Weed Control Efficacy and Crop Damage by

Weed Control Efficacy and Crop Damage by

Carfentrazone-ethyl (Aim®) Herbicide on Sweet Corn

Jim E. Wyatt, Patricia Brawley, Robert M. Hayes and Craig H. Canaday

Interpretative Summary

Carfentrazone-ethyl caused an initial necrotic spotting on sweet corn leaves but had no effect on plant height or dry weight at 10 or 20 days after treatment. Redroot pigweed was suppressed but not controlled for the season. Entireleaf morningglory populations were insufficient for complete data collection but the herbicide showed promise in areas where plants were present. Annual grasses and yellow nutsedge were not controlled by carfentrazone-ethyl.

Introduction

Carfentrazone-ethyl is an herbicide approved for use on sweet corn. In past tests, it has been found to damage corn by causing necrotic spotting of leaves, breakage of the leaf midrib, and "buggy whipping" of leaves. This latter condition is thought to be due to application of the material when leaves are wet, resulting in concentration of the herbicide in the whorl. This test was conducted to study the effects of carfentrazone-ethyl damage on sweet corn at four rates and at three stages of development and to determine the efficacy of the herbicide on weeds prevalent in the plots.

Materials and Methods

An experiment was conducted in 2002 at the West Tennessee Experiment Station, Jackson, to determine injury to sweet corn by application of carfentrazone-ethyl herbicide at different growth stages and to determine the effect of the herbicide on postemergence weed control. ‘1862’ sweet corn was planted April 16, 2002. Four-row plots were 20 ft long with rows spaced 2.5 ft apart and replicated four times; two center rows were used for data collection. Treatments were carfentrazone-ethyl at 0.0028, 0.0055, or 0.0082 lbs/A active with 0.25% X-77 spreader/sticker. Treatments were applied at 3-leaf, 5-leaf, or 7-leaf stages of sweet corn growth.

Damage ratings on sweet corn were made at 3, 9, 17, 20, and 25 days after the 3-leaf stage treatment, 3, 11, 14 and 19 days after the 5-leaf stage treatment and 3 and 8 days after the 7-leaf stage treatment. Height of five randomly selected plants in each plot were measured from the soil surface to the apex of the smallest leaf at 10 and 20 days after each treatment. Five-plant samples were taken from each plot by cutting plants at the soil surface and oven drying to obtain estimates of dry weight at 10 and 20 days after each carfentrazone-ethyl treatment. Statistical analysis of plant height and dry weight data were conducted using relevant ANOVA procedures.

Results and Discussion

No effect was seen in the growth and development of the corn after plants had recovered from the initial damage of the spray. No differences were found in plant height or dry weight between the control and the full rate of carfentrazone-ethyl (Table 1).

Table I. Effects of carfentrazone-ethyl herbicide on sweet corn plant height and plant dry weight when applied at four rates and three stages of growth.

Corn stage at application time	Carfentrazone-ethyl rate/A	Mean plant height (cm)		5-plant weight (g)
		10 DAT^z	20 DAT	10 DAT	20 DAT
3-leaf	None	24.1	34.3	4.4	27.8
	0.11	25.4	37.9	4.5	34.0
	0.22	24.2	32.7	4.6	31.9
	0.33	23.4	33.9	3.7	23.5

5-leaf	None	28.6	34.4	9.8	30.3
	0.11	30.0	36.2	8.8	23.4
	0.22	27.4	37.1	11.1	29.9
	0.33	25.7	30.3	10.4	27.3

7-leaf	None	32.7	92.5	39.3	149.4
	0.11	38.5	98.7	35.9	177.1
	0.22	38.6	90.2	38.8	155.3
	0.33	39.6	94.1	31.0	160.9

^{zDays after treatment
Carfentrazone-ethyl caused considerable necrotic spotting on
the leaves and some observed "buggy whipping" of the corn. Damage
ratings for sweet corn were generally correlated with herbicide rates,
particularly for the first 8 to 11 days after treatment (Table 2.) Damage was
also progressively less as plants were more developed, with less damage on the
5- and 7-leaf treatments than on the 3-leaf treatment. By 17 to 25 days after
treatment, corn appeared to have mostly recovered from the damage.
Carfentrazone-ethyl had no effect on annual grasses or yellow
nutsedge (Cyperus esculentus L.) and damage to these weeds was not rated.
It did, however, cause considerable damage to redroot pigweed (Table 3). Damage
was more severe on weeds with 2-4 true leaves and ratings were generally
correlated with the rate of herbicide applied. Although many pigweed plants had
symptoms of damage at 19 to 25 days after treatment, most were only suppressed
and recovered sufficiently to cause major problems in the plantings in the
latter part of the growing season.
Table 2. Crop injury ratings for corn treated with
carfentrazone-ethyl herbicide at 3-, 5-, and 7-leaf stages of growth.}

Corn stage at application time	Carfentrazone-ethyl rate/A	Crop injury rating^z, days after treatment
		3 days	9 days	17 days	20 days	25 days
3-leaf	None	0^y	0	0	0	0
	0.11	70	34	6	15	9
	0.22	85	59	8	24	36
	0.33	96	68	7	28	25
		3 days	11 days	14 days	19 days
5-leaf	None	0	0	0	0
	0.11	65	9	23	10
	0.22	81	10	31	11
	0.33	88	11	26	30
		3 days	8 days
7-leaf	None	0	0
	0.11	41	23
	0.22	38	27
	0.33	69	35

^{z0=no injury; 100=100% injury
^yMean of four reps
Entireleaf morningglory populations were not sufficient to obtain definitive
control data for carfentrazone-ethyl (Table 4). Many plots did not have any
plants. Where plants were present, the damage appeared to be sustained over a
relatively long period and actually increased over time rather than decreasing
as it had done on redroot pigweed. The herbicide needs to be evaluated in an
area where entireleaf morningglory populations are high enough to get data from
each plot over a period of time.
Table 3. Injury ratings on redroot pigweed (Amaranthus retroflexus L.)
treated with carfentrazone-ethyl herbicide at 3 corn growth stages.}

Corn stage at application time	Carfentrazone-ethyl rate/A	AMARE injury rating^z, days after treatment
		9 days	17 days	20 days	25 days
3-leaf	None	0^y	0	0	0
	0.11	36	63	70	30
	0.22	96	89	82	41
	0.33	99	89	74	69
		3 days	11 days	14 days	19 days
5-leaf	None	0	0	0	0
	0.11	45	88	76	65
	0.22	89	84	87	41
	0.33	95	87	79	73
		3 days	8 days
7-leaf	None	0	0
	0.11	65	38
	0.22	74	40
	0.33	94	43

^{z0=no injury; 100=100% injury
^{yMean of four reps
Table 4. Injury ratings on entireleaf morningglory (Ipomoea hederacea
(L.) Jacq.) treated with carfentrazone-ethyl herbicide at 3 corn growth stages.}}

Corn stage at application time	Carfentrazone-ethyl rate/A	IPOGH injury rating^z, days after treatment
		9 days	17 days	20 days
3-leaf	None	-^x	0^y	0
	0.11	-	-	-
	0.22	13	35	50
	0.33	1	0	0
		3 days	11 days	14 days
5-leaf	None	-	0	0
	0.11	-	-	0
	0.22	18	20	25
	0.33	-	-	-
		3 days
7-leaf	None	0
	0.11	0
	0.22	0
	0.33	24

^{z0=no injury; 100=100% injury
^{yMean of four reps
^{xThis weed species not present in these plots}}}

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Copyright © 1999 by The University of Tennessee. All rights reserved.

This research represents one season's data and does not constitute recommendations. After sufficient data is collected over the appropriate number of seasons, final recommendations will be made through research and extension publications.