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Epilachna dodecastigma (Wied.) (Coleoptera: Coccinellidae) causes economic losses to bitter gourd, Momordica charantia L. (Cucurbitaceae) production in India and Bangladesh because adults feed on the leaves and flowers resulting death of the plant. This insect is currently controlled by insecticides, which are harmful to human health and environment. We studied the behavioral responses of E. dodecastigma females to floral volatiles and synthetic compounds comparable to floral volatiles in a Y-tube olfactometer to determine their potential for monitoring this pest. The gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) analyses of M. charantia floral volatiles revealed the presence of 20 compounds. Myrcene was predominant followed by methyl jasmonate and 1-octadecanol in floral volatiles. Epilachna dodecastigma females were attracted to floral volatiles by a Y-tube olfactometer bioassay. Females were attracted to individual synthetic 1-heptanol, s...

Momordica charantia L. (Cucurbitaceae) is an important vegetable in Asia and Africa. Larvae and adults of Epilachna dodecastigma (Wied.) (Coleoptera: Coccinellidae) consume M. charantia leaves and flowers and reduces crop production. Currently, this pest is controlled by insecticides application. Hence, it is necessary to find out allelochemicals from flowers attracting the insect, which might be used for environment friendly pest management program. Therefore, free fatty acid profile from flowers was characterized and then proposed use of a synthetic blend of fatty acids for development of baited traps. Extraction, thin layer chromatography and gas chromatography–mass spectrometry of M. charantia flowers revealed 14 free fatty acids. The free fatty acids from flowers and synthetic blends of fatty acids mimicking different concentrations of free fatty acids attracted female E. dodecastigma between 50–400 μg/mL concentrations in Y-shaped glass tube olfactometer bioassay. A synthetic blend of 112.61, 29.22,...

Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) and Epilachna dodecastigma (Wied.) (Coleoptera: Coccinellidae) are important herbivore pests of Momordica cochinchinensis Spreng (Cucurbitaceae).The volatile organic compound (VOC) profile from undamaged and mechanically damaged plants, and from plants 24 h and 120 h following continuous feeding of adult female A. foveicollis and E. dodecastigma, was identified and quantified by GC-MS and GC-FID analyses. Twenty-two compounds were identified in volatiles of undamaged plants and in 24-h and 120-h post-insect-feeding plant volatiles; whereas 21 components were detected in volatiles of mechanically damaged plants. With the exception of four compounds, 1-heptanol, 3-octanone, acetophenone and nerolidol, the emissions of all other compounds were significantly increased following insect attack. In all plants, phytol was predominant, followed by geranyl linalool and linalool. Only 2-hexanol was unique to mechanically damaged plants, and 1-octen-3-ol and farnesyl acetone were detected in volatiles of undamaged and insect-damaged plants, but not in volatiles of mechanically damaged plants. However, none of these volatile components, when tested individually, showed attraction to A. foveicollis in Y-shaped glass tube olfactometer bioassays. Aulacophora foveicollis elicited significant preference for the whole volatile blends from insect-damaged plants compared to those of undamaged plants, and volatiles from 120-h post-E. dodecastigma feeding plants were more attractive to A. foveicollis compared to those from conspecifically damaged plants. Furthermore, the finding that A. foveicollis responds to individual synthetic compounds, 1-heptanol, 3-octanol, linalool oxide, 1-octanol, nonanal, geranyl linalool and phytol, and provide a basis for new inventions on trapping tools for pest management strategies.

Epilachna dodecastigma (Wiedemann) (Coleoptera: Coccinellidae) is an important herbivorous pest of bitter gourd, Momordica charantia Linnaeus (Cucurbitaceae) plant in India and Bangladesh. Volatiles were collected from undamaged bitter gourd plants, and from plants 24 and 120 hours following the initiation of continuous adult female feeding damage, and subsequently identified and quantified by gas chromatography mass spectrometry and gas chromatography flame ionisation detector analyses. Of the 24 volatiles identified in the study, 22 were present in all three treatments (undamaged plants, 24 hours after feeding, and 120 hours after feeding), and all plants significantly increased emissions of these compounds following insect attack. In all plants, the compound 1-tridecanol was the most abundant, followed by phytol. Only two compounds were unique to insect damaged plants: methyl palmitate was characteristic of insect damaged plants, while nerolidol was only detected from plants 120 hours following insect attack, however neither of these insect-damage specific volatiles, when tested individually, elicited attraction in Y-shaped glass tube olfactometer bioassays. Epilachna dodecastigma showed significant preference for the whole volatile blends from insect damaged plants compared with whole volatile blends from undamaged plants. Further, the insect elicited attraction to three individual synthetic compounds: geraniol, 1-tridecanol, and phytol, which had significantly higher emissions from insect damaged leaves compared with those from undamaged plants.

Extraction, thin-layer chromatography, and gas chromatography–mass spectrometry of leaf surface waxes of Momordica charantia L. (Cucurbitaceae) revealed that 20 n-alkanes between n-C15 and n-C36, except n-C34 and n-C35, commonly occur in young, mature, and senescent stages. Hentriacontane, hentriacontane, and hexatriacontane were the predominant compounds in young, mature, and senescent leaves, respectively. The cuticular alkanes from young, mature, and senescent leaves attracted the female insect, Epilachna dodecastigma (Wied.), at 25–400, 25–400, and 100–400 μg concentrations, respectively, whereas the mixtures of synthetic alkanes mimicking cuticular alkanes of young, mature, and senescent leaves showed attraction at 100–400, 100–400, and 200–400 μg concentrations, respectively, in Y-shaped glass tube olfactometer bioassay. The difference in insect attraction is probably due to the absence of branched-chain alkanes in the synthetic mixtures. Individual synthetic heptacosane, nonacosane, and hentriacontane at 28.19–56.90, 32.04–64.08, and 60.44–120.88 μg, respectively, elicited attraction of the insect. A synthetic blend of 4.82, 4.91, 5.71, 6.74, 56.39, 7.94, 62.42, 120.88, and 36.33 μg of nonadecane, eicosane, heneicosane, pentacosane, heptacosane, octacosane, nonacosane, hentriacontane, and tritriacontane, respectively, was most attractive to the insect.

The present paper elucidates that 0.005 to 0.05 per cent of thiourea has no significant effect on the longevity of Epilachna dodecastigma. However, when the concentration was raised from 0.05 to 0.10 per cent (t = 7.72, P < 0.001) and from 0.10 to 0.20 per cent (t = 1.90, P < 0.20), the longevity of the beetles was significantly reduced. Further, it has also been observed that as the concentration of thiourea increases, the number of eggs laid by the beetle decreases and complete sterility was achieved when 0.05 per cent of thiourea was applied. Therefore, 0.05 per cent of thiourea concentration is the most suitable dose for the sterilization of E. dodecastigma.