354 Produce Degradation: Reaction Pathways and their Prevention
most common snail and slug pests include the brown garden snail (Helix aspersa),
the gray garden slug (Agriolimax reticulatus), the banded slug (Limax marginatusi),
the tawny slug (Limax flavus), and the greenhouse slug (Milax gagates) [50].
Snails and slugs feed on a variety of living plants and also on decaying plant
material [50,51]. On plants, they can chew irregular holes in leaves and flowers and
also feed on fruits and young plant bark. Slugs and snails prefer succulent foliage
or flowers, and thus they are primarily pests of seedlings and leafy and cruciferous
vegetables. However, they can also feed on ripening fruits in close proximity to the
ground, such as strawberries, artichokes, or tomatoes, and also attack foliage and
fruit of some trees (citrus fruits are especially susceptible to this kind of damage).
Furthermore, slugs and snails may serve as vectors of plant and animal diseases.
The control of snails and slugs mainly involves prevention (mostly removal of
decaying plant matter and their diurnal hiding places), hand-picking, trapping (under
boards, inverted melon rinds, or in baits with beer or other fermented food), installing
barriers (e.g., copper foil), and using baits with molluscicides designed to attract
and kill snails and slugs in the target area [50,51].
Metaldehyde is the most common active ingredient in the baits containing a
molluscicide [50,52]. Metaldehyde is toxic to slugs and snails both by ingestion and
by absorption by the mollusk’s foot. It does not kill snails and slugs directly unless
they eat a substantial amount, but it stimulates the secretion of large quantities of
slime, causing immobilization and eventual death by loss of water (dessication)
[1,5]. A recently registered mollusk bait containing ferric phosphate is much safer
to mammals and other domestic and wildlife animals than is metaldehyde. Ingestion
of ferric phosphate bait causes snails and slugs to cease feeding and eventually starve
to death [50]. Several carbamate insecticides, such as methiocarb, thiocarb, or
trimethacarb are also very effective molluscicides when formulated as baits [1].
11.2.5 FUNGICIDES
Fungicides prevent or destroy the growth of fungi, thus protecting growing plants
against fungal diseases and produce against pre- and postharvest spoilage caused by
fungal pathogens. Chapter 16 describes in detail mechanisms of microbial spoilage
of fruits and vegetables, including the most important produce categories and spoil-
age fungi combinations. Thus, this discussion is restricted to the use and mode of
action of fungicides serving as preventive, curative, or eradicative means in the
combat with fungi and provides a general description of problems caused by fungal
pests in produce production.
11.2.5.1 Classification of Fungicides, Their Application, and
Mode of ActionFungicides are mainly applied as sprays or dusts, and their postharvest application
also includes dipping in fungicide baths, impregnation of fruit wrappers, or incor-
poration into waxes for surface application on fruits [53]. Various seed dressing
techniques can be used for seed treatment to control seed- and soil-borne diseases,
and fumigants may also play an important role in preplanting control of soil fungi