Natural Crop Protection in the Tropics
Letting Information Come to Life
Methods of Field Protection
There are about 2,500 species of this social insect. The termite fauna of tropical Africa is the richest with regard to both genera and species. They are primarily cellulose feeders. The most common species that inflict economic damage on field crops, trees and wooden structures are the Macrotermitinae.
Meanwhile it is generally accepted that termite damage is most prevalent where plants are under stress and that vigorous, well-grown crops and trees are rarely attacked even though termites are present. This suggests that improvement of the soil, particularly greater use of compost and green manure, while not reducing termite numbers, may well reduce crop damage by providing an alternative source of food. At the same time, high organic matter levels, good moisture retention and nutrient maintenance in the soil can benefit root growth and plant production and in so doing reduce the risk of termite damage. Particularly in regions where more sophisticated measures are unavailable or too expensive, cultural measures are worth employing.
Since it is very difficult to combat termites, the thinking goes towards learning "how to co-exist with termites". For effective non-chemical protection from termites it is indispensable to understand the biology of the different types of termites, e.g. dry-wood, subterranean, mound-building, soil-feeding, surface-foraging termites etc. In contrast to chemical control, non-chemical control of termites demands a greater understanding of the biology of the particular genera and species. There are very few general rules for non-chemical termite control. Most recommendations can be contradicted by other reports, e.g. on management of organic matter and mulches. Depending on the type of manure/mulch/debris, and depending on the local termite species, the effects will be different.
Control measures can be divided broadly into those which attempt to
1) prevent termites gaining access to the plants
2) reduce termite numbers in the vicinity of the plants
3) render the plants less susceptible to termite attack
Problems with termites can be categorized according to the site where they occur, namely in the field and in tree nurseries and tree cultivation. Therefore, control methods are presented accordingly. Solutions to these can either apply for both problem areas or be specific to one of these.
General control methods
The success depends very much on the capability of the termites to replace the queen, which differs from species to species. There are suggestions to additionally remove the fungus combs or to light a fire in the mound after queen removal. In Tanzania the mounds are dug out and chicken allowed to eat up the termites.
Control methods in field
In defence of termites
An organic agriculture practitioner in India considers termites to be useful soil organisms and proposes to promote them. He spreads dry leaves, farm litter and other waste at hand and sprays water on it. By doing this he provides conducive conditions for the termites. The termites will then eat only the diseased parts of the roots and thus prevent root diseases from spreading.
In some parts of India, farmers cultivate castor (Ricinus communis) on those plots which are severely attacked by termites. The next cropping season, the termite infestation has decreased appreciably. The control effect is attributed to root exudations.
Castor press cake can be incorporated into the soil in order to control the termite infestation. It is suggested to add it into the opened furrow before sowing the crop.
Incorporating green manure
Where possible, green manure crops can be ploughed into the soil. Moisture plus organic matter attract the termites and prevent them from attacking the target crop.
Use less susceptible planting material
When comparing three stem portions of cassava for their susceptibility to termite attack after planting, the bottom part of the cassava stem had the least termite attack with 3.2% compared to 15.6% of the tip part.
Cultivating on ridges
In experiments comparing different planting practices in cassava cultivation it was found that cassava cuttings planted on ridges were least attacked by termites and had the highest yield. Ridges are usually made along contours and the soil is finally shaped into a ridge form. In these operations, termite colonies are destroyed or exposed to predators such as birds.
Timing of harvesting
Crops are more seriously damaged towards harvest than earlier in the season. Therefore prompt harvest is recommended. It has been established that for every week's delay in harvesting maize after maturity, a 3 to 5% loss of yield is possible when termites are actively foraging.
Locally available plants, plant extracts and other substances have frequently been claimed to be effective in termite control, although they have received little rigorous assessment in the field.
Below are some suggestions from field experience and research:
Aloe, Aloe vera
While planting coconut seedlings, Aloe vera cuttings are planted in the same pit to keep away termites which attack the young palm.
Crown plant, Calotropis gigantia
8–10 kg of fresh plant materials are soaked in water for at least 24 hours and then filtered. This liquid is poured on termite-infested soil. Farmers evaluate the effectiveness by placing pieces of wood at various points in the field. If the wood remains pest-free for one week, then the treatment is judged effective.
Knobwood plant, Zanthoxylum chalybeum
In order to control termites, bark from the knobwood plant is peeled and soaked in water for three days. After that time the solution is filtered and sprinkled on the area which is attacked by the termites.
Other plants mentioned in the book:
Neem, Azadirachta indica, Snake bean tree, Swartzia madagascariensis, Tobacco, Nicotiana tobaccum, Vitex doniana
Other substances mentioned in the book:
Boron dusts, Wood ash, Cow dung spray
The printed version contains more information about the following themes:
Control mehtods for seedlings and trees
© Margraf Publishers 2003