Pests and Diseases

Insect pests seldom cause serious problems in California kiwifruit. A few possible pests are discussed below.

The omnivorous leaf roller (Platynota stultano) is the caterpillar of a small moth. The caterpillar measures as much as 1 inch long. It feeds primarily on leaf tips and growing tips, and damages fruit by scarring its surface. The pest's feeding can also cause fruit deformation and premature fruit drop. Small leaf roller caterpillars house themselves in webbed, rolled leaves for protection when pupating. Employing Bacillus thuringiensis (B.t.), a bacterial organism that kills the caterpillar, is one means of control.

Although mites (Tetranychus spp.) might be present on kiwifruit, they pose no serious threat. Mites are spider-like in form, but most are too small to be seen with the naked eye. A mite feeds by piercing a leaf with its thin mouth part and removing the plant sap. Feeding may begin as early as March or April, but damage becomes more apparent in the fall. Curled, stippled, or bronzed leaves and silvery webbing on the underside of leaves indicate the presence of mites.

Scale insects (Greedy, Latania, Ivy, and Oleander scales) can cause severe problems on older mature vines. They over winter on the bark of kiwifruit trunks and cordons. In warm weather they appear on the vines as small, armored, immobile, disc-shaped objects. Scales feed on the cell sap of canes and large cordons, and reduce the vigor of affected plants. In severe cases, they also attack the fruit, causing premature softening in storage. When you find scale insects, simply crush their shells with a toothpick or small stick. Do not press so hard as to injure the plant.

Nematodes-commonly called thread worms or eel worms--are round and spindle-shaped organisms found in almost all soils. They are seldom visible to the naked eye, and are almost wholly microscopic. Root-knot nema- todes (Melodigyne spp.) can penetrate plant tissue and cause nodules or knots on roots of kiwifruit vines. They can seriously hurt the growth of young, partially established kiwifruit vines. They seldom damage mature vines that are kept free of stress. Purchase plants from a reputable nursery to avoid this pest.

Crown and root rot (caused by the Phytophthora fungus) usually occur on kiwifruit vines grown in wet soils with poor drainage or high water tables. Plant vines on mounds in well-drained soils. Avoid damaging the roots or stems of new plantings, since such damage might provide an entry for Phytophthora infection.

Good sanitation (keeping the growing area clean) will help reduce the numbers of spores, eggs, and larvae of pests that could otherwise cause problems. Remove rotting fruit and sickly growth from vines and from the surrounding area.

The common brown snail (Helix aspersa) can be a problem, especially in spring when new growth is just emerging. Use of snail baits or other methods can be used to control their numbers.

If gophers are a problem, surround the plant root area before planting with a 1-inch-thick chicken wire net screen. Gophers seldom bother mature vines enough to reduce production significantly.

If you still have pest problems in your kiwifruit planting, ask your local Cooperative Extension farm advisor for control recommendations