CONTROL OF DARKSIDED CUTWORM ON FLUE-CURED TOBACCO WITH APPLIED’ AFTER TRANSPLANTING

By H. H. CHENG, Research Station, Canada Department of Agriculture, Delhi, Ontario, Canada Tobacco Science, 1975, 19-53, p. 148-150, ISSN.0082-4523.pdf

perimental and registered insecticides as post-planting Eleven insecticides were aoolied to tobacco seedlings after treatments in controlling the darksided cutworm, which transplanting in the field for ‘control of the darksided cutworm, Euxoa messoria (Harris), in Ontario. All insecticides tested in is the major cutworm problem in the tobacco-growing 1973 and 1974 significantly reduced both cutworm-damaged areas in Ontario. This paper reports the results of field plants and cutworm populations as compared with the untreated tests made in 1972, 1973 and 1974. check, except and PP-505; in 1972 number of damaged olants was reduced but no differences were found in cut&& populations among the plots. Leptophos and N-2596 MATERIALS AND METHODS [S-tp-chlorophenyl] O-ethyl ethyl-phosphonodithioate] gave the best control, but leptophos occasionally caused phytotoxicity and Field Microplot Tests N-2596 was extremely toxic to the operator. , , DDT, endosulfana and trichlorfon showed similar degrees of effec- Two experiments were conducted in microplots in tiveness. Temophos and were numerically less effec- 1972 on Fox loamy sand with 7 treatments replicated tive than carbaryl, the standard . All materials tested four times in a randomized block design. All plots were caused no visible phytotoxicity to the tobacco plants except 6 ft long, 3 ft wide, and were located in a rye field which leptophos in the microplot tests of 1972. was heavily infested with 5th, 6th, and 7th-instar larvae of the darksided cutworm. Each plot consisted of 3 rows INTRODUCTION with 5 seedlings in each row. The tobacco seedlings were transplanted to the experimental plots on 6 June in The effect of the darksided cutworm, Euxoa messoria Experiment 1 and on 20 June, 1972 in Experiment 2. (Harris), on modern tobacco production is well estab- The plants were grown for 2 to 3 weeks after treatment lished (2, 3, 4). In Ontario, the principal co&o1 method in order to check for insecticidal injury. for larvae of this insect consists of pre-planting appli- The insecticides selected for these two experiments cations of or leptophos (5, 7, 10). These were DDT 50% WP (wettable powder), carbaryl 80% insecticides are broadcasted evenly on the rye crop WP, leptophos 45% WP, leptophos 3 EC (emulsifiable grown in rotation with tobacco, or over the soil surface concentrate), trichlorfon 5% bait, and trichlorfon 80% in the field. Although the pre-planting applications of SP (soluble powder). DDT and carbaryl, which were chlorpyrifos or leptophos will control the cutworms, used as standard insecticides, were applied at the rec- post-planting treatments are also required for the ommended rate of 2 lb AI/acre (8). The other in- control of cutworms migrating into tobacco fields from secticides were used at the same rate as the standard adjacent rye fields after transplanting (l), or for to- insecticides. Wettable powders, soluble powder or emul- bacco fields which are reinfested with other species. sifiable concentrate were applied evenIy over the entire This provides an additional protection where pre-plant- plot in an amount of water equivalent to 25 gal/acre, ing treatments fail to provide effective control. using a Knapsack sprayer. Trichlorfon baits were dis- Cutworm infestations on a tobacco field after trans- tributed uniformly by hand. All treatments were applied planting can be a limiting factor to tobacco production, one day after transplanting. because newly transplanted tobacco seedlings are very Relative effectiveness of the treatments was evaluated sensitive to cutworm damage and the damaged plants by recording the cutworm-damaged plants, cutworm usually do not recover (2, 3 I. Therefore, severe cutworm populations and cutworm mortality daily from each plot infestations on the tobaccn fields make replanting for four days. The number of damaged plants or larval necessary. mortality was expressed as a percentage of the total After DDT was removed from the tobacco recom- number of original plants or total number of cutworms mendations in 1970 (9.). carbaryl was the only insecti- found in each pIot, and the data were transformed into cide recommended in Ontario for use directly on small angular units as suggested by LeClerg et al (6). The tobacco seedlings to control cutworms in the field after transformed data were subjected to analysis of variance. transplanting. Two years of observations indicated that The Dunc.an’s multiple range test was applied to the carbaryl does not provide good clrtw-clrm control. There- treatment means. Mean values were converted to orig- fore, field studies were initiated during the growing inal wits for presentation in Table 1. season of 1972 to determine the effectiveness of ex-

The field plot trials were conducted at the Research Station, (‘anada Department of Agriculture, Delhi, On- Table 1. Efficacy of insecticides applied on tobacco seedlings after transplanting for control of the darksided ciutworm in field microplots ib Ontario. 1972. Mean No. of Rats cutworms found % plants Formulation (lb AI/Acre) per plot* oh Mortalityb damagedb Phytotoxiciv

ExDeriment I SO% WP II.3 45.6 b 40.0 ab Zbary ’ 50% WP 9.3 34.3 b 33.3 ab Leptophos 45% WP 9.8 75.3 a 21.6 a Leptophos 3 EC 16.2 85.2 a Trichlorfan 5% Bait 14.9 4.4 c z:: gb Trichlorfon 80% SP II.8 48.0 b 40.0 ab Check - 16.5 OC 70.0 c

Exoeriment 2 Carbaryl 80% WP 2 13.2 43.5 b 60.0 bc NON DDT 50% WP 2 I I .4 31.3 b 31.8 a Non.3 Leptophar 45% WP 2 I I.&. 70.6 a 33.3 a High Leptophor 3 EC 2 18.8 78.8 a 41.6 ab High Trichlorfon 5% Bait 2 22.4 7.1 c 68.4 c NOlIe Trichlorfon-. 80% SP 2 18.3 44.8 b 35.0 ab NCUle Tobacco Science, 1975, 19-53, p. 148-150, ISSN.0082-4523.pdf tario, during 1973 and 1974 on tobacco transplants of which is presently recommended for use, but trichlorfon variety Delhi 34. The experimental field was not sprayed 80% SP was numerically better than DDT 50% WP or with insecticides for several years so that the field popu- carbaryl 80’>: WP in killing the larvae. Trichlorfon 5% lation of the darksided cutworm increased in a natural bait was the least effective treatment. way. In mid-*June, 1972, a late frost resulted in frost burn All plots were 80 ft long, 13 ft. wide, and arranged in on the leaves of the tobacco plants complicating damage a randomized block design with two replications in ~1973 assessments for phytotoxicity in Experiment 1. How- and three replications in .1974. Each plot consisted of ever. symptoms of phytotoxicity with leptophos 3 EC or four rows of tobacco with 40 plants in each row, the $55 FVP were apparent in Experiment 2. All growing outside rows in each plot being i:uard rows. Vntre.ated leaves contacted with leptophos were deformed. There check plots wt’rc encircled with aluminum barrier strips was no apparent chemical injury to tobacco seedlings 8 in. high with 3 in. embedded in the ground to prevent treat,ed with carbaryl 80% WP, DDT 50% WP and tri- the larvae of the cutworms migrating to the neighbour- chlorfon 809; SP or 5% bait. Early greenhouse studies ing plots. The tobacco seedlings were transplanted into (3) indicated that carbaryl caused some slight phyto- the plots on 28 May, 1973 and on 29 May, 1974. Normal toxicity. regardless of the formulation used. The differ- tobacco cultural practices were followed. ent phytotoxic performance of carbaryl from the present Tnsectirides tested were acephate, carbaryl, chllor- studies was probably attributed to the different environ- dimeform. . leptophns, methidathion, N-i!596 mental conditions or to the different growth stage of IS- (p-chlorophenyl? O-ethyl eth) I-phosphonodithioate], the tobacco seedlings, or both. PP-505 (Chipman Chemical Limited, chemical name un- available), temophos, and trichlorfon. Standard insecti- cide was carbaryl in both years. Sprays were applied From the results of field microplot tests, it was ap- with a tractor sprayer that cleli\,ered 25 gal of liquid parent that carbaryl was as effective as DDT and is per acre at 3.5 mph and 30 psi. All treatments were currently recommended for use directly on tobacco seed- applied evenly over the entire plots one day after tra.ns- lings. Therefore, carbaryl was used as a standard insec- planting. ticide in the field plot tests. Mortality of the cutworms For evaluation of relative effectiveness of the trseat- in each plot was not recorded in 1973 and 1974. ments, cutworm damaged plants and cutworm popula- In 1!173, all materials tested caused a significant re- tions in the soil around plants from the two central duction in both cutworm damaged-plants and cutworm rows in each plot were counted weekly for 5 weeks after populations as compared with the untreated check (Ta- treatment. The number of damaged plants recorded in ble 2). Leptophos 45% WP at 1 lb AI/acre gave the best the last count was expressed as a percentage of the total control of the cutworms; however, it did not differ sig- number of original plants within the two center rows of nificantly from endosulfan 4 EC at 2 lb AI/acre, N-2596 each plot. The data were statistically treated as in the 4 EC at 1 lb AI/acre and trichlorfon 80% SP at 2 lb Field Microplot Tests. AI/acre in reducing the cutworm-damaged plants or cutworm populations. The standard insecticide, carbaryl RESULTS AND DISCUSSION 80% WP at 2 lb AI/acre was numerically or signif- icantly less effective than the other four insecticides Field Microplot Tests tested. There was no visible chemical injury to tobacco Data obtained from the microplot field trials in 1972 plants in all treated plots. are presented in Table 1. There were no significant dif- In 1974, all chemicals tested significantly reduced both ferences in the number of cutworms among the plots. cutworm-damaged plants and cutworm populations as In both experiments, all treatments significantly reduced compared with the untreated check except chlordime- the number of cutworm damaged-plants as compared form 97’-, SP and PP-505 50% WP, which were in- with the untreated check, and the cutworm mortalit) effective at the rate applied (Table 2). Leptophos 45% with all treatments was also significantly higher than WP and N-2596 4 EC or 4 F (flowable) gave the best that of the untreated check, except with trichlorfon .5(“, control of c,utworms, and there was no significant differ- bait. Leptophos, regardless of the formulations used, ence between 1 lb AI/acre and 2 lb AI/acre of leptophos, gave the best control of the darksided cutworm. In gen- or between N-2596 4 EC and 4 F. Leptophos again eral. there w(~re no signifi(:;ttIt differences among tri- caused no phytotoxicity, regardless of the rate applied. chlorfon 80’; SI’, 1)lYl‘ SO’, m-1’ and carbaryl 809; WP, The reasons for the phytotoxic performance of leptophos Table 2. Efficacy of insecticides applied on tobacco seedlings after transplanting for control of the darksided cutworm in field plots in Ontario. Mean No. of Rate -a plants cutworms per Inrect;:ide Formulatior (lb Al/acre) damaqed ’ 80 plants*

1973 Carbaryl ~O-&WP 2 II 3 b 4.5 a Endorulfan 2 56 ab 2.5 d Leptophor 45% WP I IZa 0.5 a N-2596 4 EC 31 ab 1.0 a Trichlorfon 80% SP : 5.6 a 2.0 a Check - 0 349 c 16.0 b

1974 Acephate 75% SP I 62 ab: I .7 abc Carbarvl 80% WP 5.0 abc I.0 ab Cdrbaryl : 55 abc 1.5 abc Chlordimeform :7: SP I 23 5 e 5.0 bed Leptophos 452 WP I I 9 ab 0.5 a Leptophos 45% WP 2 08 a 0.3 a Methidathion 40% WP I 93 cd 2.6 abc Temophos 4 EC 8 I cd 2.5 abc Trichlorfon 80% SP : 3 5 abc I.3 abc N-2596 4 EC I 22 ab 0.7 a N-2596 4F I 09 d 0.3 a PP-505 50% WP 17.3 de 4.8 bed Check - L 26.6 e 10.5 d --

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in I!)?‘:! are unknown. Acephate 7.5$ SP, carbaryl SOY0 ACKNOWLEDGMENT U’P or 3 F and trichlorfon SOP{ SP showed similar de- grees of effectiveness. Temophos 4 EC and methidathion Appreciation of the efforts of J. J. Hanlon during this 40”; 1VP were numerically less effective than carbaryl, study is gratefully acknowledged. which was currently recommended as a post planting treatment to control cutworms. AI1 materials tested in 19’74 caused no visible phytotoxicitv to the tobacco plants. LITERATURECITED In general, the level of cutworm infestation was heavy 1. Bllc-hr*r. G. E. and H. H. Cheng. Use of trap plants for throughout the period of this study at the Research :rttrac.tinq (.Ittworrn larvae. Can. Entomoi. 102:797-798. 1970. Station, Delhi, Ontario (Tables 1 and 2). The high pop- 2. Cheng, H. H. Assessment of tosbacco losses caused by the ulation densities of cutworm larl,ae in the field micro- darksidpd rutworm, Euxoa mexsosia :Lrpidoptera: Noctuidae), plots were due to migration from adjacent rye fields Delhi. Ontario. Can. Entomol. 103:534-541. 1971. 3. Chrnc. H. H. Greenhouse studies on insectirid;rl control of (1). Of the cutworm larvae collected from the experi- rhe d:drk\idpd cutworm on tobacco seedlings. Tob. Sci. 16:75-77. mental plots each year, an average of 96% were the 1972. darksided cutworm; Zy/, were the striped cutworm, 4. Chrng: H. H. Observations on the bionomics of the dark- Euxoa tessellata (Harris) ; 1.5% were the variegated rid,ed rutworm, Euxoa messoria (Lepidoptera: Noctuidae) in Ontario. Can. Entomol. 105:311-322. 1973a. cutworm, Peridroma sn7rcin (Hutmer) ; and 0.5% were 5. Chenp. H. H. Further field evaluation of insccticidw for Feltia dxcens Wlk. I ontrol of thr darksided cutworm (Lcpidoptera: Xoctuidaej on The results of this series of studies indicate that of Tobacco in Ontario. Can. Entomol. 105:1351-1357. 197313. 15 formulations of the 11 insecticides tested, Ieptophos, 6. LrCIerq; F.. L., W. H. Leonard, and A. G. Clark. Field Plot Tcrhniaue. 2nd ed. Burgess Publishing Co., Minneapolis. N-2596 and trichlorfon provided better control of the 173 pp, 1962: darksided cutworm than carbaryl. Of these, Ieptophos 7. Harris. C. R., H. J. Svec, and W. W. Sans. Toxicological and N-2596, regardless of the formulations used, gave \tudirs on rlltworms. IX. Laboratory and microplot field studies the best control. Unfortunately Ieptophos occasionally on cffrctiwlwss and persistence of some experimental insecticides caused phytotoxicity and N-2596 is extremely toxic to :~sed for control of the darksided cutworm. J. Econ. Entomol. 66:i99--203. 1973. man. Consequently, more research is required on these 8. Ontario Dept. Agric. and Food. Tobacco recommendations materials. Trichlorfon SOP/, SP gave consistent control for 1969. Inf. Leafl. AGDEX 181. 11 pp. 1969. and caused no chemical injury to tobacco plantings in 9. Ontario Dept. Agric. and Food. Tobacco recommendations the three years of tests. Therefore, trichlorfon could iur 1970. hf. Leafi. AGDEX 181. 11 pp. 1970. 10. Ontario Ministry Agric. and Food. Tobacco production provide a useful alternative to carbaryl as a post-plant- recommendations. Toronto, Ontario. Ont. Ministry Agric. Food ing treatment in fields. Pub]. 298. 31 pp. 1974.

(Tobacco Science 150)