|
Insects and mites damage trees in two ways:
- they directly impact tree health by feeding of various
parts of the plant, or
- they are transmitters (vectors) of tree diseases from
tree to tree.
Most insects are species specific. If a plant is highly
susceptible to a certain pest, you should avoid using it in
urban settings. The key to keeping insects and other pests from
damaging your trees is proper tree management. Insects attack
trees weakened by other agents, biotic/abiotic. The key to pest
management in urban trees involves proper selection, culture and
maintenance.
Insects affect the above-ground portion of the tree and can
be broken up into three basic categories: chewing insects,
sucking insects, boring insects.
- Chewing insects – primarily focus on the leaves
and young stems of trees.
- Eastern Tent caterpillar and Tussuck moth larvae can
defoliate mature trees in about two weeks.
- If the tree is healthy, most defoliators are merely
a nuisance and the tree will regrow its canopy with
little effect.
- Repeated defoliations of young or old trees can
weaken the tree.
- Sucking insects – include scales, mites and
aphids.
- These insects primarily attach new foliage and
stems. Rather than eating plant parts directly, like
defoliators, they pierce the epidermal layers of the
plant and extract sugars.
- These insects produce mostly cosmetic deformities on
the tree such as sooty mold, slow growth, tip dieback
and galls.
- If insects reach high populations, serious damage
can occur.
- Sucking insects are drawn to healthy,
rapidly-growing trees dominated by rapidly-growing,
sugar-rich parts.
- The best preventative control is culture.
- The use of low-nitrogen, slow-release fertilizers
will eliminate sucking insect problems.
- Boring insects – are of primary concern in
southwest Florida.
- Adult boring insects can sense stress and attack.
- If boring insects choose a healthy tree, the tree
will rebuff entry or tolerate and contain damage caused
by the attack.
- Boring insects use trees to house their eggs.
- During the larval stage, the boring insects feed on
the living tissues just beneath the bark layer.
- This feeding disrupts the water and sugar flow
in the tree, damaging living tissues in the trunk
Pest Signs and Symptoms
Pest control requires diligence on the part of the homeowner.
All trees should be inspected every month for the following
signs of pests or insects:
- chewed foliage, twigs or blossoms;
- streaked or mined foliage;
- curling or twisting of leaves;
- dieback of twigs and shoots;
- sawdust or sap leakage from stems;
- sticky honeydew on ground, stems and/or leaves;
- tents, webs or sick masses in crown;
- pitch tubes or gum masses on stems and branches.
Homeowner or managers should establish a tolerance level for
pests, based on two thresholds:
- defer pest control if you are willing to tolerate
cosmetic or aesthetic injury to the plant or
- set a tolerance or disturbance level beyond which you
will resort to a pest management response.
|