Forest Health > Insects and Diseases publication
CONCEPTS of Entomology
Insects feed on all parts of a tree (see Fig. 3 for some common insects that damage trees). Sounds ominous. Yet trees survive and perpetuate themselves. A daily contest occurs between trees and insects — usually the score is even. Insects have developed habits, capabilities, and body parts that allow them to attack a tree, but trees have developed a number of defense mechanisms. Let's take a closer look at insects.
Entomology is the study of insects. The root word entomos is Greek and was used to identify a variety of crawling and flying creatures. The word bug is widely used but is entomologically incorrect. To stay out of trouble we'll use insect.
Insects are distinguished from other types of animals by having certain structural features (see Fig. 4 for characteristic body parts of adult insects). The possession of antennae, head, thorax, abdomen, 3 pairs of legs and usually 1 or 2 pairs of wings separates adult insects from similar animals like mites, spiders, and lobsters. Also, insects develop through a progression of growth stages (see Fig. 5 for a generalized life cycle for tree insect pests). In the usual sequence the adult female insect lays from a few to several hundred eggs. A larva or nymph emerges from each egg. Nymphs grow and molt several times before becoming adults. Larvae grow and molt to an intermediate (pupal) state. After a period of time an adult insect emerges from the now empty shell of the pupa.
Insects come in a variety of shapes and sizes. The great divergence in appearance of the adults, pupae larvae, nymphs, and eggs (Fig. 5) can be confusing. To apply the best control or preventive measures, an accurate identification is needed. This book can assist in identifying the more common insect pests of trees in Florida.
Key Words
As few words as possible of entomological jargon are used in the book. Some words creep in because nobody else has come up with better ones. Besides the names given for life stages in Figure 5, the following terms are absolutely necessary.
- Frass -- solid insect excrement
- Honeydew -- a sweetish liquid excrement produced by certain insects, especially aphids and scale insects
- Pitch tubes -- hardened resin with a tube-like or balled form on the outside bark of pine trees infested by pine bark beetles
- Cocoon -- a covering, composed partly or wholly of silk, spun by a larva to protect the enclosed pupa.
Checklist of Insect Damage
Usually, evidence of damage caused by insects can be found on or in most trees, especially older trees. Table II is a checklist of some of the more common clues that indicate such damage has taken place.
If such damage is seen on or in a tree a landowner is faced with a decision — what to do? To complicate matters, insects may or may not be present. To assist the reader in making the decision of what to do, a control section is included for all pests discussed in this book. In most cases an insecticide or fungicide will be only one of several options available to the landowner. A chemical solution to the problem is not always the best or first to use. Cultural or physical control options may be the best choice.
Table II: CHECKLIST OF INSECT DAMAGE TO TREES
| Fruit |
Leaves |
Twigs/Buds |
Stem |
Roots |
Mines
Premature drop
Damaged seed
Chewed
Galls
Holes
Abnormal shape |
Discolored
Curled
Spotted
Galls
Notched
Holes
Mines
Skeletonization
Defoliation
Disfiguration with excrement |
Girdled
Galls
Mines
Pruned
Wilted twigs
Discolored
Holes
Enlarged buds |
Mines
in bark or cambium
Borer
channel into wood
Chewed
bark
Galls
Pitch masses
Fine sawdust
Sapstaining
Holes |
Girdled
Galls
Mines
Chewed
Borer tunnels into wood
Mines
in bark or cambium |
Contact your local Division of Forestry Field Office if you have questions or need assistance with a pest problem or tree care and maintenance.
Bulletin No. 196-A | Printed October, 1983 | Contact the Forest Health Section |
