural ability to withstand under extremely low temperatures and entering diapause under unfavorable low temperature conditions. The key objective of this study was to develop a cost effective technique for enhancing the storage life and predatory potential of the larvae of C. septempunctata through cold storage in conjunction with the use of nuclear techniques, gamma radiations. Results showed that the host eating potential of larvae was enhanced as the cold storage duration was increased. Gamma irradiation further enhanced the feeding potential of larvae that were kept under cold storage. Different irradiation doses also affected the development time of C. septempuntata larvae significantly. Without cold storage, the lower radiation doses (10 and 25 GY) prolonged the developmental time as compared to un-irradiated larvae. Furthermore, the higher dose of radiation (50GY) increased the developmental time after removal from cold storage. This study first time paves the way to use radiation in conjunction with cold storage as an effective technique in implementation of different biological control approaches as a part of any IPM programs

Temporospatial modulation of Lymantria dispar immune system against an entomopathogenic fungal infection.

Lymantria dispar is an economically impactful forest pest worldwide. The entomopathogenic fungi Beauveria bassiana shows great promise in pest management due to its high lethality in Lymantria dispar. A complete understanding of the immune interactions between the pest and the pathogenic fungus is essential to actualizing biological pest management. Following the infection of Lymantria dispar by Beauveria bassiana spores, we performed a time-course analysis of transcriptome in Lymantria dispar fat bodies and hemocytes to explore host immune response. A total of 244 immunity-related genes including pattern recognition receptors, extracellular signal modulators, immune pathways (Toll, IMD, JNK and JAK/STAT), and response effectors were identified. We observed contrasting tissue and time-specific differences in the expression of immune genes. At the early stage of infection, several recognition receptors and effector genes were activated, while the signal modulation and effector genes were suppressed at later stages. Further enzyme activity-based assays coupled with gene expression analysis of prophenoloxidase revealed a significant upregulation of phenoloxidase activity at 48- and 72-h post-infection. Moreover, fungal infection led to dysbiosis in gut microbiota that seems to be partially attributed to reduced gut hydrogen peroxide (H2 O2 ) amount, which indicates a significant impact of fungal infection on host gut microbes. Our study provides a comprehensive sequence resource and crucial new insights about an economically important forest pest. Specifically, we elucidate the complicated multipartite interaction between host and fungal pathogen and contribute to a better understanding of Lymantria dispar anti-fungal immunity, resulting in better tools for biological pest control. © 2020 Society of Chemical Industry.

MAMP-triggered resistance induced by elicitor protein PeBA1 derived from Bacillus amyloliquefaciens NC6 in common bean (Phaseolus vulgaris L.) against green peach aphid (Myzus persicae Sulzer)

Bacterial microbe-associated molecular patterns (MAMPs) play an important role in innate plant immunity. This in vitro study evaluated the putative role of protein elicitor PeBA1 derived from Bacillus amyloliquefaciens NC6 strain in eliciting induced resistance type responses in common bean (Phaseolus vulgaris) plants against green peach aphid Myzus persicae. Nymphal developmental time of aphids was significantly prolonged and the fecundity was significantly reduced by different concentrations of PeBA1 elicitor (i.e. 40.51, 24.91 and 16.38 µg mL-1) applied at three different temperature regimes (i.e. 21, 27 and 30 °C). Moreover, foliar application of PeBA1 elicitor protein strongly up-regulated the expression levels of salicylic acid (SA) pathway-associated genes, while the expression levels of jasmonic acid (JA) pathway-associated genes exhibited a moderate induction. Quantification by LC/MSMS revealed a linear increase of both SA and JA plant defense hormones along with the time of exposure. Our findings suggest that the bacterial elicitor protein PeBA1 could be used as an effective biological pest management tool against phloem-feeding insect pests such as green peach aphids M. persicae.

Peranan Parasitoid Telur Penggerek Batang Padi Putih Scirpophaga innotata (Walker) Pada Berbagai Fase Pertumbuhan Tanaman Padi

White stem borer Scirpophaga innotata Walkers is known as a species that always causes loss of rice yields in Indonesia and the Asia region and Australia. White stem borer attacks all stages of rice plant growth starting in the nursery until harvest. Until now, synthetic chemical pesticides are still a mainstay of farmers in controlling these pests. Then it is necessary to promote biological pest management, the use of biological agents is pest management technology because a save, economical and effective. Biological control through multiplication and parasitoid release needs to be focused on parasitoid it has adapted to the local environment. This study aims to examine the role of egg parasitoid S. innotata through the type and level of egg parasitization at various phases of rice plant growth. This research was conducted by collecting as many white rice stem borer eggs as possible based on the growth phase of rice plants, i.e. age 11-25 days after planting (DAP), 26-40 DAP, 41-55 DAP, 56-70 DAP, and 71-85 DAP. Observations were made by counting hatching and non-hatching eggs, as well as the type and number of parasitoids that appeared. The results show that the egg parasitoid found was Trichogramma japonicum Ashmead, Tetrastichus schoenobii Ferriere, Telenomus rowani Gahan. The highest level of egg parasitization is at 71-85 DAP.

Entomopathogenic Fungi as a Biological Pest Management Option: A Review

Entomopathogenic Fungi as a Biological Pest Management Option: A Review

Anti-insect activity of a partially purified protein derived from the entomopathogenic fungus Lecanicillium lecanii (Zimmermann) and its putative role in a tomato defense mechanism against green peach aphid

Many biotrophic and necrotrophic fungi synthesize proteins that may elicit induced plant resistance against different herbivore pests. This in-vitro study elucidates the sub-lethal effect of a partially-purified protein derived from the entomopathogenic fungus Lecanicillium lecanii (Zimmerman) (Hypocreales: Clavicipitaceae) against green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae), an economically important pest of many solanaceous crops including tomato. Bioassays were conducted to determine the impact of different concentrations of protein (i.e. 0.018, 0.036 and 0.054 µM) on the survival and fecundity of M. persicae on tomato (Lycopersicon esculentum) plants. Moreover, the potential role of this exogenous protein in the plant defense mechanism was assessed by expression analyses of key genes associated with salicylic acid (SA) and jasmonic acid (JA) pathways using RT-qPCR. The results indicated a significant negative effect of all protein concentrations on the survivorship and fecundity of M. persicae. The highest concentration (0.054 µM) resulted in lowest survival (46%) of aphids at 7th day post-treatment, while two other concentrations (0.036 and 0.018 µM) resulted in 61 and 71% survival rate, respectively. Similarly, lowest and highest mean fecundity rates were recorded for the highest protein concentration and the control (1.5 and 2.4 nymphs day−1 female−1), respectively. Moreover, L. lecanii-derived protein strongly upregulated the SA associated genes PR1, BGL2 and PAL, and moderately upregulated the JA associated genes LOX, AOS and AOC in protein-treated tomato plants compared to the control plants. These findings demonstrate the systemic resistance induced in tomato plants against M. persicae by the exogenous application of partially-purified protein extracted from L. lecanii, suggesting its further purification and characterization as a novel biological pest management tool against aphids and other phloem-feeding insect pests.

Differentiating between scavengers and entomopathogenic nematodes: Which is Oscheius chongmingensis?

Entomopathogenic nematodes (EPNs) continue to be explored for their potential usefulness in biological control and pest management programs. As more insect-associated species of nematodes are discovered and described, it is possible that scavengers and kleptoparasites may be mischaracterized as EPNs. If a nematode species is truly an entomopathogen it should display similar infectivity, as well as behaviors and preferences, to those of established EPN species, such as Steinernema carpocapsae. In this study we evaluated dauers of the putative EPN species Oscheius chongmingensis. We examined virulence, odor preferences as a measure of host-seeking behavior, and features of its bacterial symbiont Serratia nematodiphila. We determined that O. chongmingensis behaves more like a scavenger than an EPN. Not only did O. chongmingensis exhibit very poor pathogenicity in Galleria mellonella (wax moth larvae), it also displayed odor (host-seeking) preferences that are contrary to the well-known EPN S. carpocapsae. We also found that the bacterial symbiont of O. chongmingensis was antagonistic to S. carpocapsae; S. carpocapsae IJs were unable to develop when S. nematodiphila was a primary food source. We conclude that there is insufficient evidence to support the characterization of O. chongmingensis as an EPN; and based on the attributes of its preferences for already-infected or deceased hosts, suggest that this nematode is a scavenger, which may be on an evolutionary trajectory leading to an entomopathogenic lifestyle.

Bio-efficacy of chitinolytic Bacillus thuringiensis isolates native to northwestern Indian Himalayas and their synergistic toxicity with selected insecticides

Pesticidal properties of Bacillus thuringiensis and its associated toxic proteins is an ever-growing science with potential implications in biological pest management. In the present study 80 Bacillus thuringiensis isolates native to Uttarakhand Himalayas were evaluated for chitinolytic activity and potent ones (11 isolates) were further subjected to multiphasic characterization for their antifungal, insecticidal and synergistic properties with selected chemical insecticides. Although all the 11 potent isolates were biologically active, only three isolates (VLBt27, VLBt109 and VLBt238) showed >90% inhibition in radial growth of 3 out of 4 tested plant pathogenic fungi (Rhizoctonia solani, Fusarium oxysporum, Alternaria pori and Pyricularia oryzae). The key antagonism was manifested in the form of disruptions in growing tips and uneven mycelial thickenings. In insect bioassays (against Helicoverpa armigera, Mythimna separata and Thysanoplusia orichalcea), no considerable direct mortality was observed. However, the larval weight reduction was prominent in four isolates (VLBt27, VLBt38, VLBt109 and VLBt135) which accounts to >75% in first instar larvae of H. armigera. Joint action of these four isolates with chemical insecticides showed an overall additive interaction against Brevicoryne brassicae and synergism against H. armigera. All the isolates were compatible with tested insecticides at their field recommended doses except for chlorpyriphos with around 130 kDa protein as chitinase. The study identified VLBt27 and VLBt109, two native isolates of B. thuringiensis with potential antagonistic activity and synergism as well. These isolates have possible implications as single strategy against two diverse pest problems (pathogenic fungi and phytophagous insect) of agriculture with a view of reduced pesticide application.

Comparative assessment of the thermal tolerance of spotted stemborer, Chilo partellus (Lepidoptera: Crambidae) and its larval parasitoid, Cotesia sesamiae (Hymenoptera: Braconidae).

Under stressful thermal environments, insects adjust their behavior and physiology to maintain key life-history activities and improve survival. For interacting species, mutual or antagonistic, thermal stress may affect the participants in differing ways, which may then affect the outcome of the ecological relationship. In agroecosystems, this may be the fate of relationships between insect pests and their antagonistic parasitoids under acute and chronic thermal variability. Against this background, we investigated the thermal tolerance of different developmental stages of Chilo partellus Swinhoe (Lepidoptera: Crambidae) and its larval parasitoid, Cotesia sesamiae Cameron (Hymenoptera: Braconidae) using both dynamic and static protocols. When exposed for 2 h to a static temperature, lower lethal temperatures ranged from -9 to 6 °C, -14 to -2 °C, and -1 to 4 °C while upper lethal temperatures ranged from 37 to 48 °C, 41 to 49 °C, and 36 to 39 °C for C. partellus eggs, larvae, and C. sesamiae adults, respectively. Faster heating rates improved critical thermal maxima (CTmax ) in C. partellus larvae and adult C. partellus and C. sesamiae. Lower cooling rates improved critical thermal minima (CTmin ) in C. partellus and C. sesamiae adults while compromising CTmin in C. partellus larvae. The mean supercooling points (SCPs) for C. partellus larvae, pupae, and adults were -11.82 ± 1.78, -10.43 ± 1.73 and -15.75 ± 2.47, respectively. Heat knock-down time (HKDT) and chill-coma recovery time (CCRT) varied significantly between C. partellus larvae and adults. Larvae had higher HKDT than adults, while the latter recovered significantly faster following chill-coma. Current results suggest developmental stage differences in C. partellus thermal tolerance (with respect to lethal temperatures and critical thermal limits) and a compromised temperature tolerance of parasitoid C. sesamiae relative to its host, suggesting potential asynchrony between host-parasitoid population phenology and consequently biocontrol efficacy under global change. These results have broad implications to biological pest management insect-natural enemy interactions under rapidly changing thermal environments.

The Diversity of Arthropods Predator on Wild Plant of Rice Field with and without Pesticides

<p>Contaminated- agro ecosystem influences abundance and diversity of arthropods. The aims of this study were to analyze the diversity and abundance of pre-planting arthropod predators on wild plants in rice field with and without application of pesticides. The survey and direct observation of wild plants at the rice filed were conducted from January to March 2015, at 1 ha in Pemulutan and 1 ha in Musi 2 Palembang. Sampling of arthropod predator was conducted 8 times before the rice was grown, using insect nets. On the land without pesticide application was found 14 arthropod families which consists of 28 species and 15 families of wild plant consists of 25 species. On the land with pesticide application was found 8 arthropod families consists of 16 species and 15 wild plant families with 23 species. On the land without pesticide application was found High index of diversity (H’=3.121) and low dominance (D=0.095), while on the land with pesticide application low index of diversity (H’=2.602) and high dominance (D=0.171). It is the indicators of arthropods predator more varieties at the land without pesticide application compare to the land with pesticide application. This finding is very important for biological pest management in South Sumatra. </p>

The Herbivore-Induced Plant Volatiles Methyl Salicylate and Menthol Positively affect Growth and Pathogenicity of Entomopathogenic Fungi

Some herbivore-induced-plant volatiles (HIPVs) compounds are vital for the functioning of an ecosystem, by triggering multi-trophic interactions for natural enemies, plants and herbivores. However, the effect of these chemicals, which play a crucial role in regulating the multi-trophic interactions between plant-herbivore-entomopathogenic fungi, is still unknown. To fill this scientific gap, we therefore investigated how these chemicals influence the entomopathogenic fungi growth and efficacy. In this study, Lipaphis erysimi induced Arabidopsis thaliana HIPVs were collected using headspace system and detected with GC-MS, and then analyzed the effects of these HIPVs chemicals on Lecanicillium lecanii strain V3450. We found that the HIPVs menthol and methyl salicylate at 1 and 10 nmol·ml−1 improved many performance aspects of the fungus, such as germination, sporulation, appressorial formation as well as its pathogenicity and virulence. These findings are not only important for understanding the multi-trophic interactions in an ecosystem, but also would contribute for developing new and easier procedures for conidial mass production as well as improve the pathogenicity and virulence of entomopathogenic fungi in biological pest management strategies.

Organic farming in Indian context: A perspective

Green revolution technologies played a great role in alleviating hunger but have also resulted in some adverse effects on our natural resources. Due to these adverse effects, stress is being laid on alternate forms of agriculture that are more sustainable. Organic farming, a holistic way of farming, is one of these alternate forms that are aimed at sustainable agricultural production. It relies on crop rotations, green manures, organic manures, biofertilizers, composts and biological pest management for crop production excluding or strictly limiting the use of synthetic fertilizers, chemical pesticides, plant growth regulators and livestock feed additives. No doubt, the advantages of organic farming outweigh its disadvantages but in practical it has several constraints viz. threat to national food security, limited availability of organic manures, profitability to farmers and affordability of organic produce by consumers. Thus, a complete shift to organic farming is neither desirable nor possible in high input use areas which are the major contributors of food grains to central pool. Systematic phasing out of agrochemicals and synthetic fertilizers in these areas may be a step in right direction. ‘Towards organic’ (integrated crop management) approach for input-intensive areas (food hubs) and ‘certified organic’ approach by integrating tradition, innovation and science in the de-facto organic areas (hill and rainfed/dryland regions) will be better option for national food security, higher household income and climate resilience.

Evaluation of Stable Isotope 13C6-glucose on Volatile Organic Compounds in Different Stages of Mediterranean Fruit Fly (Medfly) Ceratitis Capitata (Diptera: Tephritidae)

The Mediterranean fruit fly (Medfly) Ceratitis Capitata (Diptera: Tephidae), as most of the Tephritidae species, is a pest of great economic importance around the world. For Integrated Pest Management (IPM) and biological pest management purposes, this research will investigate characterization of the broadest possible range of volatile organic compounds and the possible changing trends of volatile biological emissions during development stages of insect. During the last years, many types of research have been done to understand chemical communications between pest-pest interactions and about the insect responses to specific volatile organic compounds. An early comparison of the VOCs emitted from larvae, pupae and adult was performed. Our research focuses on the comparison of volatile compounds emitted from a different stage of Medfly using stable isotope 13C6-glucose. Gas Chromatography (GC) technique coupled with Flame Ionization Detection (FID) and gas chromatography with mass spectrometry (GC-MS) for identification of VOCs was employed. Head Space-Solid Phase Micro Extraction HSSPME method with Three-phase fiber 50/30 µm divinylbenzene/carboxen/ polydimethylsiloxane (DVB/CAR/PDMS) was used. The results showed that there are different chemicals emitted in a different stage of Medfly (Larvae, pupae, and adults M/F) especially in the adult stage. GC-MS detected 27 compounds from larvae, 23 compounds from pupae and 29 compounds from adults. These different VOCs emitted in different stages of Medfly were clearly displayed, and a broad range of emitted volatile compounds was successfully described. The characterization of release patterns could be useful tool for the selection of compounds and for further investigated in biological studies to understand of the key semi-chemicals involved in medfly behaviour.

Consumer Preferences for Traditional, Neonicotinoid-free, Bee-friendly, or Biological Control Pest Management Practices on Floriculture Crops

Neonicotinoids have recently been implicated by the media as a contributing factor to the decline of honey and bumblebees. We sought to better understand consumer perceptions and willingness to pay for traditional, neonicotinoid-free, bee-friendly, or biological control pest management practices as growers may seek alternative management practices to systemetic insecticides. We conducted a nationwide Internet survey (n = 3082), where consumers answered attitudinal, comprehension, likelihood-to-buy, and demographical questions about indoor (marketed in 10-cm pots) and outdoor (marketed in 30-cm hanging baskets or 10-cm pots) floriculture products. The likelihood-to-buy questions were analyzed using conjoint analysis to determine which attributes had the greatest part-worth scores or which ones were viewed most positively by survey respondents. Of the total participants, 65.1% (n = 2002) of the subjects had purchased an annual flowering plant in the 12 months before the survey. Respondents reported that the most important plant health and appearance factors that affect their purchasing decisions were that the flowering plants have no plant damage, while the second most important factor was that plants have no insects on them. The least important factor in the ranking of stated importance was that no neonicotinoid insecticides were used during the production of the plant. This finding may have resulted from 56.6% of all participants who reported that they did not understand the term. For those who viewed the indoor 10-cm flowering plants (n = 1052), the plant species accounted for 41.2% of the decision to purchase the plant, followed by production type (32.8%) and price (26.0%). All three product attributes were of equal importance to the subjects who viewed the outdoor 10-cm flowering plants (n = 1024), whereas only price had a lower relative importance when compared with production type and species for those who viewed the 30-cm hanging baskets (n = 1006). Across all three studies, use of the term “bee-friendly” had the greatest economic value because it had the highest part-worth utility score, or the greatest willingness-to-buy. For the subjects who viewed the outdoor plants, “bee-friendly” and “use of beneficial insects” had greater economic value (with positive part-worth utility scores), but “neonicotinoid-free” and “traditional insect control” both had negative part-worth utility scores, indicating they were valued less and detracted from the dollar value of the plant. The term “bee-friendly” was worth up to five times more to those respondents that had bought a plant in the last 12 months compared with those who had not. Therefore, if ornamental plants are labeled with pest management practices, most consumers value the term “bee-friendly” more and will likely discount products labeled “neonicotinoid-free.”

Industrial Production of Bacillus Thuringiensis Based Bio-Insecticide: Which Way Forward?

Considering long term negative effect of chemical insecticides on the environment and human health, globally biological pest management has been promoted. Bacillus thuringiensis (Bt) is mostly explored and commercially successful microbial insecticide. According to a report, it constitutes almost 2% of insecticide market [1]. There are at least 32 companies involved in Bt based bio-insecticide business [2]. Microbiologically, Bt is gram-positive, facultative anaerobic bacterium most common habitats of which are soil, water or plant surfaces [3]. It can produce almost nine distinct types of toxins, among them δendotoxin, which is toxic to a range of insects, is mostly studied for insecticidal application [3]. This type of toxin is also known as Cry protein or Cry toxin and belongs to a family of toxin called pore forming toxins. They can kill the larvae of different insect groups usually by forming pore in mid-gut cell membrane followed by celllysis [1]. There are at least 500 known cry gene sequences which are broadly divided into 67 groups named as Cry1 to Cry67 [1]. Expression of the genes encoding Cry toxin are controlled by certain RNA polymerase which is produced during sporulation. Cry toxin production, therefore, coincides with spore formation [2], and hence, achieving high spore count is one of the major targets of Bt fermentation.

Understanding Farmscapes and Their Potential for Improving IPM Programs

New pest management programs must strive to achieve sustained, improved crop production and profitable agriculture, while simultaneously conserving natural resources and protecting the environment. Redesigning farms to take advantage of natural biological control can improve the sustainability of integrated pest management programs. A technique common in this approach to pest management is farmscaping, which refers to the arrangement or configuration of plants that promote biological pest management by attracting and sustaining beneficial organisms. Farmscaping is an ecologically based, whole-farm approach to enhancing the efficacy and local abundance of arthropod natural enemies through modification of the environment. However, by adding these resources back to simplified agriculture systems, they provide numerous other ecosystem services such as erosion control, reduced runoff, esthetic benefits, increased revenue, nutrient management, pollination services, soil health, as well as improved pest suppression. Herein, we discuss the strategy of farmscaping, review the theory of how it can improve pest management, and discuss the practicalities and risks involved in incorporating farmscapes into integrated pest management programs.

Modern Stored-Product Insect Pest Management

Abstract Stored-product entomologists have a variety of new monitoring, decision-making, biological, chemical, and physical pest management tools available to them. Two types of stored-product insect populations are of interest: insects of immediate economic importance infesting commodities, and insects that live in food residues in equipment and facilities. The sampling and control methods change as grain and grain products move from field to consumer. There are also some changes in the major insect pest species to take into consideration. In this review, we list the primary insect pests at each point of the marketing system, and indicate which sampling methods and control strategies are most appropriate. Economic thresholds for insect infestation levels developed for raw commodity storage, processing plants, and retail business allow sampling-based pest management to be done before insect infestations cause economic injury. Taking enough samples to have a representative sample (20-30 samples) will generally provide enough information to classify a population as above or below an economic threshold.

Mathematical study of stage-structured pests control through impulsively released natural enemies with discrete and distributed delays

Many insect pest species have two major stages in their life-history: an immature larval stage and a mature adult stage. The immature larval stage may have a significant duration, during which the insect may not be the same natural predators as in the adult stage. Keeping this biological background in mind, we propose a stage-structured natural enemy–pest model with distributed and discrete delays for natural enemy and pest, respectively. It is also assumed that the natural enemies are released in an impulsive manner. The global attractivity of the pest-extinction periodic solution of the system is obtained using comparison techniques on impulsive delay differential equations. Furthermore, the permanence conditions for the coexistence of the species are explored, which indicates that the maturation time delay and the amount of natural enemies released in a pulse can affect the dynamics of the system. The threshold values for maturation delay of pest and the releasing amount natural enemy are obtained for extinction and permanence of the species. Finally, numerical simulation is given in support of validation of the theoretical results to provide a strategic basis for the biological pest management.