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Designing a Farm Forest

Planting to Reduce the Impact of Pests

Creating Biodiversity to Attract Predators
By planting a selection of tree, shrub and grass species, it is possible to create a wide range of different habitat types on a property. This will help attract a wide range of native birds, animals and insects, many of which may help control the abundance of pests, especially insects, that can affect trees and crops.

The key to encouraging predators is to provide suitable habitat. While each type of predator or parasite has its own specific habitat requirements, generally the more diverse the habitat is, the more diverse and abundant predators will be. Extremes in heat and low humidity disadvantage predatory and parasitic insects, and it may be desirable to modify the environment to favour these beneficial species.

Structural diversity is also an important micro-habitat feature. Planting windbreaks and inter-row cover crops can create desirable micro-habitats andcertain herbs and clovers can provide over-wintering sites for predatory mites in orchards. Pollen-producing plants can also encourage high populations of predatory mites. Nectar-producing plants can provide a source of nourishment for some wasp parasites. Siracid wasps in the New England Tablelands, which feed and breed on Acacia windbreaks planted around paddocks, have been shown to reduce the populations of scarab larvae in pastures. These scarab larvae if allowed to develop may defoliate Eucalyptus trees during their adult stage.
Farm forestry plantings could include a variety of indigenous species, including shrubs.

Summer flowering species attract wasps that are parasites of a variety of agricultural and forestry insect pests. Other beneficial insects that parasite insect pests include robber flies, lacewings, ladybirds, hover flies, mantids and bee-flies. For example, bee-flies lay eggs in knot-holes and are effective in controlling wingless grasshoppers.
Many mammals also control insect pests. For example, sugar gliders feed on acacia gum and eucalypt sap in winter, while in spring and summer they feed on insects including moths and pasture scarab. Sugar gliders need trees with hollows to live in, while insectivorous birds and bats use tree hollows for roosting and nesting. Lizards feed on insects and live amongst fallen timber and dead trees.
As many fauna depend upon dead timber, while others need to live in trees with hollows and knot-holes, it is important that both dead and hollow-bearing live trees are retained. Many birds rely on eucalypt trees to survive and they also require shrubs and grasses. Over 300 bird species live in eucalypt forests. Trees, shrubs and grasses provide shelter, nesting sites and food for birds, including nectar, seeds, fruits and insects.

Birds feed on a wide range of insects including those that feed on the leaves of eucalypts. Scarab beetles, leaf beetles, caterpillars and a wide variety of sap sucking insects often attack trees on farms. Isolated or scattered trees can be severely damaged by insects because they usually don't support bird populations. Densities of birds in some forests of roughly 20-30 birds per hectare can consume 250-500 grams of insects per hectare per day.

Forestry may increase the presence of pests. As well as providing habitat for native fauna, trees on farms can provide cover for vertebrate pests such as foxes, cats, rabbits and hares. Transferring areas from traditional agricultural activities to plantation forestry may increase the presence of vertebrate pests by providing protective cover for them and increases the difficulty of mounting an efficient control program.

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