Ecology of Predators
Flowering plants are important to insect predators. For some predators like lacewings and hover flies, it is only the larvae that feed on insects; the adults are pollinators, feeding on pollen and nectar. But even lady beetles, which are predators in both the larval and adult stages, supplement their diet with pollen. Predators may be helping control Christmas tree pests such as aphids and mites, but they may also be preying on other insects which are found in ground covers. The greater the diversity of plants in the ground cover, the greater the insect diversity, and more predators can be supported. In one study conducted by Dr. Logan Williams at North Carolina State University, predatory mites were most commonly found associated with plants having woodier stems such as briars. These cannot be accommodated in the field because they would interfere with Christmas tree shearing and other practices, but are welcome additions to field borders. Predatory mites were not sampled in the present study.
Gallery of Predators
The following predators were observed during the pollinator study and are important in control Fraser fir pests.
Harmonia lady beetles are frequently found in Christmas tree fields. The adults and larvae eat aphids and mites which are pests of Fraser fir. They prefer feeding on pests in trees. Christmas tree growers do not release these in their trees for pest control. Christmas tree fields are just a preferred habitat for them.
The seven-spotted lady beetle is not as common as Harmonia lady beetles but is still found.
The polished lady beetles (Cycloneda munda), like the Harmonia or seven-spot, is native to the US. It is less frequently found in Fraser fir fields. Another native lady beetle found was the pink lady beetle, (Coleomegilla maculata). Other native lady beetles observed include Psyllobora virintimaculata and Hyperaspis undulata.
By creating a habitat with many flowering plants, pollinators like these hover flies will mate and lay eggs in the Christmas trees. Their larvae which are predators will feed on aphids and mite pests.
Lacewing adults do not feed on other insects but their larvae do — eating aphids and mites. They are common in fields.
In the fall praying mantids are commonly found in Christmas tree fields. They do not feed on pests of Christmas trees but larger insects. Their egg cases can be a problem in cut Christmas trees. When brought into a warm home, they hatch out into dozens of little mantids.