Larviposition by the Tachinid fly, Sturmiopsis inferens Tns. on sugarcane shoot borer larvae was studied. One adult female laid on an average 285 maggots (range 126-521). More than 90% of the maggots extruded were free of the enveloping chorion. Less than 4% were found to be unfertilized and undeveloped. The mean number of maggots laid per host was 1.21 and more than 70% were laid at the bore hole, the remaining being larviposited near the bore hole. Larviposition began on the sixth day after emergence of the female and mating, reached its peak during seventh to eleventh days and declined thereafter. Over 90% of the total number of maggots were deposited by the thirteenth day. Some maggots (9.52%) were not extruded but remained in the fly's uterus. The number of maggots laid at a bore hole varied from one to nine, but in more than 50% of the shoots only a single maggot was deposited. The flies preferred third, fourth and fifth instar larvae and shoots having only wet frass for larviposition, although larviposition did occur in shoots having second instar larvae and freshly formed pupae.
Four pheromonal components have been detected in ovipositor washings and volatiles from female sugarcane stalk borers,Chilo auricilius Dudgeon (Lepidoptera: Pyralidae), using combined gas chromatography-electroantennography. The components have been identified as (I) (Z)-7-do-decenyl acetate, (II) (Z)-8-tridecenyl acetate, (III) (Z)-9-tetradecenyl acetate, and (IV) (Z)-10-pentadecenyl acetate by comparison of their gas chromatographic behavior with that of synthetic standards. In field tests carried out in northern India during 1982-1984, a combination of II, III, and IV in their naturally occurring ratio (8∶4∶1) was shown to provide a highly attractive synthetic source for trap use. (Z)-7-Dodecenyl acetate was found to reduce catches of maleC. auricilius, both when dispensed with the other three components and when released from dispensers surrounding a trap baited with the other three components.
Seven species of moth borers are known to cause heavy losses in sugarcane production in different parts of the country. Because of their concealed habits, the control of these borers becomes complex and hence a number of methods have been tried to suppress their field population. The sell behaviour of four species of these borers viz., internode borer, stalk borer, shoot borer and top borer have been studied in recent years and among these the internode borer and stalk borer have been found to have potent sex attractants.Mass trapping may be useful in the management of internode borer while disruption technique is likely to be useful in the case of stalk borer. In both the borer species, the synthetic pheromones will be highly useful in monitoring their activity.
The influence of constant temperatures of 27, 29, 31 and 33oC and alternating temperature of 31/33oC (18/6 h) on Sturrniopsis inferens TOWNSEND was studied during 12 successive generations. The larval and pupal periods for male parasites were 13.5 + 0.5 and 11.0 _+ 0.3 days respectively and for female 12.8 _+ 0.5 and 11.1 + 0.3 days respectively in the 1 st generation at 27 ~ C. It decreased progressively with increase in temperature. Survival of females, fertility and fecundity were adversely affected at higher temperatures. A temperature range of 27-29 ~ C appeared to be optimum for mass rearing of the parasite in the laboratory. The high~ premature mortality observed at a constant 33oC was not observed at temperatures fluctuating between 31/33oC, Presumably under field conditions, where temperature is constantly fluctuating, the flies will be able to withstand a comparatively higher temperature. TOWNSEND (Dip. : Tachinidae) is an important larval parasite of sugarcane shoot borers, Child infuscatellus SNELLEN (anon., 1971 ; KALRA & DUTTA, 1971) and C. auricilius DUDGEON (SINGH & YADAV, 1 979) in certain parts of India in recent years. The attempts made to breed it in the laboratory (DAVID et ai., 1980) and to colonize it in a new area (our unpubl, data) have given encouraging results. The success of a natural enemy in biological pest suppression depends mainly on its ability to survive in the environment. Environmental factors that influence the success of a natural enemy are weather, food, resource other than food (i. e. a particular place to live) and other organisms of the same and different species (SoLoMON, 1949). Among these factors, temperature plays a key role and affects the survival and activity of the parasite. In this laboratory study, an attempt was made to study the influence of temperature on S. inferens and to establish the optimum temperature for mass-rearing the parasite in the laboratory for field colonization. Sturmiopsis inferens MATERIALS AND METHODSA culture of S. inferens was started with puparia collected from cane fields around Coimbatore on larvae of the shoot borer, C. infuscatellus. One hundred freshly formed
Susceptibility of adults and puparia of Sturmiopsis inferens Tns. [Tachinidae, Diptera] to 9 commonly recommended insecticide sprays against sugarcane pests was determined. The chemicals tested as emulsifiable concentrates include lindane 0.1%, endosulfan 0.1%, monocrotophos 0.05 %, quinaiphos 0.05 %, malathion 0.1%, dimethoate 0.1%, cypermethrin 0.01%, fenvalerate 0.01% and decamethrin 0.0014 %. Lindane, malathion, dimethoate, monocrotophos and quinalphos were highly toxic, while decamethrin had little harmful effect to the adults when exposed for 6 h to filter paper impregnated or sugarcane shoot bits sprayed with the chemicals. However, the insecticides had no harmful effect on the puparia and adult emergence was normal from the puparia sprayed with insecticides.In another study, susceptibility of adults to soil application of lindane EC, carbofuran G, chlorpyriphos G, Sevidol G and whorl application of lindane G, chlorpyriphos G and Sevidol G was tested in pot culture. Except for soil application of lindane EC, all other chemicals had no harmful effect to the adults in pot culture experiment. In a field trial, commonly recommended insecticides against shoot borer, Chilo infuscatellus Snell. viz., soil application of granules of lindane, carbofuran, chlorpyriphos and Sevidoi and folia spray of endosulfan did not affect the parasite activity. KEY-WORDS : Sturmiopsis inferens, safety of insecticides.Sturmiopsis inferens Tns. [Tachinidae, Diptera] is an important larval parasite of several species of moth borers that damage sugarcane in India (David & Easwaramoorthy, 1986).The level of natural parasitism varied from 6.5 to 26.2 % in shoot borer, Chilo infuscatellus Snell. (David & Easwaramoorthy, 1981), 20 to 50 % in stalk borer C. auricilius Ddgn. (Singh, 1977) and 5.8 to 10.2 % in Gurdaspur borer, Acigona steniellus Hampson (Chauflhary et al., 1980). S. inferens also parasitise minor pests of sugarcane like pink borer, Sesamia inferens Wlk., and sorghum borer, C. partellus Swinhoe.In India, insecticide applications are not widely practised in sugarcane culture compared to other cash crops. However, certain insecticides are occasionally applied for the management of moth borers especially shoot borer and sucking pests like leafhopper, Pyrilla perpusilla Wlk., whitefly Aleurolobus barodensis Mask. and scale insect, Melanaspis (') Institute Publication No 1030.
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