ABSTRACT

Medicinal plant extract is used to mitigate, eradicate or cure diseases as it contains bioactive molecules. The aim of the study was to find out the most efficient and auspicious plants which are effective for controlling tea leaf’s thrips (Scirtothrips bispinosus). Five medicinal plants extracts viz. Polygonum hydropiper, Persicaria flaccida, Monochoria hastata, Sapium indicum and Annona reticulata had been used with four different concentrations in this study. One-way ANOVA and Post-hoc test along with coefficient of variation (CV) was used to fulfill the aim of the study. The study found that Persicaria flaccida and Sapium indicum are the most auspicious among all the experimented plants extracts based on both time and concentration. In the study, average mortality was found 3.1 for 1%, 6.9 for 5%, 9.6 for 10% and 11.7 for 15% concentrations, respectively. However, the mortality of thrips increases significantly with the increase of concentrations. Coefficient of variance was found minimum for Sapium indicum (0) and Persicaria flaccida (4.97) plants based also on time and concentration. Ultimately the study concluded that two plants viz. Sapium indicum and Persicaria flaccida are the most effective plants among the five experimented plants for controlling the tea thrips. For the rest of the three plants, the effectiveness could be ranked as Monochoria hastate>Polygonum hydropiper>Annonareti culate, respectively.

Key words: Bioactive, extracts, Post-hoc test, tea, thrips.

Introduction

In world, 1034 species of arthropods, 82 species of nematodes, 1 algal disease and 350 fungal diseases are associated with tea plants (Chen and Chen, 1989). So far 4 mites, 25 insects, 10 nematodes, 18 fungal and 1 algal disease and 37 preponderant weed species have been recorded in tea plantation in Bangladesh (Sana, 1989). Crop loss is, recorded about 10-15% annually, caused by pest attack (Ahmed, 2005; Mamun et al. 2016). Tea plant is exposed to attack of pests, diseases and weeds all over the season (Paul et al., 2017). Scirtothrips bispinosus of Thripdae family commonly known as Bengal tea thrips are tiny, slender and having fringed wings. Tea Thrips are prevalent in Darjeeling during summer months and its serious attacked is noticed during May and June (Bhujel et al., 2016). Scirtothrips bispinosus is responsible for devastating damage at youngest open leaves in tea plants during flashing periods. The sucking marks of thrips made thin pale lines under the leaves parallel to the main vein. As a result, normal leaves are turned into thicker, harder and often puckered as well as deformed (Saha et al., 2010). Overzealous and indiscriminate use of many synthetic pesticides during recent decades in controlling plant pests has resulted in a number of environmental and toxicological problems (Mamun and Ahmed, 2011). Reducing the release of synthetic chemicals into the environment requires the alternative sources of chemicals development that can be used safely in the management of plant pests. The increasing awareness of negative effects of synthetic pesticide on human and animal health and the agro-ecosystem, research efforts on alternative and more environmentally friendly methods of controlling pests and diseases have proliferated (Zhou et al., 2019; Hagstrum and Athanassiou, 2019). The biological activity of essential oil extracted from the leaves of Polygonum hydropiper and a compound, isolated from this plant was bio assayed against larva of mosquitoes, Anopheles stephensi and Culex quinquefasciatus (Maheswaran and Ignacimuthu, 2013). Some plant extracts possess significant ovipositor difference or antifeedant or toxic