OF THE CITRUS RUST MITE

Transcription

1 esults of this experiment re in generl greement with the results of our previous experiment (7) tht were otined under the sme grove conditions with different smple loctions. However, different grove nd sprying conditions my yield different results. On the sis of these results, it ws concluded tht s spry volume decreses, men deposit nd vriility of deposition increses. However, the trend is not consistent throughout the cnopy nd could e ffected y smple loction. Literture Cited 1. Brooks,. F Comprison of helicopter with conventionl irlst spryer in the ppliction of citrus spry progrm. roc. Fl. tte Hort. oc. 78: Brooks,. F., W. L. Thompson, nd. T. Jutrs Evluting spry equipment for Florid citrus. roc. Fl. tte Hort. oc. 76: Brooks,. F. nd J. D. Whitney Field testing irlst spryers for Florid citrus. roc. Fl. tte Hort. oc. 84: Griffiths, J. T., C.. tem, nd W. L. Thompson. 19. ossiilities for the use of concentrted sprys on citrus in Florid. roc. Fl. tte Hort. oc. 63: Knpp, J. L., D.. H. Tucker, J. W. Noling, nd V. V. Vndiver, Jr Florid citrus spry guide. University of Florid-IF Circulr 393-O. 6. lyni, M Droplet size effect on spry deposition efficiency of citrus leves. Trnsctions of the E 31: lyni, M., C. W. McCoy, nd. L. Hedden pry volume effects on deposition nd citrus rust mite control. TM T 98, esticide Formultions nd ppliction ystems 8: lyni, M. nd J. D. Whitney Evlution of methodologies for field studies of spry deposition. Trnsctions of the E 31: tern, C.., Jr., J. T. Griffiths, W. L. Thompson, nd E. J. Deszyck rogress report on concentrted sprys on citrus in Florid. roc. Fl. tte Hort. oc. 64: roc. Fl. tte Hort. oc. 12: VOLUME ND CICIDE TE EFFECT ON THE CONTOL OF THE CITU UT MITE Clyton W. McCoy, Ben Hui Lye, nd Msoud lyni University of Florid, IF Citrus eserch nd Eduction Center 7 Experiment ttion od Lke lfred, FL 338 strct. In two independent field experiments on mture 15 to 18 ft high 'Vlenci' ornge trees, residul control of citrus rust mite, hyllocoptrut oleivor (shmed) ws evluted t constnt nd vrile rte of selected cricides t differ ent spry volumes rnging from to gl/cre using n irlst spryer. The preceding pper presents dt on folir spry coverge using copper trcer methodology. In ll experiments, no significnt differences in initil mortlity or residul control of citrus rust mite on fruit ws found etween spry volumes regrdless of rte of pplic tion or cricide. esidul control ws ffected y the kind nd rte of cricide used in the test. No significnt interc tion etween spry volume nd cricide rte ws detected indicting tht cricide rte ffected the control of citrus rust mite regrdless of the chnge in spry volume. esidul control of the citrus rust mite on leves t differ ent cnopy loctions t different spry volumes ws difficult to ssess ecuse of high vriility in mite popultion den sity etween smples. esidul mite control ws significntly etter on leves in the upper compred to the lower tree cnopy. Interestingly, men cumultive mite dys on leves treted with copper (trcer) were significntly lower thn on untreted leves. Florid griculturl Experiment ttion Journl eries No. N4. cknowledgments. The uthors would like to thnk Mr. John Updike, Jr., nd Mr. Jim Bolin for providing the grove nd spryers in this study, ohm & Hs Corp., Uniroyl Corp., nd Merck hrp & Dohme es. L. for support for the reserch. lso, to Jerry Fojtik, cott Hedden nd mny others for the dedicted technicl ssistnce tht mde these studies possile. 36 The citrus rust mite, hyllocoptrut oleivor (shmed) is uiquitous on citrus in most humid citrus-growing re gions of the world where it infests twigs, leves, nd fruit of ll citrus vrieties (15, ). In Florid, the citrus rust mite (CM) is primrily pest of fruit destined for the fresh mrket though occsionlly under idel physicl nd culturl conditions fvoring the mite (15, 17), its injury from cellulr feeding cn ffect fruit growth (2), fruit drop (1), internl fruit qulity (16) nd externl fruit qulity (14, 15). ince the CM inhits the new fruit nd folige ech yer in Mrch nd pril (12) nd reches injurious popu ltion densities nytime from erly June to Novemer (3, 15, 17), it is common for growers to pply 3 to 4 cricidl sprys during the yer. This need to spry frequently for CM is influenced y its iologicl ttriutes; tht is, its inherent ility to increse to injurious densities on fruit quickly (14) nd its smll size which mkes it extremely difficult to monitor in the field in order to time cricide tretment ccurtely. ince the CM prefers to inhit the fruit nd folige of the outer cnopy of the tree (12), oth common sense nd the pulished dt suggest tht thorough spry cover ge of the totl tree cnopy is not crucil, nd it should e menle to control vi concentrte (low volume) sprying. From the pioneer works t the Citrus Experiment t tions t Lke lfred, FL nd iverside, C, studies with multi-hed spryers, ir-lst spryers, ircrft nd low volume spryers hve demonstrted successful control of citrus rust mite (4, 5, 6, 7, 9, 21) nd citrus red mite (1). ecent studies suggest tht low volume ppliction lso hs potentil for pests such s gresy spot disese tht in hit the underside of the lef (24). ecently, lyni nd McCoy (19) found tht smll spry droplets gve uniform coverge on fruit, less colescence of droplets for runoff, nd higher mortlity of citrus rust mite. Of the vrious components tht operte in spry technology, spry volume reduction is one key fctor tht roc. Fl. tte Hort. oc. 12: 1989.

2 will decrese ppliction costs (23). Environmentlly spek ing, reduction in runoff lone will minimize ir, soil, nd wter contmintion. Nturlly, the use of less wter per cre will produce svings in lor, fuel, nd mchinery cost (23). Therefore, it is resonle to ssume tht grower interest in concentrte (low volume) sprying will increse in the future. Field studies hve een conducted during the lst 4 yr to elucidte the effect of reduced spry volume on the control of citrus rust mite with contemporry cricides nd determine fctors responsile for success or filure of n ppliction (2). revious reserch hs focused on quntifiction of spry deposition on the tree cnopy in reltion to mite control. Field studies conducted in 1985 nd 1986 showed tht spry volume hd no significnt effect on men trcer deposition nd citrus rust mite con trol while higher spry volumes showed more uniform coverge thn the lower volumes (2) (Tle 1). Both this nd the previous pper (18) present dditionl reserch dt on 1) deposition chrcteristics within the tree cnopy t different spry volumes nd 2) the effect of spry vol ume nd cricide rte on the residul control of the citrus rust mite. Mterils nd Methods Field Test 1987 Experimentl design. The experiment ws conducted ner Lke Wles, FL t lcom Fruit Compny on mture 15 to 18-ft high ornge (Citrus sinensis vr. Vlenci (L.) Oseck) trees with excellent lef cnopy density. Eight tretment comintions (2 cricides, 4 spry volumes) plus n unspryed control were rrnged in rndomized lock design nd replicted 4 times. The trees were spced 2 x 3 ft with 72 trees/cre. Trees were of uniform size nd shpe nd were not recently hedged. Ech plot con sisted of 6 rows of 6 trees with ll ut the center 4 trees used s uffers to spry drift. pry ppliction. ll tretments were pplied with n engine-driven irlst spryer (FMC Model 187) with high volute oom t 13 psi nd t 1.5 mph. summry of delivery system specifictions re represented in Tle 2. prys were pplied on 17 nd 18 July fter the morning dews hd evported from the folige. Temperture rnged from 9 to 95 F nd reltive humidity rnged from 72 to % under prtly cloudy skies. cttered evening showers produced less thn 1 inch of rinfll 72 hr fter spry ppliction. Wind speed ws negligile. The mcrocyclic lctone, mectin (gri-mek 5 EC) nd the insect growth regultor (IG) difluenzuron (Micromite W) were selected s cricides sed on pre vious efficcy dt for citrus rust mite (8, 11, 13). mec tin ws pplied t.1 l..i./cre plus 1 gl of FC petroleum spry oil per cre in,,, nd gl of wter (ph 7.8). Difluenzuron ws pplied t rte of.31 l..i./cre in the ove quntities of wter per cre. rocedures for estimting citrus rust mite popultions. dult citrus rust mites were estimted on the fruit surfce y counting the numer of mites within 6 inch2 re t 2 loctions on 2 sides of fruit per plot t eye level (4 to 5 ft) with gridded 1X hnd lens t one wk prior to tretment nd t 1, 2, 4, 6, 9, 11, nd 13 wk post-tretment. Mite counting ws lwys on the 4 center trees of ech Tle 2. ummry of delivery system specifictions for citrus rust mite test t Lke Wles, FL pryer type FMC Model 187 speed spryer w/volute te gl/cre te gl/tree Delivery gl/min Disc/core no. 5./17 2.5/17 2.5/9 2.5/5 Tle 1. Effect of constnt rte of different cricides pplied t different spry volumes per cre on the residul control of the citrus rust mite on 'Vlenci' ornge t Lke Wles, FL, Men numer mites/cm2 on fruity cricide nd rte pry volume (gl/cre) wk: pre (-) nd post (+) tretment Cumultive mite dys mectin 5ECZ (.1 l..i./cre) Ethion 4EC (3.4 l..i./cre) Chlorpyrifos 4EC (2.5 l..i./cre) Fenuttin oxide 4L (1.31.i./cre) Check L I C T I O N c 246 c 247 c c 415 d 277 c 237 c d zmectin 5E pplied with 1 gl of FC petroleum oil (.%). ytretments replicted 4 times. Mens sed on fruit/replicte. Mens followed y the sme letter re not significntly different t the 5% level of proility using Duncn's Multiple nge test. roc. Fl. tte Hort. oc. 12:

3 plot. Mite time units designted s "mite dys" were clcu lted using the following formule: nd where MD: D1 D2 I CMD MD: = D1 + D2 CMD = 2 i = 1 MD; x I mite dys; i = 1, 2, 3, nd 4, men popultion density for smple dte 1, men popultion density for smple dte 2, numer of dys etween smpling dtes, nd cumultive mite dys. Men mite popultion density per 6 inch2 of fruit surfce t ech smple time nd cumultive mite dy vlues per tretment were tested for differences using Duncn's Multiple nge test. rocedures for estimting percent fruit injury. The percent fruit per tree with visile citrus rust mite injury ws deter mined immeditely fter the lst mite popultion estimte. Counts were mde with the id of 2. ft squre frme which ws positioned t height of c. 6. ft nd ner to the outer folige of the tree (22). Ech fruit within n im ginry tunnel extending from the frme to the center of the tree ws exmined for the presence of mite injury. For ech tretment, 4 frme counts, one t ech qudrnt, were tken per tree with totl of 16 trees per tretment. Field Test 1988 Experimentl design. The experiment ws conducted in the sme grove with the sme plot design s the 1987 field test, however, different trees were used in this test. Twenty tretment comintions (4 cricide rtes, 5 spry volumes) plus n unspryed control were rrnged in rndomized lock design nd replicted 4 times. pry ppliction. ll tretments were pplied with n engine-driven irlst spryer (FMC Model 187) with high volute oom (18). schemtic digrm of the spryer nd ppliction conditions nd summry of delivery sys tem specifictions re represented in the preceding pper (18). new formultion of dicofol (Kelthne MF) specifying less thn % of DDT relted impurities ws selected s the experimentl cricide sed on previous efficcy dt for citrus rust mite. Four tretment rtes,, 2, 4, nd 6 pints of formulted Kelthne MF were ech mixed with 6 ls. of cupric hydroxide (% metllic copper) in,, 2,, nd gl of wter, respectively. rior to sprying, 1 pint of Triton G-44M spry djuvnt ws dded to the tnk mix to lower the ph to 7. Dicofol ws pplied t different rtes/cre t spryer ground speeds of 1.3 mph for the spry volume of gl/cre nd 1.5 mph for the other volumes. rocedures for estimting citrus rust mite popultions on fruit. dult citrus rust mites were estimted on the fruit surfce for ll tretment comintions using the sme methodol ogy descried in the 1987 field test. Monitoring times were 1 wk pretretment nd 2, 4, 6, 8, nd 1 wk post-tretment. rocedures for estimting citrus rust mite popultions on leves. dult citrus rust mite popultions were lso moni tored on leves t different loctions within the tree cnopy only in tretments with the full rte of dicofol nd the untreted to determine the reltionship etween folir coverge t different spry volumes (18) nd mite control. s descried in detil in the previous pper, 3 leves were collected from directionl qudrnt of 4 djcent trees t heights of 5 nd 1 ft nd t rdii, outside nd 2 ft inside the tree cnopy per plot. Lef smples from ech loction were plced in zip-lok plstic gs nd plced in cooler to prevent overheting. In the lortory, the numer of dult citrus rust mites per lef were counted with stereomicroscope. esults Field Test ccording to the results presented in Tle 3, no significnt difference in initil mortlity or residul control of the citrus rust mite on fruit ws found etween spry volumes rnging from to gl/cre. The lck of reltionship etween spry volumes is reflected in oth cumultive mite dys nd percent fruit injury. The cricide, mectin, gve significntly etter residul con trol thn the untreted check (Tle 3). Where difluenzuron ws used s the cricide, mite control ppered to e significntly etter t to gl/cre compred to to gl/cre sed on cumultive mite dys nd percent fruit injury (Tle 4). This suggests tht overll coverge ws etter t to gl/cre which resulted in slightly etter residul control t 9 wk when mite popultions in the untreted check were t pek. Tle 3. Effect of constnt rte of mectin7 pplied t different spry volumes per cre on the residul control of the citrus rust mite nd percent russet to 'Vlenci' ornge t Lke Wles, FL, Men numer mites/cmtj on fruity pry wk. pre (-) nd post (+) tretment Cumultive %x (gl/cre) dys injury w c c mectin 5 EC pplied t rte of.1 ls..i./cre plus 1 gl of FC petroleum oil (.%). ymens sed on fruit smpled from ech of 4 replictions. xmens sed on 4 redings per tree, 16 trees per tretment. wmens in columns followed y the sme letter re not significntly different t the 5% level of proility using Duncn's Multiple nge test. roc. Fl. tte Hort. oc. 12: 1989.

4 Tle 4. Effect of constnt rte of difluenzuron2 pplied t different spry volumes per cre on the residul control of the citrus rust mite nd percent russet to 'Vlenci' ornge t Lke Wles, FL, Men numer mites/cm2 on fruity pry volume (gl/cre) + 1 wk. pre (-) nd post (+) tretment Cumultive mite dys %x fruit injury w c c c c c c zdifluenzuron W pplied t rte of.31 ls..i./cre. ymens sed on fruit smpled from ech of 4 replictions. xmens sed on 4 redings per tree, 16 trees per tretment. wmens in columns followed y the sme letter re not significntly different t the i level of proility using Duncn's Multiple nge test. Field Test esidul control of the citrus rust mite on fruit, expressed s cumultive mite dys from the time of tretment to 1 wk post-trement, is presented for ech comined spry volume nd cricide rte (Tle 5). No significnt difference in the residul control of citrus rust.mite t 1 wk post-tretment y dicofol ws found etween spry volumes rnging from to gl/cre for ll cricide^tes (F =.88; df = 4, 57; =.48). However, residul control (cumultive mite dys) ws significntly ffected y different rtes of dicofol (F = 1.2; df = 3, 57; <.1). No significnt interction etween spry volume nd cricide rte ws detected y F test sttisticl nlysis (F =.3; df = 12, 57; =.99) indicting tht dicofol rte ffected the control of citrus rust mite regrd less of the chnge in spry volume. s expected, residul mite control incresed with n increse in cricide rte from to 4 pints per cre, however, for some unexplinle reson, the 6 pints per cre rte of dicofol ws lest effective. This qudrtic reltionship etween rte nd re sidul control (mite dys t 1 wk post-tretment) is consis tent mong spry volumes lthough the reltionship is wek (2 =.3). No explntion for this difference in rte response cn e given since the 6 pints/cre rte ws determined to e most effective in reserch nd develop ment studies. Overll, the 4 pints/cre rte t gl/cre ws most efficcious suggesting tht smller droplet size nd less pesticide runoff ws responsile for the lowest mite dy cumultion of 5.9. esidul control of the citrus rust mite on leves t different loctions of the cnopy t the 6 pints/cre rte t different spry volumes ws not significntly different due to high vriility in mite popultion density mong sm ples (.1 to 16.5 cumultive mite dys) (Tle 6). The non-significnt NOV results indicte tht this vriil ity overpowered the effect of spry volume. Interestingly, the cumultive mite dys in the copper-treted check (179.5) ws significntly lower (t = 2.8; df = 9; =.4) thn in the check (296.1) without copper ut ws significntly higher (t = 4.59; df = 743; <.1) thn in the cricide tretments (84.4) (Tle 6). By comprison, residul mite control for ll spry vol umes ws significntly etter in the upper cnopy (1 ft) compred to the lower cnopy (5 ft) (F = 4.26; df = 1, 12; =.4) (Tle 7). However, overll spry volume comprisons of cumultive mite dys showed no significnt difference, except for the gl volume/cre where re sidul control ws significntly different etween outside nd inside, nd etween the upper nd lower cnopy (Tle 7). The differences in spry deposition within the tree cnopy shown in the preceding pper (18) were sent for mite control proly ecuse of the high vriility in mite density on leves. Discussion ccording to previously pulished reserch (2) nd the dt presented herein, spry volume hs no significnt effect on initil mortlity nd residul control of citrus rust mite even though higher spry volumes showed more uni form folir coverge (18) nd spry deposition vried within the tree. Though not conclusive, dt trends suggest tht lower spry volumes ( to gl/cre), when pplied under norml conditions, re highly effective for the contol of rust mites on fruit. ulished reserch suggests tht resons for this phenomenon re most likely relted to mite distriution on the tree (2), uniform deposition of smller spry droplets on the fruit, less colescence of droplets on fruit (less runoff) nd higher contct fre- Tle 5. esidul control of citrus rust mite on fruit expressed s men cumultive mite dys t 1 wk post-tretment t different spry volumes nd cricide rtes t Lke Wles, FL, cricide pry volume (gl/cre) rte (pint/cre) 2 Men Men zmens followed y the sme letter re not significntly different t the 5% level of proility using Duncn's Multiple nge test. roc. Fl. tte Hort. oc. 12:

5 Tle 6. esidul control of citrus rust mite on leves expressed s men cumultive mite dys t 6 wk post-tretment t different spry vol umes nd cricide rtes t Lke Wles, FL, Tle 7. esidul control of citrus rust mite on leves expressed s men cumultive mite dys t different loctions in the tree cnopy, Lke Wles, FL, cricide rte (pint/cre) Cnopy depth (rdii) Cnopy loction (height) pry volume (gl/cre) 2 NOV F - df = = , F = = 1.74 df = = 4,333 = = 4 N.. pry volume (gl/cre) 2 Inside ignificntly different t = Outside Z 66.2 Upper (1 ft) using pired t test. Lower (5 ft) Z 76.5 quency with the mite or the plnt surfce inhited y the mite (19). The uthors hve oserved colescence of drop lets t higher spry volumes tht result in lrge ptches of fruit surfce void of pesticide film. Therefore, it is imper tive tht the pplictors recognize the importnce of spryer clirtion, define wether conditions for spry ppliction nd the nture of the trget efore venturing into low volume sprying. These dt lso showed tht the residul control of cit rus rust mite differs ccording to cricide, yet the efficcy of most cricides is so good, tht they might compenste for lesser coverge in some regions of the tree cnopy nd on the fruit itself. The secret to optimum mite control p pers to e relted to timing of ppliction nd optimum coverge relted to droplet size on the trget. The dt presented herein on rte response to spry volume/cre suggest tht rtes lower thn the recom mended rte might give cceptle residul control of cit rus rust mite. Less spry runoff nd more thorough cover ge might equte to less pesticide/cre. However, more re serch is needed compring rte to spry volume/cre. 3 Literture Cited llen, J. C The effect of citrus rust mite dmge on citrus fruit drop. J. Econ. Entomol. 71: llen, J. C Effect of citrus rust mite dmge on citrus fruit growth. J. Econ. Entomol. 72: llen, J. C. nd C. W. McCoy The therml environment of the citrus rust mite. gric. Meteorol. 2: Brooks,. F Comprison of helicopter with conventionl irlst spryer in the ppliction of citrus spry progrm. roc. Fl. tte Hort. oc. 78: Brooks,. F. ndj. D. Whitney Field testing irlst spryers for Florid citrus. roc. Fl. tte Hort. oc. 84: Bullock,. C eril crol for control of citrus rust mites in Florid. roc. Fl. tte Hort. oc. 85: Bullock,. C eril ppliction of pesticides to control citrus pests. roc. Int. oc. Citriculture 2: Bullock,. C. nd C. W. McCoy ctivity of insect growth regultors versus citrus rust mite in Florid. roc. Fl. tte Hort. oc. 91: Griffiths, J. T., C.. tern, nd W. L. Thompson. 19. ossiilities for the use of concentrted sprys on citrus in Florid. roc. Fl. tte Hort. oc. 63: Jeppson, L.. nd G. E. Crmn Low volume pplictions to citrus trees: Effectiveness in control of citrus red mite nd Cliforni red scle with petroleum oils nd pesticides. J. Econ. Entomol. 67: McCoy, C. W ctivity of Dimilin on the developmentl stges of hyllocoptrut oleivor nd its performnce in the field. J. Econ. Entomol. 71: McCoy, C. W Migrtion nd development of citrus rust mite on the spring flush of Vlenci ornge. roc. Fl. tte Hort. oc. 92: McCoy, C. W vermectin Bj: novel miticide ctive ginst citrus mites in Florid. roc. Fl. tte Hort. oc. 95: McCoy, C. W. nd L. G. lrigo Feeding injury to the ornge cused y the citrus rust mite, hyllocoptrut oleivor. nn. Entomol. oc. mer. 68: McCoy, C. W., L. G. lrigo, nd J. C. llen The iology of the citrus rust mite nd its effect on fruit qulity. The Citrus Industry 69:44-49, McCoy, C. W.,. L. Dvis, nd K.. Monroe Effect of lte seson fruit injury y the citrus rust mite, hyllocoptrut oleivor, on the internl qulity of Vlenci ornge. Fl. Entomol. 59: rtt,. M eltion etween moisture conditions nd citrus rust mite infesttions. roc. Fl. tte Hort. oc. 7: lyni, M. nd C. W. McCoy Deposition of different spry volumes on citrus trees. roc. Fl. tte Hort. oc. (in press). 19. lyni, M. nd C. W. McCoy pry droplet size effect on mortlity of citrus rust mite. TM T 136, esticide Formul tions nd ppliction ystems 9: lyni, M., C. W. McCoy, nd. L. Hedden pry volume effects on deposition nd citrus rust mite control. TM T 98, esticide Formultions nd ppliction ystems 8: tems, C.., Jr., J. T. Griffiths, W. L. Thompson, nd E. J. Deszyck rogress report on concentrted sprys on citrus in Florid. roc. Fl. tte Hort. oc. 64: tout,. G Estimting citrus production y use of frme count survey. J. Frm Econ. 44: Whitney, J. D.,. F. Brooks, nd. C. Bullock esticide ppli ction methods for citrus in Florid. roc. Int. oc. Citriculture, pp Whitney, J. D., M. lyni, D. B. Churchill, J. O. Whiteside, J. L. Knpp, nd. C. Littell Ground speed nd spry volume of irlst spryers ffect copper deposition nd gresy spot control. roc. Fl. tte Hort. oc. 11:137.. others, W. W. nd. C. Mson The citrus rust mite nd its control. UD Tech. Bull pp. 4 roc. Fl. tte Hort. oc. 12: 1989.