beetles can be present from June through September. They feed on the
upper leaf surfaces, leaving a lacelike skeleton. Injured leaves may
turn brown and die if feeding is severe, but clusters are not attacked.
Juice grape vines are resistant and tolerate some damage, but vinifera
and hybrids are more susceptible.
This pest can
be a problem particularly in new vineyards using grow tubes. Frequent
monitoring is required to reduce the risk of severe damage. Japanese
beetle traps may attract beetles to vineyards, so their use is discouraged.
eggs underground in grassy areas near vineyards, preferring soil
with moisture. The white, C-shaped larvae (grubs) feed on grass
and weed roots and overwinter underground in these areas. Cultural
and biological controls of grubs may reduce subsequent abundance
beetles are about 12mm long.
Photo: Rufus Isaacs