Anandamay Barik

Free fatty acids from the weed, Polygonum orientale leaves for attraction of the potential biocontrol agent, Galerucella placida (Coleoptera: Chrysomelidae)

Extraction, thin layer chromatography and gas chromatography-mass spectrometry of leaf surface waxes of Polygonum orientale L. (Polygonaceae) weed revealed 11, 15 and 11 free fatty acids in young, mature and senescent stages. Oleic acid was the predominant in young leaves (5950 ± 111 µg); whereas palmitic acid was the predominant fatty acids, representing 4247.5 ± 23 and 6644 ± 110 µg in mature and senescent leaves, respectively. Both tridecanoic and heneicosanoic acids were not detected in young and senescent leaves, and myristic and heptadecanoic acids were not identified in young leaves; whereas lauric and nonadecanoic acids were not detected in senescent leaves. The free fatty acids from young, mature and senescent weed leaves, and the mixtures of synthetic fatty acids mimicking free fatty acids of three types of weed leaves attracted female Galerucella placida (Coleoptera: Chrysomelidae) at the minimal amounts of 2, 1 and 2 leaf equivalent free fatty acids, respectively, in Y-shaped glass tube olfactometer bioassays under laboratory conditions. Individual synthetic pentadecanoic, palmitoleic, stearic, nonadecanoic and docosanoic acids at 44.82, 9.91, 92.22, 18.33 and 15.88 µg, respectively, elicited attraction of the insect. A synthetic blend of 3.59, 7.89, 44.82, 9.91, 32.31, 18.33 and 15.88 µg of lauric, myristic, pentadecanoic, palmitoleic, heptadecanoic, nonadecanoic and docosanoic acids, respectively, indicated highest attraction of the insect.

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.

Influence of four host‐plants on feeding, growth and reproduction of Diacrisia casignetum (Lepidoptera: Arctiidae)

Effects of four host‐plants, sunflower, castor, jute and sesame, on feeding, growth and reproduction of Diacrisia casignetum Kollar (Lepidoptera: Arctiidae) were studied under laboratory conditions (27 ± 0.5°C, 12 h light : 12 h dark, 65 ± 5% RH). Total larval developmental time of D. casignetum was highest on sesame than the other three host‐plants used in this study, but pupal duration was higher on sesame than sunflower but not for other dietary treatments. The longevity of females was generally longer than males. Male and female longevity was higher in sunflower than sesame (P < 0.05), but it did not differ significantly among other treatments. Fecundity was highest in sunflower followed by castor, jute and sesame. The growth and development of D. casignetum were related to nutrient and phenol contents of these four host‐plants. Total carbohydrates and amino acids were present in rich quantities in sunflower when compared to other three host leaves, while nitrogen, protein and lipid contents were comparatively higher in sunflower and castor than jute and sesame. Phenol content was greatest in sesame, and least in castor and sunflower. Higher levels of total carbohydrates, proteins, lipids, nitrogen and amino acids including water content and lower phenol content of sunflower have influenced higher growth rate and fecundity of D. casignetum.

The Impact of Variation in Foliar Constituents of Sunflower on Development and Reproduction of Diacrisia casignetum Kollar (Lepidoptera: Arctiidae)

Effects of feeding on young, mature, and senescent sunflower leaves were studied under laboratory conditions (°C, 12L : 12D, % RH) to evaluate the impact of variation of nutrients on larval food utilization efficiency, larval and pupal development and survival, longevity, and fecundity of Diacrisia casignetum Kollar. The growth rate, which is the ratio between the dry weight gain of insect and duration of experimental period, of D. casignetum was in the order of mature leaf > young leaf > senescent leaf of sunflower. This was correlated with nutrient constituents of three kinds of sunflower leaves, which was measured by various biochemical analyses described elsewhere in the text. Total carbohydrates, proteins, lipids, nitrogen, amino acids, and water content are in greater amount in mature leaves when compared to young and senescent leaves, whereas phenol content was highest in young leaves than mature leaves. Hence, higher amount of total carbohydrates, proteins, lipids, nitrogen, amino acids including water and lower amount of total phenol content in mature leaves have influenced higher growth rate, less developmental time, and higher fecundity of D. casignetum.

Floral volatiles with colour cues from two cucurbitaceous plants causing attraction of Aulacophora foveicollis

Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) is an important phytophagous pest of two cucurbitaceous plants, Momordica cochinchinensis Spreng and Solena amplexicaulis (Lam.) Gandhi. The volatile organic compound profiles from flowers of M. cochinchinensis and S. amplexicaulis were identified and quantified by gas chromatography‐mass spectrometry (GC‐MS) and GC‐flame ionization detector (FID) analyses. Twenty nine and 28 compounds were identified in volatiles of M. cochinchinensis and S. amplexicaulis flowers, respectively. Methyl jasmonate and 3‐octanol were the predominant volatiles of M. cochinchinensis flowers, whereas 1‐octadecanol and 1‐hexanol were most found in the headspace of S. amplexicaulis flowers. Aulacophora foveicollis were more attracted by the flower volatiles of M. cochinchinensis than by those of S. amplexicaulis in a glass Y‐tube olfactometer. A mixture of 1‐heptanol, linalool oxide, 1‐octanol, and nonanal in the proportions present in the headspace of both flower types elicited attraction in the insect. From 25 cm distance, A. foveicollis displayed a preference for artificial flowers of 6.5 cm diameter of S. amplexicaulis flower colour (white) over M. cochinchinensis flower colour (white‐yellow). Finally, a synthetic blend (0.43 μg 1‐heptanol + 1.44 μg linalool oxide + 0.14 μg 1‐octanol + 1.77 μg nonanal dissolved in 25 μl methylene chloride) attracted more beetles when applied in a white artificial flower than when applied in a white‐yellow artificial flower from 40 cm distance. This finding may be helpful in the development of traps for pest management strategies.

Solena amplexicaulis (Cucurbitaceae) flower surface wax influencing attraction of a generalist insect herbivore, Aulacophora foveicollis (Coleoptera: Chrysomelidae)

Aulacophora foveicollis Lucas causes economic losses to creeping cucumber [Solena amplexicaulis (Lam.) Gandhi] growers in India and Bangladesh because adults feed on the leaves and flowers causing death of the plant. The insect is a generalist herbivore as it also causes damage to pumpkin, bottle gourd, sponge-gourd and gac fruit production by feeding on leaves and flowers of these plants. At present, insects are controlled with insecticides, which are harmful to human health and the environment. We studied the behavioural responses of adult A. foveicollis to flower surface waxes and synthetic compounds mimicking flower surface waxes 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 S. amplexicaulis flower (50 g) surface waxes indicated presence of 17.9 and 3.1 mg alkanes and free fatty acids, respectively. Seventeen n-alkanes from n-C15 to n-C34 and 16 free fatty acids from C10:0 to C22:0 were detected in the flower surface waxes. Heptacosane was predominant among n-alkanes representing 2748.1 μg; whereas, pentadecanoic acid was the major fatty acid accounting for 466.6 μg. Aulacophora foveicollis were attracted to the flower surface waxes at concentrations of 4 to 8 μg/ml, as demonstrated by a Y-tube olfactometer bioassay. Using a dose response bioassay, the insect was shown to be attracted to individual synthetic pentadecane, heptacosane, nonacosane, undecanoic acid and nonadecanoic acid at 0.70, 0.70, 1.20, 1.60 and 1.40 μg/ml, respectively. The insect displayed highest attraction to a synthetic mixture of 0.70, 1.23, 0.77, 0.84, 0.94 and 0.74 μg/ml of pentadecane, heptacosane, nonacosane, undecanoic acid, lauric acid and nonadecanoic acid, respectively, and hence, this combination might be used for insect pest management such as in baited traps.

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.

Determination of n-alkane profile through developmental state of sunflower leaves

The n-hexane extracts of young, mature and senescent sunflower leaves containing a thin layer of epicuticular waxes was analysed by TLC and GC using standard hydrocarbons. The Scanning Electron Microscopy study indicated changes in the deposition of epicuticular wax throughout the developmental stage of the sunflower leaves. The young, mature and senescent leaves contained nine, nine and five long-chain nalkanes accounting for 86.22%, 99.76% and 92.07% of the hydrocarbons, respectively. The predominant nalkane was n-C29 for young and mature leaves, and n-C23 for senescent leaves representing 35.85%, 45.37% and 68.54% of the hydrocarbons, respectively; whilst n-C24, n-C32 and n-C19 were present in least amounts in young, mature and senescent leaves indicating 0.59%, 0.83% and 0.53% of the hydrocarbons, respectively.

Long-Chain Free Fatty Acids from Sunflower (Asteraceae) Leaves: Allelochemicals for Host Location by the Arctiid Moth, Diacrisia casignetum Kollar (Lepidoptera: Arctiidae)

Abstract Extraction, thin layer chromatography and gas chromatography-mass spectroscopy analyses revealed 13 free fatty acids in young, mature, and senescent leaves of Helianthus annuus L. (Asteraceae) representing 75.65, 75.38, and 68.01% of total free fatty acids, respectively. &agr;-Linolenic acid, linoleic acid, and linoleic acid were the major free fatty acids in young, mature, and senescent leaves, accounting for 22.71, 31.48, and 30.60%, respectively. The free fatty acids from young, mature, and senescent leaves attracted the female insect, Diacrisia casignetum Kollar (Lepidoptera: Arctiidae) at minimal concentrations of 12.5, 12.5, and 25 µg, respectively; whereas the synthetic mixtures of fatty acids mimicking free fatty acids of young, mature, and senescent leaves attracted at minimal concentrations of 12.5, 12.5, and 50 µg, respectively. Diacrisia casignetum insects showed attraction toward an initial amount of individual synthetic palmitic, palmitoleic, stearic, oleic, linoleic, and &agr;-linolenic acids at 2.39, 4.63, 2.28, 3.08, 29.20, and 25.20 µg, respectively. A synthetic blend of 2.39, 4.90, 4.53, 3.14, 43, and 25.20 µg of palmitic, palmitoleic, stearic, oleic, linoleic, and &agr;-linolenic acids, respectively, the proportion present at 100 µg concentration free fatty acids of mature leaves produced highest attractions for D. casignetum and might be used for insect pest management programme such as baited traps.

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.