Fruit Pests And Diseases

Birds

Birds Pests are, alas, always with us but thanks to modem specifics there is generally no reason why they should cause serious damage to our trees or crops. There is, how-. ever, one exception against which no easy defence has yet been discovered-the birds which, it must be admitted, often add much to the enjoyment of our gardens but can rob us of our reward for a year’s care in a few hours.

As they begin to ripen, nearly all fruits are subject to bird attack but, worse than that, our chances of any crop at all can be destroyed the previous winter when birds turn to the dormant buds on gooseberries, currants, plums and other tree fruits as a source of food in hard weather. Which fruits are most liable to be attacked probably depends on the balance between the trees available and the local bird population.

To protect the buds one can apply a proprietary bird repellent spray. This can work well, for a time, but frequent renewal can be expensive and is a task easily forgotten. More lasting protection is provided by rayon web, the fine gossamer strands of which are teased out over the tree or bush. The birds hate this material but the individual threads are so fine and fragile they cause no injuries as cotton and, particularly, nylon thread can.

anti bird mesh to protect fruit trees

The only absolute protection against birds is provided by small mesh netting carefully draped over permanent or temporary supports. Plastic netting is available in many sizes and is rot-proof and very light in weight.

Both rayon web and netting will, of course, protect the ripening crops as well as the buds in winter.

Aphids

Like birds, aphids (the greenfly tribe) always make an appearance sooner or later. If unchecked they can do serious damage to the tree fruits. Although they do little apparent harm to strawberries and raspberries, their sap sucking introduces virus disease which can be fatal. Aphids tend to attack growing points first and their activities frequently cause leaves to curl. Aphid eggs over-winter on the trees.

Caterpillars

A number, notably the leaf and fruit-eating tortrix caterpillars and those of the winter moths (known as loopers’) feed on fruit trees, particularly apples, pears, plums and gooseberries. The parent moths lay their eggs in bark crevices between October and March.

Capsids

capsid bug damage on roses

These bugs hatch in spring from eggs over-wintered on the tree. They first eat the leaves and then start on the fruitlets. Apples are the most common sufferers but currants and gooseberries are attacked by related species.

Sawflies

These creatures lay their eggs in the flower of the apple or, less frequently, pear. The larva bores into the fruitlet. It will pass from one to another, spoiling each, and then fall to the ground. A mass of sticky frass (excreta) exudes from the hole where the pest enters the fruit.

Codling Moths

Codling Moths

This moth lays its eggs in early summer on leaves or fruit, and the grubs bore into the fruit to feed. These are the creatures you may find near the core when you come to eat the apple. Pears are less commonly attacked.

Spraying Programme

There are many other pests to spoil our fruit but the above-mentioned are those which do most damage. A drenching of the dormant trees and bushes in winter with tar-oil will do much to kill over wintering eggs but should only be resorted to about one winter in three because it also kills friendly insects which prey on red spider mites which may then become a menace.

A minimum spray programme starts at the green cluster stage of apples and pears to kill caterpillars and greenfly. Give a second spraying at the pink bud stage (apples) or white bud stage (pears), to deal with capsids, and a third spraying as soon as 90/0 of the blossom petals have fallen, to kill sawfly and tortrix caterpillars. In mid-June spray to deal with codling moth and tortrix caterpillars, repeating this a fortnight later. Two sprayings are essential for plums-between bud burst and the white bud stage, to control aphids and caterpillars, when the petals have fallen and the fruitlets set, against sawfly.

Further sprayings, of course, must be given if pests are seen. Aphids may appear at any time and if the fruit is shortly to be eaten it is essential to spray with something which is non-toxic to humans- derris, for example.

There are dozens of pesticides on offer in the garden shops. The labels on the bottles or packets will tell you what pests they are intended for and when and how to apply them. The important thing is to follow those directions exactly.

Fruit Diseases

Careful attention at all times to garden hygiene will do much to keep disease to a minimum. Indeed, one cannot ‘cure’ plant diseases and prevention must always be the policy. Always cut out any dead branches or shoots as soon as you notice them and bum them. Also burn any rotting fruits.

Scab

This fungoid disease disfigures the skin of many apples and pears, especially in wetter and more humid districts. It is not likely to cause much harm if you spray regularly with captan at the green cluster, pink (or white) bud and petal fall stages.

Brown Rot

Brown Rot

Concentric rings of small pustules on ripe or ripening fruit are the outward signs of this fungus. It is very contagious. Bum all infected fruit and wash your hands immediately after touching them.

Silver Leaf This may attack all stone fruits (and sometimes apples) but is particularly virulent on plums. The leaves assume a silvery tinge and the diagnosis is confirmed by a brown stain inside the wood of infected branches or shoots. The disease is spread by spores entering wounds or cuts in the bark, usually between September and May. Do not, therefore, prune in winter and cut out any dead or infected wood in midsummer. Pare all wounds smooth and cover with a protective tree-pruning paint.

Leaf Curl

Leaf Curl

A very common trouble with apricots, peaches and nectarines, causing the young leaves to become puckered and curled. Such leaves become yellow, then reddish and develop ‘blisters’. New growth is distorted.

The most likely means of control is to spray with lime-sulphur in late February or early March while growth is still dormant and just before the buds swell. Repeat in autumn just before the leaves fall. Once growth has begun in spring lime-sulphur must not be used; instead spray with captan.

Virus Diseases

Of recent years a number of fruit troubles have been found to be of virus origin. Those most likely to come to the amateur grower’s notice are those which attack strawberries and raspberries, drastically reducing crop yields. To avoid virus troubles only buy new stock from a nurseryman who takes part in the Government Certification Scheme, and spray against aphids.

Early symptoms include various leaf markings but these can easily be mistaken for those caused by mineral deficiency. If you see abnormal markings on the leaves of strawberries or raspberries, give first-aid in the shape of foliar watering with a foliar feed containing chelated trace minerals just in case the trouble is due only to a lack of iron or magnesium or other trace element. Never use suspected plants for propagation. If cropping fails, dig up and burn the offenders.

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