Scabies, a very troublesome and contageuous skin ailment, is caused by the itch mite Sarcopus scabiei. Head and body lice are dermal insect parasites on humans, pets and live stock. House dust mites cause allergy. Mosquitoes are vectors of malaria and filaria. Cockroaches, house flies, ants, mites, ticks and jiggers spread several diseases. A number of insects are pests of agricultural and horticultural crops and also cause extensive damage to grain and food in storage. The control of these arthropodal pests and parasites has been our prime, but a very frustrating, concern for a century.

A number of synthetic insecticides have been marketed, DDT being the most famous (now infamous) of them. However, with time, the insects have acquired resistance to synthetic insecticides. These chemicals and/or their harmful residues were biomagnified, causing a great deterioration in the quality of the environment. The result is that our insect control has come to almost square one. In consequence, interest in biopesticides, the natural and biodegradable alternative, has acquired a new lease of life.

The use of sandalwood (Santalum album), tulasi (Ocimum sanctum) and a few other plants in insect control is age old. Even today it looks that the best treatment for scabies is the use of sandalwood oil. A terpenoid compound from the bark of sandalwood, which is now a waste product, is a chemosterilent and metabolic deranger, of three species of moths which cause extensive damage to certain forest trees such as Ailanthus malabarica, an important source of match sticks. However, such important research findings are hardly put to use (Kameswara Rao and Sangeetaa, 1993).

Over 2,000 species of plants are believed to be insecticidal (Singh, 2000). The essential oils of Mentha citrata, Pinus longifolia, Cedrus deodara, Matricaria chamomilla (Singh, 2000) and some others (Murugan and Jayabalan, 1999) have been shown to be very effective pesticides, some on mosquitoes.

There is a greaet potential for insecticides from plants. Since metabolic pathways in plants and animals are largely similar, the phytochemical compounds with insecticidal activity can also be used on other pathogens, particularly fungi. The polysaccharide chitin (a polymer of B-1,4-N-acetylglucosamine), is the principal component of the exoskeleton in arthropods and is also a cell wall component in fungi. The molecular architecture of arthropodal and fungal chitin is largely similar. A compound that can affect chitin polymerisation would be both insecticidal and fungistatic.

In view of the current importance of bioinsecticides from plants, the list of promising species is given in Appendix 26. As mosquito control is best effected at the larval stage, larvicidal species are separated out.

PLANTS WITH OTHER THERAPEUTIC EFFECTS

In addition to the above, the following therapeutic groups have been identified for the compilation of databases:

a) Plants with latex with therapeutic properties

b) Plants with demulcent properties

c) Plants with antiasthamatic activity

d) Plants with antirheumatic and antiarthritic effects

e) Plants with expectorant activity

f) Plants with diuretic effects

g) Plants with antispasmodic effects and

h) Plants with memory enhancing activity.

DATABASE OF PLANTS USED AS FOOD

The Food and Agricultural Organisation of the United Nations has identified about 2,000 species of plants as sources of different items of food in the world. Of these, only about 20 species are important and are commonly in cultivation as the major food crops. In addition to those considered by the FAO, an additional 1,500 to 2,000 species are used as food in small local communities in different parts of the world. India is one of the countries with innumerable local plant foods. There are three objectives behind the compilation of a food plant database:

a) The first objective of a database of food plants of a defined area, is to provide detailed information on them. This will bring to light the little known uses of plants as food. Such information will help to introduce new sources of plant foods into other areas, and also to bring to light new uses of existing species. These measures will help in reducing the pressure on the overstretched conventional food plants.

On our field trips we found several species of plants are locally used as food and such uses are unknown outside the area. The following are some unconventional species used as food in some parts of the Karnataka state (Sathnarayana Bhat, 1993):