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Unhappy Strawberries?

By on June 03, 2010

Botrytis or Gray Mold on Strawberries - Photo by Gerald Holmes, Cal Poly at San Luis Obispo,

It is such a wonderful pleasure to see all those plump red berries peeking through the green.  It can bring back the wonder and joy of childhood. If you are a Grandmother, like me, the greater joy can be in watching your grand kids pour over the patch and the red toothed smiles of happiness.  So, when you find holes or mold in your luscious berries, it is time for action.  The first action is to determine what’s eating or infecting your strawberries.

Strawberry root weevil, rough strawberry root weevil, lilac root weevil and black vine weevil
rough strawberry root weevil
As adults, all four species are small, dark snout beetles.  Largest is the black vine weevil, which may reach 1/2 inch. It has characteristic patches of yellow hairs on the wing covers. Strawberry root weevils and lilac root weevils are shiny, brownish-black and about 1/4 inch long. Rough strawberry weevils are intermediate in size.

A behavioral characteristic is that, when disturbed, root weevils drop readily to the ground. They do not fly. Adults climb plants to feed at night and hide around the soil surface during the day.

Life Cycle: Root weevils overwinter as nearly full-grown, pale, legless larvae that feed on the roots of strawberry, raspberry, clover, spruce, Douglas-fir and many woody shrubs. Some black vine weevils may over­winter as adults.  Adults emerge sometime in June. Eggs apparently are laid near the crowns of plants throughout the summer.

Plant Injury: Root weevil feeding by adults produces characteristic notches along leaf margins. Euonymous, peonies and lilac are among the plants frequently damaged by adult root weevils. This damage typically is mistaken for grasshopper feeding.

Controls: can be applied to either the adult stage or the larvae.

Peaceful Valley Farm Supply Products who claim control of weevils are sprays containing pyrethrum.
Pyganic (PBT329 or 330)Safer Yard & Garden Insect Killer (PBT412),  Evergreen ( PBT350)
These sprays should be applied to the foliage and it can also be useful to treat areas at the base of plants, where the insecsts rest during the day. Control may be improved if applications are made late in the day or in evening, as the weevils become active and move onto the plants after dusk.

Larvae develop in the soil and require different treatment. Drench the soil well, so that it moves to the root zone. Parasitic nematodes of the genus Heterorhabditis (PBI044 & 046). Treatments should be made in late spring and early summer when adult feeding on leaves is observed and egg hatch usually begins. Heterorhabditis nematodes require that the soil be kept moist following application and the site should be irrigated immediately after application. Entrust

Hoplia Beetles

Hoplia beetles are close relatives of the dreaded Japanese and Chinese Beetles. They are day flyers and prefer the flowers of white to whitish flowers. The adults are small about 1/4 inch to 3/8 inch long and somewhat squarish and dorsally flattened in shape. Their ventral surface are covered with silvery and coppery colored scales while the elytra and dorsal surface is brownish to reddish brown in color. Silvery scales are also found on the dorsal surface giving the dorsal surface a mottle appearance on various shades of brown. There is only one generation per year with the adults emerging from mid March through May.

Plant Injury: Even one hoplia grub in the crown or roots will cause significant damage. If plants wilt or appear stunted and/or reddish in color, larvae may be present. Examine roots to determine if root weevil larvae are present, because cold temperatures can also induce reddening. Dig several plants and look for C-shaped grubs in the crown and/or roots.

Cultural Control :  Annual plantings, soil solarization for hoplia beetles, and crop rotation, are acceptable for use on organically certified strawberries. Preliminary research in using parasitic nematods for control of beetle larvae infesting strawberry roots has not proven successful, however, research continues.

Gray Mold

The most common disease of strawberries is gray mold, caused by the fungus Botrytis cinerea.PVFS products with label information claiming control are:

Fungastop (PBT955),   Mycostop (PFM1302 & 1301),   Serenade (PFM921)

None of this is good news but, knowledge offers the power to act.  Best of luck.  And don’t forget to invite me over when you bake that strawberry rhubarb pie.

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