LEAFLETS FOR FARMERS, NO. 14.

New Zealand Mail, Issue 1201, 8 March 1895, Page 7

LEAFLETS FOR FARMERS, NO. 14.

New Zealand Department of Agri- I CULTURE. ' John D. Ritchie, Secretary.

Hessian Fly (Gecidomyia destructor). By T. W. Kirk, F L S., &c , London. ' There are two main broods in the ye ir—namely, one in the autumn, when the flies emerge form the pupa cases, and deposit their eggs in the creases of the leaves. The tiny maggots soon hatch out, and work their way down into the crown of the root, as shown in the cut Fig. 1. The attacked plants soon become yellow and weak. The other brood appears in summer, the eggs being laid on the leaves as before. The eggs of this second brood vary greatly in number' —from as few as fifty to as many as 160. The eggs are bright-coloured, varying from pale to bright red—in some cases almost scarlet. In four or five days tiny yellowish maggots appear, and in their turn work their way down between the sheath and the stem till they reach one of the lower joints —usually the first or second—near which they settle, and suck the juices from the stem. (See Fig. 9, which shows straws with the sheath removed). I have counted as many as thirty-two clustered near a single joint. In about three weeks, the maggots, bavins embedded themselves in the straw and become full-grown, harden, turn brown, and assume the so-called chrysalis or “flaxseed” state, from which the tiny flies emerge in the autumn to attack the young wheat. Some flies, however, remain in the pupa state for over twelve months—a provision of nature to protect the species from extinction, b.it one not appreciated by farmers. The plant, being deprived of a great portion of its nourishment, succumbs according to the Re verity oi the attack ; the grain is badly developed ; the stem becomes too weak to support the weighP of the head, and bends down to the . ground. Damp, mild weather is always favourable to the development of the pest, and the attacks are more or less periodic, several years of comparative immunity, being followed by one of exceptional loss. In these, exceptional years, especiail} 7 , the artificial means of reducing ilie numbers of the invaders should be carefully used ; but it should also be borne in mind that in this, as in the light against any other pest, unanimous-action amongst neighbours

is absolutely necessary in order to obtain the greatest good ) otherwise, one man may be working hard at means of destruction while his neighbour, through carelessness, is doing his very best to increase the nuisance. The I tesdan fly attacks wheat, barley, and rye, but has never been found on oats. Remedies Suggested. In infected districts abstain for a couple of seasons from growing crops subject to attack, so as to starve the ■pesC If'this cannot be done, sow late, fn order: that the first brood may not find young wheat on which to lay its eggs. Self-sown wheat should also be cut, or it will form a harbour for the fly. Plough infested fields as soon as possible after harvest, using a skim coulter plough, so as to thoroughly bury the stubble. Carefully burn all screenings or rubbish from the thresh-ing-machine, as these form pet feet nurseries for the pest. ' Another means adopted with some success is to sow strips of early wheat as bait/ The first brood will attack these, and the whole strip is then ploughed in before the crop is above ground. .When the larvae are discovered in the early stages, dressings of fertilisers have been found of great assistance, by stimulating a strong healthy growth, and so enabling the plant to withstand an attack to which it would otherwise succumb. There are several species of natural enemies— chiefly Hymenoptera (fourwinged flies). These will doubtless, in years to come, solve the difficulty, and restore the balance of nature ; but although nature will herself, in time, cure the evil, yet in years of special attack* at any rate, the farmei cannot afford to fold his hands and wait for this. He should therefore use the mechanical means • available for the Suppression of the pest before it assumes such proportions as to be beyond control. Special reference .to the natural enemies will be made further on. ... - It has been proved that the fly will, if grain is scarce, breed on certain

grasses (Rolens lanatus , Phcelum pratense, Triticum repens, and others), so that care should be taken to clean up the rank growths on the margins and corners of fields. Considerable attention lias been paid, especially in America, to the prol ductions of varieties of wheat which, on account of the hardness of their straws, are more or less proof against the attacks of G. destructor. An effort is to be made before next season to introduce small quantities of these for experimental purposes, in order to ascertain whether they may suitably be substituted for the kinds usually grown here Brief History of the Hessian Fly in New Zealand.

Early in 1888 specimens of diseased wheat, discovered at Marton by Mr Sicely, were submitted for examination to Sir James Hector, who detected the presence of a small fly, which lie identified as the Hessian fly ( G■ destructor), and suggested that Mr G. V. Hudson, F.E.5., should be sent up to collect specimens A number of these were forwarded to England, and submitted by the Agent-General, Sir F. D. Bell, to Miss Ormerod, F.E.S, Consulting Entomologist to the Royal Agricultural Society, and Mr R. H. Meade. Both these authorities confirmed Sir James’s identification. Mr Hudson examined several farms wheio wheat was grown, and found all the crops had been more or less attacked. In his report, dated Bth February, he says that the pest had been spread in the Marton district by the constant in+erchange of straw, &0., between the farms, and by the threshing-machines which travel from one grain-field to another. He then gives a short account of the life-history of the Hessian fly as observed in other countries, after which he discusses the identity ot the Marton insect, as fallows:—“A male imago has emerged to-day, which I have carefully preserved, having previously compared it with the description of a specimen by Mr R H. Meade, of Bradford, England, who is a great authority on the Diptera. The specimen which emerged closely agreed with this description, end I think that there can be little doubt that the true Hessian fly has made its appearance here, or, at any rate, an extremely closely allied species having identical habits. I. may state that the female fly has important attributes for .. purposes of identification, and if I procure one of this sex I shall be prepared to express a very confident opinion.” With regard to the extermination of the pest, he suggests isolation of the infected district, and, inferentially, the burning of stubble. He also urges abstention from wheat-growing for two years, and mentions that large numbers of an hymenopterous parasite were observed. We shall see presently what amount of attention was paid by settlers to these suggestions, as also to. others made by Sir James Hector. A number of specimens obtained privately and bred by myself at that time did not yield so large a proportion of parasites as those reared by Mr HudI son, and of the females confined in Wardean cases, in which wheat was I growing, not one laid more than fifty eggs, hut during the 1892 and 1893 attack, which will be mentioned later, nearly three times this, number was deposited. On 38th February, Mr W. M. Masked, F.R M.S , made a communication to the Wellington. Philosophical Society, and the following is a copy of the abstract of liis paper, as published in the “ Transactiqns of the New Zealand Institute” : —“ The identification of the wheat-fly sent down from the Rangitikei district with the true Hessian fly ( Gecidomyia destructor) is a matter of some importance. The larva or maggot answers entirely to : that of G. destructor , possessing the peculiar appendage beneath the head, called the breast-bone, characteristic of the Hessian fly. The author had at first some doubt as to the veining of the wings, but has since been able to satisfy himself that the real Hessian fly has reached these islands. The Hessian fly is, however, subject to much damage from the attack of other insects—parasites, as they are called. The author reported that in New Zealand it had no sooner arrived than it was attacked by parasites in the form of hymenopterous insects, probably of the family Proctotrupidee, and indigenous to New Zealand.” On 26th April, Sir James Hector addressed the following memo, to the Hon. uhe Minister of Lands : “ The Plessian fly appeared for the first time this year in the Marton district, and affected about 200 acres of wlieafc crops. During the autumn it

spread in the direction of prevailing winds to Blenheim and Nelson, but, so far, has not been detected in other parts of New Zealand. Government took active measures to collect accurate information by observers in all parts of the Colony, and the above is the result. The settlers were also supplied with the proper appliances and instructions for exterminating the pest. “The fly appears to have been introduced, while in the pupa stage, among straw packingof agricultural machinery imported from America. “ Fortunately, the small ichneumon fly or parasite (hymenopter) that destroys the Hessian fly by depositing its eggs in the pupa Ims also been imported at the same time, and there is every reason to expect that the spread of the pest will be restrained through the operation of this natural enemy. “ The occurrence of the fly was first detected by myself in diseased grain sent to me for examination by Mr Sicely, of Marton. lat once reported the outbreak to Government, and suggested that Mr Hudson should be sent up to collect specimens I enclose his report, and also a report by Mr Maskell, F.R.M S., founded on the

examination of the specimens brought by Mr Hudson.” In a memorandum dated 9th Febiuiry, Sir James suggests that, it might be well to try to obtain “ a consignment of pupas infected by the parasitic insect.” This suggestion was submitted by the Agent-General to Miss Ormerod, and she reported so strongly against the proposed plan that it was not then acted on. The Government urged the Marton settlers to burn their stubble, &c., or to plough it well in, and for this purpose had a special plough made and sent to the district for the use of residents; they, however, offered some opposition to the use of this implement, saying that it would plough too deeply, and injure their ground, by bringing the clay to the surface. There were no means of compelling settlers to take any action to suppress the fly, and the matter was allowed to drop. Nothing further was heard of the pest in any part of the Colony until 1892. The 1892-1893 Qutrreak, This extended over a very much

larger area than in 1888, and the attack involved districts widely separated from the locality (Marton) from which the pest was originally reported. MASTERTON. In January, 1892, Messrs J. Payton and Co., of Masterton, forwarded specimens to Sir James Hector ; and no word of the fly having reached-him from Marton since 1888, he referred the communication to the Hon. the Minister of Lands, with the following report:—“This ‘grub’ proves to be the lava of the Hessian .fly ( Cecidomyia destructor ), which is a destructive pest to wheat crops. It formerly appeared at Marton in January, 1888, and was successfully suppressed by Government.” Specimens were also received by mvself from a private friend, and to these I shall refer later on.

In 1892 the present Department of Agriculture was set up, and I joined the staffat the end of July of that year. Being in Masterton at Christmas, I made a point of visiting grain-fields, collecting, information as to infected areas, &c., and on my return reported as follows :>

Wellington, 4th January, 1893. The Secretary Department of Agriculture, Wellington. I have the honour to report that, while in Masterton at Christmas, I took the opportunity of making a few inquiries respecting the Hessian fly, which is attacking the wheat crop in that district. I also visited several fields and collected, specimens, an examination of which, I regret to say, leaves no doubt that the insect is the true Hessian fly (0. destructor). Last year it was, I believe, confined to one locality ; now it has spread, practically, all round Masterton, and may be found in varying degree in most wheat-fields, threatening to become a very serious matter unless stringent measures are taken for its suppression. The area under wheat is estimated at 1300 acres. The attack is not a bad one, but, from information I received, I am afraid that in one or two cases at least the grain will hardly be worth cutting. I have prepared a leaflet, giving drawings of the fly in various stages of development, and stating as briefly as possible the life-history, and suggestions for preventthe spread of the pest. The necessity for immediate attention cannot be too strongly urged upon the j farmers, some of whom do not appear to

comprehend the danger to which they are exposed.—l have, &c., T. W. Kirk. The leaflet referred to was ordered to be printed, and, as great brevity was desired, the Marton attack was only referred to in the following words, the statement being founded on Sir James Hector’s report already mentioned :—“Some years ago this fly attacked the wheat crop at Marton, but prompt use of measures similar to those advocated above resulted in its complete suppression.” In January, 1893, the fly was reported from Balclutha in the South Island, and on the last day of the mcJnth from its original A'ew Zealand habitat, Marton. RANGITIKEI. ~V I therefore wrote to a friend in the last-named town,-Mr J. H. Bettany, and he kindly went to .considerable' trouble to collect information for me. I append an extract from one of his letters : ' . -

Marton, 31st January, 1893. Replying to your memorandum re Hessian fly in this district, I find, on inquiry, that it is pretty generally distributed all through the district; in fact, a farmer told me this evening that he did not think there was a crop here unaffected. The damage is stated to vary from about eight bushels per acre down to almost nothing. In no case can I' meet with anyone who has actually seen the fly; they have seen the maggot and the chrysalis, and noted that its attacks have been mostly in the first and second joints, inside the sheath, no other parasites having been noticed. I will procure and send you specimens of affected straw. . * •He further says that, so far as he can ascertain, the, plough sent up by Government in 1888 . was never used for the purpose' for ywhich it was intended. :

In consequence of the receipt of the above information, a set of questions was prepared and forwarded to the Inspector of Stock for the district with the request that lie would make enquiries and furnish the information desired. The form (questions and answers) is here reproduced :

1. Was the pest really suppressed in 1888 ? —No; as no steps of any kind whatever were ever taken with this object. . 2. If so, when did it reappear ? —Has been present for the last fifteen years. 3. How many farms are now affected ? —Every farm growing wheat is more or less affected.

4. What is the estimated total acreage in wheat in the district ?—Can only be known from the statistics being at present taken.

5. What acreage is affected ?—lmpossible to ascertain. '

6. What proportion of the crop is badly damaged—say, 50 per cent, and over ? In wet-lying portions about half; on dry ground only slightly. 7. What percentage of the fly is attacked by parasites (four-winged flies) ? —lmpossible to find out, as none of the settlers seem to know anything of the four-winged fly. 8. Has any systematic work been done with a view of suppressing the pest ? Please give particulars.—-I have asked a great number of farmers . this question, and all those at all likely to be in a position to know anything about it have been unanimous in saying that no steps of any kind were ever taken to suppress it. A deep-digging plough was sent up by the Government some years ago, but was never used, and is at present, I am informed, lying at the Council Chambers. 9. General Eemarks. (Please note if there is rotation of crops, or continual wheat). —Both rotation and continual wheat have been in use, and-I am informed the fly is as bad in one case as the other. I enclose a few letters which I have received on this subject, which speak for themselves; besides this I have interviewed those I was informed were in a position tfi" speak authoritatively on the matter, and their reports have all been of the same nature. ' lam expecting replies to letters from Mr "Lethbridge, Mr Howard, and others, which I will forward when received ; but these I have already interviewed personal]y, and they inform me that the fly has been in the district for the last fifteen years, and sometimes its depredations are much greater than at others. Ido not think anything can be expected from the exertions of the farmers, and the sole hope of being able to cops with the pest will be in the propagation of the natural en ca. ’.

10. Please send specimens of straw (say twenty) from various parts of the district. —lt is very difficult now to get straws affected, but thousands could have been got a month or two ago. All the statements made in the above report are fully borne out by the letters referred to, especially that the plough sent by Government was never used, and that no steps whatever were taken by settlers to suppress the pest. Luckily the hymen opterous natural enemy-i: ;i had been steadily working all these years, and destroying large numbers of the pest, or the loss of wheat in bad seasons would have been much greater. In May of this year (1894) I yisited

the Rangitikei, and while there examined some stubble-fields, and heaps of screenings, &c. These latter were found to contain large numbers of “ flax-seeds/’ many of them perfectly sound and healthy, showing'the necessity for burning or otherwise destroying all refuse of this kind. The attack is largely subsiding in this district.

BALCLUTHA. On 10th January, 1893, the fly was reported to be present in wheat in Lovell's Flat, Otago. The department at once wired the local Inspector of Stock to procure specimens, and ascertain extent of attack. The specimens forwarded left no doubt as to the identity of the insect. The following is the inspector’s report, sent in after a careful examination of the district:— 1. When did the Hessian fly first appear in your district? —It was first noticed this season. 2. How many farms are now affected ? —Most of the farms in the Counties of Bruce and Clutha are affected more or less. • ’ ..... 3., What is the estimated total acreage of wheat in the district ?—About 7262 acres in Bruce County, and about 1954 acres in Clutha County, east of Waipahi Biver. " . 4. What acreage; is affected ? —About three-fourths of the whole crop. 5. What proportion of the crop is badly damaged, say, 50 per cent, and over?— Over 50 per cent, in Bruce County, and about 10 per cent, in the Clutha County. 6. What percentage of the fly is attacked by parasites (four-winged flies) ? —Know of no parasites. 7. Is rotation of crops practised in the district ? —Yes, in Bruce County ; No, in Clutha Go.Uß.ty. ;, 8. Have any systematic measures been taken with a view to suppressing the pest ? Please give particulars.—No. 9. Please send specimens of straw (say twenty) from various parts of the district. —Forwarded.

10. General Bemaiks.—l believe the fly has been in the district for some time, but never seen, the damage being put down to other causes. In the Tokomairiro district some of the crops were so much destroyed they were not worth cutting. The Register-General issued special instructions to all collectors of agricultural statistics to make careful enquiries respecting crop-pests, especially the Hessian fly. They report it from portions of Bruce and Tuapeka and parts of Clutha Counties, North and South Wairarapa, Rangitikei, Nelson, and Blenheim. In some cases the damage is almost imperceptible, and in others amounts to several bushels per acre. , Natural Enemies. As mentioned by Sir James Hector and others, a parasitic fly was found to be present at Marton in 1888, and was again found in considerable numbers during the last attack, but it is by no means evenly distributed through the affected area. This remark also holds good with regard,|g=vthfe mure, recently invaded, districts.

,-In December, 1892, I collected 500 “ flax-seeds ” at Master ton, from three different fields; these were carefully treated, but not one contained parasites. A year later X again obtained supplies, and from 200 gathered in one field, fully 25 per cent, hatched out parasites ; while an equal number from another field, with only a road between, yielded not a single, specimen; 100 from the near edge of a third field gave a like nil result; while from another century, from the middle of. the same paddock, I obtained 20 per cent. The first lot of puparia sent from Balclutha also proved to be [free from the natural enemy, as did those obtained from the roots of a quantity of young wheat forwarded in November, 1893, by Mr J. C. Harris, of Milton ; but the latter Bendings yielded a fair percentage. This shows friendly little steadily increasing, rendering the farmer good service and

we may expect before long will do much to still further thin the ranks of the Hessian.

With a view to strengthen the force of friendly insects, the Government arranged to have some thousands of infected puparia of the Hessian fly sent from England. These were carefully packed, and came out in the cool chamber of the Gothic. Properlyconstructed breeding-cages had been prepared, and in these the “flax seeds ” were placed without loss of time, and as the tiny creatures emerged they were collected and sent to the infected districts, while any Hessian flies that hatched out were at once killed. The species introduced were Semiotellus nigripes and JPlatygaster minutus. The experiment has proved so far successful that a further supply will be obtained early next season.