Role of Pesticides in Produce Production, Preservation, Quality, and Safety 347
11.2.1.2 Problems Caused by Insects in Produce Production
and Their Control by InsecticidesThe types of potential insect pests and the degree of damage depend on many factors,
such as the climate, agricultural region, crop species and their pest resistance, and
natural predators [2]. Table 11.3 and Table 11.4 give examples of common insect
pests on fruits and vegetables in the U.S. [4]. These tables also present some of the
major problems associated with insect infestation in produce production and provide
lists of insecticides that are typically used for their control.
Insects, mainly their larvae, may feed on various plant parts, such as leaves,
tender twigs, stalks, buds, flowers, fruits, or roots, which often leads to severe
consequences if not controlled. The loss of leaves or their damage generally results
in reduced photosynthetic capacity of the plant. Thus, for most produce types, foliage
loss reduces product (fruit, root, bulb, tuber, etc.) size and quality by retarding sugar
development and, ultimately, leads to the plant’s death if the damage is extensive.
In the case of leafy and many of the cruciferous (cole) vegetables, it certainly means
crop losses, significantly reduced quality, and also increased susceptibility to micro-
bial spoilage [28,29]. Leaf-eating and damaging insects, such as leafrollers on apple
trees [30] or leafhoppers on grapevines [31], may also cause lower fruit set in the
next season.
Fruit trees infested with insects feeding on tender twigs, shoots, or branches,
such as with the oriental fruit moth or San Jose scale [32], generally show a decrease
in vigor, growth, and productivity. Similarly, most vegetables may suffer from an
attack of sap-sucking insects (mainly aphids) that also lowers plant productivity and
retards growth, leading to stunted plants with deformed stalks and curled leaves [28].
Insect-feeding on buds, flowers, and developing fruits translates directly into
decreased fruit yields or their dramatically reduced quality. For instance, the feeding
injury caused by lygus bugs (including the tarnished plant bug) on developing straw-
berries results in unmarketable, small, and deformed fruits that have either a character-
istic “cat-faced” appearance (due to the cessation of development in the area surrounding
the feeding site) or a woody texture that fails to mature (“button berry”) [33].
Feeding on fruits leads to surface damage or more serious deep tunneling, but
in any event, an economic loss results because the affected fruit is usually discarded
during postharvest sorting. Moreover, the insect damage often provides an entry
point for microbial spoilage. Similarly, larval feeding on roots renders root vegetables
(e.g., carrots, parsley, or celery in the case of carrot weevil larvae infestation [34])
unacceptable for both fresh and processing markets and generally makes the roots
more susceptible to diseases caused by soil-borne pathogenic microorganisms.
Fruit surface damages may appear as stings or scars, such as those caused by
the codling moth or leafrollers on apples, respectively [30]. On citrus fruits, citrus
thrips puncture epidermal cells, leaving scabby, grayish, or silvery scars on the rind.
Second instar larvae are the most damaging stage of the citrus thrips because they
feed mainly under the sepals of young fruit and are larger than first instars (larvae
between hatching and the first molt). As the affected fruit grows, damaged rind tissue
moves outward from beneath the sepals and appears as a conspicuous ring of scarred
tissue [35].