TREATMENT OF PESTS AND DISEASES
PRACTICALLY every flower, fruit and vegetable under cultivation has its own special pest or disease. In many cases they are beset by numerous enemies, and it is almost a wonder they survive at all. Some pests can be dealt with by spraying, others only by patient hand-picking, or scrubbing, as in the case of Scale on indoor fruit trees. Prevention is better than any attempt to cure, and good cultivation is half the battle. If plants are strong, and healthy, and well cared for, they will resist disease and grow fairly well even when attacked by pests. Nurserymen nowadays concentrate to a certain extent on producing disease-free or “immune” varieties, but weather conditions take a big hand in the game, and diseases hitherto scarce in this country may make their very unwelcome appearance during exceptionally hot or wet periods. An example of this is the Rust appearing on Onions and Leeks and also on Antirrhinums and, which has recently proved especially troublesome. Then there are invading pests such as the dreaded Colorado Beetle which attacks potato crops, and which has made one or two attempts to invade these islands. This has been somewhat “in the news” lately, and it is to be hoped that growers will keep their eyes open and report its presence so that it can be fought back successfully.
There are hundreds of, but only particulars and treatment for the most common can be given here.
American Blight. (See under WOOLLY APHIS.)
At the first sign of serious trouble from these active little insects their nest should be traced. This can easily be done by putting sugar down, and tracing the insects as they carry it away to feed their young. After a hole is made about 1 ft. deep, in the nest, an ounce of carbon bisulphide should be poured into it, and the hole stopped up immediately. The ants will be destroyed by the fumes, but the eggs and larva are not affected, so a further dose must be given about a fortnight later to kill off any that hatch out in the meantime.
Where there are trees, a thick white chalk-line round the trunk will prevent the ants from getting into the fruit and flowers, as they cannot get a foothold on the chalk.
Apple and Pear Scab
One of the worst fruit diseases. It first appears as dark spots on the leaves, and then spreads to the fruit, appearing as cracked scabby spots on the skin. Burn all fallen leaves and twigs from affected trees, and spray with Bordeaux mixture immediately the fruit has set, and again about a month later.
This disease enters the bark of the trees through wounds, often through those made by the Woolly Aphis, or untreated pruning wounds. A callous forms round the wound, which spreads and often entirely encircles a branch, which, of course, then dies. Certain varieties of Apples are more subject to this disease than others and trees in heavy, or low-lying districts, are more subject to it. All affected parts should be cut out and burned, and a winter lime-sulphur spray used.
Sometimes called Black-fly or Black Dolphin, first attacks the terminal shoots, but if not removed spreads all over the plant, covering it with a dark sticky mass. It sucks the sap from the plant and entirely ruins the crop. Pick off and burn the tips of plants affected. Spray with Quassia, or dust the plants with soot or lime.
The Black Currant’s own pest. It is a tiny insect that buries itself in the bud, causing it to swell. Badly affected trees should be dug up and burned immediately, others can be sprayed in May and June with lime-sulphur solution. The diseased buds, which are rounder and fatter than most buds, can be picked off by hand, if not too numerous, and immediately burnt.
Brown Rot of Fruit
Attacks Apples, Plums, Cherries, Peaches, and Tomatoes. Like scab, it first appears as dark patches on the leaves. Sometimes the blossoms turn brown, and the spores spread to the fruit, causing brown patches on the skin. Do not attempt to store affected fruit. Spray the trees with Bordeaux mixture when the fruit sets, or use a winter spray of copper sulphate. Remove and burn any mummified fruits found on the tree in the winter, dead leaves and twigs. Also burn all prunings.
This pest affects any kind of bulb, but is so small that its presence is only apparent when the damage is done. The foliage turns yellow, and small red rust appears on scales of the bulb. To prevent attacks of this pest, bulbs should be washed in a potassium sulphide solution. Bulbs attacked should be destroyed at once as there is no known cure.
This caterpillar when very small can be destroyed with a spray of hellebore wash and soft soap. Hand picking is as effective as any treatment, and a search for the eggs on the leaves is worthwhile.
Cabbage Root Fly
A soil fumigant should be dug in before cabbages are planted if this pest has previously been troublesome. Paraffin mixed with sand, spread round the plants, will keep off a large number of flies who normally would lay their eggs near to the root of the. The maggots, as they hatch, enter the roots in search of food, and cause the sick appearance of the plants. Any cabbages attacked must be burnt at once, as there is no cure for the trouble when the plants have turned a sickly yellow. Fumigant should then be applied to the ground. This attacks all members of the cabbage family. In districts where it is especially troublesome, it pays to buy the special felt collars supplied by nurserymen to keep the flies away from the roots. Watering the soil with a teaspoonful of strong ammonia in a gallon of water is often effective.
This insect attacks apple trees, and currants. The leaves of the apples begin to show dark brown spots in April, and the young shoots are thus retarded in growth. As soon as the fruits have set, they are covered with red or brown pimples. As the apples increase in size so the damage spreads, until the fruit drops off the tree. The insect itself is like a larger green fly, and very active. Strong nicotine wash should be used in April, and early May. A thick lime-wash applied just as the leaf buds burst, prevents the eggs hatching.
This pest becomes apparent when the foliage turns yellow and the crowns become discoloured. The plants may be sprayed with tobacco juice or paraffin emulsion, spraying well on to the crowns of the roots.
The leaves of the celery are attacked, causing them to blister and decay. Use a strong soil fumigant before putting the plants into the ground. Spray the leaves with quassia or paraffin emulsion, to keep the fly away, otherwise it appears in June, July and August. Dusting the plants with soot and lime also discourages the flies from laying their eggs. Burn all affected foliage, or pinch the “blisters” between the thumb and fingers to destroy the maggots that are developing in them.
Club Root, or Finger-and-toe
This disease chiefly affects members of the cabbage family, and. As there is no cure when the disease once affects plants, preventive methods must be taken.
Give suspected ground a good dressing of lime, at least 4 oz. per sq. yd. All diseased plants should be burned immediately, and no members of the family planted in the same plot the following season, to give the lime an opportunity of thoroughly cleaning the ground.
There are several varieties of this destructive and unpleasant pest. The Common Cockchafer usually attacks Raspberries and Strawberries, the grubs feeding on the roots of plants, and the beetles on the foliage. The Summer Cockchafer mostly attacks vegetables The Garden Cockchafer confines its efforts to Turnips, Peas and Beans, and the Rose Cockchafer, which is the beauty of the family, attacks practically all the plants affected by the others in the family, but especially Roses.
Beetles may be shaken off rose or fruit trees on to tarred boards, or removed by hand and destroyed. Do not shake too vigorously, as the beetles are inclined to fly away if awakened from their daytime sleep. Arsenate of lead may be used as a spray, but as this is poison it should only be used in the early stages of fruit development. A fumigant dug into the ground surrounding the trees destroys the larvae.
This attacks Apples, the maggots creeping into the centre of the fruit, usually through the eye. It leaves the fruit through another channel and shelters in the bark. If the apples fall, the maggotsin the soil, therefore a soil fumigant will destroy some. Grease- banding, however, provides a home for the female moths, which are wingless, and these can be removed and destroyed from time to time. Spray with lead arsenate immediately the blossom has fallen. Winter washing destroys those of the pests that hibernate in the bark.
This much dreaded pest has appeared onin several parts of the country, but is not at present generally troublesome. The full-grown beetle has orange and black striped wings, the grub is of an orange colour, and the eggs are also orange. The beetle when full grown is about I in. long from head to tail. It spends the winter deeply buried in the soil, and in late spring works its way to the surface. This is a notifiable pest, and anything resembling the Colorado Beetle, found on potato plants, should be immediately sent (in a closed tin box) to the Ministry of Agriculture, 10, Whitehall Place, London, for inspection.
Cuckoo Spit Insect
Cuckoo-spit insect, sometimes known as froghopper. Hand killing, although unpleasant, is the most effective way of dealing with this little green larva. Spraying may, however, be resorted to if the attack is a bad one, and quassia or nicotine soap is the spray to use.
“ Damping-off “ Disease
Youngare the chief sufferers from this disease, and it is encouraged by over-watering and lack of sufficient ventilation. Pull up and burn all affected plants immediately the disease shows itself, and dust the rest with flowers of sulphur. A preventive is to use formaldehyde as a soil drench.
This is a late season pest, and affectsand late roses more than any other plants. The old-fashioned method of inverting flower-pots on the heads of the stakes to act as traps has still to be improved upon. The pots should be filled with hay or straw or even tissue paper in which the earwigs can make their nests. A poison bait may be used where there are no children or domestic animals. Sodium fluoride mixed with wheat bran and molasses and spread on paper is usually effective.
Gooseberry Mildew, American
As this disease affects shoots, leaves and fruit, it is a most difficult one with which to deal successfully. It first appears white between April and June, and brown from June onwards. It is especially prevalent in warm, moist weather and in damp, low-tying positions. The bushes should be well sprayed with lime-sulphur the first week in April, and two further applications given at monthly intervals. All diseased tips of shoots should be removed and burned. A soda and soap solution applied at ten-day intervals after the fruit has set, and a strong caustic soda spray in February will also keep the disease in check.
Green-fly and Black-fly
Officially known as aphides. The green-fly mostly attacks flowers such as roses, flowering shrubs, and carnations, but the black-fly affects beans, nasturtiums, and cherries. Ladybirds deal with a large number of the green-fly, but nicotine, paraffin emulsion or quassia sprays may be used. Tar oil and caustic soda sprays in the winter will rid fruit trees of this pest.
Gummosis or Gumming Disease
Attacks cherry, plum, peach and almond trees. The disease appears as small drops of colourless gum oozing from the branches and trunk. To prevent this, great care should be taken when pruning to cover all wounds with Stockholm tar or white lead paint. Diseased branches should be cut off and burned immediately the disease appears. The spores may be washed down the trunk by the rain, so by moving the top layer of soil round the tree and replacing it with fresh soil containing some quicklime, the gumming may be checked.