DESTROYING INSECTS

New Zealand Herald, Volume LXX, Issue 21640, 4 November 1933, Page 8 (Supplement)

DESTROYING INSECTS

DUSTING WITH POISON Insecticidal dusts, which hare lately come into prominence as a means of controlling insects, may bo used as an alternative to sprays and fluids. Two types of dust are employed: (a) Dusts for use as stomach poisons against biting insects such as caterpillars; (b) contact dusts for use against sucking insects, such as aphis and plant bugs. These dusts may also be used with advantage against biting insects when the risk of poisoning prevents the use of stomach poisons such as lead arsenate. The dusts are applied by suitable means in the form of a fine cloud, so as to coat the leaves or the insects evenly with the compound. The chief advantages of dusts are that tho dustings may be carried out much more rapidly tlian in the case of wet sprays. Jhe cost of material is somewhat liicher than that of wet sprays, but this is more than offset by the increased speed of application.

ESSENTIALS TO SUCCESS A disadvantage of dusts is that certain types of weather arc essential to success, particularly in the case of contact dusts. The principal poison dust is lead arsenate, which compound is usually used in diluted form, the diluent is> often hydrated lime. Lead arsenate is present at a strength of 10 per cent. The lead arsenate may be mixed with finely powdered sulphur or dry Bordeaux powder, and the mixture will have fungicidal powers in addition. Tho . principal ingredient of dusts against sucking insects is nicotine at a strength of two to four per cent. Nicotine sulphate is sometimes used instead of pure nicotine, but since it is only 40 per cent as compared with the 98 per cent of ordinary nicotine, a greater quantity is required. The conditions for the successful application of a contact dust are as follows: Still air is essential; for example the smoke from a cigarette should ascend vertically. High air temperature is important since the nicotine requires to be volatilised by warmth before it can affect the insects. Slight moisture on the plants, such as dew is an advantage, since it assists the dust to adhere to the foliage. On the whole, the best time to apply the dusts are iu the early morning or evening.

SIMPLE IMPLEMENT The simplest implement for the application of dusts to low plants consists of a bag of coarse sackinc suspended from the end of a short pole. By jerking the pole, dust is shaken on the plants. Other and more efficient means may be purchased. These consist of beilows operated in the usual manner, or in the form of a knapsack carried on the back. The best types of duster operate by means of rotary fans, the advantage being that the dust emerges in a continuous stream. Such dusters are more efficient and economical to use.

TO CORRESPONDENTS W.B. (Whakatane).—Entelea arborescens (whau). C.J.K. (Royal Oak).—Your inquiry answered direct by post. C.C. (Tauranga) —Specimen of manuka parasite, Korthalsella ealicornioides. T.C.C. (Thames).—The weeds are:—l. Erechtites Atkinsonii (fire weed). 2. Senecio jacobea (ragwort). M.E. (Waiuku).—l. Acanthus candelabrum. 2. Tradescantia virgijiica. or spiderwort. 3. Othonna. i. Tropaeoleum pentaphyllum. H.T.L. (Parakakau).—Calodendron capense (the Cape chestnut): The tree will grow to a height of 30ft., but will not etarld much frost in the yoiing etate. It should be planted in a sunny position. "Ignorant" (Ngatea).—The specimen of creeper is Solanum jasminoides. This creeper is evergreen and will stand frost. The tips may be cut by hard weather in winter, but usually plenty of growth is mnde again in spring.

"Passions" (Henderson).—-Lime sulphur would be the best to sprav passion-fruit with now, 1 to 100. It is not advisable to spray when the flowers are open. Choose early morning or evening, when few flowers are out, or the spray will prevent setting. A good spraying with Bordeaux in winter is best.

G.B (Rotorua).—l. If your tomato plants are only 6in. high, it would be best to pick off the first flower and encourage the plants to grow. Allow one leading shoot to grow and take out all other side-shoots. 2. To prevent the cauliflowers being'eaten, e'pr&y the plants with nicotine sulphate, one teaspoonful to one gallon of or arsenate of lead powder, one dessertspoonful to one gallon, every 10 to 14 days. D.M. (Clevedon).—The carnations are affected with leaf rot. caused by the fungus Heteropntella dianthi. The " disease ia favoured by cold, wet conditions. Leaf rot can be controlled by planting only healthy cuttings. Spray with Bordeaux powder, loz. to one gallon of water, and choose a warm, well-drained position for cultivation. Your query with reference to carnation plants cannot be answered through this column, but will be posted.

" Bamboo" (Avondale).—l. The best manure to force the growth of the privet and abelia hedges would be blood and bone. Fork it in at the bass of the hedge and keep well supplied with water. 2. The only way to stop the bamboo from spreading is to dig a trench along the side. It is always best to plant one of the non-suckering varieties near a garden. 3. The weed is the narrowleaved plantain. A good dressing of lawn sand will discourage it and assist the grass to grow. The other alternative is to dig it out.

"Amateur" (Matakana).—The small matchbox of soil sent contained the following five separate epecies of soil pests:—Snake mellipedes (Julus Suttatus), the larvae of slaters most predominant (Armadilla vulgaris), root aphis (Trama troglodytes), thrips (Thrips minutissima), and a species of beetle. Th? &est remedy would be to give the patch of ground a good dressing of naphthalene flakec, 2oz. per square yard. Any pea or bean seeds sown in that position will be infested, no matter what treatment is given to the seed. All dead or decaying vegetable matter should bo removed and burned,

" Amateur" (Te Aroha).-—Tho specimen strawberry plants show no trace of disease, but they appear to have only two or three live roois attached to each. Probably, owing to late planting or uncongenial conditions, they have not mad' lufficient root to withstand the fruiting period. The plants are badly nffecteo with aphis, which would probably account for their weakened condition. As you have • not very many, it would not take long to spray the undersides of the leaves well with nicotine sulphate. one tenspoonful to one gallon of water. The fruit would not be edible for a while after spraying. Applying water with a good pressure from a hose will clear a lot if done frequently, and will also enable the fruit to be eaten.

R.H, (Kohukohuh—l. To save tomato seed, scoop the pulp and seeds into a tin or other vessel. Cover with water, and allow to stand for 24 hours. Strain the liquid off and spread seeds to dry on sheets of glass or a smooth surface. Before the seeds are quite dry rub between the hands to separate them, finish dry.ng, and keep in a dry place 2, In rendering sticky clay open enough to work, A good dressing of lime would bo beneficial. Also sow green manuring crops to dig in. such us mustard or lupins. As the humus decays very slowly in your soil, it is evident that oxidation of the soil is non-existent owint to the eoil particles adhering 100 closely. Any vegetable matter that can bo dug in will help also. Dig tho ground roughly in autumn and allow it to stay until spring. E.B CWhakntane),—The' most essential spraying against leaf curl is in winter, to prevent the spore., germinating. It is not advisable to use lime sulphur and Bordeaux together. A good spray programme for peaches and nectarine* is;— Winter: After pruning, lime sulphur, two parts in four gallons of water: when buds begin to itwell, Bordeaux powder, lib. to five gallons: petal, fall period, lime sulphur, half-pint to four gallons: every three weeks later, until fruit is ripe, lime sulphur, half-pint to four gallons. This is the spray to control brown rot, Clear up and burn all fallen curled leaves Sulphate of iron scattered round the base of the trees will be better than Epson) sails Use about lib. for four-year trees. The stron? branch frotn the base of rose tree, if i' is below the point of working, should be suppressed entirely. If it is abort, reduce its vigour by shortening back now to restore the balance of the bush. Keroß.