Natural enemies play an important role in cashew plantations, helping to bring down the population of many pests. Several pests including leaf miner, apple and nut borer, leaf folders, flower caterpillars are effectively managed by the parasitoids and predators. Thus conservation of natural enemies is important in an ecosystem.
The following possibilities through environmental modifications shall help to increase the population of natural enemies.
Habitat enrichment and provision of supplementary food for the natural enemies
Beneficial insects often need an alternate food supply in addition to the pest prey, oviposition sites or shelters. Many natural enemies, including the parasitoids and adults of predatory insects like lacewing bugs, syrphids and minute pirate bugs need nectar of flowers, pollen or honeydew of insects as a source of its nutrition. Thus, maintaining a diverse landscape with suitable flora in borders or patches of small patches of grasses and flowering plants shall provide food and shelter for these natural enemies helping them to survive better.
After introduction of ant colonies into cashew plantations, their population can be sustained initially and enhanced by providing supplementary foods like fish meal.
Judicial use of insecticidal sprays
Most insecticides sprayed to kill pests also harm beneficial insects to a greater extent. Hence, sprays should be taken up on crops only when it is necessary based on the economic threshold thresholds of the pests.
Reducing the overall use of broad-spectrum insecticides whenever possible will be generally helpful in protecting natural enemies. Avoiding spraying on the non-target regions like tree trunks, soil and patches of grasses and shrubs in the surroundings help the natural enemies to survive on them.
Control of honeydew-feeding ants
In cashew trees, ants especially red ants (Oecophylla smaragdina), Anoplolepis gracillipes, Monomorium sp. and Crematogaster sp. are commonly seen tending the aphids and mealy bugs.
These ants protect the pests and drive away their natural enemies, thus management decision has to be carefully made based on the pest intensity.