LEAFLET FOR FARMERS.

Cromwell Argus, Volume XXVII, Issue 1359, 7 May 1895, Page 6

LEAFLET FOR FARMERS.

Potato- moth, Potato Tuber-moth, Potato grub ( Llta Solandla).

By T. W, Kirk, F.L.S., etc., Lono.

Fig. 1. Potato in state of putrefaction after being bored by the grub. Fig. 1. Grub, about average size. Fiu. 3. Head and first three segments, upper side, enlarged. Fig. 4. Ditto, under side. Fig." 5. Moth, natural size. Fig. 6, Ditto, magnified ; this cut shows the body rather too pointed, and without the hairs on the last segment. Fig. 7. Fore leg of moth, magnified. Fig. 8. Hind ditto. Fig. I from nature; ligs. 3 8 after I?rend), the markings on Figs. 5 and b slightly altered. _ The grub of this very destructive moth has long been known in many parts of the world, and for a very long period has caused enormous loss in some districts in Australia. Kor is it a stranger in Hew Zealand —some of the North Island growers have had bitter experience of its destructive powers. The caterpillar, or “grub, is from to (jin in length. The color is dirty-white, with a pinkish, or sometimes greenish, tinge, ihe head is dark, occasionally almost black. On reaching the tuber it eats galleries in all directions, and so induces putrefaction, it attacks potatoes both in field and store. _ . Arrived at maturity, the grub takes up a position on the outside of a potato, piece ot earth, or any other convenient object, but usually near the mouth of its gallery, and spins a covering like a roof merely—not a true cocoon—of dirty white silk, ihe chrysalis measures about three-tenths of an inch ; and the time spent in this stage varies from eighteen to twenty-seven days. The moths usually pair within twenty-four hours after emerging, and eggs are laid within the next forty-eight hours ; but it is probable that other layings will take place, for the moths live for several weeks ; and in one case, at least, the in'otl/took the male three times in eight days, and fresh eggs were deposited after each time within twenty-four hours ot the event. I am unable, at present, to say whether this is common with the species. I isolated two females, after impregnation, in order to ascertain how many eggs were laid. The first deposited 117, and the other 123. The first wore all deposited^in the eyes of a potato lying on the lloor of the breeding-cage ;in the second case the potato had been carefully covered with earth, and young shoots had developed to the length of about 2£in., and the moth, being unable to get at the tuber, deposited her eggs on these shoots ignite close to the ground. These and other results, _ obtained from examinations of specimens reared in confinement, agree well with the description given by Mr Tepper, Mr French, and other writers on the subject. The moth is very active both on foot and wing, taking short quick flights, and running rapidly; it is a night flier, and is attracted by light; this I know to my cost, as opening the breeding-cages one night to try the effect of a strong light, some of my best specimens flew straight at the lamp and were spoiltThe markings of the moths vary, and I believe that the tracings on those that pupate in the stalks are darker than on those that come from the tubers. Further experiments arc, however, necessary before this can be stated positively. The tobacco crop in some parts of New South Wales, and I am informed in Queensland also, has been attacked by this pest. The fact that it feeds on other plants besides those of the lolanaceic cultivated for food, will increase the difficulty of dealing with it. The measures adopted must be preventive rather than curative. In infested districts it will be well, if possible, to abstain from growing potatoes for a season or two; failing this, take care that all sets are sound and free from eggs, and the •'round thoroughly clear of weeds ; p'ant rather deeper than usual, keep well earthed up, and bag as soou as possible after digging. Stow in a moth-proof room, and examine from time to time to ascertain if any gtuhs have been gathered along with the crop; if so, remove the affected tubers, otherwise the potatoes will soon become a mass of putrefaction. At stated above, the moth is a night-flier, aud attracted by light; therefore cheap forms of lamps or fires may be used with advantage, and will destroy hundreds. A good plan is to place a light canvas screen of convenient size on either side of the lamp. This screen should be smeared with grease, treacle, or other sticky substance. The number of moths thus captured will be surprising. The lamp and screens may easily be removed from place to place- The lamps should also be used in the stores or pits, Never throw info-ted potatoes on the rubbish heap. This is only increasing and spreading the pest —providing the very conditions it rejoices in. Always destroy all grubs by soaking the potatoes in water for some days before giving to the pigs, or, if not required for the pigs, soak in the same way before burying ; or, better still, burn the lot. Mr Allan Wight has observed that grubs hatching in tne stalk ara frequently slow in eating their way to the tubers, and has proved that harrowing off the tops somewhat early and burning them in heaps is very beneficial—always provided that the potatoes have been kept well earthed up. Mr French states that air-slaked lim>, well harrowed in before p'antiug, has been found of great advantage. He also suggests that p tato.is should be so p’anted as to allow of the use of the strawsonizer to distribute tar-water or other fluid obnoxious to insects, and so largely prevent the laying of eggs, Mr Allan Wight, of L’teroa. the well known etomologist, considers I Ala Solauclla a native of this country, and states that it formerly fed larg-dy on the bulrush or raupo Typha AnyuslifAin), ;m d that as this were used fo • thatching potato houses, the insect soon discovered that the tubers were more to its liking. It is quite certain, however, that the species has been known for many years as a potato pest, even in this hemisphere, being reported from Tasmania in 1854, just about the date wnen Mr Wight first observed it on the raupo It L not nulik 4y 0 at it was brought ao New Zealand in some of the earliest importations of tabors, and took to other plants in consequence of the scarcity of potato's ? I have proved by experiment that it will feed on Solatium aviculare, a native of this colony. Tar water is prepared as follows : tp, cod tir, boiled in one gallon of water, and, after boiling for some time, diluted with 59 gallons of fresh watc". This must be stirred till well mixed ; it is then ready for use.