Pest Control Approaches Research Articles

Erythritol, a non-nutritive sugar alcohol sweetener and the main component of truvia®, is a palatable ingested insecticide.

Insecticides have a variety of commercial applications including urban pest control, agricultural use to increase crop yields, and prevention of proliferation of insect-borne diseases. Many pesticides in current use are synthetic molecules such as organochlorine and organophosphate compounds. Some synthetic insecticides suffer drawbacks including high production costs, concern over environmental sustainability, harmful effects on human health, targeting non-intended insect species, and the evolution of resistance among insect populations. Thus, there is a large worldwide need and demand for environmentally safe and effective insecticides. Here we show that Erythritol, a non-nutritive sugar alcohol, was toxic to the fruit fly Drosophila melanogaster. Ingested erythritol decreased fruit fly longevity in a dose-dependent manner, and erythritol was ingested by flies that had free access to control (sucrose) foods in choice and CAFE studies. Erythritol was US FDA approved in 2001 and is used as a food additive in the United States. Our results demonstrate, for the first time, that erythritol may be used as a novel, environmentally sustainable and human safe approach for insect pest control.

Screening of liquid media and fermentation of an endophytic Beauveria bassiana strain in a bioreactor.

A novel approach for biological control of insect pests could be the use of the endophytic entomopathogenic Beauveria bassiana isolate ATP-02. For the utilization of the endophyte as a commercial biocontrol agent, the fungus has to be mass-produced. B. bassiana was raised in shake flask cultures to produce high concentrations of total spores (TS), which include blastospores (BS) and submerged conidiospores (SCS). The highest concentration of 1.33×109 TS/mL and the highest yield of 5.32×1010 TS/g sucrose was obtained in the TKI broth with 5% sugar beet molasses which consists of 50% sucrose as a carbon source. In spite of the lower sugar concentration (2.5%) the amount of TS could be increased up to 11-times in contrast to the cultivation with 5% sucrose. The scale-up to a 2 L stirred tank reactor was carried out at 25°C, 200–600 rpm and 1 vvm at pH 5.5. A TS yield of 5.2×1010 TS/g sucrose corresponding to a SCS yield of 0.2×1010 SCS/g sucrose was obtained after 216 h. With regards to the culture medium the cost of 1012 TS amounts to 0.24 €. Plutella xylostella larvae, which were fed with oilseed rape leaves treated with spores from fermentation resulted in 77 ± 5% mortality. Moreover, spores from submerged cultivation were able to colonize oilseed rape leaves via leaf application. This is the first report of fermentation of an endophytic B. bassiana strain in a low-cost culture medium to very high yields of TS.

Molecular characterization and functional analysis of a putative sex-peptide receptor in the tobacco cutwormSpodoptera litura(Fabricius, 1775) (Lepidoptera: Noctuidae)

The sex-peptide receptor (SPR) acts in Drosophila females to detect male sex-peptide (SP) and trigger changes in female behaviour. Further study on SPR and its ligand family from different taxa will not only provide insight into ligand–receptor coevolution but also facilitate finding new approaches for pest control. Our previous studies on the tobacco cutworm Spodoptera litura (Fabricius, 1775) showed that mating usually results in marked changes in female behaviour and determined that factors from male accessory gland (MAG) secretions play a key role in such switches in females after mating. In the present study, we report the cloning of a transcript encoding a G-protein-coupled receptor from S. litura. This 3 kb transcript contains an ORF encoding a protein of 421 amino acids that shared significant amino acid identity to the SPR identified in Drosophila. Real-time PCR showed that the expression levels of the receptor in adults correlate well with the process of sexual maturation and mating rates; mating resulted in distinct sexual dimorphic differences in gene expression. Our results suggest that this gene is involved in mediating reproductive behaviour in adult moths. To test the hypothesis, we further studied the possible function of this receptor (SplSPR) on mediating female post-mating behaviour by using RNA interference (RNAi) and treatment with MAG secretions. RNAi reduced the expression levels of SplSPR by 65–88% and significantly prevented the effect of MAG secretions. Injection of MAG secretions causes normal virgin females to behave as though they had mated (they are sexually unreceptive and start to lay eggs), whereas SPR RNAi females fail to respond to MAG factors and continue to show virgin behaviours (lay very few eggs and copulate readily). These results support the hypothesis that the SplSPR functions in mediating female post-mating behaviour and the existence of an SP-like ligand in MAG secretions in S. litura.

Comparative metabolite profiling of foxglove aphids (Aulacorthum solani Kaltenbach) on leaves of resistant and susceptible soybean strains

Aphid infestations can cause severe decreases in soybean (Glycine max [L.] Merr.) yield. Since planting aphid-resistant soybean strains is a promising approach for pest control, understanding the resistance mechanisms employed by aphids is of considerable importance. We compared aphid resistance in seven soybean strains and found that strain Tohoku149 was the most resistant to the foxglove aphid, Aulacorthum solani Kaltenbach. We subsequently analyzed the metabolite profiles of aphids cultured on the leaves of resistant and susceptible soybean strains using capillary electrophoresis-time-of-flight mass spectrometry. Our findings showed that the metabolite profiles of several amino acids, glucose 6-phosphate, and components of the tricarboxylic acid cycle were similar in aphids reared on Tohoku149 leaves and in aphids maintained under conditions of starvation, suggesting that Tohoku149 is more resistant to aphid feeding. Compared to susceptible strains, we also found that two methylated metabolites, S-methylmethionine and trigonelline, were either not detected or decreased in aphids reared on Tohoku149 plants. Since these metabolites function as important sulfur transporters in phloem sap and osmoprotectants involved in salt and drought stress, respectively, aphid-resistance is considered to be related to sulfur metabolism and methylation. These results contribute to an increase in our understanding of soybean aphid resistance mechanisms at the molecular level.

The Trojan female technique: a novel, effective and humane approach for pest population control

Humankind's ongoing battle with pest species spans millennia. Pests cause or carry disease, damage or consume food crops and other resources, and drive global environmental change. Conventional approaches to pest management usually involve lethal control, but such approaches are costly, of varying efficiency and often have ethical issues. Thus, pest management via control of reproductive output is increasingly considered an optimal solution. One of the most successful such 'fertility control' strategies developed to date is the sterile male technique (SMT), in which large numbers of sterile males are released into a population each generation. However, this approach is time-consuming, labour-intensive and costly. We use mathematical models to test a new twist on the SMT, using maternally inherited mitochondrial (mtDNA) mutations that affect male, but not female reproductive fitness. 'Trojan females' carrying such mutations, and their female descendants, produce 'sterile-male'-equivalents under natural conditions over multiple generations. We find that the Trojan female technique (TFT) has the potential to be a novel humane approach for pest control. Single large releases and relatively few small repeat releases of Trojan females both provided effective and persistent control within relatively few generations. Although greatest efficacy was predicted for high-turnover species, the additive nature of multiple releases made the TFT applicable to the full range of life histories modelled. The extensive conservation of mtDNA among eukaryotes suggests this approach could have broad utility for pest control.

Hybrid approach for pest control with impulsive releasing of natural enemies and chemical pesticides: A plant–pest–natural enemy model

The agricultural pests can be controlled effectively by simultaneous use (i.e., hybrid approach) of biological and chemical control methods. Also, many insect natural enemies have two major life stages, immature and mature. According to this biological background, in this paper, we propose a three tropic level plant–pest–natural enemy food chain model with stage structure in natural enemy. Moreover, impulsive releasing of natural enemies and harvesting of pests are also considered. We obtain that the system has two types of periodic solutions: plant–pest-extinction and pest-extinction using stroboscopic maps. The local stability for both periodic solutions is studied using the Floquet theory of the impulsive equation and small amplitude perturbation techniques. The sufficient conditions for the global attractivity of a pest-extinction periodic solution are determined by the comparison technique of impulsive differential equations. We analyze that the global attractivity of a pest-extinction periodic solution and permanence of the system are evidenced by a threshold limit of an impulsive period depending on pulse releasing and harvesting amounts. Finally, numerical simulations are given in support of validation of the theoretical findings.

Male Accessory Gland Secretions Modulate Female Post-Mating Behavior in the Moth Spodoptera litura

The study of male insects’ accessory gland (MAG) secretions will promote our understanding of reproductive strategies and their evolution, and will facilitate the development of new approaches for pest control. Here, we carried out a series of experiments to determine the functions of MAG secretions on modulating female post-mating behavior in the moth Spodoptera litura. Results showed that females injected with MAG secretions called and mated significantly less than controls in the night after treatment, which were independent of mechanical stimulation during mating and the presence of sperm. However, a successful mating resulted in a longer loss in sexual receptivity (lasting to the second night after mating). This study also demonstrated that MAG secretions not only triggered oviposition but also promoted egg development, which also were not dependent on mechanical stimulation during mating and the presence of sperm. MAG secretions also showed negative effect on female longevity, which may be because MAG secretions stimulate females to allocate more resources to egg development and oviposition, leaving fewer resources for survival. Results of this study also suggest that oviposition behaviors incur energy costs. The hypothesis that virgin females may conduct oosorption to prolong longevity is not supported.

Tea: Biological control of insect and mite pests in China

Tea is one of the most economically important crops in China. To secure its production and quality, biological control measures within the context of integrated pest management (IPM) has been widely popularized in China. IMP programs also provide better control of arthropod pests on tea with less chemical insecticide usage and minimal impact on the environment. More than 1100 species of natural enemies including about 80 species of viruses, 40 species of fungi, 240 species of parasitoids and 600 species of predators, as well as several species of bacteria have been recorded in tea ecosystems in China. Biological and ecological characteristics of some dominant natural enemies have been well documented. Several viral, bacterial, and fungal insecticides have been commercially utilized at large scale in China. Progress in biological control methods in conjunction with other pest control approaches for tea insect pest management is reviewed in this article. Knowledge gaps and future directions for tea pest management are also discussed.

The current status of pesticide resistance in Australian populations of the redlegged earth mite (Halotydeus destructor)

The redlegged earth mite, Halotydeus destructor Tucker, is an important pest of broad-acre farming systems in Australia, New Zealand and South Africa. In 2006, high levels of resistance to synthetic pyrethroids were discovered in this species in Western Australia. Between 2007 and 2010, the authors monitored resistance in field populations and found it had spread considerably within the state of Western Australia. Twenty-six paddocks from 15 individual properties were identified with resistance, and these paddocks ranged over 480 km. To date, resistance has not been detected in any other Australian state. Resistance in H. destructor appears to be found across the entire pyrethroid group, but not to other chemical classes such as organophosphates and carbamates, or other chemistries with novel modes of action. The high levels of resistance occurring in Western Australia have caused considerable economic losses due to ineffective chemical applications and mortality of crop plants at seedling establishment. These findings highlight the need for a comprehensive resistance surveillance programme to be developed for H. destructor within Australia. Growers need to consider non-chemical approaches for pest control and should be encouraged to implement pesticide resistance management programmes for H. destructor.

Extinction and Permanence of a General Predator‐Prey System with Impulsive Perturbations

A general predator‐prey system is studied in a scheme where there is periodic impulsive perturbations. This scheme has the potential to protect the predator from extinction but under some conditions may also serve to lead to extinction of the prey. Conditions for extinction and permanence are obtained via the comparison methods involving monotone theory of impulsive systems and multiple Liapunov functions, which establish explicit bounds on solutions. The existence of a positive periodic solution is also studied by the bifurcation theory. Application is given to a Lotka‐Volterra predator‐prey system with periodic impulsive immigration of the predator. It is shown that the results are quite different from the corresponding system without impulsive immigration, where extinction of the prey can never be achieved. The prey will be extinct or permanent independent of whether the system without impulsive effect immigration is permanent or not. The model and its results suggest an approach of pest control which proves more effective than the classical one.

Enzyme Inhibitors in Biorational Approaches for Pest Control

Conventional insecticides of broad spectrum have been widely used as the main tools for controlling insect pests. However, as the consequence of their toxicity and deep environmental impact, new biorational, and more specific approaches have been developed. In this review we present an overview of those pest control approaches which have resulted from studies dealing with inhibition of the enzymes involved in the physiology, growth, molting, development and reproduction of insect pests. These approaches involve synthetic compounds from laboratory studies and natural chemicals present in the crop plants. Recent developments using inhibitors expressed in transgenic plants are also outlined.

Combining intercropping with semiochemical releases: optimization of alternative control of Sitobion avenae in wheat crops in China

Overreliance on pesticides has large environmental and human health costs that compel researchers and farmers to seek alternative management tactics for crop pests. For insect pests, increasing crop species diversity via intercropping and using semiochemicals to alter local arthropod populations have separately proven effective at reducing pest densities. Here, we combine these two tactics in an effort to gain better control of Sitobion avenae (Fabricius) (Hemiptera: Aphididae), the English grain aphid, a major pest of cereal production worldwide. We conducted field experiments over 2 years testing the effectiveness of combining intercropping of wheat and oilseed rape with release of methyl salicylate (MeSA). We found that maximum and mean aphid densities were highest in wheat monocultures, significantly lower in intercropped plots and MeSA plots, and lowest when intercropping and MeSA release were combined by obtaining highest densities of predatory lady beetles and parasitoids rates. Importantly, grain yield and quality showed a similar pattern: they were highest for combined intercropped/MeSA plots, intermediate in plots with intercropping or MeSA alone, and lowest in control monoculture plots. Our results suggest that combining these two tactics holds significant promise for improved management of aphid populations and emphasize the need to integrate alternative pest control approaches to optimize sustainable insect pest management.

The Theory and Practice of Genetically Engineered Crops and Agricultural Sustainability

The development of genetically engineered (GE) crops has focused predominantly on enhancing conventional pest control approaches. Scientific assessments show that these GE crops generally deliver significant economic and some environmental benefits over their conventional crop alternatives. However, emerging evidence indicates that current GE crops will not foster sustainable cropping systems unless the negative environmental and social feedback effects are properly addressed. Moreover, GE crop innovations that promote more sustainable agricultural systems will receive underinvestment by seed and chemical companies that must understandably focus on private returns for major crops. Opportunities to promote crops that convey multi-faceted benefits for the environment and the poor are foundational to a sustainable food system and should not be neglected because they also represent global public goods. In this paper, we develop a set of criteria that can guide the development of GE crops consistent with contemporary sustainable agriculture theory and practice. Based on those principles, we offer policy options and recommendations for reforming public and private R&D and commercialization processes to further the potential contributions of GE crops to sustainable agriculture. Two strategies that would help achieve this goal would be to restore the centrality of the public sector in agricultural R&D and to open the technology development process to more democratic participation by farmers and other stakeholders.

From Integrated Pest Management to Indiscriminate Pesticide Use in Kazakhstan

This paper explores a strange paradox. After the fall of the Soviet system, Kazakhstan became strongly incorporated in a world that highly values sustainable agriculture and ecologically-friendly pest control. In this incorporation process, however, the country abandoned a well-established integrated pest management (IPM) system and shifted to an exclusive reliance on pesticides. This study analyses the development of IPM/ecology-based pest-control approaches in the 1970s and 1980s in the USSR, providing some detailed case studies in the Republic of Kazakhstan. It examines how these sustainable approaches to pest control were replaced by an indiscriminate pesticide use in farming practices after independence in 1991. The focus of plant protection research also shifted from IPM/ecology-based studies to pesticide testing. The paper reveals that the nature of institutional support from the state shapes the rise and fall of IPM, particularly since it is crucial for addressing the knowledge-intensive character of IPM and governing situations in which concerted action is needed.

Display female‐specific doublesex RNA interference in early generations of transformed oriental fruit fly, Bactrocera dorsalis (Hendel)

The oriental fruit fly, Bactrocera dorsalis (Hendel), is one of the most destructive pests in many Asian countries. An effective strategy to reduce fly density in the field is urgently required. Recently, the doublesex of B. dorsalis (Bddsx(f) ) has been cloned, and RNA interference (RNAi) indicates that it can reduce the offspring in vitro. In this study, a piggyBac-based construct that generates short hairpin RNA (shRNA) against the female-specific region of Bddsx was introduced into the pest to test the RNAi effects on reproductive functions in vivo. After embryonic injection and backcross, 21 transgenic lines with germline transformation were identified. Genomic DNA analysis showed that the exogenous transgene including short hairpin Bddsx(f) and a DsRed marker had integrated into the genomes of 11 transformed lines. Northern blot analysis indicated the presence of Bddsx(f) short interfering RNA (siRNA) under the control of a U6 promoter in transformed flies. As expected, the specific effects of RNAi led to the delay of egg maturation, and the offspring was significantly reduced. Reverse transcription real-time PCR further demonstrated that in vivo interference not only specifically inhibited the Bddsx(f) transcript but also repressed expression of the downstream yolk protein gene (Bdyp1). The results clearly indicate that RNAi is heritable through the expression of specific siRNA in early generations of transformed oriental fruit fly. These results can broaden the understanding of sex-related developmental mechanisms in the fly, and also offer a possible molecular approach for pest control in the future.

Effect of insect cadaver desiccation and soil water potential during rehydration on entomopathogenic nematode (Rhabditida: Steinernematidae and Heterorhabditidae) production and virulence

We examined the influence of insect cadaver desiccation on the virulence and production of entomopathogenic nematodes (EPNs), common natural enemies of many soil-dwelling insects. EPNs are often used in biological control, and we investigated the feasibility of applying EPNs within desiccated insect cadavers. Desiccation studies were conducted using the factitious host, Galleria mellonella (Lepidoptera: Pyralidae, wax moth larvae) and three EPN species ( Heterorhabditis bacteriophora ‘HB1’, Steinernema carpocapsae ‘All’, and Steinernema riobrave). Weights of individual insect cadavers were tracked daily during the desiccation process, and cohorts were placed into emergence traps when average mass losses reached 50%, 60%, and 70% levels. We tracked the proportion of insect cadavers producing infective juveniles (IJs), the number and virulence of IJs produced from desiccated insect cadavers, and the influence of soil water potentials on IJ production of desiccated insect cadavers. We observed apparent differences in the desiccation rate of the insect cadavers among the three species, as well as apparent differences among the three species in both the proportion of insect cadavers producing IJs and IJ production per insect cadaver. Exposure of desiccated insect cadavers to water potentials greater than −2.75 kPa stimulated IJ emergence. Among the nematode species examined, H. bacteriophora exhibited lower proportions of desiccated insect cadavers producing IJs than the other two species. Desiccation significantly reduced the number of IJs produced from insect cadavers. At the 60% mass loss level, however, desiccated insect cadavers from each of the three species successfully produced IJs when exposed to moist sand, suggesting that insect cadaver desiccation may be a useful approach for biological control of soil insect pests.

Is sodium fluoroacetate (1080) a humane poison? The influence of mode of action, physiological effects, and target specificity

Abstract1080 (sodium fluoroacetate)-baiting programmes are an important and often the only option for reducing the impact of invasive vertebrate pests on biodiversity and agricultural production in Australia and New Zealand. These programmes are generally recognised as being target specific, and environmentally and user safe. Nevertheless, although 1080 has few recognised long-term side-effects, its potential to disrupt endocrine systems has been recently raised, and there is some conjecture regarding the humaneness of 1080 for certain target species. However, the assessment of the humaneness of any vertebrate pesticide must be commensurate with its mode of action, metabolism, target specificity, and operational use. This has not always occurred with 1080, particularly regarding these aspects, and its overall effects. The actual risk faced by non-target species during baiting operations is not accurately reflected simply by their sensitivity to 1080. 1080 is not endocrine-disrupting or carcinogenic, and because of the lag phase before signs of poisoning occur, the time from ingestion to death is not a reliable indicator of its humaneness. Moreover, functional receptors and neurological pathways are required to experience pain. However, as 1080 impairs neurological function, mainly through effects on acetylcholine and glutamate, and as this impairment includes some pain receptors, it is difficult to interpret the behaviour of affected animals, or to assess their ability to experience discomfort and pain. This has implications for assessing the merits of including ameliorative agents in 1080 baits aimed at further improving welfare outcomes. We also suggest that the assessment of the humaneness of any vertebrate pesticide should follow the ethical pest control approach, and on this basis, believe that the use of 1080 to reduce the detrimental impacts of invasive vertebrates is ethical, particularly with respect to the expectations of the wider community.

Moss Control on Creeping Bentgrass Greens with Standard and Alternative Approaches

Moss is common on creeping bentgrass (Agrostis stolonifera L.) putting greens, and more control options are needed. Spot treatment of sodium bicarbonate (44.2 g·L−1) was compared with broadcast sprays of carfentrazone-ethyl (50.5 or 101 g a.i./ha), chlorothalonil (8.2 or 12.8 kg a.i./ha) and a tank mixture of chlorothalonil, mancozeb, and thiram (8.2, 9.8, and 11.5 kg a.i./ha) in 2006 in Lemont, IL. Sodium bicarbonate suppressed moss growth equally as the conventional products. These results led to further experiments in 2008 in which moss suppression was evaluated within standard and alternative putting green management regimes in Manhattan, KS, and Lemont, IL. The standard approach included spring and fall applications of carfentrazone-ethyl (101 g a.i./ha) for moss control, biweekly applications of urea (46N–0P–0K) at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) on a 14-day interval. Conversely, the alternative approach included spring and fall spot treatments of sodium bicarbonate (44.2 g·L−1) for moss control, biweekly applications of a natural organic fertilizer (8N–1P–3K) to provide nitrogen at 15 kg N/ha, and applications of chlorothalonil (8.2 kg a.i./ha) only when dollar spot reached a predetermined threshold level. Standard and alternative regimes were compared at both 3.2- and 4.0-mm mowing heights; synthetic and organic fertilizers applied alone without pest control approaches were included as controls. In Kansas and Illinois, moss coverage using the alternative management regime was not significantly different from that on greens managed using the standard regime. In Kansas, moss severity at a 3.2 mm was 1.6-fold higher than at the 4.0-mm height. In Illinois, sodium bicarbonate suppressed moss equivalently to the carfentrazone-ethyl treatment, and in the fertilizer-only controls, mowing at 3.2 versus 4.0 mm led to more moss coverage. These studies demonstrate that moss can be effectively suppressed on greens using spot applications of sodium bicarbonate and reduced moss encroachment is possible with higher mowing heights.

Commodification of science and the production of public goods: Plant protection research in Kazakhstan

The fall of the Soviet Union ushered in a process of commodification of science and raised new questions about the production of public goods. This paper examines the dramatic impact of post-Soviet changes on the organization and content of research on plant protection in Kazakhstan. It describes how a passive restructuring dismantled much of the research and extension infrastructure in Kazakhstan and how earlier ecological perspectives on pest control, often not recognized in the Western literature, were abandoned and replaced by short-term strategies based on imported technologies, basically pesticides. This study of the transformation of scientific research in the transition from communism to capitalism provides an opportunity to reflect on the public good characteristics of plant protection research. The analysis shows that the current commodification process and short-termism in plant protection research are incompatible with ecologically sustainable pest control approaches.

Microbial Control of White Grubs in Nepal: The Way Forward

Nepalese economy is largely dependent on agriculture. Over the time, there has been gradual transformation in the agricultural production system and the hitherto dominant chemical based agricultural system has been gradually changing with the latest aspects of bio-rational approaches. Emphasis towards these aspects has been seen both in the governmental and non-governmental level through their commitments in long term prospective plans. However, there is long way to go towards bio-rational approach of pest control in Nepal. This aspect is newer concept in case of Nepal. Institute of Agriculture and Animal Science (IAAS), Department of Entomology, Rampur, in support of Helvetas had initiated bio-pesticides production. The major effort was the production and use of biopesticide based on fungal pathogen (Metarhizium anisopliae Sorokin) against white grubs in particular and soil insect in general. The research was carried out for about a decade and results so far indicated the ample scope of producing and using this agent against this dreaded pest. The research results so far obtained are at get set position, however, to gear up the further works, it has been felt that joint efforts from possible counterparts such as Nepal Agricultural Research Council (NARC), IAAS, Department Of Agriculture (DOA), private organisations, NGOs and INGOs would be vital. It has been realised to form national working groups for the development of microbial pest control. Major lead should be taken by national organisations in full support of private organisations. This paper has been brought forth in order to bring into the information of the works so far done in Nepal and to arouse the interest among the possible counterparts, producers, consumers, planners, and policy makers. Key words: Bio-rational compounds; Bio-pesticides; IPM; Metarhizium anisopliae; White grubs The Journal of Agriculture and Environment Vol:10, Jun.2009 Page: 156-165