THE POTATO-MOTH.

Pukekohe & Waiuku Times, Volume 6, Issue 273, 8 May 1917, Page 1

THE POTATO-MOTH.

The following information regarding the potato-moth and its control was furnished by the Fields Division to a correspondent in North Otago who had forwarded a grub-infested potato together with various questions concerning the pest: The grubs in the specimen of potato submitted are the larvae of the potato-moth, perhaps the worst enemy of the potato-grower. Po-tato-moths are usually more plentiful after a mild winter. There are two broods of moths. The first, the winter brood, may destroy the young plants and thereby ruin the crop. The moths of tne second brood deposit their eggs on the potatoes themselves when the tubers are stored or are in the field. Occasionally, especially if potatoes are grown in stiff soil, the moths will crawl down the cracks in the ground and deposit their eggs on the tubers. The eggs are usually from twenty to thirty in number, and hatch in from six to ten days. In sandy soils tubers are rarely so attacked. The young grubs when hatched usually feed upon the eyes of the potatoes ; they then tunnel towards the centre of the tubers, causing them to become brownish-black, and inducing decay. Sometimes when the potatoplants are fully grown the l'emale moth deposits her eggs on the leaves. The young grubs feed on these, and afterwards gnaw their way down the main stalks, reaching the tubers below.

Fortunately for growers, the chrysalids (stage between caterpillar and moth) of the potato-moth are attacked by parasites, bacterial diseases, and climatic influences, which destroy great numbers. The caterpillar of the potato-moth usually pupates (winters-over) under the skin of the potatoo, and is surrounded or protected by dirt, excremont, etc. It may also winter-over in the sliaws lying about.

Preventive and remedial measures are us follows : Dead potato-plants, discarded and small potatoes, and rubbbh should 1 " gathered and burnt. Old sp k.- m i c;:sos in which there hav« i— n nJ.-'i 1 potatoes should b" nti.i bvil.ng water. By tins m< .•»!, any gfib chryt-a-I' is Mt'i rijt'ii in '' ■ i.: be dostroved >•••• i ' : . the grubs should up-; •*! i. 1 i > d, nor should ground whc.e mo; L-aiiocted potatoes v, ere giowu :Uo previous year be u.iwd aguiu lor potatoes I'lant tho u,.( d di'fply and keep it well covered. The ground should be pressed hrmly

down, and it is advisable to till it a second time. Never leave potatoes exposed in the field. When they are dug up they should be at once bagged and removed to storage, where they must be placed in bins, pits, or any other places where moths cannot get at them to lay their eggs in the eyes of the tubers. It is a common practice with many growers to simply heap the potatoes up in a storeroom without any covering, and leave the doors wide open. No wonder considerable losses occur. Trapping by means of lamps is of use in destroying the moths, which fly about at night. Procure an ordinary tin basin, and in this place a brick and enough kerosene to reach half-way up the brick, and on the brick a lighted lamp. The moths are attracted to the light, and, flying against the lamp, fall into the kerosene, which kills them. The basin could be placed on an ordinary box, such as a kerosene case. Several of these lamps could be, placed in a field of potatoes at night-time. When the moths commence to make their appearance it is advisable to spray the crop with some arsenical spray, such as arsenate of lead. This will destroy the young grubs as soon as they commence to feed. A good arseuical spray is prepared as follows: Boil 1 lb white arsenic and 2 lb carbonate of soda (crystals) in \ gallon of water for 20 minutes. Separately dissolve 7 lb arsenate of lead in 1 gallon warm water. When both mixtures are cold mix them to-gether Bottle into twelve 1-pint bottles, and use one bottle to 30 gallons of water. Mix the chemicals in wooden buckets. Reliable brands of ready-made mixtures of arsenate of lead are on the market for those who prefer purchasing these. One careless grower of potatoes in a district who does not take'precautions to protect his tubers from the ravages of this pest can breed enough moths to ruin his neighbour's crops. Potatoes affected slightly oi otherwise should not on any account be kept for seed. They should be boiled for pig-feed, and the bags, etc., scalded with boiling water. Clean potatoes can be kept free from the moth by careful Bealed storage, as described When they are selected for planting the seed should be treated with a weak solution of formaljn. Every care should be taken to destroy all affected potatoes, large and small, and shaws.—"Journal of Agriculture."