MEDICINAL AND AROMATIC CROPS (2+1)

Pests and diseases

Pests
There are several diseases and pests which infect this crop and result in low yields. The spotted boll worm Earias insulana and E. fabia are the most severe pests of the plant. These insects attack the plants during the flowering as well as at the fruiting stages. The growing shoots are affected by this pest. The infested shoots above the point of infestation become brown, droop and die. The attack of the pest extends from seedling to harvesting stage. During the fruiting stage, the fruits are attacked; the female worm lays eggs in the fruits. On hatching, the larvae feed on the seeds. Spraying the plant with a 0.15 to 0.2% solution of Thiodon 35 E.C. at an interval of 10-15 days from the time the crop is of one month old till harvest reduces the incidence of the pest.
The plants are sometimes seriously infested with red mites (Tetranychus telarius). The mites cover the undersurface of the leaves and suck their juice. In the later stages, the mites make a whitish net and kill the leaves. Spraying the infested plants with 0.1% wettable sulphur solution controls the pest.
Red cotton bugs (Dysdercus cingulatus), cotton aphids (Aphis gossypii), and green peach aphids (Myzus persicae), have also been observed on the plants, but these have not caused much damage to the crop.

Diseases
The young plants sometime exhibit a mosaic-like appearance on the leaves which is caused by the Hibiscus mosaic virus. Such plants have to be removed immediately.
Collitotrichum hibisci is reported to cause anthracnose. For controlling this disease, the seeds should be treated with Agrosan GN or Cerason before and the crop may be sprayed with Bordeaux mixture. Leaf-spot disease is caused by Alternaria hibiscicum, and Phytophthora spp. causes leaf blight. Fusarium wilt caused by Fusarium vasinfection has also been reported. On the drying stems and branches, a sooty black fungus (Pseudotorula verrucospora) has been observed.