Strawberry Root Weevils
Weevil Identification and Control
Autumn is a good time to lash out against these weevils by mowing the strawberry plants like you would mow a lawn, the plants will come back in the spring.
In the spring or late summer, apply parasitic nematodes which will help curtail their population expansion. For successful use of nematodes you should allow sufficient time for multiplication of the nematodes in hosts (weevil larvae) and dispersal of nematodes throughout the soil. Early- to mid-May application is optimal. The larvae are also attacked by some general predator insects including Rove and ground beetles such as carabid beetles. Some strawberry plants have a natural or bred resistance.
The spores germinate inside the grubs, and multiply rapidly in their blood. When the bacteria become very numerous in the blood they again form spores, completing the bacterial cycle. Infected grubs survive for 7-21 after their blood has become loaded with spores, particularly in low temperatures. As the grub carcass decomposes, it releases billions of new spores. It is only effective against newly hatched larvae within the soil, not once they enter the plant.
Bacillus thuringiensis (Bt), a spore forming bacteria that produces substances which are toxic to many insect species, but virtually harmless to humans and mammals is somewhat effective against the larvae stages it should be applied as soon as the presence of adults is evident, to head off the imminent egg laying and hatched larvae.
Neem based Products, such as Azatin or Azadirachtin [extract of the neem seed-] prevents the larvae from developing normally and is also a good alternative for later larval stages. These products degenerate rapidly in nature and need to be reapplied frequently. For effective use mix Neem oil with equal parts of water and saturate the ground around the plants, allowing it to soak in thoroughly.
In severe infestations, there are a number of broad spectrum pesticides registered for use against weevil, sold under varying trade names.Acephate is one I would recommend. Bonide 941 and 951, Orthene 97.4% Acephate and Agrisel Acephate are a few brands readily available to home gardeners.