Pielou, D. P.

Williams, K.

English

Journal of the Entomological Society of British Columbia

THE PATTERN AND PERSISTENCE OF DEPOSITS OF SEVIN , WITH AND WITHOUT SURFACTANTS, ON THE FOLIAGE OF FRUIT TREES II. APPLICATION BY HIGH VOLUME SPRAYER' D. P. PIF.LOU AND K . WILLIAMS " R esearch Sta tion, RGsea1'ch Branch, Ca n ada Department of Agriculture, Summerland , British Columbia Introduction In a previous pa per (5) an acco unt was giv en of the distribution and de-clin e of depOSits of Sev in ( I - na phthyl N - m eth ylca rbama te), usin g a m ethod of extraction a pplicable to th e deposit on one side of a Sin gle leaf. The in-ft uence of Plyac (active ingr edien t . polyethylene 629) on these deposits was a lso investigated. Those investi-ga tions were made using th e 'con-cen trate ' a ir-blast method of spray-in g. In concentrate spraying the wet deposit on foliage consists of a dense pattern of drops. These drops have coalesced from the smaller drops in the a ir tha t have fallen on the leaves. By correct manipulation of the sprayer, these drops do not coal-esce to the point where irregula r patches of ftuid occur, i. e ., to the point of ' incipient run-off ' (3). I n high volume spraying, on the other hand , the foli age is delibera tely drench ed with la r ge quantities of flU id , much of which ultimately fa ll s to the ground. The film of water r e-tained produces an insec ticide de-posit . which on dryin g, is different in ma n y ways from that produced by concentrate sprayin g. In this pa per an account is given of some ch a r ac-teristiCS 0 I' th e deposits from high volume a pplication . Poin ts of co m -pa ri son a nd con tras t a re made with t.he fi ndin gs in th e previous paper (5) in wh ich concentrate sprayi ng was used. 1 ContribuLion f\u . 11 0, f {e~ea rt'h Sta t iOI1 , I{e-:::-ca re h Bra nch. Canada Dep.'J. l'tlll e n l or Ag rkulture. SU111me r lan ci , Briti sh CulumiJ i.1. .2 En t o l11(J l() ~ i sl and C helllht. t' E'spect i \'l-'b'. Methods The methods, trees, a nd samplin g a rra ngem en ts were as previou sly de-scribed (5) except in a few important r espects. The sprayer used was a t ruck-mounted, gun-type m achin e. It was operated at a pump pressure of 400 pounds per squa r e inch . Th e cherry t rees were sprayed very thorou ghly, approximately 20 Imperia l3 gallons being used per tree. Sevin , 50 per cent wettable powder, was a pplied a t a rate of one pound per 100 gallons, a nd , Plyac , when in clud ed, a t one pint per 100 gallons. This is one- sixteenth the concentration used in the concen-tra te application (5). Leaf samples were ta ken immediately after the de-posits were dry, and six days later. In p lace of the device previously used (5) a n ew piece of appara tus was constructed that allowed the simul-taneous, but separate , removal of the deposi ts from th e two faces of the sa m e leaf. This apparatus is described elsewh ere (6). Since both faces of each leaf were a n a lyzed for insecti-cide it was possible to test for corre-lation be tween depos it s ize for th e two surfaces . This was not possible in th e fo rmer stud y. Chem ical analysis of the ex t r acts was m ade according to th e m ethod of Misku s, Gordon and Geor ge (4 ) . Results The m ean va lli es of deposi ts group-eel a ccord in g to sa mplin g t ime, leaf sur fac e, and treatment are show n in Ta ble 1. Rat ios, sho win g th e relation 2G 1'1:<"'. I;;ST"\'"I. . ~; II' . HI: IT . (' 01.1" .111:1.1. \'1)1. . 5~1 ( 1~162 ) . OH ·. 1. H I62 TABLE I.- The Influence of Suriace , :! nd Prese nce of Plyac, on th e Mean De posits of Sevin Produced on Cherry Foliage by Hi g h Volume Spraying . Tim e Surface Mean de pos it of Sevin , micrograms per sq. cm. Ratio : with withou t 0.56 * 0.57* With Plyac Without Plyac Lower, L Upper, U Ratio: L / U Lower L U pper : U Ratio: ' L U . 1.76 3.12 Day 0 1.39 2.43 1.27* 1.28 * (, .78 1.64 0.48 * 0.56 * Day 6 0.49 0.87 1.59 * 1.89 * All ratios s ig nificantly diffe:'e nt from the nu ll hypoth esis valu e of 1.0. between deposit size on the two leaf surfaces a nd between treatments, a re al so included in the ta ble. It will be seen that, as in concentrate spraying (5) deposits are heavier on the lower surfaces of leaves. A conspicuous ef-fect , but in th e reverse direction to that observed with concentrate spra y-in g, is also obvious as a r esul t of Plyac treatmen t. To see wh ether the values for de-posit size on th e lower leaf surfaces ranged independen tly of those on th e upper surfaces, coefficien ts of correla -tion were calculated. For deposits sampled on the day of spray a pplica -tion , the coeffici ent of correla tion be-tween the lower a ncl upper deposits was 0.3695 when Sevin plus Plya c was used ; where Sevin was used alone it was 0.3797. Examination of Table VI in Fisher and Yates Statistical Tables (1) shows that these values are highly significant (P = 0.0 1). At the sampling on the sixth day the va lues of the coefficient were, respec-tively, 0.3057 and - 0.1382. The for-m er value is significant (P = 0.05 ) but the latter is not . It would appea r , therefore, tha t initially there is a s light tendency for a heavy deposit on one surfa ce to be associa ted with a h eavy deposit on the other , and vice versa; but this relation tends to di s-appea r or be reduced witl1 tim e. TABLE 2.- Se vin Depos its on Ch l! ITY Fol iage . Sa mp les Ta ke n Immedia t ely the Spra.\· H ad D r ied . Mea n s a nd V<lr iances [or T lVo Me th ods of Applica tion , P r esence Absen ce of' PI.va c, and f OI' Upper a nc! Lo we r Leaf Surfaces . Type of spray i ng Co ncentrate air-bla st Hi g h volum e, hydrauli c Pl yac Present Absent Lea l ,s uria ce Lo\\" er Uppc r L plre r UP PH P r ese nt L()" I'C' r Uppe r Absent LO\\'e r U ppe r Se vi n de posi t. Microg r a m s per sq . cm . Mean Vari a nce 3.309 1.922 1.885 1.227 2.456 1.405 ge ne r a l me,oll . concen tra te : 2.264 1.761 1.387 3.119 2.427 ge ne ral mea n . hi g h vol um e : 2.178 1.662 0.953 0. 245 2 0.3062 0.519 1 0.501 1 1 Sig n ifi ca ntl y lowe r tha n cOl'res;Jo ndin g va riance [or concentrate a pplica tion . 2 Si g nificantl y lower than w il e n PJ ~ ' ac a bse nt in hi g h volum e a pplica t ion . There was much less varia tion in deposit from leaf to leaf th a n was observed with concentra te applica-tion . The variances, for both leaf surfaces, a nd both trea tments , a r e shown , together with the valu es for the mean, in T a ble 2. Also included in this table are some r elevant fi gures from the previous s tudy on concen-trate a pplica tion (5) together with values for the varia nce which wer e not previously published . The gen er a l mean for high-volume spraying was 2.178 microgr a m s pel' squ a r e cen t i-meter ; tha t for the concentra te a pplication of th e previous stud y was 2.264 microgra ms. The closen ess of m ean deposit in th e two se ries of experiments emphasizes the validity of comparison ot various cri te ria for the two m ethods of applica tion. Disc ussio n The results summarized in T able show tha t, as with concentrate spraying (5), si gnificantly more Sevin is deposited on th e lower sur fa ces of the leaves . With time this r a tio in-creases a s a result of a more ra pid loss from the upper surfaces. Also, as in the previous work (5) , the a ddi tion of Plyac does not alter th e ra tio of the initia l deposits be tween lower and upper surfaces. Unlike th e r esults previously obtained with con ce ntra te spra ying, however. th ere is n o evid-enc e that Plyac redu ces the ra te of cl ecline 0 f deposi ts. However , the most notewor th y point of this investigati on is th at the a ddi t ion of P lyac, instead of prod uc-ing an in crease in deposit of Sevin , as wi th concen t rate spraying (5), reduced th e ini t ia l deposits by nearly h a lf . This r eversal of effect, wh ich h olds for appl e as well as ch er ry , h as been r eferred to in a prel iminary accoun t (7) . Plyac is gene ra ll y des-cr ibed as a sticker - spr eader (2) . Ho wever . these res ults. in combina-tion with t h ose of t h e previous paper (5) suggest th at the spreading p1'o-per ties a r e predominan t in hi gh vol ume spra yin g wh er ea s th e sticking properties a re predominan t in con-centra te a pplica tion. The a bunda nce of wa ter used in high volume applica -tio n, and th e ready wet t ing proper t ies of the surfactant, ensure not only th e production of a thin film of flUid on th e leaves, but fa cilita te , a ll too well. run -off of the surplu s fluid . On th e con tr a ry, with effici en t concentrate a pplication , no run - off occurs (3) . Run-off is par t icula rly was teful wi th concentrated spray fluids . The Plyac a dditive ca nnot, un der these condi-t ions , promo te film - Jorma tion nor enha nce the effi cien cy of r un-off . The !ncr eased deposits obta ined in this form of spraying h a ve been a ttribu ted to r educed loss Jrom rebounding spray drops, a nd improved adhesion of th e discrete clus te rs of pa r t icles of Sevin (5). I n Ta ble 2 a nother importa nt e ff ect of the addition of Plyac in high volume spraying is appa r ent. Ther e is mu ch less varia bility in magnitude of deposits, betwee n leaves when this ma terial is present. Th e varia nce, for eit h er upper or lower surfa ces, was reduced to a pproximately on e h a lf by the a ddition of Plyac . On the other h a nd, the a ddition of Plyac did n ot produce a n y signiftca n t differ ence in va ria nce in conce n tra t e spraying. In the li ght of th e commen ts in the prev ious pa r agr a ph this is what one m igh t expect . Spreadin g proper t ies, SUCll as those shown by Plyac in h igh-volum e spraying. tend to p romote un ifo r m ity. But th ere is no reason wil y th e s t ickin g qu a li t ies, mor e a p -par en t in con cen t rate spraying, should promote a more un ifo rm depos it. Anoth er poi nt, apparent in T able 2, is t h at even in t h e a bsence of P lya c, lea f-to- Iea f va r ia nce is two or t l1 r ee times greater in concen tra t e than in high-volume spraying. Tlli s virtue of reduced variance, however, is bought a t the price of a grea tly increased a mount of insecticide pel' acr e for in high -volume spraying a la r ge proportion of the spray fluid ru ns off the foliage a nd is lost on th e grou nd . The proportion lost va ries with the stage of foliar growth of the trees. However, in general. high-volume spraying uses twice as m uch insecticide per ac re, and a bout 20 times as much water . to do th e same job of insect control (3). The low value of correlation be-tween fresh deposits on the two sur-faces shows th ere is a tend ency for a h eavy deposit on on e surface to be associated with a h eavy deposit on t.he other. The rela tion is not ve ry marked , however, and it tends to di s-a ppear with time presu ma bly as a result of the equa lizing effects of weathering and loss processes . Summary A study of the inte r -leaf pa ttem of deposits of Sevin on cherry folia ge has been m ade usin g high-volume methods of spr ay applicat ion. The r esu lts a r e contrasted with previous studies in which concen tra te air- blast spraying was used. As in the latter case there were no sign ifica n t differ -ences in mean deposit up to a height of 14 feet; nor were there a n y dif-fe rences aSSOCiated with differen t quadra nts of the trees . Initia lly, deposits were approximately 27 per cent high er on the lower than on the upper surfaces of the leaves. Subse-quent erosion was more rapid on the upper surface so that this disparity increased with time. This relation was not, however, as marked as in con -centrate a pplication . The addition of one pin t of Pl yac to one pound of 50 per cen t Sevin r esulted in decreased initi a l d eposits; the r everse of the r elation with concentra t e a pplication . However, th e addition of Plyac mark-edly red uced th e leaf- to -l eaf vari-ance; in contrast to concen t rate spraying, where Plyac made no ch ange . The variance was always less in high volume than in concentrate spraying. There was on ly a slight tend ency for a high deposit on a lower surface to be assoc iated with a high deposit on an upper surface; and vice versa. This correla tion was sig-nificant bu t low immediately after a pplica tion ; after six days it was r educed or a bsent. Refere nces 1. Fisher, R. A., and F. Y·ltes. 1!.153 Sb ti s ti ca l Tabl es [or Bio logical , Agr icu ltu ra l ,lllel Med ica l Resea rch . 4th ed. Oli ver and Boyd. Ed inburg h. 2. Genera l Ch emical Di vis ion. j\l !ied Chemi ca l Corporation. 1959. Plyac spreader-sticker. Bull. New YlJrk ti. N. Y. 3. Mars hall , J as. 1958. Concentrat E' s pr~lyi n g in dcc iduo us orc hard s. P ub!. 1020. Ca n. De p. Agr i. , Ottawa. 4. Misku s, R. , H . T . Gordon, and D. A. George . 1959. Co lorime tr ic determination of I -nap hthy l N-methy lcarbamaU' in agri cu ltural crops. J . Agr. Food Chern . 7: 613-614. 5. Pieluu, D. P. , a nd K. Williams. 1962. T he pattern and pers istence of depus its of Sevin. with or wit hou t surfac tant s , on th e fol iage of fruit trees. 1. Application by concentrate spr ayer. Proc . Ent. Soc. Brit. Columbia. 59 : 6. Pi e lou, D. P. , K. Wi lli ams, an d P. E. Brinton. 1962 . Diflere nces in th e deposition a nd persistence of pesticid es on th e upper a nd lower surfaces of leaves. Nature. ] 95: 256-257 . 7. Williams, K., and D. P. P ie lou. 1962. No te on t he reve rsal of su me eff ects of surface active agents or. pesticide depos its on folia ge as a r es ul t of d iffe r ent method s of applicatiun. Ca nad. EntomoJ. 94: 874-875. 

The pattern and persistence of deposits of Sevin, with and without surfactants, on the foliage of fruit trees - II. Application by high volume sprayer

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The pattern and persistence of deposits of Sevin, with and without surfactants, on the foliage of fruit trees - II. Application by high volume sprayer

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Journal of the Entomological Society of British Columbia