Special Bulletin Integrated Management of Tea Pests of Northeast India www.tocklai.org CONTRIBUTORS • Dr. Somnath Roy • Dr. Azizur Rahman • Dr. Mridul Sarma • Dr. Azariah Babu • Mr. Bhabesh Deka FOREWORD This bulletin on Integrated Management of major tea pests of Northeast India is based on existing as well as recent findings of concluded R&D projects. The pest scenario has changed considerably in recent years and some minor pests have now become major ones. Of late, high infestation by scale insects has been reported from several districts of Assam, especially Tinsukia, Dibrugarh, Sivasagar and Golaghat, which demands immediate attention. This bulletin contains brief descriptions of some major pests of tea, their biology and the remedial measures needed to form an integrated pest management strategy. I hope the bulletin proves to be beneficial to the industry. A.K. Barooah Director 21st September 2018 CONTENTS Topics Page introdUCTION 1 THE TEA MOSQUITO BUG 1 THE RED SPIDER MITE 6 LOOPER COMPLEX 10 RED SLUG Caterpillars 21 TEA THRIPS AND JASSIDS 24 SCALE INSECTS 28 TERMITES 30 TEA WHITEFLY 33 Preparation OF Plant BASED biopestiCIDES 34 at THE GARDEN LEVEL Integrated Management of Tea Pests INTRODUCTION Tea, Camellia sinensis (L.) O. Kuntze, is a perennial crop that is grown as a monoculture on large contiguous areas in India. Being a plantation crop, tea provides a relatively stable micro-climate and food supply for several notorious pests such as insects, mites, nematodes etc., which cause substantial loss of foliage. However, region-wide variation in pest diversity exists due to the influence of climate, altitude and the age of the plantation etc. This publication provides details on tea pests and their possible management strategies. In the case of complex pest situations, total avoidance of pesticides in tea is not possible; although due to the sensitive nature of the crop, pesticide use must be minimal. A tentative IPM strategy for tea cultivation in Northeast India has been proposed in this bulletin, which may ensure low–cost, eco-compatible pest management packages with minimal residue problems. Monitoring pests: Monitoring the pest is one of the cornerstones in integrated pest management. The first and probably the most important step is to divide larger areas of tea plantations into small manageable sizes (blocks), using natural boundaries such as roads, footpaths, main drains etc. to enable convenient supervision. Components of a Micro-monitoring system: • Micronizing -dividing a big division/section into blocks small manageable size (blocks) using of natural boundaries such as roads, footpaths, main drains etc. • Individual Responsibility • Accountability • Spotting/Flagging • Spraying • Post spraying survey and Re-flagging • Repeat round of spraying with different chemicals • Rehabilitatory spray THE TEA MOSQuito BUG (TMB) The Tea Mosquito Bug is considered to be one of the most serious pests of tea in almost all tea-growing countries, as it only attacks the young shoots that make up the actual crop of tea. In recent years, the long and unusual weather patterns during the peak season of activity of the TMB makes it even more difficult to control this pest. Biology of the TMB: Egg: The egg is elongated, sac like, white and about 0.8-1.0 mm in length. The position of the egg is marked by of two hairs of unequal lengths projecting from the surface. Nymph: The freshly hatched nymph of Helopeltis is dirty yellow in colour. The colour of the first and second instar nymph is greenish yellow, but it becomes green in the latter instars. Nymphs are wingless. Adult: The adult is a tiny insect with long antennae and wings. The thorax is yellow in the female and black in the male. The adult is not a strong flier, the normal range of flight being from bush to bush, between alternate bushes at a time. 1 Integrated Management of Tea Pests Egg 1st Instar Nymph 2nd Instar Nymph 3rd Instar Nymph 4th Instar Nymph 5th Instar Nymph Adult (Male) Adult (Female) Life Stages of the Tea Mosquito Bug Nature of Damage: The nymphs and adults of TMB suck the sap of the young leaves, buds and tender stems and while doing so, they inject toxic saliva which causes breakdown of tissues around the site of feeding. Within 2-3 hours of sucking, a circular spot is formed around the feeding point and in 24 hours it becomes translucent and light brown in colour. Within a few days, the marks appear as dark brown sunken spots which subsequently dry up. The badly affected leaves become deformed and even curl-up. In addition, due to oviposition, the tender stems develop cracks and over-callusing, which lead to blockage of the vascular bundle, thereby affecting the physiology, causing stunted growth and sometimes die-back of the stems. 2 Integrated Management of Tea Pests Damage symptoms of TMB Seasonal Incidence: Adults and nymphs of Helopeltis could be seen on tea bushes almost throughout the year, but peak in the incidence in Northeast India is noticed during June and July, often extending up to September, when the number of rainy days is high. In sub-Himalayan Dooars tea plantations, the population of H. theivora is abundant throughout the year. However, the lowest population of this pest is noticed during the winter months of December to February. The population usually begins to build up in the months of May/June, reaching a peak during September to November. Duration of life stages of TMB in the climatic conditions of Assam and Dooars Life stages Duration in days Nov.-Jan. Mar-April June-July Aug.-Sept. Assam conditions Incubation period 16-20 7-8 4-6 5-6 Nymphal period 19-20 16-20 9-14 8-10 Total duration (Egg to adult) 35-40 23-28 13-20 13-16 Dooars conditions Incubation period 6-18 7-15 6-8 4-8 Nymphal period 9-20 8-13 8-10 8-10 Total duration (egg to adult) 15-32 16-24 14-17 13-16 Monitoring: Initially, the sites of initial pest build-up should be detected and marked by observing feeding punctures of the Helopeltis. Upon detection of Helopeltis attack, the spotter should put flags on the affected bush. There should be a single-colored flag in the centre and four different colored flags in square formation around the affected bushes (5 rows from surrounding). Hard plucking should then be carried out to remove all the affected shoots, followed by spraying in the flagged area with the recommended insecticide. Spraying should commence from the outside, towards the central flag. Sampling Method: The percentage of infestation has to be assessed by collecting 100 shoots from the plucker’s basket and counting the number of infested and non-infested shoots to work out the percent infestation. 3 Integrated Management of Tea Pests IPM techniques for tea mosquito bug: Keep all the drains functional to avoid water logging during the monsoon. Localised depressions should be prevented. • Keep the tea fields free from weeds. • In severe infestation, level off skiff (LOS) operations should be followed to minimize the infestation by the next generation of TMB • The TMB prefers moist conditions and moderate temperatures. For that reason, populations of this pest are often higher under heavy shade. Regulate the shade in densely shaded areas by lopping the lower branches of shade trees. Moderate shade of 60% is preferable. • The side branches of tea bushes should be removed to improve ventilation and effective spraying in closely planted fields. • A closer plucking schedule helps remove the inserted eggs and the early nymphs of TMB, before they cause more damage. • The ecotone (border) between forest line and tea plantation needs to be kept clear of weeds and noneconomic plants. Bamboos near tea areas – should not make over shaded. • Uncut drain sides – ideal protected area for TMB. Therefore, side branches of the tea bushes near drain sides should be cut and attention should be taken during spraying for proper coverage. • During cold weather, pruning and skiffing should be resumed from the periphery towards the centre and around 50-60 bushes should be kept untouched for a day or two in the centre to serve as a trap for adult TMB. After thorough spraying of the recommended pesticides, these bushes should be pruned or skiffed. • During cold weather proper bush sanitation like removal of parasitic plants on tea bushes, cut all twiggy thin, diseased tea branches etc. • Alkaline wash or lime wash should be done. • If the weather is rain-free, apply a round of systemic insecticide like thiamethoxam 25WG @ 1:4000(HV)/ thiacloprid 21.7% SC @ 1:1000 (HV)/clothianidin 50 WDG@1:4500 (HV). During rainy spell, spray a round of synthetic pyrethroid, like deltamethrin 2.8EC @ 1:2000HV/ bifenthrin 8 SC @ 1:1600. • Avoid repeated application of the same chemical. • Recent studies have suggested that in certain pockets of upper Assam area thiamethoxam /thiacloprid and clothianidin at TRA-recommended dilution did not provide the desired level of control against TMB. In these areas, thiamethoxam + deltamethrin/ Bifenthrin + sticker, at their recommended doses, showed better results if proper TRA-recommended cultural practices are also followed. • Applying crude aqueous extracts of native plants viz. Clerodendrum viscosum (leaves and succulent stem), Polygonum hydropiper (leaves and succulent stem),Cassia alata (leaves and succulent stem), Xanthium strumarium (leaves and succulent stem), Vitex negundo (leaves and succulent stem) and Amphineuron sp.(leaves and succulent stem) @ 5-8% concentration may also be done in case of lowand moderate infestation of the pest. • Mixing the crude pant aqueous extracts @5% (mentioned above) with conventional pesticides at recommended dilution may help extend the spraying intervals (long term control) (New Experimental findings) • Mix 0.5% sesame oil formulation with PPC cleared insecticides recommended for TMB to enhance the efficacy of that insecticide (New Experimental findings).