DESCRIPTION OF RESEARCH PROJECT

An estimated 37% of all crops are lost annually to pests, in spite of the use of pesticidal and non-chemical controls; being insects the biggest problem with a 14% of loses (pathogens and weeds conform the other 23% with equal shares) (Pimentel, 1985). These figures tends to increase, due to reasons like planting crop varieties more susceptible to insect pests, habitat disruption of natural enemies of plagues, extensive monocultures and a demanding economy that claims for more productivity and unblemished goods. But the extensive use of pesticides has indirect costs, very difficult to calculate: disruption of pollinators, losses of wildlife, destruction of soil invertebrates, microflora and microfauna, and moreover, chronic health problems like teratogenic and mutagenic effects. The search for environmentally and user friendly products has lead to the use of biopesticides, and although currently they represent only a small fraction of the world pesticide market (4.5%), there is a forecast of growth rate for this market of 10-15%, in contrast to 2% per annum for chemical pesticides (Menn, 1999). There are various reasons for the small share: lack of broad-spectrum activity, low speed of control, residual life, shelf life and high cost when compared to chemical pesticides. Typically, the use of a biopesticides will cost between 3 to 7 times more than the chemical counterpart (Uri 1989). But the disadvantage will be probably sorted out in the near future when high demand of organic farms granted with attractive subsidies to compensate for additional cost, and globally policies press for safer material and alternatives to chemical pesticides. The main goal now is the use of insect-pest-specific insecticides, which fit well in an Integral Pest Management program (IPM), being the former one of the desirable characteristics of many chemicals produced in plants as defensive compounds. Experts in the topic like Dr. Isman (Isman 1999) predict that "the prospectus for botanical insecticides is the most favorable it has been for 50 years".

The occurrence of toxins as secondary metabolites in plants is a widespread and significant phenomenon: the result of coevolution between plants and herbivores. This is an intricate relationship where plants, that provide the source of food to animals, have evolved defense mechanisms to avoid being overeaten by using their chemical armor (Janzen 1980). Animals overcome plant defenses with a variety of responses like compound detoxification and even the transformation of these toxins into defense mechanisms against their own enemies (Harborne 1993). Since ancient times, humans have been aware of the presence of poisonous plants in their surroundings, pondered the physiological effects and have learned to identify and take advantage of these plants, using them as drugs, poisons against crop pests, for fishing and hunting and to keep homes free of insects. Recognizing potentially harmful plants and telling them apart from edible ones is a survival adaptation transmitted orally through generations in almost every culture.

Most of this valuable indigenous knowledge is rapidly disappearing because our urban society does not need to rely on wild plants for food, and synthetic chemicals solve the problems of infestations. At the same time, many useful plants are becoming extinct due to environmental change, pollution and deforestation. Very soon, we may be deprived of the possibilities of exploring the traditional knowledge of botanical pesticides, insect repellents, natural vermifuges and fish and animal poisons. A thorough documentation of each of these categories of useful plants could provide chemists with innovative models of substances with novel applications.

The purpose of this project is to collect information about toxic plants with specific uses in Cajamarca, Peru. The Cajamarca area encompasses ecological regions between 500 and 4,000 meters above see level. The region, crossed by the high altitudes of the Andes, is situated in a transitional zone, between the northern tropical Andes of Colombia and Ecuador, and the Andes of southern Peru. This ecological condition has resulted in a unique and diverse flora in the Cajamarca area (Becker 1988). Some areas still show stone terraces and evidence of human activity that suggest the land has been cultivated for at least three millennia. The introduction of European cultivated plants, domestic animals and working methods have had a huge impact on the ecosystem. The natural forest vegetation in vast zones is nearly lost, due to the high timber demand imposed since the time of the Spanish conquest and later by intensive agriculture demanding more fields and the use of forest products as fuel for cooking (Ellenberg 1979). This situation has resulted in degradation of the vegetation cover and loss of organic matter in sheet erosion, in some areas down to the parent rock.

The inhabitants of Cajamarca, Quechua descendants, still keep many of the traditions and customs of their ancestors. In part because of poverty and in part because of a strong sense of their own culture, the simple way of living of these peasant communities has continued to this day. But this could change rapidly. Migration towards more productive agricultural areas in the lowlands, increasing tourism around the region and the gold boom created by the exploitation of nearby mines, are steadily modifying not only the landscape, but the culture of the people as well (Morrow 1997).

Hypothesis

Historically, people of the area of Cajamarca used plants that have toxic compounds for different purposes, but especially as botanical pesticides and repellents. Because of the wide range of altitudes included in the region, there is also a wide variety of species and plant families throughout the ecological zones. Some of these species will have similar uses in different communities, while in other cases, the same plant will be used in different contexts by people living at different altitudes or ecological conditions. This situation, different uses for the same plants by people living in different areas, will be reflected when the same species receive different names in neighboring communities. Also, the toxicity of plants can be altered by altitude or ecological condition, and that may influence the use given to the plant by different communities. I hypothesize that the same species of plants residing in different ecological zones will be used the same way by local inhabitants in all different zones. If not, changes in chemical composition, or concentration of compounds as a result of environmental differences will be tested as an explanation. Furthermore, people living in different ecological zones will seek alternative bioactive plants for the same problem when useful plants are not common to all zones. They may also try to move plants from one zone to another where they do not normally grow; to gain easy access to plants considered to be of value.

Objectives

The following objectives will be pursued:

A. To develop a database of plants recognized as poisonous in the Cajamarca area. Of special interest will be the ones used