Pests of tulsi (ocimum tenuiflorum L ) and their management

Abstract

The seasonal occurrence and the extent of damage caused by pests of tulsi were assessed in a survey conducted at monthly intervals for one year in five locations viz., Perumpazhuthoor, Parasuvaikkal, Poojapura, Peroorkada and Vellayani of Thiruvananthapuram district. A field trial was carried out in the Instructional Farm, College of Agriculture, Vellayani to evaluate the effect of various botanicals against the pests, the spiders and on herbage yield of tulsi.

The five major hemipteran pests recorded on tulsi were Monanthia globulifera W., Aphis gossypii Glover, Cajanus cajani Maskell, Phymatostetha deschampes L. and Icerya spp. The minor pests recorded were Anchon pilosum L., Lygaeus sp., Agonoscelis sp., Leptocorisa acuta (Thunb.), Pseudococcus sp., Cyrtacanthacris sp., Syngamia abruptalis Wlk., Anisephyra ocularia Fab., Lasius sp. and Solenopsis sp. A viral disease and a fungal leaf spot caused by Colletotrichum gloeosporioides Penz. were also recorded.

The infestation by A. gossypii., Icerya spp., P. deschampes, A. pilosum Lygaeus sp., Agonoscelis sp., L. acuta, Pseudococcus sp., A .ocularia, Lasius sp. and Solenopsis sp. are being reported for the first time. The diseases are also being reported for the first time from Kerala.

All the five major pests were polyphagous in nature. The incidence of the pests and magnitude of damage caused by them varied among the different locations as well as during the different months. Both the density dependent factors like availability of other host plants and density independent factors like temperature, relative humidity and rainfall played a major role in the distribution of pests in various locations. Except P. deschampes, the population and infestation of all the other major pests were high during summer months compared to the rainy months. The population and damage by P. deschampes had positive correlation with rainfall.

The natural enemies of the pests included eight species of spiders and a dipteran (syrphid). The spiders were observed in all locations throughout the year. The syrphid Paragus serratus Fabr. was a predator of A.gossypii. An encyrtid pupal parasitoid of P.serratus was also observed. The adults of C.cajani were parasitized by Coccophagus tschirchii (Madhihassan) and the larvae of S. abruptalis were parasitized by Bracon sp.

The results of the pest management trial revealed that the botanicals were not only effective in containing the pests but also safe to the spider fauna. The treatments gave higher yield also. Among the botanicals, pongamia oil two per cent or azadirachtin 0.004 per cent or neem cake soil application @ 250 kg ha-1+ NSKE five per cent could be recommended for the control of the pests of tulsi. This would be of use in the protection of tulsi in homesteads as well as in mediculture.