The most troublesome fungoid attacks to which the strawberry is subject are mildew and leaf spot. The former, like all mildews, attacks the leaves and spreads to the fruit, these being covered with the white mycelium. The fungus is identical with that causing mildew in hops (Sphaerotheca humuli), and its development is greatly furthered by exposure of its host to cold draughts or low night temperatures. Spraying the foliage with potassium sulfide (K2S) (mixed with water at a 1:40 ratio by volume) should hold it in check, but the plants should not be sprayed when the fruit is developing. The "leafspot" is caused by the fungus Sphaerella fragariae. The first symptom of this attack is the appearance of small, circular, white spots on the leaves, having a broad, definite, dark reddish margin.

On these spots a whitish mould develops, and this is followed later by the perfect form of the fungus, the fruits of which appear to the naked eye as small black spots seated on the white dead spot on the leaf. Potassium sulfide may be used as for the mildew, or, perhaps better, Bordeaux mixture. Some recommend cutting off the leaves after fruiting and turn the beds over so as to destroy the fungus in the leaves.

The grubs of the cockchafer (Meloloniha vulgaris) and the Rose chafer (Cetonia aurata) frequently feed upon the roots of the strawberry and do considerable damage, while the larvae of the Ghost Moth (Hepialus humuli) and garden swift moth behave in a similar way. The imago of Cetonia aurala also frequently damages the flowers of the strawberry by devouring their centres, and is often troublesome in this way in forcing-houses particularly. The carnivorous ground beetles, particularly Pterostichus nigra and Harpalus rufimanus, when the fruit is ripe attack it at night, returning to the soil in the daytime. They are to be caught by placing jars containing some attractive matter, such as meat and water, at intervals about the beds with their mouths sunk level with the surface of the soil. Millipedes also are often found in the ripe fruit, but occur mostly where the soil is very rich in organic matter and poor in lime.

Cite: Wikipedia