Insect pests of selected medicinal plants : bionomics and management

Abstract

The availability of Medicinal plants is mainly from the natural resources like forests and .waste lands. Today farmers of Kerala are taking up cultivation of medicinal plants in an organised manner. A thorough survey conducted in three different localities such as herbal gardens of College of Horticulture, Vellanikkara, Thycaud Moos Arya Vydyasala, Chuvannamannu and Kottakkal Arya Vydyasala Kottakkal being listed had resulted in alarming informations. Survey was done just on ten economically important' medicinal plants, viz., Neelamari, Adapathiyan, Chethikoduveli, Thippali, Vallippala, Thulsi, Kacholam, Karalakom, Kasthurivenda and Madhunashini. Complete survey of selected ten medicinal plants indicated the presence of 57 different species of insect pests of which, 44 species are new reports, In Neelamari rate of infestation by psyllids was to a major level. Typical symptoms of 'die back' had been observed. The five minor species include webbers, flower beetles, treehoppers, pentatomids and alydids. The predatory coccinellids, ants and spiders associated with the psyllids were the other new reports. Spiders were observed to prey upon the coccinellids which inturn were psyllid predators. Occurrence of milkweed butterfly on adapathiyan was to a major level. Tachinid flies were found to parasitise the butterfly larvae. Chethikoduveli heavily infested by citraka looper was a major one. A microlepidopteran belonging to the family Cl Grassillaridae was found infesting on Thippali spikes. Spike thrips, thippali mealy bugs were the other minor pests. Vallippala semilooper, a key pest was ranked as a completely defoliating one. Its biology studied reveals that egg period to be three days, larval instars as first, second, third, fourth and fifth, prepupal and pupal duration of 2, 2, 3, 3, 2, 1, 6.4 ± 0.1956 days respectively. Total life cycle was found to, be 22.4 ± 0.1956 days. Tylophoran bug and Asclepidian beetle which were first reports. Glossy tiger in Vallippala was found on a major level. Lacewing bug were found to be major one in Tulasi. But there were numerous minor pests as Tulasi leaf webber, grasshopper, ash weevil, Pentatomid bugs and Coried bugs. Kacholam were infested

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by Lema beetle, black hairy caterpillar and swarming caterpillar which were the minor ones. Karalakom butterfly were ranked as key pest. Its biology and management using botanical pesticides were studied. The egg, larval duration of first, second, third and fourth instars prepupal and pupal stages had a duration of8.2 ± 0.1405, 7.7 ± 0.1768, 7.8 ± 0.1749, 9, 7.9 ± 0.2422,1,14.8 ± 0.1749 days respectively. Total life cycle was found to be that 56.1 ± 0.5248 days. Flea beetles were found to make the leaf papery thin. In Kasthuri venda there were two major and 11 minor pests. The major ones were found to be the pests of okra too. Major ones are shoot and fruit borer and leaf roller. Defoliator in Madhunasini were parasitised by a Hymenopteran belonging to the family Braconidae. Moth bugs and three types of passive visitors observed were also new reports. As the influence of weather parameters on the distribution of key pests were studied, it was observed that with a rise in temperature there was a flare up on Vallippala semilooper and Karalakom butterfly population. With decrease in temperature the reduction in pest population was common for both the pests. When the relative humidity was taken into account, it was evident that decrease in Vallippala semilooper population was indirectly proportional to the relative humidity but it was directly proportional to the spread of Karalakom butterfly. When the influence of wind speed was taken into consideration it was found that wind speed had no direct influence on Vallippala semilooper distribution but with regard to Karalakom butterfly the spread was more with an increased wind speed. While studying the effects of total sunshine hours in a day on the pest spread, it was clear that there was an increase in Vallippala semilooper distribution and a reduction in Karalakom butterfly population with increased sunshine hours. The evaluation of botanical pesticides revealed a maximum antifeedancy with Neem Kernel Suspension (NKS) followed by neem leaf extracts. In the case of Vallippala semilooper hyptis ranked as the next best. While it was yellow oleander for Karalakom butterfly. These eco-friendly approaches are new records.