Insects may be classified as chewing
or sucking depending upon their type of mouthparts.
Chewing Insect Damage
Chewing insects have opposable jaws that move from side to side rather than up
and down. Their damage can appear as:
1. Holes in leaves, petals or fruit caused by caterpillars
, beetles
,
grasshoppers and fly larvae.
2. Pale blotches or lines in leaves caused by tiny leafminers
feeding between leaf surfaces. Leafminers can be larvae of flies, moths or beetles.
The mines are classified by their shape, such as serpentine, blotch or trumpet.
3. Sudden wilting caused by borers feeding inside of stems. The Common
Stalk Borer , while considered a pest of corn, is a serious pest on all sorts
of garden flowers, vegetables and herbs, including roses, lilies, dahlias, mints,
tomatoes and at least 200 other host plants.
4. Plants broken off near ground level by cutworms
Sucking Insect Damage
Sucking insects do not have jaws. Their mouthparts have been modified into a tubular
"beak" which is used to pierce plant tissues and suck juices. Some feeding may
go unnoticed because there are no holes in leaves, while other types of juice-feeding
results in symptoms that might be mistaken for plant diseases. Their damage can
appear as:
1. General lack of vigor
2. Cupped and misshapen leaves caused by aphids
, psyllids
3. Severe stunting, burned appearance in a "V" pattern starting at leaf tips caused
by leafhoppers. The Potato
Leafhopper causes serious damage to dahlias, zinnias, strawflowers and many
other flowers.
4. Sticky secretions on leaves, becoming covered with mold caused by aphids,
psyllids
5. Distorted fruit, wilted leaves caused by stink
bugs
Beneficial Insects
Beneficial insects include predators and parasites.
Predators
Ground beetle
Lady beetles and their
larvae
Soldier
beetles
Syrphid fly larvae ( aphid
lions )
Firefly
larvae
Lacewing
Predaceous bugs
Hunting wasps
Preying mantids
Parasites
Ichneumon
wasps
Other small wasps
Parasitic flies
Other Arthropods
Spiders in general should be considered beneficial.
Common garden residents include orb weavers such as the Garden
Argiope and many species of jumping
spiders and crab
spiders . Orb weavers have very poor eyesight and stay in their webs.
Jumping spiders are ambush hunters with keen vision. They hide and jump out
at prey and move actively over plants. Crab spiders are also ambush hunters
and can change color to match their plant.
Mites are extremely small and may be damaging
or beneficial. The commonest mite pests are the two-spotted
spider mite and the red spider mite. These web-spinning juice-feeders
cause a speckled look on leaves. They are usually found on the backs of leaves,
but in high populations they will be all over the leaves and their webs can
be easily seen. It is difficult to identify predatory mites. They will
be fast-moving, while damaging mites are quite sedentary. Predatory mites do
not congregate in large groups, so any large population of mites on a plant
should be assumed to be damaging.
Sowbugs
and pillbugs are land-dwelling crustaceans common in damp places. They are
scavengers and of no consequence in the garden.
Millipedes or thousand-leggers resemble armored
worms with many short legs, two per side on each body segment and antennae
so short that they are barely visible. Most have 30 or more body segments. Most
are scavengers and feed on decaying plant material.
Centipedes
or hundred-leggers have longer legs which extend out from the sides of
the body and long antennae. They have a single pair of legs per body segment
and 15 or more body segments. They are fast-moving predators and they can bite.
Email any changes, deletions or additions to pests-diseases@g-e-g.org
