Effects of Several Rates of Carbofuran, Phorate, Aldicarb, Methomnl, Propoxur, and Disulfoton in the Seed Furrow on Growth and Yield of Soybeans
LEAFLET 90/MARCH, RONNIE H 1976 BASS* SHEHANE AND MAX H

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EFFECTS OF SYSTEMIC INSECTICIDES

on soybean growth and yield has aroused interest in the past few years. Wheeler and Bass (3) reported that soybean plants were taller in plots treated with methomyl and carbofuran than plants in untreated plots. Shehane and Bass (2) found that phorate, carbofuran, methomyl, and disulfoton, applied to soybean
* Former Research Assistant and Professor, respectively, Department of Zoology-Ento-

mology, Auburn University Agricultural Experiment Station. AGRICULTURAL EXPERIMENT R. Dennis Rouse, Director

plants at 1 pound per acre under various conditions produced no effect on growth or yields. Moody and Bailey (1) tested several systemic insecticides as gralular in-furrow treatments at 0.91 and 1.82 pounds of active ingredient per acre to determine soybean plant response. Significant differences in plant height were reported between treatments, and in one test between treatments and the check. In a second test (the following year) no material significantly affected plant height. They reported no significant differences in yields or seed weights
STATION/AUBURN UNIVERSITY Auburn, Alabama

between treatments and the check. Additional information would be helpful in determining the effects of various insecticides on soybeans, particularly, the effects of high rates of in-furrow treatments. Information on the effects of a wide range of treatment rates of commonly used in-furrow systemic insecticides on soybean growth and yields is reported here. METHODS AND MATERIALS This research was conducted at the Auburn University Gulf Coast Substation near Fairhope, to determine if certain systemic insecticides, when applied as pre-plant granules at various rates, would affect soybean growth (plant height and weight), weight of seeds, and yields. Six systemic insecticides were utilized at four application rates plus an untreated check. The 25 treatments were arranged in four complete randomized blocks. Insect populations were sampled throughout the course of the study and no significant populations of destructive insects occurred. The insecticides used were: carbofuran 10 percent G, phorate 5 percent G, methomyl 5 percent G, disulfoton 15 percent G, propoxur 10 percent G, and aldicarb 10 percent G. These materials were applied along with the seed in the seed furrow at rates of 1, 2, 4, and 8 pounds of active ingredient per acre. A total of 100 plots 81/2 feet wide (3 rows) and 15 feet long were used, with no alleys or buffer rows between plots. Soybeans of the Bragg variety were planted on June 17, by hand at the rate of 14 seeds per-foot-of-row. The seeds were innoculated with Nitragin® before planting. Measurements of plant height were made 2, 4, and 6 weeks (July 1, 15, and 29) after the insecticidal applications. These measurements were made by selecting 10 plants at random from the middle 10 feet of the middle row in each plot and measuring the tallest stem of each plant.

Data on plant weight (wet weight) were also taken at 2, 4, and 6 weeks after the treatments had been applied. Ten plants were selected at random from an outside row, removed from the plots and placed in appropriately labelled plastic bags. The bags were sealed to reduce evaporation from the plants. In the laboratory, soil and roots were removed from the plants and the stem and leaves of each plant were weighed. Yield data were collected by harvesting the middle 10 feet of the middle row in each plot. The soybeans were threshed with a small combine, the beans placed in paper bags and weighed in the laboratory after debris was removed. Seed weight data were obtained by weighing 100 seeds from each plot. The seeds were relatively dry at the time of weighing, since they had been harvested dry and held in the laboratory (approximately 50 percent RH) for 1 month. RESULTS AND DISCUSSION The analysis of data collected during the first plant-height measurements 2 weeks after planting revealed that plants treated with methomyl at 8 pounds per acre were significantly shorter than plants from untreated plots, see table. Four weeks after planting, plants from plots treated with propoxur at rates of 4 and 8 pounds per acre, and methomyl at 8 pounds-per acre were significantly shorter than plants from the check plots. Six weeks after planting, propoxur applied at the rate of 8 pounds per acre and phorate at 4 pounds per acre caused plants to be shorter than plants from the untreated plots. The analysis of plant-weight data collected 2 weeks after planting revealed that plants from plots treated with propoxur at the rates of 4 and 8 pounds per acre and from plots treated with phorate at the rate of 8 pounds per acre were significantly lighter than untreated check plants, see table. Four weeks after planting, plants from plots treated with propoxur at the rates of 4 and 8 pounds

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THE MEAN HEIGHTs AND WEIGHTS OF SOYBEAN PLANTS AT VARIOUS INTERVALS AFTER TREATMENT IN SEED FURROW, MEAN SOYBEAN YIELDS AND MEAN WEIGHTS OF 100 SEEDS*

Treatment Untreated checkCarbofuran --Carbofuran ------Carbofuran-----Carbofuran ---Phorate ------

Rate lb/a 0 12 4 8 1----

Height of plants in inches 2 weeks 4 weeks 6 weeks 13.5ab 12.4abcd 12.9abcd 10.7abcde 10.2bcde 12.7abcd 12.labcd 10.lbcde 10.lbcde 13.6ab 13.Oabcd 12.labcd 10.5abcde 12.7abcd 12.labcd 12.3abcd 9.5cde 13.4ab 11.6abcd 9.4de 7.8e iS.3ab 13.6ab 18.2abc 10.6abcde same letter do

Weight per plant in grams 2 weeks 4 weeks 6 weeks

Yield bu/a 48.4a 47.6a 53.9a 44.1a 49.8a 39.9ab 44.9ab 45.6ab 49.9a 53.3a 56.7a 46.7ab 45.lab 43.4ab 88.8ab 41.7ab 40.7ab 48.Oa 45.lab 37.Oab 23.4b 48.7a 48.9a 44.9ab 44.7ab

Weight in grams per 10sed 15.Oab 15.3ab 15.7a 16.2a 16.2a 15.4ab 13.9ab 14.2ab 14.6ab 14.4ab 15.2ab 14.2ab 15.9a 13.9a 12.8b 15.lab 14.4ab 14.lab 15.Oab 14.Oab 13.9ab 14.6ab 15.4ab 14.9ab 14.6ab

4.5ab 4.6ab 4.5abc 4.7a 4.4abc 4A4ahc 2 Phorate ----------4.2abc 4 Phorate --------4.labc ------------ 8 Phorate 4.2,abc 1Aldicarb ---- - -4.5abc Aldicarb -- ------- 2 4.2bc 4 Aldicarb -- -----4.Oabc 8 Aldicarb --------4.labc Methomyl ---------- 1 4.2bc Methomyl --------- 2 4.labc 4 Methomyl --------3.9c 8 Methomyl ------4.6ab 1 Propoxur-----4.2abc Propoxur ---------- 2 4.2abc 4 Propoxur ------4.3abc Propoxur --------8 4.7a 1-Disulfoton - ---4.6ab Disulfoton --------- 2 4.7a 4 Disulfoton ------4.6ab 8 Disulfoton -------*Means in each group designated by the

25.labc 2.Sab 13.2ab 70.5abc 25.4ab 2.4a 13.7ab 85.7a 23.8abc 2.Oabcde 12.6abc 69.7abc 23.2abcd 2.Oabcde 8.4bcde 50.5abc 22.Oabcde 1.7bcde 7.2cde 54.3abc 24.3abcd 2.Oabcd 11.Oabcd 68.4abc 25.Oabc 2.labc 12.7abc 61.5abc 18.7de 2.Oabcde 10.5abcd 56.labc 19.7bcde 1.6de 8.7bcde 61.3abc 24.8abc 2.4a 14.6a 74.labc 25.4ab 2.3a 14.6a 85.Oab 24.5abc 2.3a 13.Gab 71.3abc 22.8abcd 1.9abcde 11.7abc 78.7abc 24.9abc 2.3ab 14.2ab 79.3abc 23.7abcd 2.2abc 13.7ab 8.5.4a 25.Sab 2.labcd 12.labc 61.8abc 23.labcd 1.9abcde 9.8abcde 74.6abc 24.4abc 2.2abc 15.1a 74.8abc 23.Oabcd 2.labcd 9.8abcde 56.Oabc 20.labcde 1.7cde 5.6de 42.3bc 17.e 1.5e 4.5e 41.3c 25.7a 2.2abc 12.3abc 78.9abc 22.8abcd 2.2abc 11.9abc 74.labc 21.3abcde 2.labcd 11.Sabc 71.labc 19.4cde 2.2abc 9.5abcde 60.3abc not differ significantly at the 1 percent level.

per acre and carbofuran at 8 pounds per acre were significantly lighter than plants from the untreated plots. The analysis of the plant-weight data collected 6 weeks after planting also revealed significant differences at the 1 percent level, but none of the treatments were significantly different from the untreated checks. Propoxur treatments at the rate of 8 pounds per acre caused plants to be lighter than carbofuran at 1, methomyl at 2, or aldicarb at 2 pounds per acre. Statistical analysis of yield data revealed that plants treated with propoxur at 8 pounds per acre had significantly (1 percent level) lower yield than plants from the untreated check plots and several of the treated plots, see table. Seeds from plots treated with methomyl at 2 pounds per acre weighed less than seeds from several other treated plots, but did not weigh less than seeds from untreated plots, see table. There were no significant differences between

seed weights from treated and untreated plots. In general only high rates of propoxur (4 and 8 pounds per acre) seemed to have a season long deleterious effect on the soybean plant. Only at the 8 pounds per acre rate was this effect reflected in a decrease in yield. REFERENCES CITED
(1) MOODY, REYNARD AND JACK C. BAILEY.

1974. Soybean plant responses to certain systemic insecticides applied as granular in-furrow at planting. J. Econ. Entomol. 67(3): 442-4.

(2)

SHEHANE, RONNIE H. AND MAX H. BASS. 1974. Growth and yield of soybeans following treatment with phorate, carbofuron, methomyl or disulfoton. Environmental Entomol. 8(3): 574-5.

(3) WHEELER, BRENT A. AND MAX H. BASS.

1971. Effects of certain systemic insecticides on growth and yield of soybeans. J. Econ. Entomol. 64: 1219-21.

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