UPASI TEA RESEARCH FOUNDATION

Nirar Dam BPO, Valparai-642 127 | Coimbatore (Dis), Tamil Nadu, INDIA.
Recognized by DSIR

ENTOMOLOGY

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Entomology Division involve in basic and applied aspects of insect pests, particularly, biology, ecology and evolving control measures. The division evolved and recommended physical, chemical and biological method of tea pests control. In the past, extensive studies on bioecology, crop loss due to major pests such as shot hole borer (SHB), mites and Helopeltis and its control measures were carried out. Crop loss assessment due to pest incidence and economic threshold levels of tea pest were documented.

Several new acaricides/insecticides, bio-pesticides and insect growth regulators were screened from time to time for their bioefficacy against target pests, impact on natural enemies in tea ecosystem, pesticides, taint and phytotoxicity.

Most of the tea pests are highly seasonal; many attack tea only in dry season while a few are abundant in wet weather; there are a few perennial pests too. Data are available on the bioecology and crop loss caused by major pests such as pink and purple mites, thrips, tea mosquito and SHB. Red spider mite (RSM), Oligonychus coffeae has emerged as an important pest of tea in the last few years. Studies on its population ecology showed that the incidence of RSM was high during January to May and low during June to December. Populations reached a peak in March / April. Studies revealed that the mite can cause more than 18 % loss in crop when the infestation is severe.

Certain cultural operations like plucking, pruning, shade regulation and weed control can be manipulated to reduce the incidence of pests. Populations of leaf folding caterpillars such as flushworms and leaf rollers can be suppressed by manual removal during harvest. Tea mosquito laid eggs on the broken ends (stalks) of plucked shoots. Intensive removal of stalks during plucking will reduce the incidence of this pest. Weeds offer excellent hiding places and serve as alternate hosts for Helopeltis. Growth of weeds/wild host plants in and around tea fields may be controlled which will help to reduce the incidence of tea mosquito. Severity of attack by SHB increases with the age of the field from pruning. Hence, it was recommended to maintain the length of pruning cycles to 4 years in mid elevation areas. Soil application of higher rate of N:K2O @ 1:2 ratio in the first year of pruning cycle significantly reduced the SHB infestation.

The division’s multifaceted research involves biological control in terms of exploiting natural enemies and use of biological compounds to reduce the pesticide load. Neem oil, neem kernel aqueous extract, commercial formulations based on azadirachtin with or without adjuvants and botanical extracts are being evaluated against RSM. Formulations containing azadirachtin have been found effective against pink and purple mites and caterpillar pests such as flushworms and leaf rollers. Use of these neem formulations are recommended mainly to save natural enemies and to reduce the load of synthetic pesticides on tea. Although the knockdown effect is not reported in the neem products, it may act as a strong repellent, feeding inhibitor and growth inhibitor, ovicidal and ovipositional deterrent against insect pests. With the help of a project funded by the ministry of Chemicals and Fertilizers, Govt. of India, neem kernel aqueous extract (NKAE) was evaluated against the red spider mite, leaf roller, flushworm and tea mosquito infesting tea. Results indicated that NKAE @ 5.0% concentration was effective against red spider mite while application of NKAE significantly reduced the population build-up of leaf roller and flushworm when compared to untreated control. NKAE @ 5% concentration was not effective against tea mosquito. NKAE was not phytotoxic to tea and did not impart any undesirable taint to made tea.

During the last one decade, considerable efforts have been made to incorporate non-chemical control strategies and to evolve an integrated pest management programme for tea. Minor status of many of the tea pests is mainly due to the influence of the biocontrol agents. So far, more than one hundred species of predatory and parasitic insects and mites have been reported from the tea estates of southern India. Scientist realized the role of biological control agents in regulation of tea pests and generated extensive data on bioecology of major parasitoids and predators. Effect of egg parasitoid of tea mosquito and predators of red spider mites were already documented. However, at present biology and life table studies of the predatory mite, Neoseiulus logispinosus on RSM were initiated. Similarly, a mass rearing technique of green lace wing (Mallada boninensis), a predator of RSM was standardized under laboratory conditions.

Identification and exploitation of semio-chemical/sex pheromones is yet another area of research in pest management. Research on semio-chemicals using electro antennogram proved that the partially dried bark of Montanoa bipinnatifida (jungle plant commonly known as December flower) contains volatiles which can attract the SHB. Number of beetles attracted to the stem trap was more during June to October with a peak in July. Number of beetles attracted to the stems declined 15 to 20 days, after placement, indicating the need for their replacement. Scientists identified the volatiles using GC-MS and identified economically feasible commercial chemical blends besides optimization of trap blend, dispenser and number of traps per unit area for the control of SHB.

At present, studies on sex pheromones of tea mosquito are in progress. Volatile compounds released by the unmated females were extracted and subjected to GC-MS analysis. Compounds involved in the attraction and their composition were recognized. Olfactory chemo sensilla situated in the antennae of the tea mosquito showed largest response to certain mixtures in Electro Antennogram (EAG).

Evaluation of new molecule of pesticides, pesticide resistance and microbial control of tea pests are certain other major area of research where the association among the fungi, bacteria and viruses with various pest species are established. This area of research enabled the TRI to identify an isolate of Beauveria bassiana infesting the shot hole borer and pave the way to development of wettable powder formulation for the control of SHB which has been commercialized in the recent past. Bacteria, Pseudomonas fluorescence, isolated from tea soils identified as a potential biocontrol agent against control of RSM and commercialized. Sulphur formulations are effective against all types of mites, including RSM. Paraffinic oil was found effective against red spider mites. Since this oil does not leave any residues in tea, it is incorporated into the mite control programme in tea and in organic tea gardens. Extensive studies are in progress under IPDM programme.

Monitoring the pesticide resistance status of RSM and tea mosquito of south India has been initiated where the LC50 values of field collected and laboratory reared (>25 generations) mites against commonly used pesticide were established. Investigations on the integration of cultural and chemical control of tea mosquito are also in progress for evolving an economically feasible management programme against this pest. On the whole, the division’s pest management strategy involving cultural, physical, chemical and biological control measures is well received by the planters.