Hemstreet, Stuart : Stuart Hemstreet is Staff Research Associate, Department of Botany and Plant Sciences, University of California, Riverside.

Hield, Henry : Henry Hield is Specialist, Department of Botany and Plant Sciences, University of California, Riverside.

Growth control of laurel fig with chlorflurenol Henry Hield 0 Stuart Hemstreet carriers . Maintain CF125 was the only com - T h e laurel fig , Ficus nitida Thunb . , has mercially available product that met this re - been planted extensively as a street tree in quirement . southern California . Under idealgrowth con - ditions , this tree may eventually reach heights Treatment procedure as with many street trees , per - of 30 feet and , Band width is determined by multiplying iodicpruning is required to provide clearance the trunk diameter , asan index of tree size , by for pedestrian and vehicular traffic . Laurel Chemical banding a predetermined factor that characterizesthe fig is generally pruned on cycles of one to species â?? responsiveness to the chemical . The three years . maintains desirable of 0.1 per - 4 . The solution Foliar growth - inhibitor sprays speciesfactor for laurel fig is appearance with two - of 1 percent chlorflurenol in a carrier of 30 0.075 percent cent malic hydrazide ( MH ) , thirds less pruning . percent toluene and 70percent diesel oil is ap - chlorflurenol , or 0.4 percent dikegulac ( At - plied by 3 - gdlon sprayer or paintbrush to wet rid ) effectivelyreduce shoot growth for up the bark . Application should begin at the top to four months , but the hazard of spray drift of the area to be banded to allow for edge to other vegetation prevents the use of such downward flow of the solution , and should spraysin many urban situations . Trunk injec - be completed without excessive wetting be - of chemicalsfor growth control is not ef - tion low the band . Ficus , possibly because of its latex fective for Chlorflurenol results in greater growth re - content . For these reasons , we have investi - duction in pruned than in unpruned trees . gated trunk banding , using chlorflurenol Before treating severely pruned trees , where from the product Maintain CF125 , to observe most of the canopy has been removed , they its effects on growth control ( to reduce prun - should be allowed to regrow foliageto a visu - ing frequency ) and possible maintenancecost ally acceptable level . reductions . Bark banding of plant growth Treatments are reapplied when vigorous regulators has been found effective only with regrowth indicates that shoot growth inhibi - oil - soluble chemicals applied in oil - base In the city of Orange , trees grown in a high hedge that had to be Laurel fig trees in Riverside with large rounded canopies , banded pruned yearly required significantly less pruning after repeated in 1979 and 1980 ( at right ) , had an acceptable apDearance and banding treatments ( left and center ) than did the control at right . reduced shoot growth through early May 1980 . CALIFORNIA AGRICULTURE , NOVEMBER - DECEMBER 1982 9 tion is diminishing.The chemicalalso slightly ment . Pruning time was reduced only with 1981 , following repeat applications , foliage of increases the rate of aging and drop removed and pruning time were significantly the 4 - diam band ( to 6.4 minutes per tree , mature leaves . When the canopy becomes compared with 11.7 for the control ) . Both lower than in controls . somewhat open , so that occasional small bandings resulted in smaller leaves , and the Unpruned trees were treated on August 15 , openingscan be seen from below , treatments 1979 , March 20 , 1980 , and November 19 , 4 - diam application decreasedcanopy density . are discontinued . The cycle is resumed after 1980 . Growth was evaluated by measuring Street trees with large rounded canopies in a period of regrowth followedby pruning . Riverside , which were banded in 1979 and different shoots marked at each treatment 1980 , had an acceptable appearance and re - date . A consistent level of shoot growth re - Examples of responses duced shoot growth through May 7 , 1980 duction was found with the 4 - dim band In a 1978 test , large standard - size trees ( table 1 ) . With no treatment after February4 , width . Tree heights determined on October 1 were pruned on February 10 , banded with 1980 , the pruning on October 6 , 1980 , 20 , 1981 , were not different . Application of percent chlorflurenol on April 11 , and pruned showed a 69 percent reduction for pruning 1 percent chlorflurenol - carrier mixture the again on November 7 . In onegrowingseason , weight but no significant difference for a 29 over gauze , which was then covered with banding significantly reduced shoot length percent reduction in pruning time . plastic wrap , increased the growth control and pruning weight in both the 2 - diam and of Orange , laurel figsgrown in a In the city with a smaller band width . However , cover - 4 - diam band - width treatments . Shoot high hedge that required yearly pruning were ing the band can also result in trunk injury , growth , 182days after banding , was 72 cm in treated by trunk banding from 1978through and it is not advised . untreated controls , 28 cm in 2 - diam treat - 1981 ( table2 ) . Pruning results in 1978showed Gynaiko - Incidence of Cuban laurel thrip , 20 cm in 4 - diam treatments ; ments , and thrips ficorum Marchal , has decreased on no differences after one treatment ( the pruning weights were 18.6 , 11.7 , and 7.1 kg 11 / 3 / 78 application being too recent to givea chlorflurenol - treated trees . Trees 4 - diam - per tree , respectively , 201 days after treat - responseon 11 / 15 / 78 ) . However , in 1979and banded on March 27 , 1980 , were rated for thrip leaf damage on August 5 , 1980 , on a 1 ( showing no injury ) and 10 ( show - scale of TABLE 1 . Responsesof large , rounded laurel fig trees in Riversideto repeated ing severe thrip damage ) . Treated trees aver - chlorflurenoltrunk banding aged 2.2 ; untreated trees averaged 7.7 . 1 % chlorflurenol ' on Root growth has not been measured Date Date Untreated 2 - diam 4 . diam field - grown laurel fig . Measurements on Response treated evaluated control band band other tree species in the field suggest that Leaf drop ratingt 51 3179 6 / 13 / 79 2.0 1.5 1.5 root growth is reduced by a similar magni - . o 2.0 Leaf color rating $ 6 / 13 / 79 1.0 1 Growth control rating , YO 6113179 0.0 a 50 ab 66 b tude as top growth . YO Growth control rating , 7112179 0.0 34 50 Leaf drop ratingt 7112179 1.0 1 . o 1.5 Summary Leaf color rating $ 7 / 12 / 79 1.0 1 . o 1.5 Where foliar sprays are impractical , chlor - 7127179 flurenol trunk banding of laurel fig offers a Trunk ratings 12114179 11 2180 1.0 1 . o 1 . o Branch shoot breaks , length , cm 21 4180 21 4180 77 b 43ab 19a means of lengthening the pruning cycle . If we Branch shoot breaks , number 21 4180 18 19 28 disregard the one - time banding of the trees Canopy density , YO 51 7180 80a 75 b 50 c pruned in November 1978 , the measurements Growth reduction , % 51 7180 28 a 48 b 57 c after repeated banding show that chlorflur - Pruning timeltree , min 101 6180 22.1 . . . 15.6 Weight pruningsltree , kg 101 6180 91.3a . . . 28.1 b of 73 percent in shoot enol caused reductions ' Means in each row followed by the same letter are not significantly different according to Duncan's multiple range test , length , 67 percent in mass of prunings , and P = 0.05 . Scale : 1 = no leaf drop , 5 = severe leaf drop . 43 percent in pruning time . A further uncal - tScale : 1 = green color , 5 = chlorosis . culated benefit is the time saved in not having § Scale : 1 = normal smooth . 5 = rough . of to collect and dispose of thegreater masses clippings from untreated trees . TABLE 2 . Responses to repeated trunk banding of large Trunk injury has not occurred from band - laurel fig trees pruned yearly to square shape , Orange , California ing with 1percent chlorflurenol in the 30 per - cent toluene , 70 percent diesel oil carrier . 1 % chlorflurenol ' Date Date Date Untreated 2 - diam 4 - diam Tree appearance is slightlyaltered but has not Response pruned treated evaluated control band band of public concern . The reduction in long been 11I77 4127178 vegetative shoots gives the canopy a more 111 3178 11115178t 11178 uniform surface appearance . The leaves are 41 9179 slightly smaller , lighter green when young , Shoot length , cm 11179 101 3179 11127179 92b 28a 12a Ficus and have characteristicsmore similarto Wt pruningsltree , kg 11127179 58b 23ab 7a Pruning timeltree , min 11 / 27 / 79 33.3 b 30.2 b 12 a retusu . Chlorflurenol trunk banding is a reg - Growth reduction , YO 3113180 61 6180 Oa 40 b 43 b istered application and is being used by some 6 / 24 / 80 81 5180 Oa 36 b 43 b cities on their street trees . 9130180 9130180 Oa 36 b 49 b 21 9181 0 a 69 b 87c timeltree , min 8181 6 / 21 / 81 81 5181 Pruning 64.3 a 54.6 b 40.9 b Henry Hield is Specialist , and Stuart Hemstreet is Clippings , 32 - gal cansltree 81 5181 21 a 13b 11a of Botany Staff Research Associate , Department ' Means in each row followed by the same letter are not significantly different according to Duncan's multiple range test . and Plant Sciences , University of California , Riv - P = 0.05 . no significant dlfferences . tPruning results in 1978 showed erside . 10 CALIFORNIA AGRICULTURE , NOVEMBER - DECEMBER 1982