128 – II.2. SQUASHES, PUMPKINS, ZUCCHINIS, GOURDS (CURCURBITA SPECIES)
Diaphania nitidalis. The larvae of these lepidopterans are restricted to feeding on the
cucurbits, with both summer and winter squash being particularly favoured hosts.
Melonworms feed mainly on the foliage, being primarily a leaf feeder which seldom
feeds on the fruits. The pickleworm, in contrast, does feed on the fruits of squash, and
can cause serious damage. Early in the season, pickleworms bore into the stems and
terminal buds. Later in the season, pickleworms bore into the fruit from the side next to
the ground. After feeding for about two weeks, the larva moves out of the fruit to the
leaves, where it will spend seven to ten days as a pupa inside a cocoon. Pickleworm is
highly dispersive, e.g. in the United States it overwinters in south Florida, spreading
northward each spring. The pickleworm has been reported from Canada southward to
South America.
“Squash vine borer” (Melitta satyriniformis) is a diurnal species of sesiid moth
that attacks wild and cultivated varieties of Cucurbita. The moth of this lepidopteran
resembles a large wasp without the stinging apparatus. Females deposit eggs near
the base of the plant about the time the first planting begins to emerge until bloom.
A small larva emerges and enters the stem of the plant. The larva then feeds inside the
stem and eventually causes it to die. As the worm feeds, it pushes its excrement out of the
entrance hole. The worm will eventually exit the stem and enter the soil to pupate
(OMAFRA, 2011).
Hemiptera
“Squash bugs” (Anasa tristis) are Hemiptera and colloquially called “squash bugs” in
North America because some of the species are pests of squash plants and other cucurbits.
Squash bugs are quite mobile and can move easily among plants within a field and later
move to late planted fields. The insects spend most of their time within the plant canopy,
mainly around the stems and on the underside of the leaves. Both nymphs and adults feed
by sucking sap from the plant. The adults often congregate near the base of the plant and
young nymphs concentrate on the leaf where they hatch and then migrate to other plant
parts. Squash bugs can increase in numbers very rapidly and, in high numbers, can cause
plant wilting. This insect injects a toxin into the plant while feeding and this toxin results
in wilting (OMAFRA, 2011).
Whitefly (Bemisia tabaci) is reported on all continents except Antarctica.
Over 900 plant hosts are recorded and it reportedly transmits 111 virus species. Most of
these whitefly transmitted diseases are begomoviruses, although whiteflies are also
vectors of criniviruses, ipomoviruses (Adkins et al., 2006), potyvirus, torradoviruses and
carlaviruses (Markham et al., 1994; Navas-Castillo, Fiallo-Olive and Sanchez-Campos,
2011). Its small size belies its ability to move large distances (Ellsworth and
Martinez-Carillo, 2001; ISSG Global Invasive Species Database, 2011). B. tabaci is
phytophagous and has been reported to produce silvering of leaves in Cucurbita
(Schuster, Kring and Price, 1991).
Diptera
Vegetable leafminer (Liriomyza spp): Adult leafminers are small flies with a small
wing length. Adult females puncture the upper surfaces of leaves with the ovipositor for
feeding and egg laying. Adults feed on fluids that exude from the wounds. Eggs are laid
singly in separate leaf punctures and hatch within two to seven days. Larvae feed on the
leaf mesophyll for 6-12 days. Full-grown larvae slit the leaf epidermis, exit the leaf,
fall to the ground and pupate in the soil. Losses in cucurbits due to these dipterans are
