Habits
Larvae of the garden weevil tend to occur in the soil in the drip zone of vines, with comparatively fewer in the mid-row, unlike observations in Victoria where inter-rows are more heavily infested.
Weeds such as sorrel, capeweed, dock and dandelion can support large numbers of garden weevil larvae and the presence of such weeds may influence the distribution and abundance of larvae across the vineyard floor.
After emergence, adult garden weevils enter the vine canopy and tend to stay there. Adult weevils feed at night. They are inactive during the day and shelter under bark, in the crotch of branches and the main stem and around posts or plant limbs supported by wires. They can also be found under plant debris on the vineyard floor and in curled up dead leaves and in grape bunches in the vine canopy. When disturbed they remain still, feigning death and may fall to the ground. Adult weevils climb into the vine canopy via the trunk, posts, trailing canes or where weeds touch the canopy.
Damage and loss
Larvae feed on the roots of vines and other plants growing in the vineyard. Larvae feeding on vine roots can severely damage young vines such that they become stunted and appear water-stressed. The root system of mature vines would be more tolerant of feeding by weevil larvae. Control of adults would help reduce the abundance of larvae.
Adult garden weevils attack foliage, flowers, buds and fruit. Leaves usually have distinctive round holes and scalloped edges. Adult weevils can scar grapes but also destroy bunches by ringbarking the stalk. Feeding around growing tips can kill them and this can affect the structure of vines and reduce the number of buds the following season.
Garden weevil is also a pest in deciduous fruit tree orchards, especially apples, nectarines and cherries, as well as strawberries, root vegetables, asparagus and ornamentals. This insect is not a major pest of vineyards in the Swan Valley although it occurs there. It is also found in the Perth metropolitan area.