Planters Chronicle July 2015

Transcription

1 5 Pheromone traps- an efficient tool for the management of tea mosquito bug in tea B. Radhakrishnan and K.K. Srikumar UPASI Tea Research Foundation Tea Research Institute Valparai Tamil Nadu, India The tea mosquito bug (TMB), Helopeltis theivora Waterhouse (Heteroptera: Miridae) the most destructive polyphagous sucking pests of tea in India. It has attained the national importance and it was estimated that 80 per cent of the tea plantations area in India is affected resulting in crop loss to the tune of five to 50 per cent. Even complete washout of the crop can happen during peak period of the pest attack. In South India, the incidence of this pest which was restricted only to Vandiperiyar and Peermade (Kerala) areas, has recently spread in an alarming form in tea plantations of Anamallais, Valparai (Tamil Nadu). Helopeltis theivora usually prefers wet weather condition commencing from June to November.Recent years this pest has been noticed throughout the year. More than 100 host plants were recorded for H. theivora. The life cycle of H. theivora consists of three stages viz., egg, nymph and adult.climate change and favourable weather factors are the possible reasons for the sudden outbreak of this pest. Presently the only method used for managing TMB is insecticide application which is very harmful to human health and detrimental to environment. Even after the continuous use of the insecticides the control of TMB could not be achieved in many plantations. This indiscriminate use of synthetic pyrethroids and other chemicals result in resurgence of new pests, becoming a serious concern in tea. Pesticide residues in tea are causing a serious concern globally and several countries are revising the MRL of chemical pesticides downward. Pesticide residues reduce the competiveness of Indian tea in the global market.to meet the expanding demand for safer tea led to the search for more effective and alternative methods to control the pest based on sound ecological principles. The use of attractant/ pheromone traps has long been practiced by applied entomologists. The potential applicability of sex pheromones to attract insect pests is gaining momentum. Improving the non-insecticidal methods like use of sex pheromone (as lure and kill method) and biological control will have better scope to reduce the dependency on insecticidal control for H. theivora on tea. Various researchers in India demonstrated the attraction of H. theivora males to conspecific females presumably through sex pheromones. Field experiments also confirmed the attraction of male bugs of Helopeltis spp. towards virgin females. The short-range sex pheromone of female TMB elicited copulatory behaviour in males. This sex pheromone can very well be used as lure and kill method and as a monitoring tool to undertake insecticidal control in a judicious way for tea. Indiscriminate use of insecticides in tea plantations can be avoided and the potential risk of pesticidal residues in tea can be reduced. The pheromonal research on Helopeltis is being conducted for the past four decades all over the world. Several achievements has been made but the final delivery to the field has not been satisfactory. Previously the compounds such as (Z)-3 hexenyl acetate, (Z) - (3) hexenyl butanoate, (E)-2 hexenyl pentanoate, 2, 4 dimethyl pentanal and (E)-2-hexenol were isolated from H. theivora female. These compounds either alone or incombination failed to attract the males under field conditions.

2 6 Several studies were conducted at the Entomological Division of UPASI Tea Research Institute, Valparai to explore the pheromonal technique for the management of TMB. Males were attracted to virgin, laboratory reared females which were confined to tea shoots in mesh cages (Fig. 1). These observations suggested that mature virgin females of H. theivora emitted a sex pheromone which attracted males. Where aggregations of males on the tea bushes containing the cages were recorded, it was assumed that these aggregations were related to an attractant pheromone. The male attraction commenced on the fourth day after females moulted, and maximum attraction was observed on the 5th to 9th days after moulting. Females, deposited infertile eggs on or after the sixth day, continued to attract males to the sides of the cages until the last day of oviposition. Fecundity was observed in these virgin females and they attracted maximum males on 5th day when ovary development was completed and commencement of oviposition. Reproductive organs of TMB especially spermatheca secretes the sex pheromones, which is responsible for the attraction of males. Fig. 1. Helopeltis theivora males on mesh cage The sex pheromone traps of TMB using virgin females to attract the males, have been successfully demonstrated in many estates in the Anamallais. The advantage of this trap is that it is species specific. One newly hatched virgin female was placed in the central cage of the pheromone trap. Females were changed twice a week, and fed on tender tea shoots. Results (Fig. 2) indicate that the virgin female traps (pheromone traps) were found very effective in attracting thousands of males. The total monthly counts indicated that there was an increasing trend in the trap catches from August to November 2014 (Fig.3). Maximum number of catches were observed during September to November. On an average, a single trap attracted 100 to 500 males per day. This clearly indicated the remarkable effectiveness of sex pheromone trapping. Sticky traps was found to be most efficient in capturing the responded males (Fig.4). The fluctuations in TMB captures were in accordance with the population dynamics on different months in the field. Considering the importance of TMB, it would seem that pheromone traps are an urgently needed tool. Through pheromone traps all the responded males can be entrapped and population of the pest can be regulated during high pest intensity on tea. Insect sex pheromones are used in pest management for both monitoring and control. Mass trapping using pheromone traps reduces insect

3 7 Fig. 2. H. theivora males collected from a single trap Fig.3. Field study conducted in different estates of Anamallais ( )

4 8 pest populations which can lead to a reduction in damage in tea fields.the strong attractiveness of males due to sex pheromone in H. theivora provides substantial scope for exploiting this behaviour for mass trapping technique through its synthetic lure as lure and kill method as well as for monitoring of pest population to use the chemical control in a judicious way instead of scheduled way. Recently,good achievement has been made in pheromonal research. Scientists from UPASI Tea Research Institute, Valparai, Coimbatore and CSIR-Indian Institute of Chemical Technology, Hyderabad have jointly invented a natural product for the management of tea mosquito bug. This product inserted in a trap can attract and kill this noxious pest.the product is totally environmental safe, cost effective and highly efficient in trapping the adult males of TMB. Pheromones are behavior-modifying chemicals, also called semio-chemicals that act as signals to other insects of the same species. Pheromone released by one sex (i.e., female) of insect species which influences the behavior of the opposite sex (i.e., male) of the same species. In this capacity, the pheromone is capable of disrupting mating or otherwise controlling the insect population. Large scale field trial of this pheromone in Plywood block dispenser showed more effectiveness and longevity than other dispensers. In addition to its effectiveness and longevity, use of the plywood blocks with attractant lure was easy and cheap. The attractant lure injected in the plywood block dispenser kept on glue trap could effectively attract and kill the tea mosquito bug (Fig. 5). Fig. 4. Sticky trap with Helopeltis theivora males trapped As an interim recommendation these traps can be placed just above the bush canopy. The recommended number is 10 to 12 traps/ha. These traps can be effectively implemented along with other IPM practices like cultural, mechanical and chemical. The life span of the lure will vary from 7-10 days depending on the agro-climatic factors. The traps are supplied free of cost from UPASI, TRF to member estates. In future these traps will be available on a commercial scale. For the requirement of estates please contact the Director, UPASI, TRF.

5 9

6 10 Based on the results presented here traps/ha will be sufficient to control TMB populations. As part of this research, the possible use of sex pheromone traps for mating disruption should be considered. Use of pheromone baited traps can be used as a major component in the Integrated Pest Management (IPM) technique for effectively managing tea mosquito bug. Further studies on optimum dosage, duration of attraction and trap design are under progress. Acknowledgments Fig. 5. Trap with good catch of TMB The authors are thankful to M/S TATA Coffee Limited, Woodbriar Group, Bombay Burmah Trading Corporation Ltd., Murugappa Group- Parry Agro Industries Ltd., Jay Shree Tea & Industries Ltd., The Peria Karamalai Tea & Produce Co Limited, Harrisons Malayalam Ltd., POABSONS Ltd. and TN Tea Plantation Corporation Limited (TANTEA) for the necessary support provided during the field trials. PLANTERS CHRONICLE THE BEST MEDIUM OF REACHING PLANTERS IN INDIA