Methods Of Insect Pest Control Research Articles

Knockdown of MAPK p38-linked genes increases the susceptibility of Chilo suppressalis larvae to various transgenic Bt rice lines

Bacillus thuringiensis (Bt) toxins have provided exceptional control of agricultural insect pests, however, over reliance on the proteins would potentially contribute to the development of field tolerance. Developing new sustainable insect pest control methods that target the mechanisms underlying Bt tolerance can potentially support the Bt control paradigm while also providing insights into basic insect physiology. The MAPK p38 pathway is strongly associated with Bt tolerance in Chilo suppressalis, a major pest of rice. To gain insights into how this pathway impacts tolerance, high-throughput screening of C. suppressalis larval midguts initially identified eight novel target genes. Increased larval sensitivity to the transgenic cry1Ca rice strain T1C-19 was observed following RNA interference-mediated knockdown of four of the genes, Cscnc, Csgcp, Cszfp26 and CsZMYM1. Similar enhanced sensitivity to the TT51 (expressing Cry1Ab/1Ac) and T2A-1 (expressing Cry2Aa) transgenic rice lines occurred when Cszfp26 and CsZMYM1 were knocked down. All four target genes are downstream of the MAPK p38 pathway but do not participate in negative feedback loop of the pathway. These results implicate Cscnc, Csgcp, Cszfp and CsZMYM1 in the C. suppressalis transgenic cry1Ca rice tolerance mechanism regulated by MAPK p38. These findings further enhance our understanding of the MAPK p38-dependent molecular mechanisms underlying Bt tolerance in C. suppressalis and open new avenues of tolerance management to develop.

Biocontrol effect of entomopathogenic fungi Metarhizium anisopliae ethyl acetate-derived chemical molecules: An eco-friendly anti-malarial drug and insecticide.

Insect pests represent a major threat to human health and agricultural production. With a current over-dependence on chemical insecticides in the control of insect pests, leading to increased chemical resistance in target organisms, as well as side effects on nontarget organisms, the wider environment, and human health, finding alternative solutions is paramount. The employment of entomopathogenic fungi is one such potential avenue in the pursuit of greener, more target-specific methods of insect pest control. To this end, the present study tested the chemical constituents of Metarhizium anisopliae fungi against the unicellular protozoan malaria parasite Plasmodium falciparum, the insect pests Anopheles stephensi Listen, Spodoptera litura Fabricius, and Tenebrio molitor Linnaeus, as well as the nontarget bioindicator species, Eudrilus eugeniae Kinberg. Fungal crude chemical molecules caused a noticeable anti-plasmodial effect against P. falciparum, with IC50 and IC90 values of 11.53 and 7.65 µg/mL, respectively. The crude chemical molecules caused significant larvicidal activity against insect pests, with LC50 and LC90 values of 49.228-71.846 µg/mL in A. stephensi, 32.542-76.510 µg/mL in S. litura, and 38.503-88.826 µg/mL in T. molitor at 24 h posttreatment. Based on the results of the nontarget bioassay, it was revealed that the fungal-derived crude extract exhibited no histopathological sublethal effects on the earthworm E. eugeniae. LC-MS analysis of M. anisopliae-derived crude metabolites revealed the presence of 10 chemical constituents. Of these chemicals, three major chemical constituents, namely, camphor (15.91%), caprolactam (13.27%), and monobutyl phthalate (19.65%), were highlighted for potential insecticidal and anti-malarial activity. The entomopathogenic fungal-derived crude extracts thus represent promising tools in the control of insect pests and malarial parasites.

Bioinsecticidal efficacy of Eucalyptus camaldulensis (Dehn) and Hyptis suaveolens (L.) Poit. leaf extracts on Callosobruchus maculatus (Cowpea weevil)

The modern method of controlling insect pests, using synthetic insecticides has caused serious problems to human health and the environment. Hence, the need for alternative, cheap, readily available and acceptable insect pest control methods, among which are the use of plant leaf extracts. The aim of this study was to determine the bioinsecticidal efficacy of Eucalyptus camaldulensis and Hyptis suaveolens against cowpea weevils (Callosobruchus maculatus). The bioassay of the powdered methanol extracts of leaves of E. camaldulensis and H. suaveolens was carried varying quantities (3 g, 6 g, 9 g and 12 g) of powdered extracts of the respective plant samples were mixed separately with 50 g of cowpea. Synthetic insecticide, Al2(PO4)3 was used as positive control while the negative control contained no treatment. Proximate compositions of the treated and untreated cowpeas were done using standard procedures while the extracts were characterized using Gas Chromatography-Mass Spectroscopic. Although mortality rates of the C. maculatus in presence of the extracts did not follow any dose-dependant trend, the respective dosages used for treatments inhibited the growth and activities of Callosobruchus maculatus. A high rate of seed damage was observed in the untreated cowpea seeds. Gas Chromatography-Mass Spectroscopy of the extracts identified the presence of seven potential insecticidal compounds (Bargamotene, Globulol, Humulene, Linolein, Prasterone, Terpinen-4-ol and Traumatic acid) in Hyptis suaveolen. In the Eucalyptus camaldulensis extract, 13 potential insecticidal compounds (Barosma camphor, Carvacrol, Carbazon, Irone, Isoborneol, 5-methyl, 1,4-Naphthoquinone, Oleic Acid, Phytol, Piperitone, Pyrazole-3-carboxylic acid, Terpinen-4-ol, Viridiflorol) were identified. The bioinsecticidal activities of these plant extracts could be attributed to the presence of phytochemicals and isolated insecticidal compounds.

Role of adipokinetic hormone in the Colorado potato beetle, Leptinotarsa decemlineata infected with the entomopathogenic nematode Steinernema carpocapsae

The effects of the entomopathogenic nematode Steinernema carpocapsae on the Colorado potato beetle (CPB) Leptinotarsa decemlineata and the involvement of adipokinetic hormone (AKH) in the responsive reactions were examined in this study. It was observed that nematode application doubled the amount of AKH (Peram-CAH-I and Peram-CAH-II) in the central nervous system of L. decemlineata, indicating mobilization of anti-stress reactions in the body. Furthermore, the external co-application of Peram-CAH-II with the nematode significantly increased beetle mortality (5.6 and 1.8 times, 1 and 2 days after application, respectively). The mechanism underlying this phenomenon was investigated. As the effect on gut characteristics was equivocal, it was assumed that the nematodes profited from the observed mobilization of metabolites from the fat body into the Peram-CAH-II-induced hemolymph. This phenomenon supplied nematodes with a more nutrient-dense substrate on which they propagated. Furthermore, Peram-CAH-II lowered vitellogenin expression in the fat body, particularly in males, thus limiting the anti-pathogen defense capacity of the protein. However, there could be other possible mechanisms underpinning this chain of events. The findings could be theoretically intriguing but could also aid in developing real insect pest control methods in the future.

Efficacy of Diatomaceous Earth and Vitellaria paradoxa Seed Oil in Storage of Cowpea under Ventilated and Non-ventilated Conditions

Storage of cowpea is highly constrained by insect pest infestation and losses caused by the cowpea weevil (Callosobruchus maculatus, F.) are high. Several methods have been used over the years to protect cowpea grains in storage, but the use of synthetic insecticides is very dominant and this has led to problems, such as the killing of non-target species, user hazards, harmful food residues, and evolution of resistance to chemicals. A search for alternative insect pest control methods which are relatively less harmful to the user and cheaper has become essential. The effectiveness of Diatomaceous earth (DE) and Vitellaria paradoxa seed oil (VPSO) for cowpea storage in polypropylene and jute bags under ventilated and non-ventilated storeroom conditions were investigated over three months period. Crude DE was applied at a dose rate of 1 g/kg of cowpea and a diluted concentration (10% v/v) of VPSO of 400 mL was mixed with 8 kg of cowpea. Live insect count, dead insect count, and germination percentage were assessed weekly while proximate analysis was carried out before and after storage. Mean live insect count increased in the ventilated store-room from 0.67±0.34 to 36.13±19.51insects/kg after 1 month and 3 months of storage respectively for untreated cowpea. Insect population in treated samples increased from 0.38±0.26to 24.78±23.33, and from 0.17±0.30 to 10.75±5.27 for DE and VPSO treated samples, respectively. In the non-ventilated storeroom, insect population increased from 0.33±0.26 to 36.96±19.09 for untreated cowpea, 0.17±0.20 to 33.08±30.07 for DE and 0.21±5.63 to 8.17±11.30 for VPSO treated cowpea. Based on insect count, both treatments were very effective in controlling cowpea weevil in the first two months of storage, however their potency reduced by the third month. The potency of DE deteriorated faster compared to VPSO however, DE treated cowpea was most effective for retaining seed germination in both ventilated and non-ventilated storerooms. Proximate analysis showed that cowpea treated with both treatments had similar nutrient composition after storage. Diatomaceous earth and Vitellaria paradoxa seed oil have potentials in their raw form for short term insect pest control in the storage of cowpea.

Assessment of pesticide residues level in watermelon fruits [Citrullus lanatus (Thunberg) Matsumura and Nakai] in Lower, Central and Upper Badibou Districts in North Bank Region, of the Gambia

Field and laboratory studies were conducted late 2019 in three districts of the Gambia’s North Bank Region; namely, Central Badibou, Lower Badibou and Upper Badibou to ascertain the pesticide residue level in watermelon fruit, determine the insect pest control methods, types of pesticide, frequency of application, and pre-harvest interval observed. Multistage sampling technique was used in selecting the research respondents. Eighty-five (85) farmers were identified; forty-five (45) were randomly selected as research respondents. Data was collected using structured questionnaires. SPSS Software was used to analyse the questionnaires and Gas Chromatograph to determine the pesticide residue level. Data obtained were analysed and compared with the European Union Maximum Residue Limit (MRL). The results of the analysis revealed that the farmers used chemical control method in watermelon production, and applied at frequency of once in every two weeks. Furthermore, the results indicated that the chemical applied at flowering stage and the pre-harvest interval (17-21 days) ranked the highest. The pesticides residues found in the watermelon samples were Dimethoate, Profenophos, Dicofol, Cypermethrin, Lambda-cyhalothrin, Permethrin and Deltamethrin and most were above the MRL. The presence of pesticides residues in the watermelon samples calls for strict regulation on the use of pesticides on watermelon. Further study is recommended in other fruits and vegetables grown in the country especially in the studied region.

Plant Allelochemicals as Sources of Insecticides.

Simple SummaryDue to the banning of many synthetic pesticides, current intensive farming systems require us to develop new approaches to integrated pest management. Devastating pests rarely occur in the wild and medicinal plants because of effective defense mechanisms. In contrast, only some of these defense mechanisms are found in cultivated crops. Biocidal compounds, derived from various wild and medicinal plants, are bioactive, biodegradable and constitute an ecological method for the successful management of insect pests. Therefore, an extensive study of various wild crops and some weeds is essential to identify new and potential plant species with insecticidal compounds. In this review, we describe the role of plant-derived biochemicals that are toxic to insect pests. Biotic stress in plants caused by insect pests is one of the most significant problems, leading to yield losses. Synthetic pesticides still play a significant role in crop protection. However, the environmental side effects and health issues caused by the overuse or inappropriate application of synthetic pesticides forced authorities to ban some problematic ones. Consequently, there is a strong necessity for novel and alternative insect pest control methods. An interesting source of ecological pesticides are biocidal compounds, naturally occurring in plants as allelochemicals (secondary metabolites), helping plants to resist, tolerate or compensate the stress caused by insect pests. The abovementioned bioactive natural products are the first line of defense in plants against insect herbivores. The large group of secondary plant metabolites, including alkaloids, saponins, phenols and terpenes, are the most promising compounds in the management of insect pests. Secondary metabolites offer sustainable pest control, therefore we can conclude that certain plant species provide numerous promising possibilities for discovering novel and ecologically friendly methods for the control of numerous insect pests.

SUSCEPTIBILITY OF SOME SOYBEAN VARIETIES TO CERTAIN PIERCING-SUCKING INSECTS UNDER THE FIELD CONDITIONS OF NORTH DELTA

Tolerant varieties to insect species represent one of the simplest and important methods of insect pest control to minimize the insecticide hazards. Therefore, susceptibility of five soybean varieties to infestation with some piercing-sucking insects: aphids, Aphis spp.; whitefly, Bemisia tabaci (Genn.) and leafhoppers, Empoasca spp. were evaluated at Sakha Agric. Res. Station Farm, Kafr El-Sheikh Governorate during 2016 and 2017 seasons. The obtained results showed significant differences in susceptibility between the tested soybean varieties to the mentioned insects for every season and from season to another. In general, the population density of whitefly and aphids were higher in the first season than the second one, while the reverse was found for leafhoppers. Based on the grand mean number of the two study seasons, variety Crawford was significantly the most infested variety to infestation with leafhoppers and aphids, while the least infested variety for aphids was Giza35 and for leafhoppers was Hybrid30. As for the whitefly, Giza35 significantly was the most infested variety, while Crawford was the least infested one. In respect to the resistance status of the tested varieties to the insects, Crawford and Hybrid30 showed susceptiblity to aphid infestation, while the other varieties exhibited low resistance. Giza111 and Giza35 appeared as susceptible for whitefly, Giza21 and Hybrid30 showed low resistance, while Crawford was moderately resistant. Concerning leafhoppers, Giza111 and Crawford were susceptible. Giza21 showed low resistance, while Hybrid30 was moderately resistant.

Plasma-based organism evaluation equipment using atmospheric-pressure plasma jets: Efficacy for controlling insect pests

Abstract Alternative insect pest control methods are necessary for efficient pest management with reduced dependency on pesticides. Here, we report the biological responses of several insect species to, and the insecticidal efficacy of, reactive oxygen species (ROS) generated using atmospheric-pressure plasma jets. Plasma-based organism evaluation equipment (PBOEE) consisting of a plasma-generating acrylic chamber, plasma-maintaining acrylic chamber, and plasma efficacy evaluation container was developed. The PBOEE system enabled determination of the insecticidal efficacy of ROS free from the adverse effects of high temperature; moreover, four different exposures could be achieved within one run. The biological responses of five major insect pests (Aphis gossypii, Bemisia tabaci, Helicoverpa armigera, Tetranychus kanzawai, and Thrips palmi) were assessed, with a focus on knockdown time, recovery time, and median lethal time (LT50). With short-term exposure (

Sickly Sweet: Insecticidal Polyols Induce Lethal Regurgitation in Dipteran Pests.

Polyols are commonly used in food and medicines as sweeteners and preservatives but may also have insecticidal properties against some species of Diptera. Here we compared the insecticidal activity and feeding response of glycerol and propylene glycol (PG) on two tephritids: Anastrepha ludens and Anastrepha obliqua, and the drosophilid Drosophila suzukii. First, flies were exposed to solutions of 50% sucrose and the two polyols at concentrations of 1.67 M, 2.78 M and 4.18 M for 24 h and then observed at 24 h intervals for a period of three days. Both polyols elicited strong regurgitation behavior in the three flies and killed them. Regurgitation apparently also reduced flies’ body weight, and this was particularly apparent in insects that fed on 4.18 M PG solutions. A high percentage of individuals exposed to PG solutions perished after 72 h. The number of proboscis extensions, which is associated with feeding preference, was lower in the 4.18 M polyols + sucrose mixtures than in the 50% sucrose solution. Glycerol had a lower insecticidal effect in Anastrepha spp. and very little insecticidal effect in D. suzukii. Finally, elevated regurgitation and mortality was confirmed in A. ludens treated with 1.0–2.78 M of erythritol plus sucrose. Our results demonstrate that PG, and to a lower extent glycerol, have the potential for being used as a safer method of insect pest control. The hyper-regurgitation response may contribute to the insecticidal properties of these polyols in Diptera.

Assessment of the pure sowing of different legumes and in mixtures with grass on productivity and damage level by Sitona spp. and Otiorrhynchus ligustici (LINNAEUS, 1758) (Coleoptera: Curculionidae)

Abstract This work examined the impact on productivity of the cultivation system of perennial legumes such as sainfoin (Onobrychis viciifolia), bird’s-foot trefoil (Lotus corniculatus) and alfalfa (Medicago sativa), grown pure and in binary mixtures with cocksfoot and on damage caused by root pests of Sitona spp. and Otiorrhynchus ligustici. It was found that the productivities of aboveground and root biomasses in binary mixtures were significantly higher compared to the corresponding legume monocultures on average by 30.7 and 39.7% respectively in mixtures with sainfoin, by 15.0 and 73.1% in mixtures with bird’s-foot trefoil, and by 18.7 and 49.6% in mixtures with alfalfa. The weight of dry aboveground biomass in the pure leguminous crops slightly exceeded that of the corresponding leguminous components in the mixtures, whereas the productivity of cereal plants in mixed crops was significantly lower compared to the pure cocksfoot on average by 38.5, 47.0 and 51.7% in mixtures of sainfoin, bird’s-foot trefoil and alfalfa respectively. A similar tendency was observed with regard to dry root biomass. Damage to nodules by Sitona larvae in mixtures decreased significantly: on average by 33.5% (sainfoin + cocksfoot), by 50.3% (bird’s-foot trefoil + cocksfoot) and by 55.6% (alfalfa + cocksfoot) compared to pure grown legumes. The damage caused by Otiorrhynchus ligustici, as expressed by the length of gnawed furrows, in the mixtures with sainfoin, bird’s-foot trefoil and alfalfa decreased considerably - by 12.5, 77.8 and 59.5%, respectively - compared to the pure crops. The damage caused by the аlfalfa snout beetle had the most significant negative effect on aboveground and root biomass productivities. Mixed cultivation systems of forage crops are an economically and ecologically sustainable method of insect pest control.

The insecticidal potential of venom peptides.

Pest insect species are a burden to humans as they destroy crops and serve as vectors for a wide range of diseases including malaria and dengue. Chemical insecticides are currently the dominant approach for combating these pests. However, the de-registration of key classes of chemical insecticides due to their perceived ecological and human health risks in combination with the development of insecticide resistance in many pest insect populations has created an urgent need for improved methods of insect pest control. The venoms of arthropod predators such as spiders and scorpions are a promising source of novel insecticidal peptides that often have different modes of action to extant chemical insecticides. These peptides have been optimized via a prey-predator arms race spanning hundreds of millions of years to target specific types of insect ion channels and receptors. Here we review the current literature on insecticidal venom peptides, with a particular focus on their structural and pharmacological diversity, and discuss their potential for deployment as insecticides.

Characterization of a Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae) – derived chitinase and its potential for pest control

The larval endoparasitoid Toxoneuron nigriceps (Viereck) (Hymenoptera: Braconidae) has a toolbox of biological weapons to secure for host colonization and the successful parasitization of its host Heliothis virescens (F.) (Lepidoptera: Noctuidae). The cDNA of a putative chitinase has been previously isolated and initially characterized from teratocytes of this parasitoid among the plethora of molecules available in the venom and calyx fluids injected by females, oral and/or anal secretions released by the parasitoid larvae and/or produced by the expression of genes of the symbiotic associated polydnavirus. This putative chitinase has been initially associated with the host cuticle digestion to allow for parasitoid egression and with the asepsis of the host environment, acting as an antimicrobial. As chitinases are commonly expressed in plants against plant pathogens, the chitinase derived from the teratocytes of T. nigriceps is a potential tool for the development of insect pest control methods based on the disruption of the perithrophic membrane of herbivores. Therefore, we aimed to characterize the activity of the putative chitinase from teratocytes of T. nigriceps (Tnchi) produced using the Escherichia coli expression system and its potential to control H. virescens larvae when expressed into transgenic tobacco plants. The purified E. coli-produced Tnchi protein showed no chitinolitic activity, but was active in binding with colloidal and crystalline chitins in water and with colloidal chitin in buffered solution (pH=6.74). Transgenic tobacco plants showed no enhanced chitinolitic activity relative to control plants, but survival of three-day old larvae of H. virescens was severely affected when directly fed on transgenic tobacco leaves expressing the recombinant Tnchi protein. Some properties of the Tnchi protein and the potential use of Tnchi-transgenic plants to control plant pests are discussed.

Phenotypic impacts of PBAN RNA interference in an ant, Solenopsis invicta, and a moth, Helicoverpa zea

Insect neuropeptide hormones represent more than 90% of all insect hormones. The PBAN/pyrokinin family is a major group of insect neuropeptides, and they are expected to be found from all insect groups. These species-specific neuropeptides have been shown to have a variety of functions from embryo to adult. PBAN is well understood in moth species relative to sex pheromone biosynthesis, but other potential functions are yet to be determined. Recently, we focused on defining the PBAN gene and peptides in fire ants in preparation for an investigation of their function(s). RNA interference (RNAi) technology is a convenient tool to investigate unknown physiological functions in insects, and it is now an emerging method for development of novel biologically-based control agents as alternatives to insecticides. This could be a paradigm shift that will avoid many problems associated with conventional chemical insecticides. In this study, we selected the PBAN gene and its neuropeptide products as an RNAi target from two insect groups; a social insect, the fire ant (Solenopsis invicta) and a non-social insect, the corn earworm (Helicoverpa zea). Both insects are economically important pests. We report negative impacts after PBAN dsRNA treatment to suppress PBAN gene transcription during developmental and adult stages of both species, e.g. increased adult and larval mortality, delayed pupal development and decreased sex pheromone production in the moth. This is an important first step in determining the multiple functions of the PBAN gene in these two insects. This work illustrates the variety of phenotypic effects observed after RNAi silencing of the PBAN gene and suggests the possibility of novel biologically-based insect pest control methods.

Short-term anoxic conditioning hormesis boosts antioxidant defenses, lowers oxidative damage following irradiation and enhances male sexual performance in the Caribbean fruit fly, Anastrepha suspensa

Most organisms are repeatedly exposed to oxidative stress from multiple sources throughout their lifetimes, potentially affecting all aspects of organismal performance. Here we test whether exposure to a conditioning bout of anoxia early in adulthood induces a hormetic response that confers resistance to oxidative stress and enhances male sexual performance later in life in the Caribbean fruit fly, Anastrepha suspensa. Anoxic conditioning of adults prior to emergence led to an increase in antioxidant capacity driven by mitochondrial superoxide dismutase and glutathione peroxidase. When exposed to gamma irradiation, a strong oxidative stressor, males that received anoxic conditioning had lower lipid and protein oxidative damage at sexual maturity. Anoxia conditioning led to greater male sexual competitiveness compared with unconditioned males when both were irradiated, although there was no effect of anoxia conditioning on mating competitiveness in unirradiated males. Anoxia also led to higher adult emergence rates and greater flight ability in irradiation-stressed flies while preserving sterility. Thus, hormetic treatments that increased antioxidant enzyme activity also improved male performance after irradiation, suggesting that antioxidant enzymes play an important role in mediating the relationship between oxidative stress and sexual selection. Furthermore, our work has important applied implications for the sterile insect technique (SIT), an environmentally friendly method of insect pest control where males are sterilized by irradiation and deployed in the field to disrupt pest populations via mating. We suggest that hormetic treatments specifically designed to enhance antioxidant activity may produce more sexually competitive sterile males, thus improving the efficacy and economy of SIT programs.

Factors determining the use of botanical insect pest control methods by small-holder farmers in the Lake Victoria basin, Kenya

A farm survey was conducted in three representative administrative districts of the Lake Victoria Basin (LVB), Kenya to document farmers’ indigenous knowledge and the factors that influence the use of botanicals instead of synthetic insecticides in insect pest management. A total of 65 farm households were randomly sampled using stratified sampling procedure. The maximum likelihood log model was used to determine factors that influence use of botanical and synthetic insect pest control methods (PCM). Results revealed that female gender as household head (HH) and age significantly (P < .001) increased the likelihood of a household using botanical PCM in the field by 0.15 and 0.021, respectively. In storage, female gender and severity of pest infestation significantly (P < .001) increased the probability of a household using botanical insecticide by 0.814 and 0.738, respectively. On the contrary, education of HH (0.342) and ownership of title to land (0.512) significantly (P < .001) reduced the likelihood of using botanical PCM in the field, while traditional rank (0.910) and cash rank (0.744) of the crops reduced the likelihood of using botanical insecticides in the store. With respect to synthetic pesticides, gender (3.407), area cultivated (0.295) and expected yield (5.315) significantly (P < .001) reduced likelihood of their use in the field, while food rank (3.967) reduced the probability of use in storage. In storage, female gender, crop type, food and traditional rank of crops were also the most important factors determining the use of botanical control methods. In conclusion, the study established that female gender, literacy levels, wealth endowments in form of land and old age are key determinants of botanical insecticides use in small-holder farming systems in the LVB, Kenya. It is recommended that the Government of Kenya enacts policies that empower youth and female gender economically in subsistence farming with the aim of improving their educational levels and farming skills to modernize agriculture among the rural communities. Key words: Botanical, synthetic pesticide, insects, pest control method, determinants, small-holder farmers.

Farmers' knowledge and experience of indigenous insect pest control in the Eastern Cape province of South Africa

This study was conducted to document the knowledge of small-scale farmers regarding indigenous insect pest control methods in the Eastern Cape, South Africa. A survey was carried out using a combination of questionnaires and Focus Group Discussions. More than 70% of the farmers were literate, with both males (46%) and females (54%) actively involved in farming. 58% of the farmers were pensioners. Crops cultivated included maize and vegetables. The level of pest awareness among the farmers was high (92%), with over 70% of farmers relying on synthetic insecticides for pest control. 63% percent of the farmers were, however, were aware of indigenous methods of insect pest control. Unfortunately, such methods are currently being neglected and knowledge of their application was found to be eroding. It is necessary to re-popularise the indigenous methods of insect control given that they are mostly safer and cheaper than synthetic insecticides. Keywords : farmers' knowledge; indigenous insect control Indilinga Vol. 5 (2) 2006: pp. 167-175

Sterile insect release method as a control measure of insect pests: A mathematical model

Recently non-conventional approaches of pest control are getting much more importance in different parts of the world. The main reason behind this is the long list of side effects of conventional approaches (use of pesticides etc.). The present paper focuses on one such extremely useful method of insect pest control, namely the Sterile Insect Release Method (SIRM), by using a mathematical model. A blend of dynamical behaviours of the model is studied critically, which, in turn, indicates the relevance of the method. The effect of uncertain environmental fluctuations on both fertile and sterile insects is also investigated. Our analytical findings are verified through computer simulation. Some important restrictions on the parameters of the system are mentioned, which may be implemented for a better performance of SIRM.

Modelling selection for resistance to methods of insect pest control in combination

The development of resistance to insecticides is now widespread among insects. Other methods of pest control are also potentially at risk of encountering resistance. A modelling approach is presented here to evaluate the effects of combining methods of insect pest control on the selection for resistance to the control methods. This analysis is based on partitioning the total mortality acting on a population into its constituent components from all known sources, and these are related to selection for resistance. When two control methods are used in combination, selection for resistance against the two is a linear function if the two don't interact, otherwise it may be sublinear or supralinear. A specific example is presented using a model of the Olive fruit fly (Dacus oleae Gmel.) and employing food-baited and pheromone-baited traps for control. The control methods that appear least likely to encounter resistance are natural enemies and the use of pheromone traps for male annihilation. These should be integrated into a control program where possible to minimize the development of resistance to other control methods being used.

Combining methods of insect pest control: Partitioning mortality and predicting complementarity

SummaryAn age‐structured population model is used as a vehicle for presenting a method for the analysis of interactions between pairs of insect pest control methods. This analysis is based on partitioning the total mortality acting on a population into its constituent components from all known sources. Pairwise critical mortality curves are then constructed which represent the combined mortality required for eradicating the pest population. Effort curves are then constructed from computing the mortality resulting from a given amount of control effort. The convolution of the critical mortality curves and the effort curves then yields the isoclines formed by the effort required of two control methods in combination to achieve eradication. This analysis allows the prediction of either synergism or interference between the control methods and also helps explain patterns observed in previous modelling of such combinations of pest control methods.