Integrated Pest Management for Stored Grain: Potential Natural Biological Control by a Parasitoid Wasp Community.

Insect contamination of stored grain is a major concern for the grain industry. Phosphine is currently the standard fumigant used to control insect pests in stored grain. However, some species and populations of insects that infest stored grain exhibit resistance to this fumigant and consumers are concerned about pesticide residues. Therefore, alternative methods of effective pest control are needed to partially or completely replace the use of phosphine. There is growing interest in biological control via parasitoid wasps. However, there is evidence that biological control will succeed only if used alongside other pest-management measures. Integrating biological control with the use of chemical insecticide is challenging and may lead to severe reductions in parasitoid survival and success. The main aim of the current study is to shed light on a greatly overlooked issue: the parasitoid community found in stored grain before and after phosphine treatment. The current study results indicate that there is a high level of parasitoid biodiversity within grain stores. We found common parasitoids at both semi-arid and Mediterranean sites, suggesting that those parasitoids can be active across a wide range of abiotic conditions. This research indicates that the community may recover even though phosphine has an immediate negative effect on a parasitoid community. Nevertheless, the parasitoid wasps seem to reduce the host population insufficiently. In light of the findings presented here, those interested in implementing pest-management strategies that include both phosphine treatment and biological control should consider conservation and augmentation of the naturally occurring parasitoid population. These studies should take into account interactions between and within parasitoid populations and phosphine distribution within the grain storage. To limit the effect of phosphine on the parasitoids, pest-management strategies should also reflect careful consideration of the timing of phosphine treatment and the need for sufficient refuge for the parasitoids.

Coarse and nano emulsions for effective delivery of the natural pest control agent pulegone for stored grain protection.

BACKGROUND: One of the most significant contributors to the global food crisis is grain loss during storage, mainly caused by pest insects. Currently, there are two main methods used for insect pest control: fumigation and grain protection using contact insecticides. As some chemical insecticides can harm humans and the environment, there is a global tendency to reduce their use by finding alternative eco-friendly approaches. RESULTS: In this study, the natural pest-managing agent pulegone was encapsulated into coarse and nano emulsions. The emulsions were characterized using spectroscopic and microscopic methods and their stability and pulegone release ability were examined. The insecticidal activity of the prepared formulations against two stored product insects, rice weevil (Sitophilus oryzae L.) and red flour beetle (Tribolium castaneum Herbst), was demonstrated. The nano emulsion-based formulation offered significant advantages and provided powerful bioactivity, with high (> 90%) mortality rates for as long as 5 weeks for both insects, whereas coarse emulsions showed high efficacy for only 1 week. CONCLUSION: The developed pulegone-based nano emulsions could serve as a model for an effective alternative method for pest control. Although pulegone is from a natural source, toxicological studies should be performed before the widespread application of pulegone or pulegone-containing essential oils to dry food products. © 2017 Society of Chemical Industry.

Rapid Detection and Identification of Mycotoxigenic Fungi and Mycotoxins in Stored Wheat Grain.

This study aimed to assess the occurrence of toxigenic fungi and mycotoxin contamination in stored wheat grains by using advanced molecular and analytical techniques. A multiplex polymerase chain reaction (PCR) strategy was established for rapid identification of mycotoxigenic fungi, and an improved analytical method was developed for simultaneous multi-mycotoxin determination in wheat grains by liquid chromatography-tandem mass spectrometry (LC/MS/MS) without the need for any clean-up. The optimized multiplex PCR method was highly specific in detecting fungal species containing species-specific and mycotoxin metabolic pathway genes. The method was applied for evaluation of 34 wheat grain samples collected from storage warehouses for the presence of mycotoxin-producing fungi, and a few samples were found positive for Fusarium and Aspergillus species. Further chemical analysis revealed that 17 samples contained mycotoxins above the level of detection, but only six samples were found to be contaminated over the EU regulatory limits with at least one mycotoxin. Aflatoxin B1, fumonisins, and deoxynivalenol were the most common toxins found in these samples. The results showed a strong correlation between the presence of mycotoxin biosynthesis genes as analyzed by multiplex PCR and mycotoxin detection by LC/MS/MS. The present findings indicate that a combined approach might provide rapid, accurate, and sensitive detection of mycotoxigenic species and mycotoxins in wheat grains.

Activation of octopaminergic receptors by essential oil constituents isolated from aromatic plants: possible mode of action against insect pests.

As a result of screening a large number of essential oils from Israeli aromatic plants and their biologically active constituents, we isolated two oils with high activity against several stored-product insects. In this study the effect of these compounds on the acetylcholinesterase and the octopamine systems in insects was studied in order to elucidate their mode of action. Inhibition of acetylcholinesterase activity in vitro was evident only at high concentrations (10(-3) M) and could not account effectively for the low-dose mortality for some stored-product insects observed in vivo. However, the essential oil constituents were found to cause a significant increase in the levels of the intracellular messenger, cyclic AMP of abdominal epidermal tissue in the model insect, Helicoverpa armigera Hübn. The effect was significant even at low, physiological concentrations (10(-8) M) when tested directly on abdominal epidermal tissue preparations in vitro. This intracellular response was found to resemble closely the significant increases in the levels of the cyclic AMP of abdominal epidermal tissue due to treatment with the neurotransmitter/neuromodulator, octopamine. Subsequent treatment with the octopaminergic antagonist, phentolamine, effectively inhibited the cyclic AMP levels induced by essential oil treatment, indicating possible competitive activation of octopaminergic receptors by essential oil constituents.