CONTROL OF CODLIN MOTH

Hawke's Bay Herald-Tribune, Issue 65, 3 April 1937, Page 19

CONTROL OF CODLIN MOTH

New Spray Under Test : in U.S.A. RED VARlEtlES AFFECTED H'aWke!i"B^" efchaMist« afe always interesteid .in any spray programme which 'will give greater conirol of codlin, moth. Siicli control still consists in the dqrreot and careful use of insectieides. One of the big" problems has been to ■find an -effective insecticide that would offer less of a hazard to the consuinerthan those now inj use. The iise of aisenical spray s is still the only effective mefhod of controlling the oiotli, but owing to the tolerance fegarcdng drscniCat residue under the kealth regulations ahd the added ♦ ost of washiilg fruit after picking ihe search is bein§j continually cafried oii for A nonpoisonouS spray that will contfol this orChard pest. it has been thought for some timo that some 'organio fcompounds might fulfil these requirements, and henc© niany materials of this nature hav4 been. examined and tested OUt undcf field and laboratory cofiditions. One compOund. amotig these is ghotv'ing inord promise as an effective insecticide for ihe codlin moth than any other organio material so far tested. This material is kfaotvn as Phenothiazitte, and has been developed by cbem* ists and entomologists of the United States Department of Agriculture. It is made by combifaing. diphenylamine with Bulphur, forming a neutral compound containing the elements nitrogcn, hydrogen, catbOtt and sulphuf. Wbeti pure it is in the form of Jight yellow leaflets. AlthoUgh* idsoluble in water .it mixes readily if a ,wetting agonb, •suoh as soap, is used-. It is thus auite easily handled, no coinplicated mixturo being necessarv. Retults of triaiaMr B. J. Newcomer, of the • Bur^au of Entomology and Plant Quaranrine, U.S. Department of Agriculture, wriiing in the American pUbiication, ,B«-ti ter Fruit for February," says ihat after tiro years' experience of Phenothiazine in the Pacific North-weSt orcit* ards definit© statements can ' be madts regarding its effectiveiiess and beiiaviour. Under field conditions -the res,uifei have not been altogether - favourable, and it will be necessary to learn some thing further about its behaviour i;nder varioUs conditions before any recommendation regarding its general us«dan be made. So far it has been lound tq be ttiofe effective in cotttroiling ihe codlin moth tban any other material dhat the Bureau of- Entomology ha* triedMr Newcomer says--^-' 'Compared with a standard treatment of lead arsenate, used at the rate of 31b. to 100 gallonS with soap, we get less than hali as much wormy fruit attd only one-tenth as many gtings. Oompared wxth caicium arsenate or zino arsenate ised at i lb. to 100 gallons with mineral oil emu!sified with casein or with triebhanolamine oleate we get about the same percentage of wormy fruit and onlv one-sixth a® many stings. This abil'ty to reduce greatly the number oi stings is onq of the remarkable things about phenothiazine. It apparently destroya the young) worms much more rapidly than do the arsenicals. '■In all of these tests the same number of eover sprays was applied and about 20 gallons wer© used for uiedi-um-sized treeS. "The results just mentioned were obtained with 31b. of phenothiaziae to 100 gallons witb which a little soap was used. We experimented with su»ailer quantities, and found that Vrhere the infestation was not heavp li lb. was also more effective than the otbor materials. Probably 2 or 3 lb. wouid

be necessary for heavy iniestations. "Considering control alone, tben, phenotlliazine has definite ad'anrages over any of the other materiais iued. "You will be interested to know what sort of a residue problem the use of , phenothiazine would create. The Department of Agriculture is looking into this matter, and while the investigatiou is not yet complete, present indications are that the small quantity of residue left on the harvested fruit will probably not be a hazard to the health of the eonsumer. "Phenothiazine leaves a dark green, almost black residue on the fruit, and it would be very desirabl© to remove this so that the fruit would present an attractive appearance to the eonsumer. Tests made this season indicate rather definitely that at least 90 per cent. of the residue cau be removed easily. Effeot on Colour. "The effeot of a spray material on the fruit and the trees, as well as the effect on the men handling it, has tq be considcered, and here we have a somewhat different story to tell. "In 1935, we poted a very defiuitei effect on both size and colour o'f Rorue apples. Apples sprayed with phenothiazine had the appearance of being less mature than apples sprayed with lead arsenate. They were greener and smaller. We therefore enlargd our tests in 1936 to include Rome, Delicious, Jonathan and Winesap apples, and Winter Nelis pears. Altogether, we sprayed about 250 trees in three orchards six or seven times, using nearly 6001b. of phenothiazine. We thus had an opportunity of observing the effect of the material under a variety of conditions. ' 'Phenothiazine reduce* the colour of

red apples somewhat. , On the basis bf extra fancy , c.olour,- the xeduction when 31b. of the material was used was about as • follows.:— -J onathan,. • 4 . ,per cent. ; Red Delicioui, 6 per ' cent. ; Rome, 17 per cent. j. and Winesap, 19 per cent. in all. of our .tests, this differenee wds m'ore th'aii offset'By the great recluctian in "stings and ■ wqrm r hqlete, . aiid wou^d probably be true in 'any orchard prbducirig ' 20 " per ,'ceht. ^or " more Of bleihished fruit. 'Iii- clean -orchards,- the: differenee •- in- colour woufd i probabjy , npt be altogether offsetf at least with" the, Wihesap 1 afld 'Rome Varieties. ' Latqr picking might cbtaffensate for this dif- ' ference in colour to some extent- . "Size 'is not materially 'affect'ei In/ 1935 thefe seemed to'be a reduction in ;the Size of Rome : apples foUowing- the' use of 41b.- of. phenothiazinej- but this year the reduction did not. occurt.jal-? though". niany of 'the same. trees werev used. LikeWise, no sigriificant reduction occurred in Jonathans, Delicious,- Winfisaps or Winter Nelis this season. , " . . ' / No Injuify To Trfgs. " ' "There is no evidence that the trees were affected. Some people who saw them thought the leaves were more leathery than those sprayed With lead arsenate,- and . Some marginal folikge browning appeared. This browning Was not 'ConsiStent, howeV6r, and it may -have been dtie to some other cause. If the -.trees had been 6eridUsiy injured this would haVe heen refleetfed in the ■ cortdition of the fruit. , - •' 'Phenothiaiziiie ' has some definite effects on the orchard men. It cause® ja burnittg of the skin similar to a mqderately seVer© sunburni "This was especially noticed in hot weather by the meh who sprayed the trOeS. Gne" or twb iheUwho thinned .the crop complained of irritation, and the face of one, who had a sattdy colaplexion and who was particUlai'ly sUScfeptible, was seVel'ely sWollefi, and required treatment by- a physiciaii. One of the pickers developed welts on his armS Whei'eVer therd Were scratches, apparentiy^'frPm tbe plien'othiazine. Most of the thi&ners and pickers, hoWever, appeared "to be unaffeoted. "At present the cost of phenofiazine ' is higher - than that of lead arsenate/ but this would undoubfedly be reduced if- the demand for the material were sufficiont te justify1 production dn a commercial basis ... "At the . beginning it Was said 'that we are not ready to recominend. ph'efiqthiazine. Before we .can do this, wfi must learn more about its effect on thfe coloiir of red apples, especially Winesap. aild'DelicioUs, nnd.it must be. tested pn 1 other varieties of apples and pears. Further' iflforniation must he obtained rqlativ© to its effOct on hum'an beingS, both externally and internally. We are not eatisfied with the wetting agents used. "We expected to continue working with phenothiazine, and hope to come to a decision in the near future as to whether or not it can he used."-