Nayan Roy

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.

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.

Life Table and Nutritional Ecology of Epilachna vigintioctopunctata Fab. (Colioptera: Coccinellidae) on Three Host Plants

Host preference in relation to life table parameters and nutritional ecology of Epilachna vigintioctopunctata Fab. were studied under laboratory conditions. The pest, E. vigintioctopunctata showed more feeding preference and higher reproductive growth to its host plant, Solanum melongena followed by S. nigrum and Momordica cochinchinensis . The developmental duration of their neonates was shorter with higher adult longevity, fecundity, hatchability, and accumulated survivability in S. melongena followed by S. nigrum and M. cochinchinensis . The feeding indices and population parameters of E. vigintioctopunctata were significantly higher (P < 0.05) on S. melongena relative to the other host plants. The pest on S. melongena has shorter mean generation time (T c ) of 59.10 days with higher net reproductive rate (R 0 ) of 16.63. Their generation survival (GS) on S. melongena (0.582) is significantly higher than S. nigrum (0.568) and M. cochinchinensis (0.550) with reverse of total generation mortality (K) of 0.290, 0.308 and 0.376, respectively. These differences in the nutritional ecology and demographic parameters are due to the variation in their phytochemical regime of respective host plants. Thus, the study may help to find the most vulnerable stage (egg and pupal stage) of this pest for appropriate control measures and also supports the use of S. nigrum as an alternative host towards S. melongena and as a trap crop towards M. cochinchinensis to avoid or minimum invasion of this pest for sustainable agriculture.

Amino acids through developmental stages of sunflower leaves

Abstract The PICO-TAGanalysis of proteins revealed that 17 protein-bound and 18 free amino acids were present throughout the developmental stages of sunflower leaves. The total protein-bound amino acid content was much higher than total free amino acid content throughout the development of sunflower leaves. The contents of protein-bound and free amino acids as well as essential and non-essential ones displayed different patterns with leaf maturation, suggesting that total protein levels are poor predictors of the nutritive status of leaves.