LIBRARY STATE PLANT BOARD Hov«mb«r 194S BI-216 UNITED STATES DEPABTIffifIT OP AGHICXJLTinffi Agriotiltural Research Adminlttration Bur«ftu of Batonology «iwi Plant Quarantine BCPBBIMHITJI. IffimODS IK IIAKIHG ORCHAfiD TESTS FOR CODLING MOTH OONTHDL IN IHE 1?EST 3y E, J. Newjoner and ?• P. Dean, Dlvlelon of Pruit Insect Inresti gat ions, and C, C. Cassil, Dirision of Inseotioide Investigations-i/ Contsntt fttge 9 Introduction •.•..•..••••• * Desipa of experi««nt« ••••«•••••••••• 2 Variation within a tree ..^ ••••••• 2 Tree-to-tre« yariation •••••••• 3 NuBJber and arrangenent of replicates •• * Hetiiods of spraying .••• • ^ Exaadnation of fruit ••••••••• • •••• " Prelijainary examinations ••••• 7 Ihianed fruit • ^ Dropped fruit ••••••••••• ••••• » Harrested fruit » Accuracy of observers •••• •••••^•. •♦•••• H Methods of recording data ••••••... 15 Field reoortl sheet ••••••••••••••• 1* SuBBary sheet ••••••••••••••••••••••••••••••• ^^ Methods of determining effect of tests on trees and fruit •••••••.•••••••••••♦•• *• Spray deposits ••• \ Presentation of data *' »»»ry 2Q Literature cited • l/ ▲okBovledgsneatLts are aade to B, A. Porter, B. R. Yin Leeuwen, F. M. Hadley, and M. A. Tethers, of the Bureau of ftitoaology and Plant Quarantine, and to K. W. Babeook, formerly of «ie Bureau, for ■way helpful suggestions and for assistanoe in securing data. - 2 - IHTBODUCTIOH Ihe oodlln€ '*'>^ ( C>rpooapaa pononella L») ii tk« K>st ijLlttPioua iniaot meay of apples and pears in the United States, gyslop (6) estiaatee that tiie arerage annual Uss eaoaed by this iiweot in tiie United States is 113,500,000. and that the average annxial cost of oontrolling it is #17,600,000, BAking a total cost of 131,000,000. Much ezperi- nantal w)rk, designed to improve the means of oontrol, is therefore constantly being done. It is thus important that accurate and depsndable experimental methods be used by inves- tigators. A combination laboratory and field method for testing codling moth inseotioides has been in use for some years by Steiner (S) with very dependable results. Several methods adaptable^for use in the orchard alcne have been «ployed, motably those described by Marshall and Groves (7), Outright and Diets (2), and Hansberry and Richardson (4). The purpose of this circular is to present the methods used by the Bureau of ftitonwlogy and Plant Quarantine in orchards in tixe Pacific Horthwest, in the belief that they will be of value to other inveetigators in iMs field, parti- cularly in «ie West. HESIGS OF SKPESIHBfTS Variation is an inherent part of biological experiments, There is also «ie vmriation #iieh the investigator introduces, and the effect of which he wishes to measure. In order to do so, he Most know something about the inherent variation in order te reduce it as aoch as possible. In experimenting with tiie codling moth, «ie inherent variation due to the host, er tree, earn often be greatly re- duced by choosing trees for iiie eaqperiment tiiat are as near alike as possible in variety, siie, vigor, and load of fruit. Svsm when this has been done, there is still a variation in infestation, both from tree to tree and within the tree. Variation within a Tree Variation within the tree refers to the different degrees of infestation that may be found in different parts of the tree. Fruit in the tops of sprayed trees is often wormier than that in «ie lower parts. Fbr exaaple, Childs (1) indicated in 1920 that apples crowing abo-re «ie 12-£bot level on sprayed treee v^y be from Jf to 5 times as won^ as apples grmring Is ss than 12 feet from the grcuad. ii*!l«t trtm a maibmr of Bmaui Xt—b In thr«« spr«y«4 jtlAtui v»r« aoEaalsWl ftt TaJclBa^ lath., ■•p«r«t« rvoords b«lag k«pt of tfa* frvlt aboTO tad below a Una 10 fo«t trtm thm grovnd* &• tr««« ir»r« 20 to 26 f««t hig^* Th* mabar of wormB p«r 100 apples in tho upper part* of Um troos magod froB 1*9 to T«S tiaios as nan;^ as la Hm latnr p^rts^ probably booaus* ttio upfpsr parts vtro loss thoroni^y sprayod* Thoro IMS Tory little difforaoaeo. hoiroror, in tho total ambor of injuries (noms and stints) in the upper and lever parts of liie trees, the ui^er parts hating an aremge of 1*2 tines a« ■any injtirles per 100 ep^les as the lever parts* This was, of ocurse, beoanse there vere fewer stings ia fruit over 10 feet from the ground thaa in that in the lower parts of the tree* Ihis Indieates strongly that aost of the differsnee in infesta- tion oeteeen the horisontal halres of the trees was due to the differsnoa in spraying ratftxer than to any inherent differenoe* There is some eridsnoe, also, tiuit there any be eome differenoe in infestation ia the different -rertieal portioas of a tree* Ihese Tariations sake it neoessary, in aaking determinations of the infestation resultiag froa different spray treatments, to use a repressntatiTe let of fruit froa all parts of Hf tree* Tree*to-Tree Variation Tree-to-tree Tariation is illustrated in figure 1, A, uhioh repres«&ts an apple orchard, the indiyidnal trees bidng repressnted by ^e peroentages of uDrmy fruit on tiiose trees at harrest* The trees were sprayed as unifomly as possible witii lead arsenate, and yet there is not only muoh variation in the pere«itage of worny fruit betwesn the eenter of the orohard and the left and right edges of it, but also some -var- iatlcm between adjaosnt trees. Most of Idiese trees were sprayed ia tiiis rnnuier for two suooessiTO seasons in order to find out idiether oertain trees hare a tendenoy to be worqy year after year* The peroentages of womy fruit on 60 of these trees in -tiie two years had a positive oorre- latien of 0*460* Bven thou^ ttxis is sipiifioant, the ezeep- tions to this tendsnoy oonprised at least 60 pereent of t^e trees (fig* 2,A), and this would interfere seriously with trying to detenaine any oopeoted infestation of a partioular tree* It aig^t be thought that this Uok of high oorrelation was due to variation in the sise of the erop, and some of it nay have been, as tiiere was Kuoh more variation of this kind liie seeond year than the first* The eoeffioient of oorrelation between worainess and site of orop the first year was only -0*145, whioh ia not cigiifieant, and -ttie seeond year it was -0*412, liiioh is sipiifioant* me first year the erop on 80 peresnt of the trees - 4 - raig^d between 1,800 and 2^700 apples par traa, not a Taxy graat -variation^ but in Htm saoond yaar it rangad bat«a«b 200 and 1,600 apples par tree on Hf aaas paraantaga of traas, a Boeh greater ^variation. Apparently not BBoh oorrelation ba- tvesn aronBlness and orop sise nay be expeotad, vnleas the tariation in the latter ia eonsidarably sore than 100 paresnt, as it mia the seeond year. A aonqparison «as aade of the irorainess on the trees haTixig a lariatioa in orop sise of not orer 100 peracit in the tao sttoeeeding years (fig* 2,B), and it is erident that the degree of voxviness on ihese Trees the seoond year oonld not hare been aoourately anticipated • Variation between treea is greater than "variation iriLthin trees, and it is therefore important to hare Hi* trees used for BMsuring the -value of a treataMct seattered at random throne- out the experimental orehard, and to use snou|^ trees to otsx^ eome most of tixis -variation* Vunber and Arrangsmsnt of Bepliaatea A study uas made of ^e nnaher and arraagsmsnt of repll- eates in the unifomly sprayed orchard just diseussed* Ibur arrangements of seven hypothetieal trsat— ts vara made (fig* 1» A, £9 C, and D) to determine uhidi one uould result in the least Inhe^remt Tariation* Sinee all -bhe treea were sprayed alike, these hypothetieal treataeots -were not aetually different, and -therefore, if they were properly arranged, there Aould be mo signifioant difference be-bireen ihsm in spi-te of the great tree- to--bree -variation in this orchard* Ttrel-ve trees were Inolmded in each of the seven hypothetioal treatments in arrangsmsmts £, B, and Cp thus using all of the 84 trees, but in D only 8 trs^es," ehosem at random, wwr9 included in eaeh treatment* In aetaal practice it is oftsn desirable to omit eertain trees #Lioh may be small, or of some other -variety, or mhioh oay ha-ve a light orop, ae this arrangsment is not an unnsual one* Ihe trees not used in D are indicated by the letter X* An analjrsis of variance mas then made for eaeh arrange- msat, since Ihls s-ta-tiatical mebhod separates the -variation due to different eaiues* z/ Axrangaaeat A is an unrep^ieated set-up of sev^u treatments, eaeh eooposed o7 a ooaimot group of 12 trees] arrangement B is similar except that the 12 trees are for 2/ R>r further iafonaation on ihe analysis of vmrianoe amd on correlation the reader is referred to "Statistical Methods*, by Oeo* W. Snedeoor, published by Collegiate Press, Ine*, Amss. leva. 5 - •t^« most p«rt in & double row. Statistical analysos show a highly sipaificaat difforeooe between treatments in both arrangements (table l), which cannot be true, since all trees were sprayed alike* This treatment difference shows that there is an area differonce in worm population within the orchard* Hence neither of these arrangements can be depended on to show the actual yalue of treatments, although they have been anich used in the past and are still used to some extent. The need of replication is CTident. One of the better replicated arrangements is that shown in Cy where each of teren treatments comprises four replicates of Three trees each* Ho significant differsnce can be shown between the treatments in this arrangement; and the difference between the four blocks, each of i^ich contains one replicate of each treatment, only approaches significance. Table 1.«-J^aaly8is of 'Tarianoe of four arrangements of codling moth treat- ments in an apple orchard. ^^'*^*' Source of variation ment Degrees of freedom Stan of squares Mean Square Tbtal 83 5,486 Between treatments 6 1,289 215 Between trees within treatments 77 2,197 29 7.41** B Ibtal 85 5,486 MIB ^^ Between treatments 6 1,525 221 7.89** Between trees within treatments 77 2,165 28 — C Tbtal 85 5,486 ••. «. Between treatments 6 550 92 1.88 Between blocks 5 452 161 5.08 Interaction (error) 18 875 49 Mlhin replicates 66 1.611 29 — D Total 55 1,917 ™ _ Between blocks 7 595 85 5.42** Between treatments 6 280 47 1.88 Interaction (error) 42 1,043 25 tSi 6 - ScplftBAtiont Ihe vumn square is the Tariance, and F ia the ratio of rarianoe due to two oauses. In A, for ezaxaple, 215 is the variance between treatjunts and 29 is the variance due to other causes I 215 divided by 29 gives 7,41« irtiieh is highly significant at odds of 99 to 1. The greater variance between parts of an orchard than between adjacent trees, nentioned earlier, and often noted in studies of codling-xaoth control, has led to the use of a still different set-up, shown in D (fig« 2). Here each treataent is replicated ei^t tises on sTngle trees, scattered over the orchard so that one tree is in each of the ei^t blocks ^own in the figure. ?rom the standpoint of accuracy, i^is arrange- ment is fully as good as £, if not better; and it is a better arrangemfltit from a practical standpoint, since only two-thirds as many trees are required to get dependable results. It has been successfully used for two seasons, in making comparisona of 7 to 12 treatments. It is probable that a somewhat larger number of treatments could be compared accurately, although the number should be limited to itmt can be studied adequately* Unsprayed checks are usually unnecessary and are undesirable, as they would be likely to become so wormy that they would influence the results. A standard treatment, such as one oommonly used by growers in the area, should be included as a check OA the expezdmental treatments. By using an arrangement such as D, then, accurate re- sults may be obtained in an orchard having much variation in infestation, ranging in this case from 1 percent to 89 percent wonny fruit. UEIEODS OF SPBAriKG A portable spray machine is the most convenient type for experimental spraying in the orchard, since relatively small quantities of material may be used in it. Some accurate method of measuring less than full tanks should be provided, either in -ttie form of a measuring stick or of pete )cks set in the end of the tank at different levels* The accessory equipment and the pressure ahould approximate those used by good growers in the area. Under the arrangement of replicates described above, the individual trees to be sprayed alike will be scattered over the orchard. The most convenient method of ipraying such a set-up of trees is to place the spray machine at a place where water is available, lay pipes from it into the experimental block, and use it as a stationary outfit. The pipes and outlets should be placed so tiiat all trees can be reached ^rith 100 or 125 feet of hose for each gun. If there are two ope ^tors, -tiiere should be two leads of pipe so that one man can wo k from each lead. - 7 - de tim« required to do this experimental ap raying -will Tary -with the siie and nunber of trees used, end the equipnent available* Ithen using a SOO-gallon stationary outfit as described above, axul spraying 8 large trees re- • quiring SO to 40 gallons per tree, two men oan oomplete a trea talent in about am hour. A set-up of 7 to 12 treatnents ean -tiius be sprayed in 1 to l-JI^ days. Since different materials are used for tiie various treatznents, care must be taken that t^e trees are sprayed with the correct material. Tags of different colors, carrying tiie nuabers assi^ed to the treatments, are helpful in locating the trees. If materials having dissimilar appearance or odor are used in succession, the operator can easily tell liien the new material has reached the gun. In moving the hose from an outlet near the spray tank to one faz*ther away, it diould be raneDibered that the material in the pipe between the two out- lets is not the new material, and the more distant outlet should therefore be opened and the old material run out before the hose is attached. EXAMINATION OP FBUIT Preliminary fisaminations Preliminary examinations of the fruit on ^e trees xoay be made at any time to determine tentatively the relative value of the treatments. It will suffice to walk around the tree, examining only fruits that can be reached from the ground, ;)otting dom at intervals in a notebook the nmber examined and the mtniber that are wormy and stung. In 2 exam^ inations of this type, made in June, records were coxq)ared from 5,200 apples examined from the ground and from 6,400 apples from the entire tree. The apples examined from the ground averaged 2.3 and 8.0 percent injured, and those from the entire tree averaged 3.5 and 4.4 peroent injured, respeo- tlvely. The records of the fruit examined from the groxind tell the same story as those from the entire tree, except that the percentages are lower. An examination of 100 apples per tree in this nmaner will be sufficient. To test this, three lots of 100 apples on each of 12 trees sprayed with lead arsenate were eoctained in June, with the following results j Pereoit Perosnt WD my ttung I«t 1 0,0 3.2 I^t 2 0.1 2,9 I^t 3 0.1 3.8 Average o.l 3.3 «,. ^nation i. not f «* -""f .r^'C^trrbfr to «»»ln. -or. than 100 f"""' "?/^„i"tir^ get . T,ry ean b. r.aoh«l f nm the 6«und.^*j^» T^tidng^SO fn.lt. good 14» of th. roUti^. if"^*^'",^,,,!^!,^?, ««idn«- tlon.. It 1. not P"J^"%f ^^^flj^drtsabl. merely to reoord «rM «id »tt»e'i "^ " ^L^;, th. nuBber of Injuri.s per the pereeatage of injured 'T^* •'J"\„ desired. *e fniit. 100 fruit.. If -°" ""7*:.^re^»?ion. aooirat. deter- SL^-onr-l'b."!^ r^rturi.. -orded earlier. minned Pmlt J , .* -h4«h 1. takm fro« the tree, in Jane ft, ailaned f^*; *lf ^i^frLrd. of infe.tation. or July, -y *• «^'"£f :t,i?."S^ iniry -»oh inf..tation. h:^ "flsVr;: r r^e-tZi-::^^" «'- oi per. eeat mvmy* Th« quantity of ^^*^™*Ji' IT^ the total crop, tad ,«g« fitm none to at least 65 P''^*^^ J^.^J ^^4. of ttxin- ^ ^riation ^uld influaao^ ^.^.n^'^Lif/es of -r»y fruit nine were i««l^^- ^^f fte ahdim; In onshard A, from 28 from some aotoal *'^^«°*' *''* "Z^ fVom the various treat- to 40 percent of the crop ^» ^^"^t^.fTSorbetween the percent- ^r^! 'r:"rc*^4t -re ^je^^injhe^^^^^^^^ ^e en>p that ^ ^^^-^-^^'j;*:;; ^t Tf line as reg^ni. record, good. Treatments 7,9, "^ J^J "^^ J .^ ^^p «iirmed in these irTtle^n^ *r^ -^- '-^"-^^^^ « --"* " the total. In orchard A there iR>uld have been no "^•^f *f *^; '•" fZrl.^ S^rha'e influ«»ed the eonolu.ion. d««.. if ^' reeord. from the thlnninge had been inoluded. - 9 Dropped Vroit Separate examinations of dropped fmit, oosdng fron* the trees betireaa the time of -Oiinning and harvesting, are usually not necessary in arid regions. The fruit does not rot rapidly and it is usually in reoo citable oonditlon at harrest, ^rhen it nay be gathered, along with fruit dropped by the piekers, and put in boxes, and a proportionate quantity of it nay be inoluded in the sample taken Arom the orop as a whole* Hansberry (Z) , examining data from 48 apple trees in Iowa, found a very'^high oor relation between wo mine ss with and without the inolusion of drops," and conoluded that dependable results oould be obtained by examining only the harrested fruit. At Yakima, Wnsh., an examination of the separate records of dropped and harvested apples from 41 trees showed a correlation between wominess, with and without the inolusion of the dropped fruit, of 0.949, iihlch is hi^ly significant and thus substan- tiates the above conclusion. Separate examination of the dropped fruit therefore appears to be tmneoessaiy, except that it aig^t be advisable if there is a large amount of it or if some other unusual condition exists. Harvested Fruit Harvested fruit should be examined rapidly in order that the grower nay remove it promptly from the orchard* It is im- portant that only enou^ be examined to get an accurate deter- mination of the infestation or other effect of the treatment, as handling is likely to affect the quality someidxat. Sinoe variation wiliiin the tree is less than lixat between trees, it is less In^rtaut to examine all the fruit on each tree than to examine some fruit from all the trees, provided a r^resentative saaiple is taken. In the West it is customary to pick fruit into a bag or bucket holding about a bushel, whioh is then en^ptied into a bushel box. Thus each box will normally contaiii fruit from a restrioted portion of the tree, and a sample made up of about equal aunbers from each box will be repressntative of the entire tree. If the dropped fruit is plaoed in boxes before the sample is taken, this part of the orop is also included. Sinoe the actual number of fruits per box will vary someirtiat, it would be a little more accurate to take an equal volume from each box. If done carefully, this would be slower than taking an equal number, and the latter method has been found to be accurate by ooaqparing it with «xe method of examining all the fruits from a good many trees. - 10 An estimata of the total number of fruits on the tree should be obtained before the saaple is ohosen. sinee oompan- •ons of ttie size of ^e crop in the different treatments are desirable. Counts were made of various proportions of the t^tal cn^p on sprayed trees ooiapared with the aotual total, and i?\«.8 ?^d that if the fruit in 25 percent of the boxes taken at random, was oounted, the error would not arerage over 40 fwits per thousand. Since the error might be either plus or minus, the average error for a numher of ^f^^lf^^Jj^^^ ^^ same treatment should not bo over 1 percent, which is not large J^ugh to affect the results materially It i* therefore suffi- cient to count 25 percent of the fruit to obtain an accurate estimate of crop site. After tills count has been made, the sample may be taken, •nd there is an advantage in having each sample consist of •xactly the same number of fruits, as computation of the data is si^lift^i. Aay reasonahle number will do «^%^.^j:^;j,°^ Bntomology and Plant Quarantine has used samples of 250 fruits for determining the percentage wormy and stung, and smples of 50 injured fruits for determining the number of woms and stings per hundred fruits. If a more accurate estimate of the latter is desired, all the injured fruits in the sample of 260 may be scored for number of worms and stings. Before deciding on these numbers, a study of data from various apple orchards was made in the Bureau, and by calculat- ing standard deviation liie sajnpling error of one or more lots of 50 apples taken from different population levels was determined. It was found that little practical reduction of the sas^ling error was obtained at any population level by using more than 250 apples to determine percentage of injuries, or more than 60 injured apples to determine the average number of injuries per hundred apples. This conclusion was checked in the field by comparing results obtained from 250-apple samples witti tiiose obtained from tiie entire crop from a good many trees, as men- tioned above. The sampling laethod was found to be accurate, workable, and economical of time. If there are 26 boxes of fruit to be sampled, tiie sample of 250 apples will of course be obtained by taking 10 fruits at random from each box. If the nxnnber of boxes is not evenly divisible into 250, it is still practicable to take a sample of eocactly 250 fruits, Fbr example, if there are 14 boxes, 18 fruits are taksn from each box, making 252, and then 2 are put back. If there are 19 boxes, 13 fruits are taken from each box, making 247, and th«i 3 more are chosen at random from the iMxes. In otiier words, a number -Aioh will most nearly total 250 is taken from each box, and then enough fruits are added or taken away to bring the sample to ;^st 250. By working out these numbers in advance - 11 for any number of boxes likely to be aoioountered and providing eaoh observer with a oard shoiring the numbers to be taken as well as the number to be added or subtracted, samples of 250 fruits oan be taken aoourately and without loss of time* A portion of sxieh a table is shown belowt Number Number of or fruits taken boxes from each box Number added or subtracted Number Number of Number of fruits taken added or boxes from each box subtracted 18 14 -2 21 12 -2 19 IS 43 22 11 48 20 12 no 25 11 •3 Ihe sas^le oan be conveniently checked by a crew of tiuree observers, two making the examination of Ifae fruit and the third recording -the results of the examination on tally ^eets or field record sheets (fig* 4). The frui-t is exam- ined one at a time, the observer calling out the condition of each fruit ao that it can be recorded. Detailed records of each injured fruit are kept on the right-hand portion of the tally sheet until 60 such fruita have bem recorded. The rest are then recorded on the left-hand portion. (Details of recording the data are given on page IS under "Metiiods of Recording Data"). If the fruit is ll^tly in- fested, tno observers can work about as fast as three, one of tiiem not only examining fruit but also making the records for both* Other methods of scoring or tallying the fruit, auoh as by means of a battery of tally registers, one for each type of record desired, may be used, and sane of these methods are described by Outright and Diets (2^) and >y Haaaberry Mad Siohardson (4)* Ihree men can sort out and examine a sample of 250 fruits in about 15 minutes, and the estimation of the total suniber of fruits should not take more than another 5 minutes* It will take 15 or 20 minutea for tno or three men to grade the fruit for color, if that is to be done, as mentioned on page 17 * Aoouracy of Observers Thm aoouracy of the observers sho\ad be carefully eheoked before the actual examination of fruit begins, and in the ease of inecxperisnoed men some training will be neces- sary* Pbr this purpose, a lot of 100 apples, including a eonsiderable nnmber injured by the codling moth, should be laid out in rows on a table out of doors or in a room where there is plenty of sunlight. Each apple should be carefully - 12 - •oor«d by at least two •xperianoed obserrars, in the xa&xmer that is to be used in praotioe, and an agreonent reaohed as to the ezaot muBber of id ras azid stings on each i^ple. Then the oiiier observers should score the apples « and their re- sults should be compared with the actual condition of the fruit. If oare is taken to keep the apples ig. the same rela- tire positions on the table, it is th«i possible to go back and show each obsenrer Just where he made mistakes and nhy. In testing the aoouraoy of obsenrers, it has been fbund that errors made by experienced man often cancel each olher out, and that the final result on 100 or more apples is likely to be quite accurate. This is shown in table 2. Ikble 2.— Arerage percentage Tariation from correct score of percentages of wormy and •tang apples and numbers of woras, stings, and total injtiries found by six observers Observer HbroDy Stung Ifoms Stings Injuries A B C D ^0.4 ♦0.8 +0.0 +1.7 -4.5 -6.7 +4.5 -6.5 -2.5 -1.5 -7.1 + 2.5 -18.5 -16.6 -2.5 -16.5 -11.5 -10.0 -4.4 -7.7 Average +0.7 -5.0 -2.1 -15.2 -8.4 B P -2.9 +7.4 +4.7 -14.0 -19.7 +S.4 -6.2 -26.4 -12.1 -12.0 Observers A to D had had several years* eoqperienoe, and their scores did not vary from the correct score onough to affaot conclusions drawn from tiie results. Observer £ was less accurate in scoring wozms but scored the stings about as aooxirately as the more eocperienoed men. Observer P was as accurate as E in total injuries, but had a tendency to call some of the stings worms, that is, he recorded more worms and fewer stings than the others did. It mis found that most of -ttie errors made were due to xmcertainty as to nhether to re- cord a giren injury as a wozm or a sting, or due to orerlook- ing snail stings. Such tendencies can be more or less oorree- ted ivith a little practice. The distinetton between worms and •tings riionld be thorou^ly understood, as well as the impor- tance of recording all stings, no matter how small. A good miy of differentiating worms from stings is to consider as worms all injuites having a surfaoe diameter of more than one- eighth inch or that are so freshly made that it is erident 15 the worm is still ali-rs, and to oozxsider all other injux^es as stings. It will help the observer to cut open some apples after he has scored them in order to ferify his decisions, although a practice caimot be nade of doing this in the course of regular escandnations of fruit. Actually, howcTer, with the scores shown in the table, and with fruit that was 10 percent wormy, observer E would have recorded 9.7 percent wormy fruit, and observer F, 10.8 percent wormy firuit, neither of iriiioh is a very serious error. A very interesting point is shown in table 2, namely, that there is more accuracy in recording percentages of wormy and stung fruit than numbers of worms and stings. The ex- perienced observers averaged three tijaes as far off en number of worms as on percentage wormy, and more than four times as far off on number of stings as on percentage stung. It is also evident that the average of the records of sevei^l ob- servers is likely to be more nearly correct than the record of any one observer. If the four experienced observers had examined about equal proportions of the sample fruit trtm. a treatment that had 10 percent of wormy apples and 30 percent of stung apples, they would have recorded the fruit as 10.1 percent wormy and 29.1 percent stung. If 10 worms and 30 stings per hundred apples had been present, they would hav« recorded 9.8 worms and 26 stings. UETHODS OF RECORDING DAIA The amount of data recorded from the fruit depends on the infonnation desired. The simplest record would consist only of the total number of fruits and the total number of wormy fruits, from iddoh the percentage of the latter eould be figured. In most tests of insecticides, however, it is ia^or- tant to record both wormy and stung fruits, as some materials reduce the number of stings much more than others. This may be done by recording as wormy all wormy fruits, and as stung all fruits that are stung but not wormy, the total of Hm two being the total injured fruits. But it is more accurate to record separately all the wormy fruits and all the stxing fruits, regardless of whether the other type of injury occurs on them, and to record also the fruits that are both wormy and stung in order that the aggregate of injured fruits may be computed. It is often desired to know, also, how many woms or stings there are per 100 fruits, and this requires a record of the total number of worm entrances and stings. Whether the investigator should record the percentage injured or the nuaiber of injuries per 100, or both, depends on the use he is to make of his results. If he desires them 14 oU.«fIy for praotloftl ut« In showing fruit grovers idutt to •xpoot from Tarlous trea-taaasxts « then parositagos should ba used, 8ino« tbay show th« affoot on the orop from th« stand- point of yield. As alre&dy indicated, also, it is possible for obserrers to record the perooitage of wonay and stung f raits more accurately than the ntnber of wonas and stings. If the figures are to be used for naking careful scientific deductions, then the nunber per 100 fruits is more desirable* In the case of heary infestations, the intensity of attack can be better differentiated, and it is also possible to calculate from these numbers the total number of worms and stings per tree, should that infoniation be desired* As a matter of fact, the correlation between percent- age of wormy fruits and number of worms per 100 f raits, etc., is to high that usually the same conclusions are drawn from eitiier method. Fbr example, the records from 219 trees hav- ing a mayinun of 25 peroent of wormy apples showed the highly significant correlation between percentage wormy and number of WDzns per 100 apples of 0.950. Field Beoord Sheet Printed or mlmeogn^hed field record sheets are con- renient for recording data in the orchard, especially if tally registers are not used, as mentioned above. A form commonly used in the Bureau of Entomology and Plant Quarantine is •howii in figure 4, and this has been filled out in facsimile of an actual record sheet from an insecticide experiment. A supply of these sheets can be carried on a clip board, a separate sheet being used fbr each tree. At the top of the sheet are the initials of the obser- Ter idio made the record, followed by those of an observer who assisted. This record is sometimes of use in ooznreoting errors or doubtful entries. The other entries at the top are self-ucplanatory, "plat" in this case being synonomous with "treatment." Hhen tiie examination of a sample is begun, each injured fniit is scored on the basis of actual number of worms (W) and stings (S), and these are recorded in the right-hand block of squares \mtil 60 injured fruits have been eocamlned. Each ver- tical pair of squares is used for recording 1 fruit. In Idiis case, the first S injured apples examined each had 1 worm, the fouj^ had 2 worms and 1 sting, etc. The remaining fruits are then merely scored as "wormy" (W), "stung" (S), or "both" (B), and these records are placed in the left-hand block of squares. In this case, among -tiie apples that were left, there were 6 wormy, 2 stung, and 2 both woray and stvng. - 16 Provloualy, th« nioflber of boxes and number of fruits oounted have been recorded belov the right-hand bloolc of squares* Im this instanoe there were 20 boxes of picked apples and 3 boxes of TAndfalls, the latter totalling 657 apples; and 5 boxes containing 90S apples were counted* These figures, and the number of apples, in the saaple, are all tfafit need be entered during the field exaadnation* At some convenient time, usually after the harvest is oTer, the oomputations shown are made* Blrst, the total worms and total stings in the right-hand bloolc are calculated, as well as the total wo nay and stung fruits and the averages, expressed as worms per wormy apple, stiags per sttmg apple, and injuries per injured apple* Then the total wormy and stung, in tiiis case 56 and 24, are sntered in the appropriate col- xxmns in the left-4iand block, and the total clean, wormy, and stung apples in the entire sample are calculated, as well as -tiie percentages o In liiis example i^ere were 44 wonny and 28 stung, or a total of 72; but tiro apples in the left-hand block and 10 apples in the right->hand bloolc, or a total of 12, were recorded as hotti wormy and stung, hence there were only 60 different wornQr and stung apples, leaving 190 clean* In the lower part of idie form the average number of apples per bushel is entered, con^)uted from picked fruit only, since dropped fruit is usually shriveled and small, and also the total numbers of apples in t^e various cate- gories are shown. "Total worms," for example, is obtained by multiplying "apples -wsnny" by "average worms per worny apple," in this case 761 x 1.S3 » 999. A simpler form oould be used if only percentages were desired or if tally registers were used* Summary Sheet Further calculations are made on another form, called a siamnary sheet (fig* 5). This sheet may be used for sum^ marl ting data from dropped fruit and harvest examinations from individual trees, and also for bringing togettier the data from all trees treated alike. In the example, the data from 8 trees sprayed with a treatment tiiat was numbered 9 are shown. Referring to tree No. 8 it will be seen liiat the fig- wes, with the exception of those under the heading "Average No. per 100 apples," have been copied from the field record sheet (fig. 4). These averages are obtained by dividing the total number of apples into the total of worms, etc. In this case the equation is 999 + 4269 x 100 = 23*4 worms per 100 apples* Bie treateent totals are than calculated, the per- centages being sinqpl© averages. The heading "Average No. per injured apple" refers to the type of injury listed in the sub- heading, and means "worms per wormy apple", "stings per stung UBRARY cT/kTE PLANT - 16 - apple", and "injuries per injured apple". If, however, this sheet is being vised to ohtsiin the season totals of samples of dropped and harvested fruit from a single tree, liiese percent- ages and averages mxiat he weighted on the basis of the number of fruits in each sanple, in order to give each sampling its proper importance. The average yield in n\nnber of apples and nuaiber of bushels, and the site of the fruit, shown at the bottom of the sheet, are all simple averages, the latter being the average of the number of apples per bushel shoim on the field r•oox^i sheets for the trees included in the summary. The method of obtaining data of this type is not accurate enough to warrant showing percentages or "average No. per 100 apples" to more than one decimal place. The "average No. per injured apple" should be calculated to two decimal places, how- ever, in order to increase the aocux*acy of the calculations made from these figures. Much time may be saved by using a calculat- ing machine for the vairious computations. All resxilts should be checked by another individual, and products and quotients may be quite accurately checked with a slide rule. METBODS OP DETEanNING EFFECT OP TESTS ON TREES AND FRUIT New materials or combinations should first be tested on a tree or two, or even on a branch if there is a possibilily of more than nominal injury from them. The tests can then be enlarged if major injtiry does not occur. Materials should be tested on all the eoomon varieties gronn in the region, sinoe instances have been recorded of a material causing practically no Injury to some varieties of apples and serious injury to others. Obseirvations should be made for eeveral seasons and In more than one orchard, because effects of the materials are very likely to be influenced by weather, cultural conditions, and -the vigor of the trees. Frequent examinations should be made in order not to overlook any dropping of a portion of the foliage that may occur, ^ich might result in smaller fruit. Premature dropping of the fruit should also be observed. Some materials may affect the site or color of the fruit, and a rough idea of the relative site may be obtained by oal- oulatiag the average number of fruits per picked box from the ooiuits -tixat have been made. A more accurate method of comparing not only the size but also the rate of growth consists of making periodical measurements of selected fruits at intervals from the time thinning is done until harvest. This is done by taking the circumference with a steel tape graduated to millimeters. Harley and Masure (5) and others have used the rate of fruit enlargement "as an index of tree response to various factors affecting tree growth and behavior," and they consider it suffi- - 17 oi«nt to have complete records from 25 normal fruits from each treatment, distributed about equally on several trees, and as nearly the same size as possible irtian chosen. To insure having this manber at the end of the season, 30 to 40 fruits should be included to start with. Figure 6 shows the results of such a series of measurements from two treat- ments, and it indicates that the effect on size was a gradual one in this instance. The color of fruits, particularly of red apples, may be affected by some insecticides. To determine this, the harvested fruit may be graded according to grading rules in force in the region. It is advisable to use all the fruit from as many trees as possible, as trees sprayed alike often prodyce crops with widely varying degrees of color. SPEAY DEPOSITS In maMng tests of insecticides, it is very important to have a chemist working along with the entomologist* Meth- od* of controlling the codling moth have reached the point where compatibility of materials and composition of emulsions and stickers are sdl-important. An ezperienced chemist is required, not only to devise effective mixtures but also to determine the deposit of the toxic material on the fruit, for on the quantity of this deposit is dependent to a considerable degree the control obtained. For this purpose, chemical an&lys / ses should be made before and after each application of apray^ Ihe development of spreaders and stickers may be cited as an example of the value of such chemical analyses. In "this way it was learned that some spreaders caused the toxic mater- ials to run off the fruit, tiius defeating their purpose. Means of correcting this fault were worked out, and now, for example, the deposit and contix)l obtained from 1 pound of phenothiaiine in 100 gallons are Just as good as were obtained a few years ago from S pounds. PKESEHTATION OF DATA. Sufficient general information about the tests should be given to enable the reader to judge for himself the value of the results. This shoxild include number and dates of applica- tions, methods of mixing sprays and of spraying, method of tak- ing results, and any pertinent infonnation about the weather or other factors that might influence the results. Any effect on the trees or crop should be mentioned. The materials used s/ It is not within the scope of this circular to dis- cuss the methods of snalyses or of collecting samples for analyses, 18 • should b« suffioiontly described so the reader will know Just what "ttiey are* Only results that are disoussed in the text should be shown in tables. A eonpaot way of presenting a season* s results from three orchards is shown in table S (page 19). This table shows, among other things, that in two of the three orchards there was no significant difference in results from lead arsenate with spreader and tank-mix nico- tine bentonite, as regards number of worms per 100 apples, but that there were fewer total injuries in the latter treatment, and in orchard C the number of these was significantly less. The conclusion from these particular tests w>uld be that nice- tixks bentonite, as \ued, was as good as lead arsenate with spreader in preventing mrminess of fruit, and someiriiat better in preventizig stings. Percentages of wormy and injured apples could be shown in the same manner, but it should not be neces- sary to use both methods of presenting results in the same publication. SUMMARY Because of the large amount of experimental work being done on the codling moth, it is desirable to ha-ve somewhat standardized methods of maViTig orchard tests of insecticides. Dependable oor^>arisons may be made by spraying single tree plots replicated eight times, and a ccnveziient way of doing this is to lay pipes in the experiAtental block and use a portable spray machine as a stationary outfit. Preliminary indications of the Talue of the test materials may be obtained by examining 100 fruits per tree without removing them. Thinned fruit need not be examined, but fruit dropping later should be looked at unless it will remain in recognisable condition at hazTSst. Final determination of infestations may be made by examining a representative sample of 250 fruits from each tree. Two experienced men can make this examination in 15 or 20 minutes. It is desirable also to make an estimate of the total number of fruits per tree and of any damage the insecti- cide may have done to the fruit on the tree. Data may be recorded on field record sheets and the desired computations made later and transferred to suxomary sheets for permanent record. Chemical analyses of spray deposits should also be made. Data may be presented in compact tabular form by showing only the number of worms and injuries per 100 fruits, and also showing the differences required for significance at odds of 19 to 1. - 19 - 9 5 Si ;^ W ^ o rl • o •o o 11 »« Q< t 5S CUr-l il§ 43 ri 15 ^8 I ^ i£ 0> lO t- o • • CO ;o « O o cs. Q -* II it - 20 - LITEHATORE CITED (1) Chllds, L. 1920. Spray gun T«rsus rod and dust in apple orchard past control* Oregon Agricultural Brpt. Sta. Bui. 171, 46 pp., illus. (2) Outright, C. R«, and Diets, E. ?• 19SS* The technique of codling noth field ezperimegits . Jour. Soon. Ent. 26: 392-401, illus. (3) Hansberry, T. R. ^ 1936. An inTestigation of codling moth populations as they affect control experiments. Thesis sub- mitted to the graduate faculty of lona State College for the degree of Dootor of Philosophy. (IMpublishad.) Abstract in loifa State College Jour. Sci. lit 68-65. (4) Hansberry, T. R. . and Richardson, C. H. 1935. A design for testing technique in codling noth spray experiments. Iowa State College Jour. Sci. lOt 27-55. (5) Harley, C. P., and Masure, M. P. 1958. Relation of atmospherio conditions to enlargement rate and periodicity of Mnesap apples. Jour. Igr. Research 57 t 109-123, illns. (6) Hyslop, J. A, 1958. Losses occasioned by insects, mites, and ticks in the United States. U. S. Dept. Agr., Bur. Ent. and Plant Quar. E-444, 57 pp. (Processed.) (7) Marshall, J., and Groves, K. 1956, Field Biethods for investigation of codling moth insecticides. Jour. Boon. &it. 29t 1157-1144, illus. (8) Steiner, L. P. 1959. Ihe laboratory- field method for testing codling moth inseotioides. U. S. Dept. Agr., Bur. Ent. and Plant Quar. B-488, 10 pp., illus. (Processed.) I 8 s • = s g 3 2 fc Si » 1 ej 2 a « «0 Q 9 1 e»i - « 9 io m • h- K • 2 ♦ fi t K 2 ♦ w (0 <0 2 ♦ K ♦ K fi « « « « K 4 r — • « lO « • • »- = 2 » = K M A m to C ♦ 2 « 1 « 1 2* CD 4> • T) o cq lid -P ^P due • bO « • bO •o d 5 ri « •d • « d tt rt ••> • p^ fi 3 • g 45 "O •« *l O rH -P rt . 5 •H o o :3 q •H Tic .O -ri «^^ ^ • rt -^ -p • d • U «S p-l .H «B -P o • m rH f -P Pi »< 40 PERCENT WORMY fO 10 1935 1936 Figure 2.— A, Percentages of wormy apples on 60 trees \jjiiformly sprayed with lead arsenate in two euocesslTe years; B, sajae, including only trees having variation in crop sire o7 not over 100 percent. ft ilOHi AMdOM lN33d3d Figure k*- laae of obserrar CODLUa MOTH IHVESTI01TI0I8 Field Record Sheet CC^. ^ c.c.c. Date OCT 22 1949 Type of exaHlnatloii harvest Locelltj Yakima, VVaaii. Orchard Le Vesconte Plat *y BepUcaUon Tree ^ ■nahAT* o^ ■ui'MW Total aad percent and etoDg applea Clean Woraj 8tunff w IHI / C s II Z B II 2 X w s B w 8 B W 8 B w 8 B ,?C. ^Y T7 8 1 B Total /?0 v/ ^? Peroent 7o /7-C //.z Peroeat inj ared U¥'0\ Iwiber of stlnga Total axul aarerage / / tinge per injured ^ / / a£pl2_io2SftBy ^ Total injuriea Total injured J^C Arerage /' 33 ▲Terage injuriea per Injured apple J3 Jo 2. y^ ^ y ^ z? ^Y J'Zf Ho. Appleai in aaaple. ^^^ per buahel / P^ C lo. Buahela in lot eoimted Applea oouBted 20 / 3 ^ ^6-7) TOTALS Applea t V-^^7 2£L Total Woraj Stung Injure d /^JS' 12, Applea t Clean_ Total Woraa Total Stinga cT 7^^ JZV^ 11±_ AII^ /^~77 o ^ I I I to 1 s ■ ^Mq l^ Q O^ ^ ^ ^^ wm y>>^ Q ** «S' p^ >*^ ^^ N h I ^1 ^ W 5^ rr>< ^<| N Vi ^ 1 i 1 1^ n , 1 — 1 ^S 5:^ I r^ Oi ^ ^ 1 W ^' ^ ,> -^ n ^' r< ^; sa. *- ^< VS >sfl ^ If 3 1 ^ v: ^^ ^*. V v: 1 ^:^ ^^ §: < B 5 :^ II ^ v: X. V. V. x.| ^- ^ ^ 1 ^,^ ?^ ^ rc»! >^ $: i;^ 1 *V. vC v; <; V ^ v: 1 9 b^ "c^ t^ Isjl^ ^i M CJ-* ^ i 4^ nS ^- 0^ ^^ ^- $ 1 Nfi s& >^ ^ H Vi ^i SS s. 1 ^ 1 "^i ?i T>ilT>r; ^ N ^ ^ 1 vSl vb!^ O; s^ W o sfi 8 ^1^ i^i^ ^'^^ V/Ti ^> s 8 K)| ^v ^1 V. ^ tv ^ 1 8 s Or 1 s ^ ^ 1 ^ ^ vs ^ Vri O ^^ >f 0^ 1 ^ ^ 'S ^ K • C ^1 8 ^1 ^ S3 ^ $ ^ VA ^ § ^ ^ 0« ^^ *w ;)r> r^ brv T>s «^ ^ (g VT= ^ •^ ^ N V. ^< 1 1 0© 1 ^ ( m II \ ^ ^ >^ V, s^ b^ >^ ll ^i: UNIVERSITY OF FLORIDA ililillllilllilliiliil 3 1262 09239 5408 omeuMriRiNot 9f MPtii in mM: if r I R - • - t i . 8 }6