THE EFFECTS OF POST-EMERGENCE HERBICIDE TREATMENTS ON SUGARCANE IN SOUTH AFRICA. -. harvest, the crops had recovered. Yield reductions were

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1 Proceedings of The South African Sugar Technologists' Association June THE EFFECTS OF POSTEMERGENCE HERBICIDE TREATMENTS ON SUGARCANE IN SOUTH AFRICA By P. E. T. TURNER South African Sugar Association Experiment Station, Mount Edgecornbe Abstract Results of nine postemergence herbicide phytotoxicity experiments are reported. The experiments were conducted on medium to heavy soils at Pongola in the northern irrigated part of the industry or on light soils at Shakaskraal on the Natal north coast. Tests were conducted using the recommended rates of herbicide combinations and double these rates, applied directly over the sugarqane foliage at a susceptible stage of cane growth (about 400mm leaf ). The standard treatment, diuron + 2,4D + S, was included as a basis for comparison, and alternative standards such as paraquat, or Lasso + atrazine + paraquat, were included when new com, binations used for a similar purpose were tested. Of the newly registered herbicides, Bladex Plus + S was safer to use than the standard diuron + 2,4D + S, while the effects of Bimate + S appeared to be similar to those of the standard treatment. MSMA was more damaging than the standard treatment but not as phytotoxic to cane as was paraquat, either alone or in combinations with diuron. The new combinations of registered herbicides were in general no more phytotoxic than the equivalent standard treatments. Symptoms of phytotoxicity included leaf chlorosis and necrosis, stunting, and the effects on stalk. Where these effects persisted until harvest yield reductions were also measured. In general, most combinations caused mild to severe early stunting of the cane but by the time of. harvest, the crops had recovered. Yield reductions were common when the cane was sprayed at a late stage of growth ( > 500 mm cane leaf ). Reduction of yield would not be expected from any of the treatments tested provided that they were applied at the optimum cane growth stage or that the spray was directed away from the sugarcane foliage. Introduction Weeds competing with sugarcane have been shown to reduce yields substantially under South African conditions (Thompson4). Traditional methods of handweeding and mechanical cultivation in sugarcane production have now largely given way to weed control by means of herbicides. This is due to the comparatively long duration of weed control obtained with herbicides; to the fact that selected chemicals control weeds in the cane row without damaging the crop appre~ia~bly; and to the ability of herbicides to kill weeds before they compete significantly with the crop. A problem nevertheless arises when a herbicide that controls weeds effectively may cause some damage to sugarcane as well (Richardson" Richardson3). Symptoms of herbicide damage may take the form of chlorosis or necrosis of the leaves, swelling of root bands, poor germination or tillering, spikiness of leaves or stunting of growth. A reduction in cane yield may result. Thus any herbicide which is potentially useful in sugarcane must be tested for its possible phytotoxic effects on the crop. This is done by means of phy Jtotoxicity trials which involve tests conducted initially in pots, and subsequently in pre and postemergence field experiments with plant and ratoon cane growing on two soil types. Standard combinations of pre or postemergence her,bicides, applied at the recommended rates and twice the recommended rates, are included in the experiments for purposes of comparison. The results of nine postemergence experiments are reported here. The standard postemergence treatment in cluded in the experiments was diuron + 2,4D + S (sur factant). Previous work with 2,4D has shown that the stage growth at the time of application and the method of application both play important roles in determining the degree of phytotoxicity caused to cane. Applications made directly on the cane row caused yield reductions when there were more than three unfurled leaves per shoot at the time of application. The reductions in yield were less when sprays were directed lover the interrow and away from the sugarcane foliage at the same growth stage (Richardson3). Ln these experiments it was desirable to include a treatment which was more likely to cause some herbicide damage to the crop and therefore the' herbicide combinations were applied directly over the cane foliage at a susceptible stage of growth, when leaf was about 400mm. Sometimes, when new herbicide combinations were being tested for the control of weeds in unusual circumstances, the combinations currently recommended for such situations were also included in the experiment. Since NCo 376 is currently the most widely used variety in the South African sugar industry it was used in all the experiments reported here. Materials and Methods The experiments were conducted using a randomised block design with six replications. Plots consisted of five or six cane rows eight metres long, one metre at each end being discarded at the time of harvest. The two outer rows were also discarded, leaving net plots of three or four rows six metres long. Experiments were conducted either on plant or ratoon cane at Pongola in the northern irrigated area of the industry or at Shakaskraal on the Natal north coast. A floodjet was used to apply the chemicals in all experiments. The output was approximately 300 llha and the pressure used was I00 to 200 kpa. Symptoms of leaf were rated using a linear L 9 scale (I = no effect and 9 = dead). counts and s to the top visible dewlap were recorded at intervals throughout the period of crop growth. The cane in the experiments was burnt prior to harvesting and each plot was sampled for sucrose, brix and moisture determinations. Soil characteristics at the site, stage of crop growth at the time of spraying, month of spraying and weather conditions at the time of spraying and submuently are presented for each experiment in TBble. Details offhe chemicals which were used in the experiment are given in Appendix.

2 A Proceedings of The South African Sugar TecHnologisfs' Associalion June 98 Results and Discussion Experiment In this experiment with plant cane growing in a sandy loam soil, Lasso + atrazine + paraquat was included as an extra standard treatment for comparison with Dual + ametryne f paraquat. All the treatments which included paraquat ed the cane foliage severely. Double rates were lonly slightly more severe than single rates and all symptoms disappeared in time. Stunting stalks at an early age was marked as a result of all herbicide treatments and the paraquat treat ments were more severe than the standard treatment, diuron + 2,4D + S. Differences in stalk, although not very obvious, persisted to the time,of harvesting the crop when it was 5,5 months old. Although yield differences did not obtain a level of statistical significance, low yields were associated with short stalk s, indicating that phytotoxic effects may have been real. In general the results suggest that treatments including paraquat were more damaging than was diuron + 2,4D + S, but that Dual was slightly less damaging than Lasso in the combinations with paraquat. Following the treatments TABLE Experiment details Experiment No. or ratoon cane Soil series Month of spraying Cane leaf (mm) Rainfall on day of spray (mm) Within one week of spray (mm) Age at harvest (months) Makatini Makatini Makatini Maka tini April December January January September January December November November TABLE 2 on the crop, mean cane yield and crop characteristics following treatment with herbicides in Experiment Treatment Diuron i4~' S;... Diuron + 2,4D S... Lasso atrazine paraquat... Lasso atrazine paraquat... Dual atrazine + paraquat... Dual ametryne Jr paraquat... Dual + ametryne $ paraquat... 2,O, ,O + 2,..., +,O + 0,2.. 3,84 + 2,O + 0,4.. 5,76 + 2,O + 0,4.. 2, +,O + 0,2.. 5,76 $ 2,O + 0,4.. ratlng 8 DASt 2,7 4,s 5,s 4,7 5,o 5,s $ ,48 2,46 2,46 2,37 2,40 2,39 2,47 2,39 (OOO/ha) LL ,3 ~~DD%(O,OS) 2,25 LSD (0,Ol) 6,47 * Surfactant added at 0,2% v/v t DAS Days after spraying f MAS Months after spraying TABLE 3 on the crop, mean cane yield and crop characteristics following the harvest of Experiment 2 Control... Diuron + 2,4D'+ S"... Paraquat... MSMA+S'... Bimate + S... Bimate + 2.4D'/ S' '.. Diuron + sencor + TCA ' Dual + arnetryne + TCA 4 S' 2,O +, ,6... 4, , ,0 + i,&....,6 +,4 +,9 2,O +,s + 2,38 5 DAS,3 63 4,s 2,7 2 3 Early crop effects ,75,73,72,s,73,77,,72 pop'tion (000fha) mass 0,7 0,68 0,64 0,67 0,65 0,68 0,65 0,62 (tlha) cv % 5,o 72 LSD (0,05) 7,94 7,67 LSD (0,Ol) 0,66 0,29

3 Proceedings of The South African Sugar Technologists' Association June 98 0 with paraquat, early stunting of stalks indicated that double Experiment 2 rates were only very slightl~ more damaging than sing' ln this experiment with plant cane growing in a sandy rates, whereas with diuron + 2,4D + S the difference besoil, paraquat was for with tween the standard and double rates was more marked. s, however, showed that the effects of MsMA. paraquat treatments were more persistent than those of Symptoms of leaf soorch were apparent soon after spraying and were more marked due to spraying with paraquat than diuron + 2,4D + S. Diuron + 2,4~' k S"..... Dual arnetryne... Dual + ametryne + paraquat... Dual ametryne S... Dual + ametryne + S... Bladex Plus S Bladex Plus + S TABLE 4 on the crop, mean cane yield and crop characteristics in Experiment DAS,s MAS,s MAS I I I I cv %,8 7,0 LSD (0,05) 20,94 0,35 LSD (0,Ol) 28,lO 3, TABLE 5 on the crop, yield and crop characteristics in Experiment 4 Diuron + 2,4D'+ S"... Diuron + 2,4D + S... Arnetryne MCPA S... Ametryne + MCPA + S... Ronstar + MSMA + S... Stomp + MSMA + S... Bimate + 2,4D 4 S... Rate in kg or,.!. 2,O, ,0 2,... 2,s, ,O 2,... 0,75 + 2,6... 2,O + 2,6... 3,O $, DAS ,8 $ ,72 2,58 2,56 2,59 2,54 2,60 2,66 2,45 w@/ha) CV % 69 3,4 LSD (0,05) 2,40 5,5 LSD (0,Ol) 6,68 7,39 TABLE 6 on the crop, cane yield and crop characteristics in Experiment 5 Control..... Diuron 4 2,4:~ 4 s.... Paraquat + diuron... MSMA + diuron... Ametryne + Sencor... Birnate..... EL ,4:~ + s... Ametryne + 2,4D + S... 4,O 2,... 0,s +,s ;8 + 2,8... 3,o...,2 2,... 4,8 + 2,... 3 DAS 3 MAS 3 MAS mass 7;h pop'tion (000ha) Mean yield cv % 8,3 3,9 LSD (0,05) 0,24 2,5 LSD (0,Ol) 3,74 6,3

4 02 Proceedings of The South African Sugar Technologists' Association June 98 with MSMA. Other treatments produced relatively little leaf and all visible symptoms disappeared in time. MSMA at 6,5 //ha resulted in less leaf, stunting of stalks and reduction in stalk than did paraquat at 3,O [/ha. However, none of these differences was substantial. Paraquat and Dual + ametryne + TCA + S appeared to be more damaging than other treatments and resulted in lower yields (ns), whereas there was no indication of a yield reduction due to the standard diuron + 2,4D + S treatment. Some herbicide treatments reduced the mass per stalk but the effects were largely overoome by increased stalk s. in the rates at which herbicides were used became unimportant. Experiment 5 MSMA + diuron again caused far less severe leaf than did paraquat + diuron, the effects of which persisted in terms of stalk and ultimately in yield (ns). None of the other her,bicide treatments including the standard diuron + 2,4D + S treatment, reduced yields to a statistically significant extent in a trial which had a relatively high coefficient of variation (4%). Paraquat + diuron also caused stunting which persisted through to harvest, a lower mass per stalk, and a yield de Experiment 3 pression which did not quite attain a level of statistical significance. All the other herbicide treatments caused early chlarosis and necrosis resulted soon after spraying stunting but yields were affected slightly if at all. lncreased all herbicides except Bladex Plus. Similarly, all treatments stalk s due to these treatments tended to compenstunted growth except Bladex Plus, and the effects persisted sate for the reduction in average stalk mass. until harvest. The results indicate that treatments which included para ~~~~~i~~~~ 6 quat caused greater initial stunting of the crop than did diuron + 24D + S and all the other herbicides, but cane A typical pattern of early crop stunting was apparent due yields were not affected. The addition d paraquat to Dual to all herbicide treatments in this experiment. + ametryne increased the phytotoxic effects considerably which included paraquat were again more damaging than in the early stages of crop growth. Even a very high rate was diuron + 2,4D + S. Dual + ametryne in combinaof ametryne in combination with Dual was less damaging tion with paraquat was more damaging than was Lasso + than were the paraquat mixtures. atrazine with paraquat, despite the fact that the latter combination contained four litres of paraquat per hectare, com The application of Bladex PIUS resulted in the highest yield pared with only three litres per hectare in the former which was associated with a heavy stalk mass. treatment. Experiment 4 Marked leaf soorch symptoms and stunting resulted from all herbicide treatments soon after spraying. The stalk differences persisted until the time of harvest and contributed to the depressed yields due to all treatments, although the yield reduction from applying Ronstar + MSMA + S did not attain a level of statistical significance. The cane was at a later stage of growth (600 mm'leaf ) at the time of spraying than was the case in the other experiments reported here, and this factor is thought to be mainly responsible for the persistence of treatment effects. Relatively small yield differences were statistically significant because of the high degree of precision of this trial. The standard treatment was no less damaging than were other test treatments. It was also apparent that, at the late stage of growth at which this experiment was sprayed, differences The highly significant yield reductilons reached in this experiment can again be associated with a later stage of cane growth (600650mm leaf ) at the time of spray application. Apart from the combinations which contained paraquat, none of the herbicide treatments was more phytotoxic than the standard diuron + 2,4D + S treament. Yield reductilons at the time of harvest were associated with the crop stunting which occurred after spraying. Experiment 7 Early leaf symptoms werie apparent following most treatments but they were not always associated with subsequent reductions in stalk. The standard diuron + 2,4D + S treatment caused little leaf but severely stunted the cane. Velpar K5, even at low rates, produced leaf symptoms but caused little stunting. TABLE 7 on the crop, yield and crop characteristics in Experiment 6 Diuron + 2,4~' + S"... Lasso atrazine paraquat... Dual ametryne paraquat... Dual ametryne 2,4D + S... Dual + ametryne + S... Ametryne + ioxynil + 2,4:~.. Lasso + diuron + ioxynil + 2,46'.. Diuron + paraquat + S.... 4,O 2,.. 3,84 2,O 0,s.. 4,O 3,O 0,6.. 4,O 5,O + 2,.. 4,O + 6,O... 5,O +,75.. 3,84 + 3, ,6 + 0,4... MAS MAS ,,73,82,70,,93,83,,74 (OOO/ha) cv % 738 LSD (0,05 9,80 LSD (0,0) 3,26

5 p~ Proceedings of The South African Sugar Technologists' Association June Although differences in yield were not statistically significant, they were clearly associated with harvested stalk. In most cases reduced stalk s were associated with increased stalk s. No herbicide treatments in this experiment suppressed cane yields more than did diuron + 2,4D + S. Experiment 8 symptoms were evident following all treatments but were relatively mild except in the case (of MSMA + diuron. Early stunting d cane was also apparent follow ing all treatments but the effects,of double rates of Birnate and MSMA + diuron were not greater than were those due to the single rates. Only Velpar + diuron at a high rate resulted in a statistically significant reduction in cane yield, but treatment with the lower rate of Velpar + diuron and with diuron + 2,4D + S also tended (ns) to result in lower yields. Shorter stalk s at the time of harvest were often associated with higher stalk s, the latter compensating for what would otherwise have had an adverse effect on yield. TABLE 8 and yield and crop characteristics in Experiment 7 Diuron+2,4D'$<... Diuron + 2,4D + S... Velpar K5... Velpar K5 (directed)... Velpar K5... Bladex Plus... Velpar... Velpar... Rate in kg or I... 2,0+,44 4,O + 2,... 2, , ,9... 2,O... 0,675..., ,s 4,8, ,3,s 4,3 4 4,5 3,8 2,24,95, 2,25 2,22 2,4 2,22 2,2 2,04 (000/ha) (tlha) TABLE 9 Early treatment effects on the crop, cane yield and crop characteristics in Experiment 8 cv % 7,o 0,7 LSD (0,05) 5,98 6,05 LSD (0,Ol) 2,66 2,76 Control Diuron 2,4D $ s... MSMA d~uron S... MSMA diuron + S... Birnate S... Birnate S... Velpar + diuron Velpar + diuron Rate in kg or I 8 DAS mass,05 0,96 0,98 0,98 0,,Ol 0,9 0,96 (rn) 2,68 2,55 2,64 2,58 2,60 2,63 2,58 2,56 pop'tion (000Iha) Mean yield CV % 5,6 5,3 LSD (0,05) 9,59 8,63 LSD (0,Ol) 2,87,58 TABLE 0 on the crop, yield and crop characteristics in Experiment 9 Control..... Diuron + ~P:D 4 s... Dual arnetryne... Dual + ametryne + paraquat Bladex Plus + S..... Ametryne + ioxynil + 2,4D Lasso + diuron + ioxynil + 2,4D Rate in kg or I 4,O 2,... 4,O 6,O... 4,O + 2,O + 0,4 9,O... 3,0 + i,i5.. 3,84 + 4,04 + ;4 22 DAS 32 2,7 4, ,5 MAS 96 topulation /, control 2,5 MAS mass 0,84 0,73 0,78 0,75 0,80 0,73 0,76 2, 2,76 2,80 2,78 2, 2,73 2,73 pop'tion (000/ha) Mean yield ,4 ED70,OS) 5,77 6,9 7,66 LSD (0,Ol) 2,22 0,3

6 04 Proc 'eedings of The South African Sugar Technologists' Associution June 98 Experiment 9 Early stunting and leaf symptoms were apparent following all treatments but the effects had disappeared by the time of harvest. However, those caused by applying Bladex Plus and Dual + ametryne were minimal. In this experiment flowering occurred in the unsprayed control plots and in those plots treated with Bladex Plus and Dual + ametryne, but not in the plots which received other treatments. Because flowering can affect yields of sugarcane, the differences in yield between treatments in this experiment may have been partially due to flowering. The treatments which caused the greatest amount of crop and stunting initially would prabably have depressed yields to a greater extent if flowering had not occurred. Newly Registered Three new herbicides, a number of new combinations and changes in rates (of application of older products have recently been registered. Phytotoxicity assessments were based on the results of the experiments reported here, and in some cases the results of additional experiments. Bimate Bimate has been registered for use as a pre or postemergence treatment in plant or ratoon cane. It oonsists of a mixture of tebuthiuron and diuron in a ratio of : 2 formulated as a 75% wettable powder (WP). Preemergence treatments on plant cane caused no damage whilst in pot trials where the treatments were applied over the cane ioliage, yields were markedly reduced in comparison with those obtained from unsprayed control plots (Anon*). The effects tended to be more damaging than those resulting from the standard diuron + 2,4D + S treatments, particularly in sandy soils. The three experiments reported here in which Bimate was included alone were experiments 2, 5 and 8. Single rates caused very little stunting at an early stage of growth and although yields were lower than those obtained when single and double rates of diuron + 2,4D I S were used in plant and ratoon cane respectively on a sandy soil, the differences did not attain a level of statistical significance. In Experiment 8 with ratoon cane growing in a heavy soil, stunting was marked at an early stage of growth but yields obtained when both single and double rates of Bimate were used proved to be superior to those obtained when the combination of diuron + 2,4D + S was applied at double the recommended rate. A subsequent experiment conducted in sandy soil showed that Bimate applied at the double rate stunted the cane severely and reduced yield. It is evident from these results that in sandy soils Bimate is slightly more phytotloxic to cane than is the standard diuron + 2,4D + S treatment. In heavier soils however the reverse appears to be true. BIad ex Plus This compound consists of a mixture of cyanazine and atrazine in the proportion 2: and is formulated as a 50% suspension concentrate. Results from a pot experiment showed reductions in fresh mass of plant cane in both light and heavy soils due to treatment with Bladex Plus. The effects were similar to those obtained when the standard treatment was used on a sand but less severe on heavy soil. Preemergence sprays d Bladex Plus in field experiments caused yields to be no different from those obtained when the standard Lasso + atrazine treatment was used. Lasso + atrazine in many experiments (Anon) has caused no yield reduction compared with the unsprayed controls. Hence Bladex Plus can be considered safe to use when applied to sugarcane fields before the crop has emerged. Bladex Plus was included as a postemergence treatment in Experiments 3, 7 and 9. Very little stunting of the crop was evident in the early growth period (of ratoon cane in a heavy soil, and the effect did not persist for long. It was far less severe than that produced by diuron + 2,4D + S. In ratoon cane on a light soil and in plant cane on a heavy soil no stunting occurred at any stage. Yields obtained after treatment with Bladex Plus were in all cases better than those obtained after treatment with the standard diuron + 2,4D + S, but only in one instance did this difference reach a level of statistical significance. Bladex Plus can thus be considered as a very safe herbicide for use in sugarcane fidds. Dual + ametryne + paraquat Pot experiments with combinations of Dual + ametryne or Dual + atrazine + paraquat showed that severe reductions in mass of plant material resulted after postemergence applications, whilst without paraquat Dual + atrazine had no adverse effects on growth (Anon). These oombinations were included in Experiments, 3, 6 and 9. Whenever herbicide combinations that included paraquat were used, severe stunting occurred. Only in two experiments did the effect of stunting diminish to any extent before the time of harvest. In Experiment 9 cane flowered in the unsprayed control plots, but flowering was inhibited in the plots treated with Dual + ametryne + paraquat and diuron + 2,4D + S. In the absence of flowering treatment differences would probably have been larger than those actually observed. The long period from the time of spraying to the time of harvest in Experiment may have accounted for the recovery in the treated plots in terms of stalk s. In most cases the yields obtained when this herbicide combination was used did not differ significantly from those obtained from unsprayed controls, or from plots treated with diuron + 2,4D + S or Lasso + atrazineo+ paraquat. However, the yields were always lower than those obtained from the unsprayed control plots and in Experiment 6 the yield was lower than that from cane treated with Lasso 9 atrazine + paraquat to a statistically significant degree. In this instance a higher rate of ametryne was used and this may have been responsible for the greater effect. Most treatments caused a reductiton in yield and this was probably associated with the late stage of crop growth at the time of spraying. It is probable that the effect of Dual + ametryne + paraquat on yield will generally be more severe than the effects of diuron + 2,4D + S and the severity will depend primarily on the stage growth at the time of spraying. MSMA + Diuron MSMA (monosodium methane arsonate) has recently been registered for use in sugarcane fields in South Africa. Since it is readily adsorbed and inactivated on contact with the soil it is used only as a postemergence treatment. Results from a pot experiment showed that the mass of plant material produced was reduced following treatment with MSMA when compared with the production from unsprayed control plots but the reduction was not as great as that resulting from treatment with the standard diuron + MCPA + S (Anon). MSMA was included in Experiments 2, 5 and 8. When paraquat or paraquat + diuron were included as standard late postemergence treatments, mofie leaf was noted

7 ; Proceedings of The South Afrcan Sugar Technologists' Association June 3 /' from the standard treatments than from the MSMA treatments. Similarly, early stunting effects were more prontounced following the standard paraquat treatments and eventual yields were more adversely affected (ns) by the paraquat than by the MSMA treatments. Yield reductions tended to be similar to or slightly greater than those when diuron + 2,4D + S was used on light soil, whereas the reverse was true on heavy soils. In general some leaf and stunting occurs soon after application of MSMA. The effect on yield is similar to that from using diuron + 2,4D + S, and it is slightly less than when combinations including paraquat are used. Newly Registered Combinations New oombinations of previously registered herbicides include the following :, Dual + ametryne + S : at higher rates of 2,O + 3,O ( or kg ). Dual + ametryne + 2,4D + S :,4,O + 2,O 2,5 +,44.,; Ametryne + MCPA/2,4D + S :,5 2,5 +,44. Ametryne + Sencor :,6 2,4 +,4. DS). Ametryne + ioxynil + 2,4D :,5 2,s + 0,675 (Actril DS). Lasso + diuron + ioxynil + 2,4D :, 2,2 + 2,O + 0,675. These treatments, with the exception of Dual + ametryne ; and arnetryne + Sencor, were similar to the standard diurlon + 2,4D + S treatment in #their effects on cane growth. Early stunting was clearly evident but yield reductions were usually not statistically significant except when the stage of cane groyth was later than mm leaf at the time of spraying. Dual + ametryne and ametryne + Senccrr were slightly less phytotoxic than the other combinations. APPENDIX Chemicals and formulations used in the experiments Conclusion The nine postemergence phytotoxicity experiments reported bere have shown that marked leaf and stunting of sugarcane growth is commonly caused by most herbicide combinations sprayed directly over the cane POW. The per sistence of these effects and reductions in cane yield depend largely on the stage of growth of the cane at the time of spraying. Differences in the severity of phytotoxic effects between treatments were most marked when the crop was young and indicated that most new herbicides and herbicide combinations were no more damaging to sugarcane than were the equivalent rates (either recommended or twice the recommended rate) of the standard postemergence treatment diuron + 2,4D + S. An exception was the oombination Dual + ametryne + paraquat which in three out of five experiments induced a marked early stunting growth and caused yields to be slightly lower than those from control plots. Bladex Plus (on the other hand showed very small effects at any stage of crop growth and it is therefore safer to use than the standard diuron + 2,4D + S treatment. In general, reductions in yield are unlikely to result from the use of recommended rates d any of the combinations tested, provided that they are applied at a young stage of cane growth or that spraying foliage is avoided to a large extent. In instances where full cover applications are necessary, severe leaf and early stunting may be exuected but vield reductions will be small if the cane is at a )oung stag; of growth (less than 400rnm leaf ) at the time of spraying. REFERENCES. Anon (6980). Unpublished reports. S. Afr. Sug. Assoc. Exp. Stn. 2. Richardson, F. E. (%9). Injury to sugarcane by 2,4D formulations. SASTA Proc 43 : Richardson, F. E. (2). Critical growth stages for 2,4D phytotoxicity to sugarcane in South Africa. SASTA Proc 46 : Thompson, G. D. (96). A weed experiment at Illovo. SASTA Proc 35 : Common name alachlor... ametryne... atrazlne... atrazine + cyanazine... 2,4D dimethylamine salt... 2,4D + ioxynil... diuron... diuron + tebuthiiron... hexazinone... hexazinone + diuron... MCPA (potassium salt)... metolachlor... metribuzin... MSMA... oxadiazon... paraquat... pendimethaiii... TCA... Trade name Lasso 384 EC... Gesapax 500 FW... Gesaprim 500 FW... Bladex Plus Sc... Farmers 2,4D Amine... Actril DS... Farmers diuron... Bimate 75 WP... Farmers du Pont Velpar... Farmers du Pont Velpar KS... Farmers MCPA... Dual 720 EC... Sencor 70% WP... Daconate 6... Ronstar... Gramoxone... Stomp 330 EC... Farmers TCA... Manufacturer/Distri butor Monsanto... Ciba Gejgy... Ciba Ge~gy... Shell... Triomf Farmers Organisation.. May & Baker Triomf Farmers organisation.. Elanco... du Pont... du Pont Triomf Farmers'organisa'tion.. Ciba Geigy... Bayer..... Diamond shamrock... May & Baker... Triomf Farmers Organisation.. S.A. Cyanamid Triomf Farmers ~rganisatjon.. Formulation* 384 g/r ec 500 g/r sc 500 g/r sc g/l sc 720 g/r sol c glrec 800 g/kg wp g/kg wp 900 g/kg sol p g/kg sol p 400 g/l' sol c 750 g/r ec 700 g/kg wp 720 g/r ec 240 g/r ec 200 g/t! sol c 336 g/r ec 950 g/kg sol p *ec = emulsifiable concentrate sc = suspension concentrate sol c = soluble concentrate wp = wettable powder sol p = soluble powder