Pathology ABSTRACT INTRODUCTION

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1 Pathology EFFECTS OF SOME NEMATICIDES ON PLANT NEMATODES AND SUGARCANE YIELDS Wray Birchfield USDA, Louisiana Agricultural Experiment Station Baton Rouge, Louisiana ABSTRACT Field application of some recently discovered nematicides has resulted in increased sugarcane yields in Louisiana. During the past 5 years, the following granular materials applied to plant cane gave the best nematode control and the highest yields in tonnage and sugar per acre: 2-methyl-2-(methylthio) propional-dehyde O-(methylcarbamoyl)-oxime (aldicarb); O,O Diethyl Op-(methylsulfinyl) phenyl phosphorothioate (Bay 25141); O-ethyl S-S-dipropyl phosphorodithioate (VC 9-104); and Ethyl 4 (methylthio)-m-tolyl isopropylphosphoramidate (Bay 68138). None of these materials was toxic to sugarcane at dosages used nor reduced sugar per ton. All helped to control nematodes, were effective at low rates and were easy to apply. The best of the halogenated hydrocarbons used was l,2-dibromo3-chloropropane (DBCP), which also increased sucrose in some years. Fburteen genera of plant nematodes were found associated with sugarcane in Louisiana. The most harmful species are believed to be the following: Me/oidogyne incognita, Pratylenchus brachyurus, P. zeae, Trichodorus christiei, Tylenchorhynchus martini, and Hop/o/aimus tylenchiformis. INTRODUCTION Few references are found in the literature on the effects of nematicides on plant nematodes and yield response in sugarcane. Most of the reports deal with the use of conventional halogenated hydrocarbons. Roman and Badillo (5) found different rates of DBCP reduced nematode populations when introduced to the field in irrigation water. However, the nematode population later returned and increased above the original. No significant differences in sucrose percent, cane or sugar per acre were obtained with this chemical and means of application in Puerto Rico. Dick (3) in South Africa applied ethylene dibromide (EDB), DBCP and 1,2-dichloropropane, 1-3 dichloropropene (DD) in 12 field trials. These chemicals increased sugarcane production an average of 9 tons per acre. Four of the field experiments showed increases with these chemicals which were significant at the 1% level and another 4 trials showed differences with these materials at the 5% level of probability. Due to the high cost of these materials in that area the economics of soil fumigation remained in doubt. Chu and Tsai (2) published results on the use of EDB and DD over a period of 3 crop years. EDB at 40 gals per ha and DD at 60 gals per ha gave increased yields of practical importance. The increased yields with EDE 1022

2 WRAY BIRCHFIELD 1023 and DD applied in spring and in autumn were enough for a substantial net profit. Hu et a1. (4) confirmed the beneficial results from soil fumigation of sugarcane in Taiwan with EpB, DD, and bbcp. These chemicals were not only effective against nematodes but stimulated andimproved cane roots. These' workers obtained 10-20% increases in tons per ha. An average of 4.5 tons increase per ha was obtained. This amounted to $16-21 of net profit per acre. Winchester (6) reported on the use of EDB, dichloropropene and Dasanit on sugarcane in Florida. These materials used in large dosages in" creased plant vigor and reduced root-knot nematodes. They were not phytotoxic at the high rates employed. More recently Winchester (7) reported on a series of experiments in Florida to determine the effects of newer type chemicals on nematodes and sugarcane yields. These nematicides were evaluated on both peaty muck and sandy soil against root-knot and other plant nematodes. Application of some of these materials resulted in striking yield responses. According to Winchester his results indicated that significant yield responses might be obtained with economic rates of some materials where the reduced vigor was due to nematodes. In other reports Winchester (8,9) used several nematicides to control root-knot and stunt nematodes of sugarcane. These materials increased sugar per acre by 29-38%. Wismer (10) applied DBCP to control Pratylenchus zeae in Hawaii. No significant differences in yields of sugarcane were obtained. Therefore, he did not consider the application of DBCP to sugarcane in Hawaii to be advisable. During the last 7 years intensive work has been done in Louisiana with the new systemic type nematicides applied to sugarcane compared with conventional halogenated hydrocarbons (1). The object of this paper is to report the effects of these systemics on nematode control and sugarcane yields in terms of tons per acre, sucrose percent, sugar per acre, and sugar per ton of cane. MATERIALS AND METHODS Field tests were made on Mississippi alluvial soil of the Mhoon series, predominately infested with T. martini, P. brachyurus, and T. christiei. Other kinds of nematodes were fewer in number. We used a randomized block design with 3-10 replications of each treatment in 2-3 row plots each feet long, with rows spaced 6 feet apart. The organophosphate and carbamate nematicides were applied as granular formulations in October or November at planting time, while the halogenated hydrocarbons, except 1,2-dibromo-3cchloropropane (DBCP) R, were applied 2 weeks before planting. Granular materials were distributed evenly in the opened furrow with the' seed cane at planting time and incorporated by disc-hillers as the cane was covered. The halogenated hydrocarbons were injected in the center of the row at l-ioot intervals with a fumigfrn 2 weeks before planting. An emulsifiable mixture of DBCP and pentachloronitrobenzene (PCNB) (Terrachlor) R was sprinkled in the open furrow at planting time at 8.6 lb of active DBCP and 8 Ib of PCNB per acre on a 6-foot row spacing. Granular nematicides applied in 1968 with a commercial, gravity type applicator, distributed the materials on top ofthe sugarcane at planting time. One row plots each 195 It long replicated 5 times were used. Two crops were harvested from this experiment. Miscellaneous

3 1024 PATHOLOGY nernaticides were used in small plots in , but dosages were reduced from previous experiments. Two to 3 soil samplings at approximately 3-month intervals were made after treatment to determine nematode control. These were made from I-pint soil samples collected with a I-inch diameter soil sampling tube inserted inches deep in the center of the rows. Six borings were composited from each plot from alternate rows (2 borings from each ft of row). The soil borings were standardized to -l-pint samples from each plot and processed by a modified water sieving and Baermann technique with a 24-hor separation time. The water from the Baermann apparatus containing separated nematodes was standardized to 100 cc for each sample. A 10-ml aliquot was placed in a Syracuse watchglass, and nematodes were counted on i the surface area with the aid of a stereoscopic microscope. The total number per pint of soil was then computed. During the growing season observations were made for phytotoxicity and groyvt:,ii responses. In the fall, I year after planting, the sugarcane was harvested by hand. A tractor-drawn hydraulic lift equipped with scales was used to record the weights from each plot. Sucrose' content was determined from 5 stalks taken from each treatment by conventional methods. The pounds per plot were converted to tons per acre, and the sugar per ton and sugar per acre were calculated by standard computations. R SULTS Results of the tests are given in Tables 1-7. In 'the 1966 tests all treatments effectively reduced the nematode population by April 15. (Table I) Nematode control did not persist through harvest and final sampling on October 25. The lowest nematode counts were recorded,with I,3-dichloropropenes and methyl isothiocyanate mixture (DD-MENCS) (Vorl ex) R at both sampling dates; I, 3-dichloropropenes and related chlorinated C 3 hydrocarbons (I,3-D) (Telone) R; and I,3-dichloropropene and I,2-dichloropropane mixture (DD) (D-D) R. Intermediate reductions in nematode populations were obtained with 2,3,4,5-tetrachlorothiophene (TD-I83) (Penphene) R; 2-methyI-2- (methylthio) propionaldehyde 0- (methylcarbamoyl) -oxime (aldicarb) (Temik) R; and O-ethyl S)S-dipropyl phosphorodithioate (VC-9I04) (Mocap) R which produced from 2.3 to 4.6 tons of sugarcane per acre increase without adverse effects on sucrose. This is 13-19% increase in sugar per acre. The 1967 test recovered few plant parasitic nematodes from each treatment at the March 21 sampling (Table 2). This included the nontreated check, but the number of nematodesincreased greatly in all treatments by the November 6 sampling date. The fewest were recorded in thedbcp, the DBCP-PCNB, and Mocap treated plots. There was no reduction with Temik and O,O-diethyl 0-[ (p-methylsulfinyl) phenyl] phosphorothioate (B-2514I) (dasanit) R at the first sampling date. Fewer numbers were recorded at the second sampling, although these numbers were significantly lower than the control. The DBCP PCNB mixture resulted in the lowest number of nematodes at the second sampling, but it showed phytotoxicity to sugarcane. Temik, Dasanit, and Mocap gave the highest yields in tons per acre and sugar per ton. These did not reduce sucrose content. DBCP-PCNB and DBCP gave an increase in sugar per tonof sugarcane. Temik produced 4.6 tons more sugarcane than the check, with 16% more sugar

4 : Table I. Results of 1966 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP 44-lDI. ;.- ><: Amount/acre, formula- No. of nematodes/pint soil Yields 1::0 Chemicals tion, and appl. method 4/15 10/25 Tons/acre Sugar/ton Sugar/acre o :I: "l:j Control Nontreated check 463 b ab t:;:j DD 8 gal, act., injected 188 a a t" 0 1,3-D 7 gal, act., injected a TD lb, act., emul., sprinkled 205 a a b TD Ib, act., 10%.g, spread 382 ab a DBCP-PCNB 1:2 gal, sprinkled 245 a a vt lb, act., spread 291 a b bc VC 9-lD4 4 lb, act., 10% g., spread 325 ab c DD-MENCS 3 gal, act., injected 149 a ab Aldicarb 4 }b, act., 10% g., spread 260 a c Table 2. Results of 1967 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP Chemicals Amount/acre, formula- No. of nematodes/pint soil Yields tion, and appl. method 3/21 11/6 Tons/acre Sugar/ton Sugar/acre Control Nontreated check 76 ab bc DBCP 8.6 Ib, act., sprinkled 31 a bc DBCP-PCNB 8.6 Ib:4 Ib act., sprinkled 42 a a Aldicarb 4 Ib, act., 10% g., spread 94 b c B lb, act., 10% g., spread 71 ab bc VC lb, act., 10,% g., spread 49 ab ab J"-:) (Jc

5 1026 PATHOLOGY per acre; and Dasanit gave 2.3 tons increase with 10% more sugar. Mocap and DBCP-PCNB were phytotoxic and decreased yields in this test. In the 1968 test all chemicals used, except Mocap, significantly reduced the nematode population at the earliest sampling date (Table 3). The lowest nematode populations were recorded from plots treated. with Temik, DBCP, Dasanit, and N- (4-bromo-3-chlorophenyl) -N methyl urea (C-6313) (Maloran) R. l:' Temik, Mocap, Dasanit, and DBCP significantly increased cane yields. Increases I) ranged from 4.6 tons with Maloran to over 11.3 tons with Temik and 11.5 t?ns with Mocap. DBCP and Dasanit increased yields by 7.5 and 8.5 tons per acre, respectively. Calculated increases in sugar per acre with all materials ranged from 27-40% per acre. Use of DBCP again resulted in an increase in the amount of sugar per ton. The average increase in cane yields for 3 seasons with Temik on plant cane of the CP variety was 6.9 tons per acre, or about a 25% increase. No statistically significant adverse effects on sucrose were indicated during the 3 years with Dasanit, Temik, and Mocap. Except for DD and Telone all materials used are experimental and at the time of this report do not have registry for commercial use on sugarcane. In 1969 a field test was made using a commercial type applicator to apply granular materials of the newer type nematicides which had previously given the best results, namely,' Temik, Dasanit, and Mocap. Nematodes were significantly decreased by these materials bilt the yield of sugar was not affected as had been previously noted. No significant differences were obtained between treatments in tons of cane per acre or in sugar per acre. The reduced rates employed with a commercial applicator and a very dry harvest season were believed to be responsible for the results. In 1970, 2 additional materials were included' in a field test with the other most promising materials employed previously. These were: ethyl 4 (methylthio) -m-tolyl isopropylphosphoramidate, (Bay 68138, Nemacur) R; and 2,4-Dimethyl-2-formyl-1, 3-dithiolane oxime N-methylcarbamate (MBR 6168, Tirpate) R. Significant nematode control was obtained with these materials as well as with Temik, Mocap, and DBCP used in this test. Only Temik gave an increase in yield of sugar per acre with over 2,000 lb ofsugar per acre above the nontreated check, Temik increased the average tons per acre by 6.7 tons, Mocap by 5.3 tons, and Nemacur by 4.7 tons per acre. Tirpate appeared to reduce sucrose at the 2 lb per acre rate. Yield declines in 1st and 2nd year stubble were measured in 2 miscellaneous nematicide tests. The first of these tests was' treated and planted in 1967 and the second in Harvests were made in 1968, 1969, and A decrease in tonnage for the successive years Was recorded, as shown in Tables 6 and 7. In the test started in 1967, the yields declined in the 1st year stubble from 30-52% compared with the plant cane and 21-39% further decline in the 2nd year stubble compared with the 1st year stubble. Temik, Dasanit, and Mocap treatments produced over 2 tons more sugarcane in the 1st year stubble than did the checks. Maloran and DBCP treatments did not maintain increases in the 1st year stubble. None of the treatments held the tonnage up to an economical level in the 2nd year stubble nor significantly higher than the nontreated checks. No stubble decline occurred in the test planted in The

6 Table 3. Results of 1968 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP Chemicals Amount/acre, formula- No. of nematodes/pint soil Stand tion, and appl. method - 11/29/67 3/20/68 count Tons/acre Control Nontreated check b lola 32.4 a Aldicarb 4 lb, act., 10% g., spread a 123 b 43.7 b B lb, act., 10% g., spread a 136 c 40.9 b VC lb, act., 10% g., spread ab 117 b 43.8 b (; lb, act., 10% g., spread a 118 b 37.0 ab DBCP 8.6 lb, emul., sprinkled a 115 b 39.9 b Yields " "l:j Sugar/ton Sugar/acre M t'" t::l Table 4. Results of 1969 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP Chemicals Amount/acre, formula- No. of nematodes/pint soil Stand Yields tion, and appl. method 2/13/69 7/2/69 count Tons/acre Sugar/ton Sugar/acre Control Nontreated check c 242 a Aldicarb 3/4 lb, act., 10% g. spread bc 294 c B-2514l 3lh lb, act., 10% g. spread ab 305 c VC lh lb, act., 10% g. spread a 293 bc NB. -0 M -J

7 Table 3. Results of 1968 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP Chemicals Amount/acre, formula- No. of nematodes/pint soil Stand tion, and appl. method ll/29/67 3/20/68 count Tons/acre Control Nontreated check ll2 415 b lola 3204 a Aldicarb 4 Ib, act., 10% g., spread a 123 b 43.7 b B Ib, act., 10% g., spread a 136 c 40.9 b VC Ib, act., 10% g., spread ab ll7 b 43.8 b (; Ib, act., 10% g., spread a ll8 b 37.0 ab DBCP 8.6 Ib, emul., sprinkled a ll5 b 39.9 b Yields co H g l'l:j Sugar/ton Sugar/acre t;:j t-< o Table 4. Results of 1969 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP Chemicals Amount/acre, formula- No. of nematodes/pint soil Stand Yields tion, and appl. method 2/13/69 7/2/69 count Tons/acre Sugar/ton Sugar/acre Control Nontreated check c 242 a Aldicarb 3/4 lb, act., 10% g. spread bc 294 c B * lb, act., 10% g. spread ab 305 c VC * Ib, act., 10% g. spread 632 H20 a 293 bc N.S '0 -:J

8 1028 PATHOLOGY Mocap treated plots yielded 3 tons more in than in 1969 and over 5 tons more than the nontreated control in the Ist year stubble. Better stands and root Table 5. Results of 1970 nematicide test for control of plant parasitic nematodes on sugarcane, variety CP 55'30. Chemicals Amount/acre, formula- No. of tion, and appl. method nematodes/ Yields pint soil Tons/acre Sugar/ton Sugar/cre Control Nontreated check 840 e Aldicarb 2 Ib, act., 10% g., spread 147 a Bay Ib, act., 15% s- spread 387 c VC Ib, act., 10% g., spread 507 d !l134 MBR Ib, act., 10% g., spread 247 b DBCP 9 Ib, emul., sprinkled 440 c Table 6. Sugarcane stubble decline in tons per acre after treatment with nematicides in 1967 and yield harvests in 1968, 1969, and 1970.,:;' Chemicals Amount/acre, formula- Yields in tons per acre tions, and appl. method Control Nontreated check 32.4 a 19.5 ab 15.4 A1dicarb 4 1b, act., 10% spread 43.7 b 22.4 b 15.4 B Ib, act., 10% spread 40.9 b 22.2 b 17.6 VC lb, act., 10% spread 43.8 b 21.6 b 15.3 C Ib, act., 10% spread 37.0 ab 18.6 a 11.4 DBCP 8.6 lb, ernul. sprinkled 39.9 b H1.8 a 14.7 Table 7. Sugarcane stubble decline in tons per acre after treatment with nematicides in 1968 and yield harvests in 1969 and Chemicals Amount/acre, formula- Yields in tons per acre tions, and appl, method Control Nontreated check Aldicarb %. lb, act., 10% g., spread B % Ib, act., 10% s- spread VC ,1, Ib, act., 10% s- spread

9 WRAY BIRCHFIELD 1029 systems established in plant cane with some nematicides are believed to cause better yields in the l st year stubble. REFERENCES 1. Birchfield, Wray Nematicides for.control of plant-parasitic nematodes on sugarcane in Louisiana. Plant Disease Reptr., 53: Chu, H. T., and T. K. Tsai Study of the effects of soil fumigation to the growth of sugarcane. III. Increase of cane yield and its economic value. Rept. Taiwan Sugar Expt. Sta., 30: Dick, F The sugarcane nematode problem in South Africa. Sugar jour., 50: Hu, C. H., T. K. Tsai, and H. T. Chu The nematode investigation in sugarcane fields of Taiwan and effects of soil fumigation. Proc, ISSCT, 13: Roman, J., and J. Badillo Response of a sugarcane nematode population to the addition of nematocides in Irrigation water. Puerto Rico Univ. Jour. Agric., 49: Winchester, J. A Control of root-knot nematodes on sugarcane. Sugar jour., 28: Sugarcane research. Everglades Sta, Mimeo Rpt., EES69 1O Sugarcane nematode control in Florida Proc. ISSCT, 13: ',1968. Chemical control of nematodes in sugarcane. Down to Earth, 23: Wismer, C. A Soil fumigation test harvested. Ann. Rpt. HSJ>A Exp. Sta., 33.