Nupur Sarkar

Free fatty acids from Momordica charantia L. flower surface waxes influencing attraction of Epilachna dodecastigma (Wied.) (Coleoptera: Coccinellidae)

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, 45.23, 101.76 and 65.73 μg/mL of palmitoleic, stearic, oleic, arachidic and docosanoic acids, respectively, was most attractive to the insect, and could be used as a trapping tool for pest management.

n-alkanes in epicuticular waxes of Vigna unguiculata (L.) Walp. leaves

Abstract The n-hexane extracts of young, mature and senescent leaves from Vigna unguiculata (L.) Walp., commonly known as cowpea, containing a thin layer of epicuticular waxes were analysed by thin-layer chromatography, gas chromatography and gas chromatography-mass spectrometry. Samples (100 g) of young, mature and senescent leaves indicated the presence of 14, 15 and 14 long-chain n-alkanes, accounting for 6380 ± 77.2, 8774 ± 70.1 and 5686 ± 76.0 μg (mean ± SE), respectively. The predominant n-alkane was hentriacontane (n-C31) in all three types of leaves, representing 1490 ± 20.3, 1543 ± 17 and 902 ± 9 μg in young, mature and senescent leaves, respectively, while pentacosane (n-C25), pentatriacontane (n-C35) and n-C25 were present in the lowest amounts in young, mature and senescent leaves, accounting for 33 ± 0.3, 34 ± 1.2 and 56 ± 0.7 μg, respectively.

Momordica charantia L. (Cucurbitaceae) floral volatiles causing attraction of Epilachna dodecastigma (Coleoptera: Coccinellidae)

ABSTRACT 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, sabinene, myrcene and ocimene at 16, 1, 20, and 8 µg/25 mL methylene chloride in a dose response bioassay, respectively, and hence, these compounds might be used for insect pest management strategies such as baited traps.

Effect of bitter gourd (Cucurbitaceae) foliar constituents on development and reproduction of Epilachna dodecastigma (Coleoptera: Coccinellidae)

The Influence of young, mature and senescent leaves of bitter gourd Momordica charantia L. (Cucurbitaceae) on the feeding, growth and reproduction of Epilachna dodecastigma (Weid.) (Coleoptera: Coccinellidae) were studied under laboratory conditions (27 ±0.5 °C, 12 h light: 12 h dark photoperiod, 65 ±5% RH). Larval developmental time of E. dodecastigma was longest on senescent leaves followed by young and mature leaves, whereas the pupal period was shortest on young and mature leaves. The longevity of females was generally higher than males. Male and female longevity were highest on mature leaves and lowest on senescent leaves. Fecundity was highest on mature leaves followed by young and senescent leaves. The growth and development of E. dodecastigma were related with nutrient and phenol content of three types of bitter gourd leaves. Carbohydrate content was higher in young and mature leaves, whereas protein, nitrogen, amino acid and lipid content were in greater quantities in mature leaves followed by young and senescent leaves. Phenol content was greatest in senescent leaves and least in mature leaves. Higher level of carbohydrates, proteins, lipids, nitrogen and amino acids including water content and lower phenol content of mature leaves had Influenced higher growth rate and fecundity of E. dodecastigma.