Bug Helopeltis Theivora Research Articles

Behavioural Response and Mass Trapping of Males of Tea Mosquito Bug Helopeltis theivora Waterhouse

Tea mosquito bug (TMB) Helopeltis theivora Waterhouse is one of the major pests in both south and north Indian tea plantations. This study was conducted to find out the behavioral responses of male TMB for developing a mass trapping technology. The study shows that TMB male’s behavioral response was high towards the thorax extract of virgin females, virgin female body wash and live virgin females. Males’ antennal responses were high towards to thorax extract of virgin females; the same sources performed well against male TMB under field conditions too. Caged virgin females provide prolonged attraction throughout their lifespan; in contrast, thorax and virgin female body extracts’ attraction rate lasted only up to 24 hr but achieved a significant attraction rate over male TMB. Caged female and thorax extract could be the effective tools for mass trapping, monitoring and controlling of TMB through mating disruption.

Evaluation of profenofos against tea mosquito bug Helopeltis theivora waterhouse on tea

Two field experiments conducted to evaluate the efficacy of profenofos (from a new source) along with standard checks against tea mosquito bug, Helopeltis theivora Waterhouse on tea revealed it to be effective in controlling the pest. Profenofos 50 EC @ 1000 g a.i. ha⁻¹ recorded an average reduction of 79.35 and 77.11 per cent damage by tea mosquito bug at Iyerpadi estate and Lower Paralai estate, respectively. Its application @ 800 g a.i. ha⁻¹ was equally effective and recorded an average per cent reduction of 73.89 and 76.69 per cent damage in the two respective field trials. The recommended dose of profenofos @ 500 g a.i. ha⁻¹ was also on par with the two higher doses with an average per cent reduction of 67.71 and 76.69 damage by tea mosquito bug in the two trials, respectively.

Sex-based variation in insecticide susceptibility and tolerance related biochemical parameters in tea mosquito bug Helopeltis theivora

Helopeltis theivora, one of the major pests of tea from North east India, reported to acquire tolerance against commonly used synthetic pesticides. Study on relative toxicity of both sexes of H. theivora along with their detoxifying enzyme levels were carried out to assess developemnt of sex-based tolerance of pest against the pesticides. The present study showed that female develop more tolerance among H. theivora population than male. Relative toxicity tests showed that LC50 was higher in female than male H. theivora. This result reflects in general, sex level difference in tolerance status of the pest along with corresponding changes in the quantities of detoxifying enzymes. Female of H. theivora showed significantly higher general estearse and glutathione-S-transferase activities than that of male; however there was no significant difference in cytochrome P450 activity. The total body lipid content was also found to be higher in female than male, which indicated female attribute to be more tolerant than male. Body weight of female was significantly higher than that of male, which showed positive correlation with general esterase and glutathione-S-transferase. Hence, on application of recommended dose of pesticide, chance of survivability of female is better in field, leading to addition of more tolerant forms.

Efficacy of certain common ferns against red spider mite Oligonychus coffeae and tea mosquito bug Helopeltis theivora infesting tea

In search for botanicals as an alternative remedy to synthetic chemicals in the pest control of tea plantations, ferns such as Adiantum raddianum, Asplenium aethiopicum, Cyclosorus interruptus, Dicranopteris linearis, Diplazium polypodioides, and Pteridium aquilinum were evaluated against the two major pests of tea, red spider mite Oligonychus coffeae Nietner and tea mosquito bug Helopeltis theivora Waterhouse, which are the foremost seasonal pests in tea fields, causing severe crop loss. Apart from synthetic chemicals, only the neem kernel extract is recommended in tea fields. The aqueous extracts of ferns were screened at different concentrations against these pests under laboratory and field conditions. The extracts of P. aquilinum and D. linearis showed good contact toxicity at a 5% concentration to O. coffeae. The acaricidal activity was observed in the order P. aquilinum > D. linearis > C. interruptus > A. raddianum > D. polypodioides > A. aethiopicum. Under field conditions, the extract of D. linearis and P. aquilinum showed a 50% reduction in the population of red spider mite and caused no phytotoxic effect to tea leaves. But their insecticidal activity was less pronounced against H. theivora. They exhibit antifeedant activity, which was sustained only for 24 hours. The photochemical screening of extracts showed a qualitatively increased level of saponins in P. aquilinum, D. linearis, and C. interruptus. The study shows that the aqueous extracts of D. linearis and P. aquilinum can be incorporated in the mite control programme in tea.

Insecticide susceptibility and activity of major detoxifying enzymes in female Helopeltis theivora (Heteroptera: Miridae) from sub-Himalayan tea plantations of North Bengal, India

Despite the continuous use of synthetic insecticides during the last two decades, the tea mosquito bug Helopeltis theivora Waterhouse still exists as the most destructive pest of tea in North East India. The susceptibility levels of the female sucking bug collected from conventional (synthetic insecticide treated: Terai and Dooars plain regions) and organic (synthetic insecticide untreated: low-altitude Darjeeling region) tea plantations of the northern part of West Bengal to two synthetic insecticides, quinalphos and cypermethrin, and the activity of three principal detoxifying enzymes were assayed. Compared with the susceptible Darjeeling population, the Terai and Dooars populations showed a resistance factor at the lethal concentrations for 50% level ranging from 547- to 2680.87-fold and from 3810- to 7480-fold for quinalphos and cypermethrin, respectively. General esterases (GEs), glutathione S-transferases (GSTs) and cytochrome P450-mediated mono-oxygenases (CYPs) also showed an increased activity in the Terai and Dooars populations compared with those from Darjeeling. Defence enzyme activity was enhanced by 15.4- and 17.6-fold for GEs, 1.8- and 1.9-fold for GSTs and 2.1- and 2.4-fold for CYPs in the synthetic insecticide-treated H. theivora populations when compared with the untreated Darjeeling populations. Electrophoretic analysis for GEs showed a higher level of expression for esterase I–VI isozymes in the Terai and Dooars populations when compared with that in the Darjeeling populations. This study reveals a reduced efficacy of quinalphos and cypermethrin against field populations of H. theivora, possibly due to enhanced activities of GEs, GSTs and CYPs. The findings may be used in developing integrated resistance management strategies that can help in the effective control of this major tea pest.

Fitness traits of insecticide resistant and susceptible strains of tea mosquito bug Helopeltis theivora Waterhouse (Heteroptera: Miridae)

AbstractWe compared the biological traits of insecticide resistant and susceptible field populations of tea mosquito bug Helopeltis theivora Waterhouse. The insecticide resistant population of the conventional Tea Estate “Chuapara” of the Dooars, Jalpaiguri, differed significantly from the susceptible strain of the organic Tea Estate “Makibari” of Darjeeling. Both these tea plantation areas are located in the northern part of West Bengal, India. Adverse changes in biological and developmental traits were observed mainly in: (i) reduction in oviposition period; (ii) fecundity; and (iii) prolongation of nymphal and total developmental period. However, all other parameters such as pre‐ and post oviposition periods, egg incubation period, hatchability and adult longevity were not significantly different. These results clearly demonstrated that only certain fitness components in the resistant strains appear to be adaptively changed and lowered.

Development of resistance to endosulphan in populations of the tea mosquito bug Helopeltis theivora (Heteroptera: Miridae) from organic and conventional tea plantations in India

The tea mosquito bug Helopeltis theivora (Waterhouse) is an important economic pest of tea in India. The development of resistance in H. theivora populations obtained from a conventional plantation and an organic plantation was studied in the laboratory for five generations, and associated changes in life cycle traits were assessed. Selection using sub-lethal concentrations of endosulphan resulted in a 4.4-fold increase in insecticide resistance ratio from the F1 to the F5 generation in the H. theivora population from the conventional plantation. By the F5 generation, nymphal duration was higher and fecundity was lower in the endosulphan-selected strain than in the non-selected strain from a conventional plantation and the susceptible strain from an organic plantation. These findings have practical implications for insecticide resistance management of this important sucking pest of tea.

Impact of environmental factors on infestation of tea leaves byHelopeltis theivora, and associated changes in flavonoid flavor components and enzyme activities

Attack of tea plant (Camellia sinensis (L.) O. Kuntze) leaves by the tea mosquito bugHelopeltis theivora (Hemiptera: Miridae) was positively correlated to temperature and rainfall, and partially to humidity, as determined in 12 varieties during the period 2000–2002. The insect attack was severe during the months of May–September, which had high temperature and rainfall, and led to severe loss of biomass due to curling and drying up of the leaves. The biochemical response of these 12 varieties of tea to attack by the insect was determined with special reference to oxidative enzymes and flavonoid flavor components. Insect attack led to an increase in the activities of the oxidative enzymes peroxidase, ascorbate peroxidase and polyphenol oxidase. Activities of phenyl alanine ammonia lyase generally decreased as a result of insect attack, which was significant in the United Planters Association of South India (UPASI) varieties. A significant decrease in polyphenols was also obtained in UPASI varieties. HPLC analysis of catechins revealed a decrease in some of the catechins in the infected leaves. Analysis of theaflavins from infusion of healthy andHelopeltis-infested tea leaves revealed no changes.

NEW RECORDS OF HEXAMERMIS (NEMATODA: MERMITHIDAE) PARASITIZING THREE SPECIES OF SLATEROCORIS (HEMIPTERA: MIRIDAE)

The parasitic juveniles of mermithid nematodes attack a variety of hosts from 15 insect orders (Welch 1963, 1965). Little is known of the extent to which they are parasites of Miridae. Menzel (1922) and Cobb et al. (1927) recorded parasitism of the bug Helopeltis theivora Waterh. by Mermis sp. and by Agamermis paradecauta Steiner, respectively. A related mirid, H. antonii Sign., was reported parasitized by Mermis sp. (Menzel 1922), and by A. paradecauta and Hexamermis microamphidis Steiner (Steiner 1925). Recently King (1969) found that the mirids Sahlbergella singularis (Hagl.) and Distantiella theobroma (Dist.) were hosts of the genus Mermis Dujardin.