Horticulture Principles and Practices

FIGURE 7–12 Corn earworm damage. (Source: Photo provided
courtesy of Oklahoma Cooperative Extension Service, Oklahoma State University)
FIGURE 7–13 Leaf miner damage on spinach. (Source: Photo provided
courtesy of Oklahoma Cooperative Extension Service, Oklahoma State University)
7. Leaf miners. Leaf miner damage is visible as tunnels between leaf surfaces
(Figure 7–13). These tunnels are caused by larvae of flies such as the serpentine
leaf miner (Liriomyza spp.). When a leaf is heavily infested, it yellows and eventually
drops. Leaf miners attack a variety of garden plants such as tomato, pepper,
eggplant, and especially lettuce and melon.
8. Spider mites (Tetranychus spp.). Mites are piercing or sucking insects that live
on the undersides of leaves. They vary in color from reddish-yellow to light
green. They attack a variety of garden crops, especially tomato and cucurbit.
After feeding, the leaves appear bronzed or discolored. Severely attacked plants
whither and drop. Spider mites have the capacity to produce six to ten generations
each year. They devastate ornamentals, fruits, nuts, vegetables, and
numerous other species.
9. Thrips. Sucking insects, thrips are very common in the garden. Plants attacked
have distorted leaves. Onion thrips (Thrips tabaci) and western flower thrips
(Frankliniella occidentalis) are two of the most common thrips in the garden
and landscape.
10. Aphids. Also called plant lice, aphids are common on young leaves and growing
tips of stems. One of the most common of the aphid species is the green peach
aphid (Myzus persicae), which attacks many garden crops. Aphid populations are
effectively held in check where natural enemies such as lacewings occur. This
sucking insect affects many ornamentals, orchard crops, and vegetables. They
are important because they are able to transmit a number of viruses that cause
devastation to horticultural crops, examples being cucumber mosaic, bean
mosaic, and lettuce mosaic. Aphids cause plants to grow with less vigor.
11. Ants. Ants are common in the garden and the landscape. One of the most common is
the Argentine ant (Iridomyrmex humilis). It feeds on honeydew secreted by aphids.
The leaf cutter ant (Acromyrmex spp.) cuts pieces of leaves for food.
7.4.7 CONTROL
Insects are commonly controlled by the use of chemicals. However, they may be controlled
by cultural, legislative, and biological methods. Control methods are discussed in detail in
Chapter 8.
7.4 Insects 229