Horticulture Principles and Practices

Egg
FIGURE 7–3 Life cycle of an
insect with incomplete metamorphosis.
Adult
Naiad
Naiad
Egg
FIGURE 7–4 Life cycle of an
insect with complete metamorphosis.
Adult
Larva
Pupa
Classification Based on Feeding Habit
Insect pests can also be classified based on how they inflict damage on the plant through
their eating habits. On this basis, there are two categories of insects: chewing insects and
sucking and piercing insects.
Chewing Insects Chewing insects, as their name implies, chew plant parts (e.g.,
petals, leaves, stems, fruits, and flowers) during feeding. They have chewing mouthparts.
Their damage is not limited to the aboveground parts of plants but also includes roots. This
group includes larvae such as caterpillars and grubs, as well as adults such as grasshoppers,
beetles, and boring insects. The tissue of the plant is destroyed in the process of feeding,
the damage caused being more serious as the insect matures. Damage from chewing
insects is easy to identify (Figure 7–6). Symptoms include the following:
Defoliating. Insects such as leaf beetles, caterpillars, cutworms, and grasshoppers
devastate the foliage of plants by chewing portions of leaves and, in severe
cases, stripping the plant completely of leaves. Defoliation causes a reduction
in photosynthetic area, thereby reducing plant vigor and productivity.
7.4 Insects 225