GardenLine | Common Saskatchewan Pests | Strawberry Pests

Strawberry Weevil:

Description/Damage:

The strawberry weevil is a dark brown weevil, 2-3 mm (0.08 to 0.12 in) long, with light spots and a long snout, and is known for cutting the stems of blossoms in early spring, as the first blossoms open. The eggs are laid in the blossoms before it is cut and it is in the cut bud that the larvae matures.

Symptoms:

The adult chews holes into the leaf petioles, which are more conspicuous than the blossom stem stubs and therefore a sign of the weevil's presence.

Control:

As there is only one generation a year, only one pesticide application is necessary for control of the pest.

Strawberry Root Weevil

The strawberry root weevil attacks not only strawberries, but various wild and cultivated plants.

Description/Damage:

The damage is mostly done by the white, legless, brown- headed larvae (grubs), which feed on the crown and roots. The plants will become stunted with the leaves bunched together and darkened. The adult weevil is a hard-shelled, dark brown beetle, about 6 mm long (1/4 in), with a short snout. It cannot fly, but chews characteristic notches around leaf margins and may chew small holes in strawberry fruit.

Life cycle:

In late-May to June, the adult beetle (all females) emerge from the soil and approximately 2-3 weeks later, lay 200-300 small, white, spherical eggs near host plants. The larvae feed on the roots, some developing into adults in the fall which overwinter, while others overwinter as larvae and complete their development in the spring.

Control:

The best control is to kill the adult beetle before they lay their eggs. Apply the following treatments where fresh leaf notches are seen, before the blossom period or after harvest:

Malathion 50% EC: 3-6 ml/L water.
Diazinon (Basudin) 12.5% EC: 8 ml/L water.
Methoxychlor 25% EC: 8 ml/L water.

Tarnished Plant Bug:

This insect attacks cultivated and wild plants (such as beets, cauliflower, celery, lettuce, potato, pear, strawberries, and many flowers).

Description/Damage:

The nymphs and adults are sucking insects which cause blossoms, young pods and fruit to drop; older pods and seeds to become pitted, distorted and discoloured (cat-facing); heavily infested plants may wither and die.

The adults are small, cryptic (tan-green-brown-black) and about 6 mm long, with a lighter triangular scutellum (hard plate or scale), and often black tips at the end of their wings. Nymphs are usually green with numerous black spots on their backs.

Life cycle:

The adults seek out weedy patches or hide under debris, to overwinter. In the spring they feed first on fruit tree buds and then move on to other plants and lay their eggs in stems, leaves and flowers. The nymphs hatch and then feed for 3-4 weeks. They have 1 to 3 generations a year in Saskatchewan.

Control:

Remove weeds and crop residue from susceptible crops in the fall. In the spring, remove winter annual weeds. Tilling the soil discourages overwintering adults. Destroying infested fruit and twigs on fruit trees and not growing alfalfa (an alternate host) near susceptible crops are also a means of keeping the insect under control. In small areas, use white sticky traps to catch insects in spring before they lay their eggs. Insecticide application may be used prior to bloom, if populations warrant this, but beware that pollinators will also be affected.

Mites and Spider Mites:

Description/Damage:

Both adults and nymphs suck sap from the foliage. Leaves appear blotched, speckled and grey and often fall off. The mites may be tiny whitish, greyish or greenish specks on the underside of foliage, usually associated with a very fine webbing.

Life cycle:

Overwintering adults are found in the trash cover and other protected habitats. They can be seen in the spring as soon as foliage appears. All stages may be present at one time with 4-5 generations per year.

Cyclamen Mite

Description/Damage:

Immature and adult stages both injure plants. Mites are white to pale yellow and can only be seen using a magnifying glass due to their small size. Leaves become wrinkled and plants are unthrifty. Fruit is either absent or poorly formed.

Life cycle:

They do not like the sun and live mostly in the folds of unopened leaves.

General control for Mites:

Spray Kelthane 18.5 EC at 6 ml/L of water when growth begins in the spring and later when necessary. Do not use within 7 days of harvest.

White Grubs:

Description/Damage:

White grubs, which are 2-4 cm (0.8-1.6 in) long, are the larvae of June beetles and related species. They are common on land that was in sod in the previous year. The grubs feed on the roots of the strawberry plant usually killing it. Dig up any dead plants and look for the presence of this whitish grub, which is usually tightly curled into the shape of the letter "C".

Control:

Flour in warm water controls grubs as it sticks and dries on their soft bodies. Diatomaceous earth is a contact insecticide, but is rather expensive. Bacillus popilliae, a milky spore disease, sold under the tradenames of Doom or Japidemic will control grubs for many years. However, it takes time to build up in the soil in order to take effect.

SOURCES:

Agriculture Canada; Strawberry Culture in Eastern Canada; 1983.

Publication Agdex 624-1; Control of Small Fruit Pests; 1982.

Julie Soroka, Agriculture Canada; Plant Bugs.

N.J. Holliday; Agdex 624, Manitoba Agric.; Insect Control on Fruit Plants 1990-1991.

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.