In an ideal world no sprays would be required, but there are occasions when the control of a pest or disease becomes desirable, since the yields and qualities of the unsprayed trees or bushes may be severely reduced. The newer varieties of fruits frequently have some resistance to specific pests or pathogens and one could imagine a situation in the future when a spray programme may not be required. It is possible to grow some types moderately successfully unsprayed but frequently these are the less commercial varieties.
The types of problems are as follows:-
1. Mineral deficiencies – The major nutrients, N, P205,K3L0 are usually applied as base or top dressings but may usefully go on as a foliarduring the summer. Magnesium, manganese and iron deficiency are frequently seen and these may be treated by foliar sprays. The
apple disorder ‘bitter pit’ may be reduced markedly by calcium nitrate sprays from June to August at weekly intervals.
2. Fungal problems – Most of the fungicides give protection, I.e. the new foliage is protected from invasion by the hyphae of the fungal organisms. The original fungicide – Bordeaux mixture – works on this principle. It is still very effective against a wide range of pathogens, but in use there is the risk of scorch, also there is a white deposit which is somewhat unsightly.
A whole new range of systemic fungicides are coming on to the market. These are absorbed by the plant, and from within the sap of the plant the resistance to the fungus is conferred, e.g. Benlate. Some strains of fungi may be able to use a range of such materials over a succession of treatments to reduce the chance of resistance developing.
3. Pests – The sucking pests like( ) and capsid bugs may do extensive damage to fruit, the and the shoots. ( may also commonly carry virus infections.) The chewing pests like caterpillars of the winter moth may devour the early leaves, setting back growth and development. Codling moth caterpillars may damage the fruitlet, as may the tortrix moth, earwigs, late aphids and the capsid bug.
The fruit tree red spider mite sucks the green out of the leaves and in severe attacks the trees may turn brown, I.e. all the leaves brown with no green left by August. A spray programme is usual for commercial growers, since the varieties which sell well may more easily be blemished by pests or disease agents. Clearly the control of these problems leads to increased profitability and that is why the grower may have very expensive – equipment to spray with and he may choose to apply costly but cost effective sprays. The good grower is unlikely to apply sprays which he does not feel will be well justified by increases in the marketable yield.
A great deal is said by the environmental lobby -against the use of sprays. There are points on which they are clearly right, but as this time is a period when enough suitable varieties with natural resistance (for example to apple scab disease) do not exist, then sprays have a place almost vital to the survival of the industry. (Appletake quite a few years before fruiting and many years before a good evaluation can take place.) Pheromone traps are available for control of the codling moth, and no doubt there will be many more fundamental developments yet. The I.H.R., fruit research station at East Mailing in Kent has programmes for integrated controls using predators and plant
One of the organic ways of reducing apple scab disease is to spray the foliage after picking in the autumn, with a nitrogen rich liquid manure. This aids both the development of the fruit buds for the following year and the leaves when they fall are more palatable to worms. Their activities destroy the leaves and so tend to eliminate a source of overwintering scab infection.
APPLE SPRAY PROGRAMME
Crop stage Dormant
Local wound treatments against apple canker, e.g. Mildothane.
Apple scab sprays start and these are repeated at approximately 10 day intervals. Materials in use include Captan and Mancozeb.
sprays start and these are repeated at approximately 10 day intervals. Materials in use include Nimrod, Benlate and Mildothane. In some years aphids and winter moth caterpillars have huge populations early on which may be controlled.
Pink bud – Control of pests – aphids and winter moth
caterpillars (also the rare pest of sprayed trees – the apple sucker). Products like Rogor and Gamma HCH.
Blossom – Only fungicides would be applied and these
in the early morning or evening (to reduce the interference to bees pollinating the).
80% of petal fall – Control of apple sawfly and the fruit tree
red spider mite. Dimilin and Kelthane are used. The red spider mite quickly develops resistance to sprays and the commercial grower has available sprays from 8 chemicalso that life for this pest has its hazards.
Around mid to late June, codling moth and tortrix moth are likely to require treatment in gardens. Dimilin, Decis and Permethrin are in use. The one spray treatment kills both pests. Two or three sprays may be required, two to four weeks after the first spray.
From mid July, a storage rot called Gleosporium may require protective sprays, in use is Captan, Benlate and Mildothane. Gleosporium is worst on calcium deficient trees – foliar feeds with calcium nitrate are commonly used. Bitter pit is a symptom of calcium deficiency. This shows as brown spots inside the apple and as lenticel spotting.
Red spider sprays may be required in July.
There is a reason for the use of each material specifically linked with the life cycle of the organism to be controlled.
Some of the problems illustrated with apples (pears suffer very similarly)
Codling moth maggot
Cut open apple showing the frass filled middle.
A frost eve seen looking at the nose of the apple.
A cut apple showing internal
corky bitter patches.
It often affects the bigger