Bioecology and management of mulberry leaf roller diaphania pulverulentalis(hampson)(lepidoptera: pyralidae)
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Date
2005
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Department of Entomology, College of Horticulture, Vellanikkara
Abstract
Investigations were carried out on the “ Bioecology and management of mulberry leaf roller, Diaphania pulverulentalis (Hampson) (Pyralidae : Lepidoptera ) simultaneously in the department of Entomology, College of Horticulture, Vellanikkara and in Kottat village of Chalakkudy area of Thrissur district during April 2004 to March 2005. The objectives of the study were to find out the biological aspects of leaf roller namely, fecundity, duration of each life stage, number of larval instars as well as bioecological aspects like identification of collateral hosts, natural enemy complex and the correlation of weather parameters on leaf roller incidence and also the pest management issues like population counts at before and after treatments and per cent leaf damage per harvestable shoot.
Relative humidity at morning and evening was negatively correlated to larval population and shoot damage in both the open and intercropped system of cultivation. Photo phase showed significant positive relation on larval population in open and intercropped system of cultivation. Precipitation showed significant negative correlation on the larval population in the intercropping system of cultivation. The number of larvae per plant and shoot damage varied from month to month on mulberry. The number of larvae per plant was 1.56 in June, ascended to 5.37 by December. It came down to 1.47 in the following March in open system of cultivation. The number of larvae per plant was 1.94 in June, ascended to 7.26 by December. It came down to 2.25 per plant by the following March in intercropping system of cultivation. The shoot damage increased from 37.13 (June) to 72.83 (December). It came down to 36.96 by the following March in inter cropped system of cultivation. The shoot damage ascended from 28.5 (June ) to 75.83 (December). It came down to 45.46 per cent by the following March in open system of cultivation.
The biological studies on the leaf roller revealed that the fecundity was 157 eggs with a range of 117 to 211eggs per female. The biological studies in peak season (October to December) recorded the egg period as 4 days, individual larval periods as 1.714, 2.5, 3.214, 3.28 and 3.92 days for the I, II, III, IV and V instar larvae respectively. The pupal period was 7.95 days, the adult male longevity was 8.15 days and the adult female longevity as 10.225 days.
The biology in lean season (February – March) recorded the incubation period of egg as 3.3 days, individual larval periods as 1.516, 2.009, 2.471, 2.52 and 3.5 days for I, II, III, IV and V instar larvae respectively. The pupal period was 7.95 days. The adult male longevity was 8.15 days and female longevity was 10.225 days. The total development period varied from 23.25 days during the lean season to 28.01 days during peak season.
There are many natural enemies affecting different life stages of leaf roller. Bracon hebetor, Chelonus sp. and a mermithid nematode parasitizes the larvae. Tetrastichus howardi attacks the pupae. The spiders Tetragnatha sp. and Philodromus sp. predated on the leaf roller.
The experiments on the collateral hosts showed that the existing weed flora in and around mulberry garden, were not the hosts of leaf roller. The leaf roller did not feed on the leaves of related plant species to mulberry like Jack, Hibiscus and Cucurbits.
The evaluation of different management practices against leaf roller showed that the integration of the practices like clipping of top leaves, inert soil dust application and the application of dichlorvos 0.1 per cent as the best treatment than the individual treatments concerned for the reduction in larval population and shoot damage. The management practices were not pronounced in summer season (February to April). The results were almost similar in open, intercropped system of cultivation. The chemical treatment with dichlorvos at 0.1 per cent afforded greater reduction in pupal population than other treatments.
Dichlorvos exhibited greater ovicidal action by recording the hatchability of 43.33 and 16.67 per cent at 0.1 and 0.2 per cent concentrations respectively. The probit analysis if dose mortality response of dichlorvos at different concentrations showed that 1.73 per cent as the LC50 value. The time mortality response of dichlorvos at 0.1 per cent showed that 17.12 hours as the LT 50 value. The experiments on food consumption and utilization indices recorded that the approximate digestibility (AD), efficiency of conversion of ingested food into body tissue (ECI) and the efficiency of digested fool into body matter (ECD) were 53.3, 37.34 and 25.23 per cent respectively.
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