FORESTS Departiuent of WESTEBNAUSTBALIA

ODC 441:414:12:232.32

ResearchPaper 6l 1980

FORESTS DEPARTIuENT OF WESTEBNAUSTBALIA

/i

- ,; t*,,. iff HERBICIDES FOR USE IN WESTERN AUSTRALIAN FOREST NURSERIES

by C.J. SCHUSTERand R.R.A.FREMLIN

SUMMARY

The effectiveness of several pre- and post-emergent herbicides was tested on nursery beds in softnood (Pinus radiata D. Don) and hardwood lEucaJVpxus diversicoTor F. Muell,) nurseries. In both nurseries pre-emergent herbicides lrere lhe more effective in controllj.ng weeds. They also had no severe adverse effect on the lree seedlings, especially in the softwood nursery.

The nost effective pre-emergent herbicide in both nurseries was nitrofen, whilst propazine was also effective in the softwood nurserv and diphenanid in the hardwood nursery. INTRODUCTION (3.4 kg.ha-I a.i.). However, neither could be used on E. deLegatensis R.T. Bak.i The Forests Departnent of Western only linuron vras satisfactory hrith this Australia operates ti'i'o nurseries in the species. Propazine was most effectively lower south-west of western Australia, used to control broad-leaved weeds, which produce open-rooted stock for field while annual grasses were better plantings. One at Nannup raises controlled with tbe use of chlorthal. approxirnately two million radiata pine lPinus radiaXa D. Don) seedlings annually' van Dorsser (I97I) observed that and the other, at Manjinup, raises lodgepole pine (P. contorta Dougl. var. approximately three million karri fatifoTia wats. ) was susceptible to (Eucaigptus diversicoTor F. Muell. ) applications of pre-emergent herbicides, seedlings annually. with the exception of chlorthal. chloramben (5.6 kg.ha-' a.i.) and In both nurseries weed control measures nitrofen (5.o k9.ha-' a.i. ) showed are necessaly. The vreed species, if left potential for use as post-energent untreated, compete with the tree herbicides with Douglas fir (PseudotseuEra seedlings for noisture, nutrients and nenziesii (Mirbel) Franco) r whilst growing space (swarbrick, 1976), and this nitrofen vras the only post-energent can cause reduced growth, lack of vigour herbicide amongst those tested that did and death. It is also more difficult to not affect lodgepole pine seedli.ngs tift the seedlings in preparation for adversely.

t,lqrrLrrrv vu !. The residual effects of herbicides Different herbicides are effective in could determine their future use in controlling different types of weeds. forest nurseries ' However, irrigation crop plant tolerance of the various and cultivation before and after crop herbicides also varies considerably. removal increase the activity of soil micro-organ i sms, the most inportant In the hardwood nursery, linuron (o'7 deactivating agents for herbicides, by kg.ha-l active ingredient, a.i.) is increasing soil moisture and aeration be currently used as a Pre-energent herbicide (Swain, 1970) . They could therefore and no post-emergent herbicide is applied. useful in minimizing the residual In the softwood nursery, propazine (1.1 effect of herbicides. kg.ha-l a.i.) j.s used as a pre-energent herbicide and nitrofen (9'o k9'ha-r a.i. ) The trials reported here exarnined the as a posl-emergent herbicide. (Simazine weed control properties and the effect on vras formerly used as a pre-emergent tree seedlings of a wide range of pre- herbicide in the softwood nursery but. its and post-emergent herbicides. Many had not use has been discontinued. Its long been used before in Western Australian residual life in the soil (swain, 197o) forest nurseries. Recomnendationsfor has been detrimental- to pines, and the future prescriptions are presented. weed population now consists of sPecies that tolerate it. ) In both nurseries the I. SOFTWOOD NURSERY pre-emergent herbicides are appl ied irunediately after seeding. METHOD Many researchers have studied the Tria1 plots were 30 n long and 1.2 rn effects of herbicides in both softwood wide (the normal h'idth of a nursery bed). and hardvroodforest nurseries with the Each contained six rows of P. -radiata aim of clarifying crop plant and weed seedlings. responses so that effective herbicide regirnes can be prescribed. The pre-emergent herbicides tested in the softwood nursery were nitrofen "Tok Kurth and Van Dorsser (1969)' for (trade name E-25") 'diphenamid example. studying three pre-emergent ("Enide 50") and propazine ("Gesarnil"). herbicides, found that propazine and The post-emergent herbicides tested vJere chlorthal were effective for use with nitrofen. gllptlosate ("Round-up") and a P. radiata, and that the tree seedlings mixture of terbuthylazine and terbumeton "Caragard" could tolerate very high aPplication rates ( ) . The herbicides were aPPlied with a the necessity for a great number of logarithmic sprayer (Fig. f) . This replications. machine applies a continually decreasrng amount of herbicide across a plot so that a wide range of application rates can be The logarithmic sprayer aPPl ied tested. Using a known initial application 138 1.ha-l of herbicide per plot through "T rate, the effective application rate at jel' nozzLes, ab a travelling speed of any place within the ptot can then be 60 m.rnin-r. The travelling speed was calcutated. The logarithmic sprayer wag tirned by pacing one-metre steps along a used in these trials because it obviates marked tape, to a one-second pulse.

!'IGUREI: The logarithnic sprayer used to apply a consistently decreasing amount of herbicide across the trial plots

TABLE I Application rates (kg.ha-r a.i.; of herbicides applied to softwood nursery plots

Eerbi.cide I a.1. Initial rate Final rate

Nitrofen 25 lo. 9t 1.90 Pre- Dj.phenamid 50 IO.26 1.30 ernergent Propaz ine 50 3.73 o.09

Nitrofen 25 r6.78 2.I8 Post- Glyphosate 36 o.67 o.09 emergent Ter bu thyla z i ne- 50 3.73 o.o9 terbuneton There were two replications for each application rates rnere highest, the pre-emergent herbicide and one replicati.on distance to where each vreed species was no for each post-emergent herbicide. Table 1 longer controlled was measured. This t1'as shows the initial and final application generally taken as the point at which rates across the plot for each herbicide. cornpetition became adverse to the pines. Some preliminary screening h?as carried out The application rate of the herbicide at to determine the most likely range of this point was then calculated for each effective application rates for each weed species. herbicide. There were no control plots because sorne degree of weed suppression is Since none of the herbicides damaged considered necessary. the pine seedlings, no assessment of the seedlings was undertaken. The pre-emergent herbicides were RESULTS applied when the pine seed was solrn in mid- october, nine nonths prior to planting out Table 2 shows the conparative the seedlings, The post-emergent effectiveness of pre- and post-emergent herbicides were applied 55 days after herbicides, indicating for each the sowing, when germination of the pine application rate at lrhich weed control seedlings was completed. was effective without damage to the pine seedlings. Also included is a cost per Effectiveness was assessed lol days hectare (chenicals only) for spraying at after appLication for the pre-emergent these rates in 1979. herbicides and 52 days after application for the post-emergents, From the Nitrofen and propazine were the two initiation point of each p1ot, where most successful pre-emergent herbicides.

TABLE 2 Effective rates of application, cost and effectiveness ln controlling weeds for pre- and posL-energent herbicides in the softwood nurserv tri.a1

Initial Effective Cost,/ha Weeds not Herbicide r ate 1979 controlled .i\ 1kg.ha-l a. (k9.ba-' a. i, ) ($ Aust ' )

Nitrofen 10.91 3.86 96.95 1*. 8, tt, t2

Pre- Diphenanid IO.26 4.46 118. 13 I, 4, 5, 8, TL, ernergent L2

3.73 o. 09 Ir IIr IJ

Ni trofen 16,78 10.50 264.20 6t 7,8,9, lo

LL uryPrru>q Ls o,61 o.24 L2.25 6, 7, 8, 9, emergent Terbuthylazine- 3.73 1,86 22.20 2 te rbumeton

*Key to weed sPecies l. Cgnodon dactg fon 6. Anagallis arvensis IL. Echinochloa crusgaLfi 'l 2. ConvoTvuJus arvensis . Rumex aceXoseLla !2. Trifoliun subterraneun 3. Arctotheca caTendufa B. Sonchus ofexaceus rJ. utgtLdLt4 >allvutt!4ttr ., . cQ'l.lttulu 11!9L atu 9. Lotus nanot 5. ?TichocJ-ine spathuTatun lo. conzga bonatiensis Neitber affected the gernination and and each contained six rows of growth of pine seedlings, even at their E. divers icoJ-or seedlings. highest rates of application. While propazine is nuch cheaper to apply for The pre-emergent herbicides tested satisfactory weed control, it was not were nitrofen ("Tok E-25"), diphenanid effective in controlling EchinochLoa ("Enide 50"). propazine ("Gesamil") and crusgaffi, Cqnodon dacxgTon and Digjtatja chlorthal ("Dacthal") . They \aere applied sanguinalis, a1I sunmer-growing grass at the time of sowing in January (mid- species. Nitrofen, however, was capable sumner). The post-emergent herbicides used of effectively controlling D. sanguina-Lis, were nitrofen' glyphosate ("Round-up"), a and gave linited control over the other mixture of terbuthylazine and lerbuneton spec]'es. ("Caragard"), and nonosodium methylarsonate (MSI4A) ("Daconate 8"). They were applied Of the post-emergent herbicides ' 30 days after the pre-energent herbicides, terbu thylaz ine -terbume ton and nj.trofen lvhen the kalri seedlings vrere at the six- proved to be the nost effective. leaf stage (approximately 5 cm tall) r this Glyphosate was not totally effective is because eucalypts are more prone than (Swarbrick, within the range of applications tested, pine seedlings 1976) to but to increase the application rate damageby the herbicides used in this would probably result in damage to the trial, lthich are laf,gely for the control pine seedlings (increased application rates of broad-leaved weed species. f glyphosate had been observed to danage P. radiata seedlings in preliminary There were two replications for eacb tr ials / . herbicide and control treatment. The logarithmic sprayer was used' as in the Nitrofen destroyed E. crusga-ZJi at all softwood nursery, to distribute the appl-ication rates across the plot. herbicide at a steadily decreasing rate Terbu thylaz ine-terbumeton was the most across the plots. Table 3 shows the effective in conLrolling the broad initial and final application rates for spectrum of weedsi however, it can control each herbicide. E, crusgalli effectively only if it is sprayed immediately after emergence. It was observed to cause sone damage to pine The assessment techniques d i f fered seedlings at 8 kg.ha-r a.i. in preliminary from those used for Lhe pines because, field tr ials. while weed conlrol was regarded as the prime objective in the softwood nursery, the effect of the herbicides on the tree 2. HARDWOOD NURSERY species was the nost important factor in the hard\,r'oodnursery. Here, seedling METHOD counts vrere regarded as a better Trial plots lr'ere the same size as indication of treatnent success than a chose in the softwood nursery (3o x I.2 m) , visual assessnent of weed or tree

TABLE 3 Apptication rates (kg.ha-r a.i.) of herbicides applied to hardwood h'rrc6ru hl ^1-.

Herbicide g a.i. rnlt1a_L rate Fi.nal rate

Nitrofen 25 t4 .91 1.90 Pre- Diphenamid LO.26 r.30 emergent Propaz]'ne 50 3.73 o.09 'I chlorthal 75 L4.78 ?O

Nitrofen 25 16.78 clyphosate 36 o.67 o.09 Post- Te!buthylazine- 3.13 o.09 emer9enc terbumeton MSMA 80 o.09 seedling growth. Of the post-emergent herbicides, ler buthylaz ine-terbuneton gave unsatisfactorlt Each 30 m plot had seven I n sub-plots karri survival. The anomalous survival located along it at a 5 n spacing from the figure for the first sub-plot (O-l m along beginning of the plot. In each sub-p1ot the plot) vras caused by complete survival the number of tree seedlings per row and in an outside row of the bedr the other thei.r top height (assessed as the mean five rows in the plot contained very few doninant height) were recorded two nonths seedlings. This may have been due to a after the application of the pre-emergent sprayer rnalfunction or to a light wind, herbicides and one nonth after the causing the herbicide to drift despite the application of the post-emergent herbicides. plastic shield surrounding the spray. In addition, the presence and abundance of weed species were recorded on a subjective Glyphosate produced acceptable karri scale of ground cover ranging from O survival only below an application rate of (nil cover, i.e. total r,reedcontrol) to 5 O.12 kg.ha-r a.i. Nitrofen had only (total weed cover) , a value of I (2 weeds mininal effects on karri survival at per row, slight occurrence) being regarded appli.cation rates above 8.91 k9.ha-l a.i., as effective weed control. This figure and MSMAproduced only marginal survival is the equivalent of 30 smal1 weeds per above an application rate of O.98 kg.ha-I square netre of nursery bed. At this density of weed growth karri development and growth are not seriously inhibited, Tables 4A and 48 contain karri height Each weed species was identified, and a growth data for both pre- and post-emergent point in the plot rrhere control ceased to herbicide treatments. be effective was assessed (i.e. where weed cover exceeded 1 on the subiective Tf ^nnaAt"q fh^l- fha hra-amard6h+ scale ) . herbicides, while producing higher kalri survival rates (Figs 2A and 28), also tend Height was once more assessed three to produce taller seedlings, Of the pre- nonths afler treatment in the plots treaLed energent herbicides nitrofen seems to alLow with the two most effective pre-emergent the greatest height growth at most rates of herbicides. This was necessary because application. When used as a post-energent, some differences in height growth had however, it seems to have an inhibiting become obvious between the treatments. effect on height growth, although not to the same extent as glyphosate or RESULTS terbu thylaz ine-terbume ton .

Karri survival, conpared with the The small size of the seedlings in optimum stocking for karri nursery beds sections of the control treatnent is due (23 seedlings per metre) , is shown for to weed competition. pre- and post-emergent herbicides in Figures 2A and 28 respectively. (The The two herbicides to shovr greatest figures show mean results for the two promise for weed conlrol hrere nitrofen replications. ) (used as a pre-emergen!) and diphenamid, The results of the second height growth Of the pre-emergents, only propazine assessnent, carried out on these plots significantly reduced karri seedling three months after spraying, are given in gernination and survj.val. OnIy at Table 5 (data for the two replications application rates below O.5 kg.ha-r a.i. have been averaged ) . did propazine allow an adequate karri stocking r all other pre-emergent Diphenamid inhibited karri heigh! herbicides tested gave acceptable karri gro\a'th significantly three months after survival rates. application. At three of the application rates there were significant growth The poor stocking in sections of the differences (p < O.O5) between the two control (untreated) plot was caused by herbicide treatments. At all other extrene competition from Runex aceXoseTl"a application rates, the nean dominant and Chenopodiun puniTo, both of which heights in the nitrofen treatment exceeded create a dense ground cover. those in the diphenamid treatments. FIGURE 2A: Karri seedling survival I weeks after treatment wj.th pre-energent herbicides

KEY!

Nitrofen

Diphenamid

Propazine

Chlorthal

Control

t0 15 20 Distance alohg bed (m)

9,. FIGURE28: Karri seedling survival 4 raeeks after treatment with post-emergent E20 herbicides

KEY:

: t5 Nitrofen

'i clyphosate :10 Terbuthylazine- terbuneton E 2- MSMA

Control

t0 t5 20 Dist a nce along bed (m) TABLE 4A Mean dominant height of karri seedlings (cm) two nonths after pre-emergent herbicide appl-ication

Distance along bed (m)

Herbicide o-I 5-6 10-L1 15-16 20-2L 25-26 29-30

Nitrofen 6 o Diphenamid 4.5 6 Propazine 4 4

Chlorthal 4 i

Control 5 ?

TABLE 48

Mean dominant height of karri seedlings (cn) one month after post-emergent herbicide treatment

Drstance along bed (n)

Herbicide o-1 5-6 10-t1 ls-16 20-21 25_26 29_30

Nitrofen 3 4.5 4,5 Glyphosate 1 2 2 4.5 'l Terbuthylazine- ? I J 4.5 terbume lon MSMA 3

Control 3.5 1 5

TABLE 5 Mean height growth of karri seedlings on plots sprayed vrith nitrofen (pre-energent) and diphenamid, three monlhs after lreatmen!

Herbicide Distance along Application Mean dominant bed (m) rate height (cm) (Kg.na'a,r.)

14.9I 9.29 ! 2.O5* 5-6 1o,49 11.08 t 2.86 10-1I 7.39 13.95 t 3.Ooa Ni trofen t5-15 5.19 13.98 ! 2.954 13.96 J 3.744 25-26 2 -57 II.74 ! 3.22 'I -30 On 29 LJ.ZL ! L. T'

LO.26 7.O8 ! L.92 't 5-6 .2L 5.73 1 0.97a to-11 5.08 6.25 r 1.O94 Diphenamid I5-16 J.J/ 6.2I ! L.2Ia t Ft 1I.15 1 2.93 2s-26 L.77 rv,zJ a I.5 tt 29-30 1.30 11.69r 0.66 * indicates 95t confidence interval about lhe mean a indicates a significan! difference at p < O.O5 belween karri height growth after treatment ra'ith herbicj.des at comparable rates of application The results of the assessnent of r,reed ptots, aI1 the pre*emergent herbicides control effectiveness, based on the offered a good degree of weed control. subjective assessment scale of I to 5, are ProPazine was the most effective of the given in Figures 3A (pre-energent pre-emergents as it gave satisfactory herbicides) and 38 (post-emergent weed control at an application rate of herbicides), O.9 kg.ha-r a.i, (approximately $11.50 per hectare, I9?9); however, it caused severe When conpared to the control (untreateC) karri mortality (Fig. 2A) . Chlorthal was

FIGURE 3Ai Pre-emergent herbicide weed control in the hardrrood nursery.

;^ KEY i

.: Nitrofen o, Diphenamid

Propazine

,'.,. chlorthal ,/ Control 3

t0 l5 20

Distance along Deo (m)

FIGURE383 Post-energent herbicide weed control in the hardwood nursery

----r r___-- KEY: .: E3 Nitrofen

1""'"" clyphosate ': Terbuthvlazine- terbuneLon

MSMA

Control !l B

lo 15 20

Distance along bed (m) only satisfactory at application rates Except for nitrofen, the post-emergen! higher than 7,3 kg.ha-' a.i., while herbicides decreased karri survival belo\{ diphenamid rarassatisfactory at the required nursery stocking level. application rates above 2.7 kg'ha-' a.i. Furthermore, they achieved weed control Both of these herbicides appeared to have only at high rates of application. no detrimental effecLs on karri qermination and survival. Of the two pre-emergent herbicides that gave both satisfactory weed control and ceneralLy, the post-emergent satisfactory karri survival rates, herbicides gave less effective weed diphenanid at the appropriate rates of control than the pre-emergent herbicides. application severely reduced karri height only terbuthylazine-turbuneton hras growth when compared with nitrofen and the effective at most application ratest untreated control. neither MSMAnor glyphosate showed effective weed control at any application In the karri nursery, therefore, a rate. Nitrofen showed satisfactory pre-emergent application of nitrofen at control of monocotyledonous species at an apptication rate of 3.65 k9.ha-l a.i. application rates above 2.11 kg.ha-l a.i., would be the most effective weed control although its effectiveness as a post- treatment. at the same time allowing emergent herbicide is inferior to that when satisfactory karri. survival. Although a it is used as a pre-energent. post-emergent herbicide should not be necessary, a further application of DISCUSSION nitrofen at a rate of 8.9I kg.ha-l a.i. should prove effective. weed ccntrol in both nurseries was best achieved using pre-energent herbicides. Hartley (1964) suggests that the main In the softwood nursery none of the disadvantage of pre-emergent herbicides is herbicides affected the P. radiata their dependence on subsequent climatic seedlings at any of the application rates. conditions for their effectiveness. This The most effective and least costly has led to variable results h'ith the use herbicj.de application would be a pre- of pre-ernergent sprays. However. they are emergent appli.cation of propazine at used widely where irrigation is practised O.49 k9.ha-r a.i, ($6,80 per hectare, 1979). and are effective because the assured Alternatively, nitrofen at a rate of supply of noisture decreases the 3.86 kg.ha-l a.i. could be used. but this inportance of the general clinatic vrould be nuch more expensive ($96.95 per conditions. hectare, 1979), Neither of these prescriptions wi 1I completely control With this in mind it is likely that cgnodon dacxgfon, a perennial weed species, pre-emergent herbicides will continue to or Echinochfoa crusgafTi, However, most be the most effective herbicides for use other weed species are adequately in Western Australian forest nurseries. controlled by these pre-emergent herbicides. CONCLUSIONS Post-energent herbicides in the softwood nursery were not as successful as Pre-emergent herbicides proved to be the pre-emergents in controlling weeds. nost successful in reducing weed However, g1!'phosateat O.2 kg.ha-la.i., conpetition in both the hardra'oodand terbu thylaz ine -terburneton at I.86 kg.ha-l soflwooC nurseries. Of these propazine a.i., and nitrofen at to,50 kg.ha-] a.i. and nitrofen were the most effective in provide partial weed control. both nurseries. Hor,Jever.propazine is not effective against monocotyledonous species. In the hardwood nursery, most of the It also adversely affects karri germination pre-emergents controlled vreeds effectiveLy, in the hardr,/ood nursery, and is hence not Lotus ninor being a rnajor exception. suitable for use there. Neither herbicide However, several of Lhe herbicides also has any effect on the gernination and severely affected the germination and growth of pine seedlings. survival of the karri seedlings. Only nitrofen and diphenanid at aLl rates If a post-emergent application is tested did not affect karri. necessary then nitrofen can be used in both

lo nurseries, although it is not effective KURTH,I.R. and vAN DoRSSER,J.C. (1969). against dicotyledonous species. Tolerance of ten tree species to TerbuthyLaz ine-terbuneton can also be propazine, dacthal, and linuron pre- used in the softnood nursery, where it emergence sprays on seedbeds. Research does not affect ehe tree seedlings. Leaflet 26, New zeal.and Forest service. SWAIN,D.J. (1970). llerbicide residues in NOT E the soil. Agricultural Gazette of since the trials were carried out, New south Wales 81, 4oo-4o1. nitrofen has been withdrawn from the SWARBRICK,J.T. (1976). The AustraLian market in Australia. WeedControl Handbook. (Third ed.). REFERENCES uo*3li3l"il'31;.'?ilfrT:''":::!li'113.,,.n HARTLEY,c.S. (1964). Herbicide behaviour into weed control in forest nurseries. in the soil. In: The Physiology and New zealand Weed and Pest control Biochemistry of Herbicides (Ed. Conference, Proceedings 24, 56-58. L.J. Audus). London, Academic Press. pp.11l-16r.