SCIENTIST'S TRIP ABROAD

Northern Advocate, 18 February 1926, Page 6

SCIENTIST'S TRIP ABROAD

DR. TILLYARD’S INTERESTING PLANS. A WIDE SEARCH FOB PARASITIC INSECTS. SOME PLANS Foil THE BLACKBERRY PEST. ' It was pleasant to see Dr. Tillyard, of the Cawthron Institute, busy in Wellington recently, after Ids recovery from a very serious illness, which has kept him from active work for a lengthy period. He resumes with his old-time enthusiasm, and planned to leave New Zealand by the Aorangi on February 10 with an important ' programme of research for the benefit of agriculturists and fruitgrowers. Dr. Tillyard was good enough to explain in advance what he hopes to do, knowing that your readers take an interest in his work, which he appreciates. Seven weeks will be spent in the .United States, and Dr. Tillyard, who will be accompanied by Mrs. Tillyard, •to assist him in a secretarial capacity, will then visit England and the Continent,- re turning to New Zealand about October next.

•FIGHTING THE BLACKBERRY. “Yes, 1 am going away full of pro- j blems, in the hope of getting a solution to at lea.-i some of them,” he remarked.! “The in;; in hope centres around the blackberry pest. At the recent conference of the .Nurserymen’s Association in Dunedin some of the speakers seemed to take n pessimistic view, »but I have hope oi tackling it in a now direction, ’based on ;lm long and successful fight in Ansi r.iiia against the prickly pear. A few veers ago ir was thought impossible to use injects against a weed, but I have two good precedents in suggesting such a course in remm! to the New Zealan blackberry problem. The first is in connection with the control of the Lerttana in Hawaii. It was a very bad weed there —in New Zealand a very beautiful pot plant; it. grew sixteen feet high into an impenetrable i hicket. But in Hawaii the Lentana is no longer uncontrollable. Thej introduced a butterfly and a fly. One cats the buds and the other eats the seeds; Between them they prevent the plant from seeding, and it has to die. ■: Then it can be ploughed in, rotten, and there is no trouble in keeping the land clean. PRICKLY PEAR CONTROLLED. “The other precedent is in connection with the Australian problem of the | prickly pear, which ruined millions of ; acres of huid. They tried chemistry, ' they tried rolling them down with'tanks, ; but it was useless. Then insects were ‘ experimented with. Thirty different species live on the cactus in America, 1 and they tested out three in Australia. First the insects were tried but on i* plants of economic value, for this is an 1 important matter which wo always keep in mind in the introduction of insect

parasites. They are tested out under laboratory control on various kinds of food, and if any insect shows a liking for some plant which is of economic value, then that at once indicates that it would he unsafe to liberate it in the country. The first insect which the Australian authorities liberated on cactus areas was the cochineal, which destroyed .5000 acres of one species of cactus in two years. But it would not attack another kind of cactus which covers millions of acres, so the problem was only half sovlcii. However, they had a valuable clue, so they sent, across and got supplies of another species of the cochineal, and when this was established in Australia on the hitherto intractable cactus it cleaned it up. The prickly pear fell rotten to the ground after the attention' of the cochineal, and it could be ploughed in. Thickets 12 to 20ft high —so thick that even a dog could not get through them —have rotted away. This little insect, like a tiny mealy bug, rots them to pieces. “I have been in close touch with this development, and through the good offices of the Australian Prickly Pear Board I have their reports even in advance of those which have been published. These show that there is a moth in the Argentine which is a great factor in control, and that there is also a red spider, closely allied to the one which troubles the apple tree in this country, which absolutely cuts the prickly pear to bits. They have also under consideration a promising bacterial treatment, but one difficulty over the bacteria is that it shows a tendency to infect the melon and similar economic plants. A fungus was tested out under the conditions which I have mentioned as affording precautions' against letting loose a I new disease on the producer, and- this was dropped because it caused rot in apples.

POSSIBLE DANGER TO - RASPBERRIES. “In dealing with the problem of the blackberry,” Dr. Tillyard continued, “we have to remember that it is closely allied to Ihe useful raspberry and the loganberry, which is a raspberry and bramble cross. We have to make up our minds that to kill the tremendously damaging blackberry we may have to damage the raspberry, though'a suitable spray would protect the latter. In my search for a parasite for the blackberry I shall restrict myself to the genus

rubus, which comprises the raspberry, loganberry, the ornamental blackberry, and the lawyer vines, and the Japanese winebcrry. The Americans are very keen, and have offered to help me in every possible way, though the blackberry to them is not a pest —it'is valued because.it is under control. They have studied the insects which live on the blackberry, but their study is just from the reverse angle to the one we have to adopts They study them to protect the blackberry, but we are after its destruction, and so will study the insects which destroy it in order to extend their numbers. We intend to collect in the autumn, and, by special* arrangements with the Department of Agriculture, consignments will he brought via the Panama Canal in cool storage to Nelson. When they arc bred they will be tested on the apple, pear, peach and plum, so that if we introduce them generally there will be no danger to fruit, excepting the possible damage to the raspberry, which I have suggested.” FORESTRY PROBLEMS.

Troubles associated with trees, in Hew Zealand—the pine, spruce and oak aphids, the scales, and the giant horntail, which takes the tops off the pinus insignis—are other interesting problems .which Dr. Tillyard will always have in mind when he is in touch with the scientists abroad. He will look for an Parwig control, supplies of which had failed owing to the unfortunate illness of the English operator. ' There is an Earwig Bureau in the'“United States which Dr. Tillyard will consult. He will arrange for continuation of supplies of the green lacewing, and hopes to be able to look into the methods by which the pear-leaf curling midge has been dealt with, so as to co-operate in this field with Mr. David Miller, of the. Department of Agriculture. WORK AT CAWTHRON INSTITUTE. Everyone will be very interested to learn how. the work of the ’ Cawthron Institute is progressing. Dr. Tillyard mentioned that the green lacewings were doing very well when he left Nelson, and a colony established on Mr. Stead’s infected trees at Ham, Riccarton, were also getting on favourably. Out of 1900 imported from the States,*,lßso were alive, and CCO were sent to Riccarton. The second generation has been reared to the pupae stage from the egg. If this method of control is successful, it will be tried in the Christchurch Domain, where there are half-a-dozen trees in a dying condition Giving to oak aphis and oak scale.

One of the fascinating features about the work of the entomologist is that he is always encountering fresh problems, and Cawthron Institute is struggling with the ■ age-old “sex , problem.” Fortunately, in this' instance, it can be watched by humans quite dispassionately. Habrolepis dalmanni is the parasite of the oak scale. The unfertile female lays eggs which produce only males, but the progeny of the fertile female is exclusively female, as far as can be seen by observation. The mating of these parasites was too thorough, it appears, with the result that the family was exclusively male. Obviously the breed would die out if this persisted. In extreme cases, the males have been eliminated, and the females continue to produce females. The solution is to arrange with the ."Washington Bureau which forwarded the first consignment to send alternate colonies of male and female. As for the value of the parasite, that has been- well proved, for the percentage of parasitism is over 90. £3o, as Dr. Tillyard remarked, it looks like splendid control when the thing is going properly. The insect is a very beautiful one, twice the size of the aphelinus mali. of metallic green colour with bars of colour on the wings. It seems very hardy, and could be sent long distances in a glass tube. PEAR SLUG PARASITE. As for the pear slug parasite about which your correspondent made sympathetic inquiries, as of a useful member of the parasitic family. Dr. Tillyard said it is over three years since the first consignment came from Rothamstead- It got through the winter; but the first spring was dry, and nothing came out. In the spring of 1924 20 females were produced; they went into the ground for the winter, forming their cocoons, and the staff watched anxiously for the results. Every single one came out a male. This balancing of the sexes is a problem, but it can probably be got over by prv renting too thorough a mating. To revert to Dr. Tillyard’s travel plans. If only a fractional part of his problems can be successfully overcome, the cost of the tour will be repaid hundreds of times in one season. One can only wish him well, and particularly that his health, now slowly improving, will become- thoroughly established.