IMPACTS OF MULBERRY CROP PEST CONTROL AGENTS ON THE SILKWORM BOMBYX MORI

Transcription

1 CHAPTER - 1 IMPACTS OF MULBERRY CROP PEST CONTROL AGENTS ON THE SILKWORM BOMBYX MORI 1. INTRODUCTION Sericulture is an agrobased industry providing a good income to thousands of rural people. Silk the Queen of Textiles an outcome of sericulture activities has a number of applications. The texture, lusture, tensile qualities, comfort, adaptabilities to all climatic conditions, ability to take up dyes are some of the qualities of silk that makes the silk from the mulberry silkworm, Bombyx mori an unequalled textile material. Of the different types of silk (Mulberry silk, Tassar silk, Muga silk and Eri silk), Mulberry silk has an increasing demand globally. To produce this silk the silkworm, Bombyx mori has to eat large quanties of Mulberry leaves during their larval stages. The silkworm Bombyx mori is a voracious feeder of mulberry leaves and this insect is strictly monophagous. For increasing silk production, it is imperative to provide good quality mulberry leaves. Mulberry plant is a perrenial plant belongs to the genus Morus. There are a number of species in genus Morus, of which Morus indica is commonly cultivated in South Tamil Nadu. In M.indica serveral races are developed every year and the most important varieties are M.indica, V2,V5, MR2, S32, S34, S36 etc., A good variety of mulberry plant like V2 or S36 yeild more than 50,000-65,000 kilogram of leaves in a year in one hectare area. The production of mulberry plant is checked by pests and disease attack. Because of pest attack many farmers 1

2 remain uninvolved due to the risks in moriculture based sericulture. The common diseases that affect the mulberry leaves production are viral diseases (Mycoplasma, leaf mosaic virus), bacterial diseases (leaf blight, rot diseases), fungal diseases (white rot disease, violet rot disease, fusarium root rot disease, shoot fungal disease, wilt disease) and nematode diseases (root knot) etc., Besides diseases, pests are the serious threat to the mulberry plant. To control pests if pesicides are applied indiscriminatively, the pesticides will reach the silkworm through the feed they consume and paralyses its life and activities. Hence, it is a matter of great concern to produce several plant based chemicals that can enhance immunity Every day new products like seriboost and nutraceuticals are introduced to minimize pest attack on mulberry plants. However many farmers are still applying Dichlorovos and neem based pesticides. The remnants of the pesticides present in the mulberry leaves will definitely affect the silk production. Hence it has become essential to evaluate the toxicity of commonly used pesticides on the life cycle of Bombyx mori For the present study the commonly used pesticides, Dichlorovos and Vijay neem were selected and their sublethal treatment on feeding, growth and commercial characteristics of the silkworm Bombyx mori were traced. COMMON PESTS OF MULBERRY PLANT (Zheng Ting-Zing et. al., 1994) I. Leaf eating pests 1. Maragaronia pyloalis Leaf roller pest 2. Spilosoma obliqua Bihar hairy cater pillar 3. Spilosoma dalbergiae Hairy cater pillar 4. Amata passalis - Wasp moth 5. Mimastra cyanura Almond leaf beetle 6. Euproctis fraterna Tussock caterpillar 2

3 7. Myllocerus viridanus Greenish white weevil 8. Episomus fugulus weevil 9. Ailopus sinulatrix short horned grasshopper 10. Diplosis mori Gall midge. II. Sap feeders 1. Emposca flavescens Leafhopper 2. Nezara viridula Pentatomid bug 3. Maconellicoccus hirsutus Mealy bug 4. Pseudaulacapsis pentagona Grey scale insect 5. Saissetia nigra Black scale insect 6. Aonidiella auranti Red scale insect 7. Pseudodendrothrips mori thrips 8. Tetranychus equitorius - Mite III.Borer Pests 1. Sthenias grisator Stem girdle beetle 2. Apriona germaria Stem borer 3. Batocera rufomaculata Stem borer 4. Simoxylon pubens powder pest borer. COMMONLY USED PESTICIDES TO CONTROL PESTS IN MULBERRY GARDEN IN TAMILNADU 1. Dimethoate (0.2%) 2. Dichlorovos DDVP (0.02%) 3. Monocrotophos (0.01%) 4. Phosphamidon (0.05%) 3

4 5. Malalthion (0.1%) 6. Vijay neem (0.5%) 7. Acetamiprid (0.05%) 8. Dimethoate (0.05%) 9. Aldrin (0.01%) 10. Quinalphos (0.05%) 4

5 CHAPTER - 2 OBJECTIVES OF THE STUDY In the present study sublethal toxicities of the pesticides that are applied for pest management in the mulberry garden and adjacent fields are evaluated. As pesticides are potential toxicants to interfere with the physiological process including enzymatic activity, reproductive activity and silk secretion activity, some of the pesticides leave residues and give biomagnification. Knowlingly or unknowlingly farmers apply pesticides to protect mulberry crop in an indiscriminate way. The entry of these pesticide molecules through mulberry leaves into the various instars of Bombyx mori hampers the exzyme secretion responsible for silk thread formation during cocooning in the fifth instar stage. Unless the toxicity of these pesticides are thoroughly studied with reference to energeties, economic characteristies, reproduction and development etc the success of sericulture farming will be in vain. So the present study is designed to help the farmers to minimise economic loss and maximise their yield. The objectives of the present study are the following. 1. Evaluation of Sublethal toxicity of the commonly used pesticides in the mulberry gorden Dichlorovos and Vijay neem. 2. Effect of sublethal doses of Dichlorovos and Vijay neem on mulberry leaves utilization and growth of Bombyx mori. 3. Evaluating the effects of sublethal doses of Dichlorovos and Vijay neem on the reproductive performance and longevity in Bombyx mori. 4. Effect of selected pesticides on the development of Bombyx mori. 5. Analysis of the effect of sublethal doses of Dichlorovos and Vijay neem on the economic characteristics of silkworm namely cocoon weight, shell weight, 5

6 shell ratio, sericin and fibroin content silk filament length, reelability and filament denier. 6. Finding out the effect of sublethal doses of Dichlorovos and Vijay neem on the histology of selected organs of Bombyx mori. 1. Evaluation of sublethal dose. 2. Toxicity of sublethal dose after chronic treatment on the following parameters. 1. Food utilization of Bombyx mori. 2. Reproduction and Development in Bombyx mori. 3. Commercial characteristics of Bombyx mori. 4. Histopathological changes on selected organs of Bombyx mori. 6