Pest Management in Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 382

discussed here are based on studies conducted on the management of pests of
exotic fruit trees and forestry species. The recommendations given below
should be selected and adapted to suit the farming system, geographical and
climatic conditions of the location, and the prevailing pest complex.
20 . 5.1 On-farm pest management
In order to reduce pest problems and ensure a healthy crop in the orchard, first
and foremost fruit tree growers should adopt GAPs. Growers should integrate
suitable techniques and procedures into one harmonious and concerted strategy
for the effective and efficient management of fruit trees. This means that IPM
practices for all classes of pests in the orchard, including insects, mites, diseases,
weeds, birds and rodents, must be woven together with all of the horticultural
practices that are consistent with an overall sound approach to crop production
(Prokopy, 1994). The major steps to be taken are discussed below.
Site requirements
Tree species vary in their site requirements, soil physical and chemical
properties, soil microbiological associations such as mycorrhizas, and cultural
procedures (Cordell et al ., 1989). Ecological studies have shown that although
many miombo fruit tree species grow naturally over a range of environments,
they are sensitive to site conditions (Mwamba, 1983; Ngulube et al ., 1995; van
Wyk and van Wyk, 1997; Hall et al ., 2002). Pest problems become most severe
when the requirements of a tree species are not fully met. Therefore, the first
step in managing pests is to establish the orchard on an appropriate site.
Cultural practices
Several horticultural practices may be applied to complement pest management
in orchards. These include maintaining tree stability in the soil to permit the
establishment of a strong root system, ensuring adequate nutrient and moisture
availability for tree and fruit growth, and pruning trees in a way that optimizes
fruit yield and quality. Too much nutrient flux into trees, especially uptake of
nitrogen, may prevent good coloration of fruit and lead to poor storage quality.
This may also reduce the efficiency of mycorrhizal fungi. This in turn may lead
to more rapid development of arthropod pests, such as aphids, that require
succulent foliage (Prokopy, 1994). Pruning of excessive growth of succulent
foliage and woody tissue will improve fruit colour, and by lowering relative
humidity within the tree canopy it can reduce fungal diseases. Roots should not
be damaged in the orchard as this may become an avenue for infection by
wood rot fungi. When a fruit orchard is established on a former forest area, all
tree stumps down to 1 cm should be dug out and taken away to reduce the risk
of infection by Armillaria .
Orchard ground cover competes with trees for nutrients and moisture.
Therefore, it is advisable to keep understorey vegetation to a minimum.