Abstract
Bionomics, extent of damage and management of jute yellow mite, Polyphagotarsonemus latus, (Banks) were studied in the laboratory and field during March 2010 to September 2012. The incubation period, larval period, pupal period, total developmental duration, adult longevity, sex ratio, preoviposition and oviposition period of the yellow mite varied in three successive generations. Parthenogenetically reproduced offspring's were male and required significantly less time to complete the development than the sexual form. High mite population occurred during the last week of May to the first half of June and reduced sharply reaching to a minimum in the second half of July after heavy rainfall. A much higher mite population was found on the lower surface of the leaves than upper surface. Maximum mite population occurred in the upper canopy consisting of top five apical leaves. Higher number of yellow mite was found at noon than the other period of the day. More infestation was recorded in the early sown jute plants than in late sown plants. Damage symptom was categorised into six rating scales depending on difference in mite infestation. In rating scales 1 and 2 slight change in colour and shape of the leaves occured but in the scale 3 the apical leaves turned to deep brown and curled downwards severely. In rating scale 4 more than 7 leaves turned coppery brown and were dropped from the still alive top shoot but in scale 5 it showed a leafless dead top shoot. The jute plant attained its maximum height of 358.15 cm in rating scale 0 followed by 351.15 cm in the scale 1 and the lowest of 192.83 cm in the scale 5. Yellow mite infestation caused increased number of internodes but shorter in size. The highest fibre yield of 3.38 ton/ha was obtained from rating scale 0 and the lowest was 2.31 ton/ha in the scale 5 resulting in the yield loss of 39%. The number of flower seed pod/plant, seeds/pod and seed weight were also highest in rating scale 0 and all the parameters showed the lowest value in the scale 3. The morphological changes in the plants were associated with the feeding damage in mesophyll tissue and development of lesion and necrosis of abaxial epidermal layer and spongy parenchyma in the plants of rating scale 2 and 3. The jute accessions 1510, 890 and 33-1-244 (A)2 showed 9.75, 9.68 and 9.93% yellow mite infestation in net house and the accession 1510 and 890 which showed 9.90 and 10.23% infestation in the field could be considered as tolerant planting material for the low infestation. Several predator of jute yellow mite, viz, Predatory mite, Thrips, Minute pirate bug, Lady bird beetle, Red bug, Mirid bug, Spider, Slender spring tail and Thrips were studied in the jute ecosystem with their seasonal incidence and predation performance. The neem seed kernel extract, mahogany seed extract and spent tea extracts were found highly effective showing reduction of 70.12%, 68.43% and 65.09% plant infestation by yellow mite while jute seed extract, green neem leaf extract and turmeric powder extract were moderately effective and Mahogany leaf extract was least 55.32% effective against jute yellow mite. The acaricides Ethiosul 46.5 EC @ 0.13%, Haysulf DF 80% @ 0.06%, Aimcoflo 80 WDG @ 0.35%, Thiovit 80 WG @ 0.06%, Ambush 1.8EC @ 0.004%, Omite 57 EC @0.06% and Sharper 5 WDG @ 0.005% resulted in above 90% mite mortality. All the tested acaricides with the selected doses showed reduction of plant infestation above 85% indicating high efficacy against the pest jute yellow mite.