Botanicals as Grain Protectants

Prevention of food losses during postharvest storage is of paramount economic importance. Integrated pest management is now a widely accepted strategy in pest control including postharvest infestation control which involves the use of chemical (contact/residual) insecticides along with fumigants. The use of synthetic chemical insecticides is either not permitted or used restrictively because of the residue problem and health risks to consumers. In view of the above, there is a need for plants that may provide potential alternatives to the currently used insect control agents as they constitute a rich source of bioactive molecules. Available literature indicates that plant could be source for new insecticides. Therefore, there is a great potential for a plant-derived insecticidal compounds. This paper focuses on the current state of the botanical insecticides as grain protectants and its mode of action

Botanicals as grain protectants

Prevention of food losses during postharvest storage is of paramount economic importance. Integrated pest management is now a widely accepted strategy in pest control including postharvest infestation control which involves the use of chemical (contact/residual) insecticides along with fumigants. The use of synthetic chemical insecticides is either not permitted or used restrictively because of the residue problem and health risks to consumers. In view of the above, there is a need for plants that may provide potential alternatives to the currently used insect control agents as they constitute a rich source of bioactive molecules. Available literature indicates that plant could be source for new insecticides. Therefore, there is a great potential for a plant-derived insecticidal compounds. This paper focuses on the current state of the botanical insecticides as grain protectants and its mode of action

Acetylcholinesterase inhibition by biofumigant (Coumaran) from leaves of Lantana camara in stored grain and household insect pests

Recent studies proved that the biofumigants could be an alternative to chemical fumigants against stored grain insect pests. For this reason, it is necessary to understand the mode of action of biofumigants. In the present study the prospectus of utilising Lantana camara as a potent fumigant insecticide is being discussed. Inhibition of acetylcholinesterase (AChE) by Coumaran, an active ingredient extracted from the plant L. camara, was studied. The biofumigant was used as an enzyme inhibitor and acetylthiocholine iodide as a substrate along with Ellman's reagent to carry out the reactions. The in vivo inhibition was observed in both dose dependent and time dependent in case of housefly, and the nervous tissue (ganglion) and the whole insect homogenate of stored grain insect exposed to Coumaran. The possible mode of action of Coumaran as an acetylcholinesterase inhibitor is discussed

Isolation and characterization of biofumigant from leaves of Lantana camara for control of stored grain insect pests

Due to environmental concerns, health hazards to man and the evolution of resistance in insect pests, there have been constant efforts to discover newer insecticides both from natural sources and by chemical synthesis. Natural sources for novel molecules hold promise in view of their eco-friendly nature, selectivity and mammalian safety. We have isolated one natural bioactive molecule from the leaves of Lantana camara named Coumaran, based on various physical-chemical and spectroscopic techniques (IR, H-1 NMR, C-13 NMR and MS). Coumaran is highly toxic and very low concentration is needed for control of stored product insects. This molecule has potent grain protectant potential and caused significant reduction in F1 progeny of all the three species in the treated grain and the progeny was completely suppressed at 30 mu g/l. The differences in germination between the control and treated grains were not significant. The lack of any adverse effect of Coumaran on the seed germination is highly desirable for a grain protectant, becoming a potential source of biofumigant for economical and environmentally friendly pest control strategies against stored grain pests during storage of grains or pulses. (C) 2013 Elsevier B.V. All rights reserved

Oviposition site-selection by Bactrocera dorsalis is mediated through an innate recognition template tuned to γ-octalactone.

Innate recognition templates (IRTs) in insects are developed through many years of evolution. Here we investigated olfactory cues mediating oviposition behavior in the oriental fruit fly, Bactrocera dorsalis, and their role in triggering an IRT for oviposition site recognition. Behavioral assays with electrophysiologically active compounds from a preferred host, mango, revealed that one of the volatiles tested, γ-octalactone, had a powerful effect in eliciting oviposition by gravid B. dorsalis females. Electrophysiological responses were obtained and flies clearly differentiated between treated and untreated substrates over a wide range of concentrations of γ-octalactone. It triggered an innate response in flies, overriding inputs from other modalities required for oviposition site evaluation. A complex blend of mango volatiles not containing γ-octalactone elicited low levels of oviposition, whereas γ-octalactone alone elicited more oviposition response. Naïve flies with different rearing histories showed similar responses to γ-octalactone. Taken together, these results indicate that oviposition site selection in B. dorsalis is mediated through an IRT tuned to γ-octalactone. Our study provides empirical data on a cue underpinning innate behavior and may also find use in control operations against this invasive horticultural pest

Schematic representation of the response of flies with different rearing histories towards γ-octalactone. <i>B. dorsalis</i> was reared on 3 different hosts.

<p>The final (third) generation gravid females were used in oviposition bioassays. A one-tailed <i>t</i> test revealed a significant difference (<i>P</i><0.0001) between Test (OL, γ-octalactone present) and Control (No OL, γ-octalactone not present). One-way ANOVA between the tests of group 1 (mango), 2 (banana) and 3 (guava) showed no significant difference in the mean no. of eggs laid.</p

γ-Octalactone is an oviposition stimulant and an oviposition site recognition cue.

<p>(a) The clear discrimination of the untreated (No OL, γ-octalactone not present) half (A) and γ-octalactone treated (OL, γ-octalactone present) half (B) by <i>B. dorsalis</i> in a single plate two-choice assay. (b) Number of eggs laid into treated and untreated pulp (one-tailed paired <i>t</i> test, <i>n</i> = 30, <i>t = </i>11.27, <i>df</i> = 19, <i>P</i><0.0001). Error bars = standard error of mean.</p

EAG and ovipositional response of <i>Bactrocera dorsalis</i> to varying concentrations of γ-octalactone.

<p>Control = Hexane; SEM: Standard error of mean; Means within a column followed by the same letters ^a or ^b are not significantly different at <i>P</i><0.001 (ANOVA); ppm: parts per million.</p

Behavior and egg-laying response of <i>B. dorsalis</i>.

<p>(a) Behaviour assay where <i>B. dorsalis</i> were presented with a filter paper disc containing γ-octalactone. Arrows show the hallmark oviposition behavior of extending the ovipositor and probing action (for better view watch <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085764#pone.0085764.s003" target="_blank">video S1</a>). (b & c) Egg-laying response of <i>B. dorsalis</i> to a pulp disc with γ-octalactone (Test) or without (Control) in a 24-h oviposition bioassay. More eggs were laid on the test disc (<i>P</i><0.0001, one-tailed paired <i>t</i> test of non-transformed data). Error bars = Standard error of mean.</p