Influence of Biochemical Parameters of Different Hosts on the Biology of <Emphasis Type="Italic">Earias Vittella
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Proc. Indian Acad. Sci. (Anim. Sci.), Vol. 96, No.3, May 1987, pp. 329-332. C(: Printed in India. Influence of biochemical parameters of different hosts on the biology of Esriss vittella (Fab.) (Noctuidae: Lepidoptera) R SUNDARARAJ and BV DAVID Fredrick Institute of Plant Protection and Toxicology, Padappai 601 301, India Abstract, The present study aims to understand the influence of biochemical parameters of the host plants viz Abelmoschus esculentus L., Gossypium hirsutum L. and Ahuti/on indicum G. Den. on the reproductive biology of Earias tittella. The results indicate remarkable variation in the biochemical parameters of host plants which affected significantly the growth index and reproductive potential of the insect species. Decrease in body weight, fecundity, prolongation of larval period, percentage of larva becoming adult and adult longevity of both male and female was observed when reared on Abutilon indicum which had less amount of reducing sugars, protein and free amino acids but had high amount of non reducing sugars. Decreased larval period, increased fecundity and adult longevity were observed when reared on cotton and okra which had high amount of reducing sugars, free amino acids and protein. There was no significant difference in the amount of total soluble sugars'among the 3 hosts tested. The growth index and fecundity of Earias uittella are apparently high on okra than on cotton. It is observed that high amount of reducing sugars, free amino acids and protein seems to be favourable for increase in fecundity of Earias tittel!a. Keywords. Earias rittella: reproductive biology: okra: cotton; Abutilon indicum; biochemical parameters; incidence. 1. Introduction The pest status of an insect species depends on its ability to breed on a variety of host plants, comparative growth rate, fecundity, population dynamics and distribution (Ananthakrishnan 1977). It was reported by Khan and Rao (1960) that preferred hosts have a great influence on oviposition, fecundity, developmental period and longevity of adults of Earias vittella (Fab.) and E. insulana (Boisd.). Mehta and Saxena (1970) were the first to study the role of ovipositional responses of E. vittella in its establishment on different plants. Subsequently in 1973, they reported that growth of E. oittella varies with the degree of consumption, nutritive value and utilization of food from different plants. The insect grows best on diet whose nutritive value and degree of conversion into body matter are high. Krishna et al (1977) reported on oviposition in E. oittella in relation to adult nutrition, mating and some environmental factors. Vishwapremi and Krishna (1974) working on E. vittella brought to light the need for a carbohydrate diet, especially raffinose during its adult stage for achieving maximum fecundity. Hiremath (1984) investigated the host preference of E. oittell« on 7 different hosts under field conditions and the effect of these host plants on development, longevity and fecundity. Mani el al (1986) studied the effects of larval food quality of okra and Hibiscus rosasinensis on egg output and viability in E. oiuella. The present study aims to relate the biochemical nature of 3 host plants viz Abelmoschus esculentus L., Gossypium hirsutum L. and Abutilon indicum G. Den. with the reproductive biology of E. oittel!a. 329 330 R Sundararaj and B V David 2. Material and methods Three plant species viz A. esculentus (okra), and G. hirsutum (cotton) grown in fields and A. indicum found along the bunds in the campus of the Fredrick Institute of Plant Protection and Toxicology, Padappai, were taken up for investigations. From the laboratory culture of E. vittella adequate number of larvae were obtained for the studies. On each of the host plants viz A. esculentus (epicarp removed okra fruit), G. hirsutum (opened tender bolls of cotton) and A. indicum (opened young fruits), hundred freshly hatched larvae were released and the duration of larval and pupal stages, adult longevity and fecundity were also recorded. The studies were replicated thrice. Simultaneously, samples of the larval food material were analysed for reducing sugars, total sugars, free amino acids and protein. Ethanol extracts of the larval food material were obtained by using 80~~ ethanol. The reducing sugars were determined first and subsequently the nonreducing sugars in the extract were hydrolysed to reducing sugars and the total sugars were estimated by Nelson's (1944) method. By subtracting the reducing sugars from the total sugars the nonreducing sugars were estimated and expressed as glucose equivalents. Free amino acids were estimated by Moore and Stein's (1948) method and protein by Lowry's (1951) method (Mahadevan and Sridhar 1982). 3. Results and discussion The data presented in table 1 shows the developmental period, longevity, survival, weight of fourth instar larva, pupa and adult, fecundity and growth index of E. vittella on 3 hosts viz okra, cotton and A. indicum. The biochemical constituents of the larval food viz the seeds of the 3 host plants with regard to reducing sugars, nonreducing sugars, free amino acids and protein are furnished in table 2. The duration of larval and pupal period was considerably longer on A. indicum being 18·33 ± 3·70 and 13-03± 3·11 days respectively and the toal developmental period worked out was 32·10 ± 2·98 days. On the other hand, the total developmental period was the shortest on okra (26'90± 3-20 days) while slightly more on cotton being 27·90 ± 3·12 days. The percentage survival has been found to be the lowest on 'table 1. Biology of £. vitteUa on three different hosts. Duration (days) Total deve- lopmental Survival Growth Host Incubation Larva Pupa period (days) (Y.J index' Okra 4·5H:(}32 12-73*2041 1l-16±2'79 2&90;:1:3-20 68-OO±S·72 2·52±o-21 Cotton 4·SS±(}41 13-76±HO 12·36±2·S4 27-90±3-12 67-lX)±9-()<) NO± 9-09 A. illdicum 4·SH:(}38 18'33*3-70 13-ll3±H1 32-l0±2·98 26-33 ± 3'29 l-{12±(}13 Longevity (days) Weight (g) Host Male Female Fecundity IV instar Pupa Adult Okra 1(}76±2-20 14-60±H2 3S<Hi7± 28'77 C-084:l: oo11 (}()69 :l:0-005 0·024:l:(}()()4 Cotton 9-33:1:2-84 14'13:1: 3-()<) JOl-66± 14-52 (}()77:!: oo14 (}{)68 :l:(}009 0-023:1: (}()6 A. indicum 6-23:1::2045 9-90:l:2-98 135-00:1:: 2(}()5 (}()50:l:: oo13 (}()45:l: 0-005 0'014:l:0-003 Survival (%) 'Growth Index- Total developmental period Biochemical parameters ofdifferent hosts on E. vittella 331 Table 2. Biochemical constituents" in seeds of three hosts of E. vittella. Reducing Non reducing Total soluble Free amino Host sugars sugars sugars acids Proteins Okra 5·66 12-45 17·58 2·73 15·10 Cotton 5·88 13-34 18·62 2·65 14·64 A. indicum 1·74 16·38 18'12 1·85 12·02 *Values in mgjg (mean of 3 replications). A. indicum being 26·33±3·29 as against very high levels (67·00±9·09 to 68·00± 5'72% respectively) on cotton and okra. The growth index was also found to be poor in A. indicum and was fairly high in okra and cotton. The fecundity, longevity of adults and the weight of fourth instar larva, pupa and adult on okra was compara tivelyhigher than that of cotton. In these aspects there has been considerable reduction in case of A. indicum. The duration of larval and pupal periods, adult longevity and fecundity observed in the present study on okra, cotton and A. indicum are in conformity with the observations of Hiremath (191:!4). Vedamoorthy and Reed (1977) reported that the spotted bollworms E. vittella and E. insulana exhibits marked preference for various host plants. Vishwapremi and Krishna (1974) observed maximum fecundity in E. vittella when the larvae were reared on developing seeds of okra. It is obvious from the present study that okra and cotton are the most favoured hosts. This finds correlation with the high level of reducing sugars, free amino acids and proteins and low level of nonreducing sugars. In the unfavourable host namely A. indicum, reducing sugars and free amino acids are very low. The nonreducing sugars are considerably high and protein content is also comparatively very less. However, there is no much variation in the level of total sugars. Though Mehta and Saxena (1973) studied the nutritive value of host plants, there is no quantitative indication of the various biochemical parameters. Only qualitative assessments have been presented. It is evident from the present study that a high level of reducing sugars, free amino acids and proteins and low level of nonreducing sugars in the food plants of okra and cotton favour high fecundity, survival and quicker development of E. vittella and these nutrients are found in less amount in the unfavoured A. indicum. In this connection it may be of interest to note that high level of reducing sugars in Brassica campestris has been correlated with high level of infestation of the agromyzid pests viz Liriomyza brassicae Rilay and Chromatomyia horticola Gour (lpe 1985) and in rice increased amount of free amino acids was correlated with its susceptibility to yellow stem borer (Vidyachandra et aI1981). Though A. indicum was found in large numbers in the campus and throughout the state, periodical surveys revealed no natural infestation and the nonpreferred nature of the host might probably be responsible for this. In Karnataka, on the other hand infestation of E. vittella on A. indicum was observed and the mean number of fruiting bodies damaged was 0·\0 as against 5·74 on cotton and 60·68 on okra.