BULLETIN MARCH 399 1970 PERFORMANCE of HERBICIDES for WEED CONTROL in PEANUTS Agricultural Experiment Station AUBURN UNIVERSITY E. V. Srmt, Director/ Auburn,, Alabama CONTENTS Page MATERIALS AND METHODS---------------4 - 5 RE SUL T S - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - V ern olate - - - - - - - - - - - - -- - - - - - - - - - - - - - - Be ne fi n - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Benefin Combination ----------------------- - 5 - 7 --------- 11 Din o seb -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 1 Diphenamid, 2,4-DEP, Naptalam, and Sesone------------15 N itralin - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 18 Ala c h 8 --------------------1 io r ----------------------- DC PA - - - - - - - - - - - - - - - - - - -- - -- - - - - - - - - - - - - - - - - - - - - - 2 1 S UM M AR Y -- - - - - - - - - - - - - - - - - -- - - -- - - - - - - - - - - - - - - - - - - - - 2 1 LIST OF HERBICIDES MENTIONED ------------------------- 23 FIRST PRINTING 4M, MARCH 1970 Performance of Herbicides for Weed Control in Peanuts GALE A. BUCHANAN, Assistant Professor of Agronomy and Soils RAY DICKENS, Assistant Professor of Agronomy and Soils EARL R. BURNS, Instructor of Agronomy and Soils ROBERT M. McCORMICK, Instructor of Agronomy and Soils VALUATION OF HERBICIDES for weed control in peanuts began in Alabama in the early 1950's. This early research led to the recommendation of dinoseb (dinitro) in 1960. Application was made at "cracking time" of the peanuts. Further experimentation led to the inclusion of 2,4-DEP and sesone to the list of herbicides recommended the following year. From 1961 until 1966 there were no revisions or additions in the recommendations of herbicides for peanut weed control in Alabama. Under optimum conditions, the recommended herbicides controlled many of the weeds, such as crabgrass and Florida purslane, that plagued peanut growers during the early part of the growing season. However, such weeds as sicklepod, nutsedge, Florida beggarweed, cocklebur, Texas panicum, and tall and snallflower morningglory were not adequately controlled. Another impetus to expanded research was that considerably lower rates of herbicides were recommended in Florida and Georgia than in Alabama. This caused some degree of confusion for producers living near the borders of these adjoining states. In 1966 a greatly expanded research program on weed control in peanuts was initiated. The objectives were to evaluate both experimental and currently recommended herbicides at various rates of application and to study several methods and times of application. Various experiments included preplant incorporation, preemergence, cracking-time, and postemergence treatments. E 4 ALABAMA AGRICULTURAL EXPERIMENT STATION MATERIALS AND METHODS Experiments were conducted on Dothan loamy sand at the Wiregrass Substation, Headland, Alabama. Natural weed infestations were predominantly crabgrass, goosegrass, crowfootgrass, Florida beggarweed, sicklepod, morningglory, and Florida purslane. Other weeds occurring in the experimental areas included Texas panicum, nutsedge, lambsquarters, and pigweed. Major peanut weeds are listed below, and most are illustrated on pages 12-13. WEEDS IN PEANUTS Crabgrass Goosegrass Crowfootgrass Sicklepod (coffeeweed) Tall morningglory Smallflower morningglory Florida beggarweed Carpetweed Bristly starbur (Texas spur) Texas panicum Cocklebur Florida purslane Nutsedge purple Nutsedge yellow Pigweed, redroot Lambsquarters Digitaria sanguinalis (L.) Scop. Eleusine indica (L.) Gaertn. Dactyloctenium aegyptium (L.) Richter Cassia obtusifolia (L.) Ipomoea purpurea (L.) Roth Jacquemontia tamnifolia (L.) Griseb. Desmodium tortuosum (SW.) DC. Mollugo verticillata (L.) Acanthospermum hispidum DC. Panicum texanum Buckl. Xanthium pensylvanicum Wallr. Richardia scabra (L.) Cyperus rotundus (L.) Cyperus esculentus (L.) Amaranthus retroflexus (L.) Chenopodium album (L.) Soil in the experimental areas was turned each winter and seedbeds prepared in March or early April by disking and leveling. Treatments were randomized in a complete block design with four replications. Plots were four rows wide and 20 feet long. Alleys 20 feet wide separated the replications. Herbicides were applied broadcast in 16-19 gallons of water per acre at a spraying pressure of 30 psi, using a tractor-mounted, compressed air sprayer. Treatments involving preplant incorporation of herbicide were applied first, incorporated with either a double section disk harrow or a power driven rotary hoe, and then peanuts were planted on all plots. After planting, preemergence applications were sprayed on the appropriate plots, followed later by postemergence and cracking-time applications. Check plots without herbicide treatment were included in each replicate. PERFORMANCE OF HERBICIDES IN PEANUTS 5 Early runner peanuts were planted in all experiments. Two of the four rows in each plot were mechanically cultivated to control weeds. The other two rows were left uncultivated to observe the number, species, and competitive effects of weeds surviving the herbicide treatment. Peanut yields were taken on the cultivated rows only, to permit measuring possible injury from the chemical treatment where weed competition was not a factor. Counts of grass, broadleaf weeds, and peanut plants were made 4-6 weeks after application of the herbicides. Weeds were counted in a 12-inch band 20 feet long over each row, except where weed populations were uniformly high only 2 feet of band was counted. Peanut injury and control of grass and broadleaf weeds were rated visually periodically throughout the growing season. Peanut yields were measured as pounds of unshelled pods per acre. During the past 4 years, over 50 different herbicides (not including combination treatments) were evaluated for weed control in peanuts. Many of the herbicides showed some potential. Severe crop injury by some herbicides eliminated them from further consideration. The herbicides discussed in this bulletin have been found promising with respect to weed control and minimal crop injury. RESULTS Vernolate Early grass control with vernolate was consistently good at rates of 2 pounds per acre and above, Table 1. However, 2.5-3.0 pounds were required for full-season grass control. Control of Texas panicum, a large-seeded grass, was poor at rates that controlled other grass species. Considerable variation in broadleaf weed control from year to year was obtained with vernolate. This yearly variation was not related to rate of vernolate as much as to the predominant broadleaf weed species in the experimental areas used each year. Florida purslane, carpetweed, and redroot pigweed were controlled well by vernolate, while morningglory, sicklepod, and Florida beggarweed were not, especially late in the growing season. One of the major advantages of vernolate for peanut weed control is its activity against nutsedge. Although complete control can seldom be achieved, vernolate is the most effective herbicide available for suppressing this weed in peanuts. 10s TABLE 1. INFLUENCE OF VERNOLATE APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF PEANUTS Herbicide, rate /acre ----------168 157 Stand count'Weed Weeds control and injury ratings Grasses' Broadleaf weeds 2 Cent rass Peanuts Broadleaf Early 284 51 Crop injury 2 Yield, 4 Late 0 Early 26 28 Late Early . Late p ounds 1966 Vernolate, 1.0 lb. Vemnolate, 2.0 lb. Vernolate, 8.0 lb. 159 155 66 5 335 344 76 94 0 91 5 18 38 25 0 9(1 r- Vernolate, 4.0 lb. Vernolate, 1967 5.0 lb. 157 --------------------159 162 189 13 3 651 44 196 175 329 29 84 99 0 90 88 93 0 C heck ---- ------- -Vernolate, 2.0 lb.-180 Vernolate, 3.0 lb.-------------------Check --------------------------- 33 35 50 0 30 44 0 15 0 0 5 0 2 58----------------88 186 200 - 1 167 25 0 9 0 14 342 327 221 176 183 358 99 0 83 92 98 98 0 98 0 22 87 73 91 0 93 0 91 96 100 100 0 97 97 96 99 12 0 0 0 0 O2 0 0 0 0 0 2 2 0- 2,268 2,395 1,801 1,949 2,294 2,312 2,359 1,871 - c) rI 1968 Vernolate, 2.0 lb. Vemnolate, 2.5 Vemnolate, 3.0 lb._-----lb.------- Vernolate, 4.0 lb. Check -- - - - - - - - 1969 Vernolate, 2.0 lb. Vemolate, .2.5 124 134 S197___________________ 28 - 142 S---------- 5 10 23 c r I- 131 1,819 0 94 69 67 91 0 7 5 Ma lb .------- Vemnolate, 3.0 lb._-----Vernolate, 4.0 lb. Check-- - - - - - - - - 92 ____________ 108 85 ____________ 106 ____________ 109 109 28 137 1 279 10 13 11 11 704 95 92 93 99 12 99 97 96 99 0 I 1 10 0 z -O -Z 1 Number of plants per 80 feet of row on 12-inch band. 2 0 = no control; 100 = complete control. 0= no injury; 100 - complete kill. 'Pod weight of unshelled peanuts per acre. 0 -- PERFORMANCE OF HERBICIDES IN PEANUTS 7 Some injury to peanut seedlings by vernolate occurred each year. Stands were not affected, but injury was expressed as leaf seal or sticking together of the margins of the leaflets and general stunting. In all cases this injury was slight at rates below 3 pounds per acre and there were no yield reductions with rates as high as 4 pounds. Benefin Benefin was highly consistent when applied at 0.75-1.5 pounds per acre and incorporated into the soil prior to planting. In all instances, 0.75 pound provided acceptable grass control throughout the season, Table 2. Lower rates were adequate for grass control in only 2 of the 4 years. At rates giving good control of grass weeds, the degree of broadleaf weed control varied with density of particular species. Although pigweed, Florida purslane, carpetweed, and other small-seeded weeds were controlled, such large-seeded species as morningglory, sicklepod, cocklebur, and Florida beggarweed were not controlled. Benefin does control Texas panicum, which is usually not adequately controlled by many other common peanut herbicides. Peanuts were not significantly injured by benefin at rates considerably above those required for weed control. Herbicides applied preplant are incorporated with any one of various implements that mix the herbicide into the soil to various depths. Experiments in 1968 and 1969 to determine if depth of incorporation would be a factor causing injury to peanuts with high rates of benefin showed depth of incorporation had no effect on stands, peanut injury, yields, or weight of seedling peanuts, Table 3. Apparently peanuts germinate and root in benefin-treated soil without injury. Weed control was excellent with all depths of incorporation at rates tested. Another factor that may vary is the delay between application of the herbicide and incorporation into the soil. In a 1969 experiment with benefin, however, there was no effect on weed control from delaying incorporation up to 24 hours, Table 4. Only slight losses in efficiency were noted from 48 hours' delay. If lower rates of herbicide had been used (1.15 pounds per acre in test), the effects of delayed incorporation probably would have been greater. Other research has shown that volatilization of benefin from the soil to the atmosphere is a major process causing loss. TABLE 2. INFLUENCE OF BENEFIN APPLIED PREPLANT INCORPORATED ON WEED CONTROL, INJURY, AND YIELD OF PEANUTS Stand count' Hebcdrt/ceWeeds Peanuts Grass Broadleaf Hebcdrt/ce 1966 Benefin, 0.37 Weed control and injury ratings Broadleaf weeds2 Crop injury2 Grasses' Late Early Late Early Late Early 74 90 94 96 95 Yield,' pons lb. Benefin, 0.75 Benefin, l.00lb. Benefin, 1.50 lb---------_--------Benefin, 3.00 lb.-------------- lb. -------------------- 146 159 154 157 138 27 14 16 2 1 237 116 87 60 23 Check --------------------------1967 -----Benefin, 0.25 lb. Benefin, 0.37 lb.----_._--_SI -----____ --- 161 192 651 3 328 79 7 6 0 80 63 0 80 80 98 96 0 26 61 67 70 96 98 0 92 96 95 98 0 55 92 94 96 96 0 26 45 64 78 73 0 71 48 58 82 92 95 0 100 100 98 100 0 0 17 15 38 65 69 0 0 0 10 10 0 0 0 0 0 4 0 0 0 0. 0 41 0 0 0 0 0 0 0 0 800 s00 0 ------ -- _---------------- .------ _ --------- _-------- 189 180 58 36 189 Benefin, 0.50 lb. Benefin, 0.75 lb. Benefin, 1.00 lb. Benefin, 2.00 lb. Check - - - - - - - - - 1968 Benefin, 0.25 lb. Benefin, 0.50 lb. Benefin, 0.75 lb.Benefin, 1.00 lb. C heck- ------------- --1969 Benefin, 0.25 I, - ----------------- 192 .------------------ _ 194 .---------_ 182 199 ------------------_------------1--- 18 .------------------. 130 .------------------ _ 135 .---------_ 117 .----------. 103 .---------_ 110 12 14 1 166 1 1 0 0 69 48 10 342 200 173 165 57 358 87 96 99 0 97 97 96 100 0 131 1,819 ------------ 0 0 0 0 0 0 0 989 0 0 0 700 0 0 2,005 1,506 2,078 2,695 2,123 2,187 1,801 C 2,123 1,822 2,366 1,876 1,871 m Benefin, 0.50 lb.--------43 101 3 I - -----------------Benefin, 0.75 lb. --------108 3 6 ---- ------Benefin, 1.00 lb._________ - --------18 92 2 Benefin, 2.00lb. - 279 704 Check -- - - - - - ------------- --- ------------------------- ----------------109 1Number of plants per 80 feet of row on 12-inch band. 20 no control; 100 - complete control. _--------- lb.--------- 217 17 83 174 84 93 98 94 100 12 'Pod 0 87 75 96 92 97 12 no injury; 100 - 0 17 5 30 74 0 96 0 10 85 0 0 complete kill. 0 --- z -I weight of unshelled peanuts per acre. z m 0 z TABLE 3. INFLUENCE OF DEPTH OF INCORPORATION OF BENEFIN ON WEED CONTROL, PHYTOTOXICITY, AND YIELD OF PEANUTS, 1968-69 0 17 0 '77 Stand count Incorporation depth, benefin rate /acre 0-2in.,1lb.Peanuts Weeds Grass Weed control and injury ratings controF Injury' Seedling 4 Yield, pounds'L, Paus '68 '69 240 236 219 224 195 226 233 205 Grasses Broadleaf 1 Gascnrl '6-8 100 100 100 100 100 100 100 100 100 0 '69 100 100 100 100 .100 100 100 100 100 0 Inuy '68 5 3 7' 0 7 5 0 2 2 0 '69 0 0 wt., grams 4 '68 1 0 0 0 0 0 0 0 '69 0 0 0 0 0 0 0 0 '68 3 0 1 6 3 2 2 4 '69 0 0 0 0 0 1 0 0 0 3 '68 76 62 67 '69 79 87 86 '68 __ ___ '69 _ 2,759 2,931 2,986 02mi.,2lb.- 0-2in.,41lb04 in.,2lb- 0-4in.,llb.- 0-4in.,41lb._ 0-8in.,21lb. 0-8in.,llb.- 208 242 226 211 213 226 222 m 0 0 0 82 100 2,650- __ m 0-8n.,41lb._ Check _______ 204 208 0 0 0 60 11 204 220 405 SNumber of plants per 80 feet of row on 12-inch hand. 2 0 = no control; 100 = complete control. 0 - no injury; 100= complete kill. 235 0 0 0 0 0 66 70 68 73 73 70 97 80 70 77 73 77 2,523 2,541 -__2,895 __ 2,487 __-_ 2,487 __ 1,770 __ __ z c I4 aken ''PTod from 2 feet of row approximately 60 days after planting. weight of unshelled peanuts per acre. TABLE 4. INFLUENCE OF TIME OF INCORPORATION AFTER APPLICATION OF 1.15 POUNDS TOXICITY, AND YIELD OF PEANUTS, 1969 OF BENEFIN ON WEED CONTROL, PHYTO- 0 Time from application to incorporation, hours 0---------------------------------------35----------------------------10-----------------------------24------------------------------ Peanuts 186 193 203 182 194 Stand count1 Weeds Grass Broadleaf Grass control' Weed control and injury ratings Broadleaf 4 control wt., grams Crop injury' 0 0 0 0 0 Seedling 79 90 90 96 87 Yield, 5 pounds 0 0 2 2 0 0 0 1 4 1 98 100 100 100 100 100 100 97 99 96 8,122 2,904 3,095 3,104 2,922 48-----------------------------168 1 120 (rain)---------- --------------202 24 Check--------------------------195 12 1 Number of plants per 80 feet of row on 12-inch band. '0 - no control; 100 - complete control. ' 0 - no injury; 100 - complete kill. TABLE 5. 1 2 12 ing. 90 31 0 75 7 0 0 0 0 84 81 89 2,859 2,575 2,949 r- Taken from 2 feet of row approximately 60 days after plantX Pod weight of unshelled peanuts per acre. 1968 F WEED CONTROL AND CROP INJURY WITH VARIOUS HERBICIDE COMBINATIONS OF BENEFIN WITH VERNOLATE AND 2,4-DEP, Stand count' Herbicide, rate/acrePent Benefin + Benefin ± vemnolate, vemnolate, 0.75 ± 1.5 1.0 + 2.0 Weed control and injury ratings Grasses' Early Late 97 100 86 90 Weeds Paus Grass Broadleaf 300 260 0 1 4 15 Broadleaf weeds Early Late 91 97 26 62 Injury' Early Late 0 0 0 0 lb.---------lb. --------- - m Benefin + Benefin Benefin Benefin vernolate, 1.0 + 3.0 lb.--_------2.0 3.0 lb.------3.0 lb.-------- ± ± Check--------------------------------- -319 215 ' Number of plants per 80 feet of row on 12-inch band. '0no control; 100 - complete control. 3 0 = no injury; 100 complete kill. + 2,4-DEP, 0.5 + 2,4-DEP, 0.5 + 2,4-DEP, 1.0 + lb.---------- 326 262 2 0 19 2 9 3 100 100 96 100 97 96 98 83 100 97 97 25 65 60 53 2 5 2 5 0 0 0 2 --278 254 7 1 361 0 0 0 0 0 0 z PERFORMANCE OF HERBICIDES IN PEANUTS '11 Incorporation of the herbicide increases its contact with the soil and aids its retention. Benefin Combination Under some conditions the use of two herbicides concurrently will give better weed control. An example is where nutsedge and Texas panicum are problem weeds in peanuts. In these areas, a combination of vernolate (having nutsedge activity) and benefin (having Texas panicum activity) probably would be advantageous. When weed species present are poorly controlled by the individual herbicides, however, using a combination of the herbicides probably will not improve weed control, Table 5. Dinoseb Application of dinoseb at cracking time of peanuts has long been a standard weed control practice, but recommended rates of application have ranged from 1.5-4.5 pounds per acre. Dinoseb may act as a preemergence herbicide in some instances, killing seedling weeds as it is absorbed through the roots, and it may act as a contact herbicide and kill weeds after absorption through the foliage. This herbicide is excellent for use on newly emerged weeds, with rates as low as 1.5 pounds per acre giving excellent contact kill of small grass and broadleaf weeds in 1967 and 1968, Table 6. Dinoseb at rates above 3 pounds exhibits some preemergence activity against weeds that germinate after the herbicide is applied. Duration of this preemergence activity increases with increasing rates of application, as shown by the late season ratings for grass and broadleaf weed control, Table 6. Weather conditions should be considered when choosing a rate of dinoseb. At temperatures less than 60°F the amine salts of dinoseb have little contact activity, but at 85°F or higher they are extremely toxic to plant foliage. High humidity, dew, or a light shower tend to increase plant absorption of dinoseb, increasing its phytotoxicity. Another factor that has great influence on effect of dinoseb is size of weeds at time of herbicide application. Weeds are most susceptible when they are just emerging. (Some seedling weeds, especially grasses, are very tiny at emergence. They are not noticeable during midday, but show up readily in the early morning after a heavy dew. If examination must be made at midday, detection can be improved merely by extremely close observation.) 12 12 ALABAMA AGRICULTURAL EXPERIMENT STATION 3> T fl r-J a r Cr bg ra Gaosegr Crowfoc Sicklepo senna Tall mo S mallf Ic glory Florida Texas p Cockleb Florida Purple i Yellow i Pigweed I S' 4 ~*1 I- Vt N, PERFORMANCE OF HERBICIDES IN PEANUTS 13 0y / /;\ rye P Vt/f ' vrs < / C '4 I' grass (left), coffee ght) ningglory ter morning'eggarweed in icurn ursiane utsedge utsedge *7 I V 4 ~ 4: i TABLE 6. INFLUENCE OF DINosEB APPLIED AT CRACKING TIME AND POSTEMERGENCE ON WEED CONTROL, INJURY, AND YIELD OF PEANUTS Herbicide, rate/acre 1967 Dinoseb (cracking), 1.5 lb----------. Dinoseb (cracking), 3.0 lb----------. Dinoseb (cracking), 6.0 lb. ----------Dinoseb (cracking), 9.0 lb----------. Dinoseb + dinoseb +1-dinoseb', 6.0 + 1.5 + 1.5 lb. Check ------------------------- -1968 Dinoseb (cracking), 1.0 lb. Stand count' Weeds PausGrass Weed control and injury ratings Crop injury' Broadleaf weeds' Grasses' Early Late Early Late Early Late Broadleaf pons 1,742 1,896 1,624 1,878 1,878 1,885 Yield, 163 168 171 155 171 162 199 195 163 198 121 130 121 105 8 1 4 0 0 25 1,174 1,540 2,900 2,029 1,500 1,182 279 1,068 11 3 0 1 3 378 457 671 59 559 196 19 27 970 87 97 96 100 100 0 83 85 81 0 10 52 72 0 20 76 62 96 96 0 86 96 97 100 98 0 80 87 86 0 15 58 60 90 95 0 0 0 17 0 17 12 45 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 0 0 P- Dinoseb (cracking), 2.0lb. Dinoseb (cracking), 3.0 lb. C heck --------------- -1969 Dinoseb (cracking), 1.5 lb. Dinoseb (cracking), 3.0lb. Dinoseb (cracking), 1,894 2,167 1,622 1,854 1,325 1,879 1,779 1,520 C C r- 9.0 lb. Check -- - - - - - - - ' Number of plants per 80 feet of row on 12-inch band. ' 0= no control; 100 - complete control. '0 0-=Do injury; 100 = complete kill. 4Pod weight of unshelled peanuts per acre. Six pounds applied preemergence followed by 1.5 pounds at cracking and 1.5 pounds postemergence. 0 15 44 0 68 99 93 0 m m m Ma z OI Zn PERFORMANCE OF HERBICIDES IN PEANUTS 15 Another factor that may account for erratic results with dinoseb is the rainfall pattern. If weeds and grasses are sprayed when they are small with 2 pounds per acre or more, overall control will probably be excellent if the soil surface remains dry. On the other hand, abundant rainfall soon after application of a low rate encourages germination and establishment of another population of weeds following those killed by the first contact. The optimum time for application of dinoseb is after the most rapid emergence of weed seedlings and before their increased size and resistance. Of all the herbicides used in peanuts, dinoseb is by far the most toxic. It is very toxic not only to plants but to livestock and humans. (The acute oral LD5 0 for rats is about 40 mg. per kg. of body weight.) Dinoseb can be safely applied if sound procedures are followed during application. Thorough washing of exposed body areas and changing clothing if one becomes contaminated will lessen the possibility of injury from dinoseb. Diphenamid, 2,4-DEP, Naptalam, and Sesone Diphenamid (Enide, Dymid), 2,4-DEP (Falone), sesone, and naptalam (Alanap) are often used in combination with dinoseb to give more preemergence control and extend the length of weed control. Diphenamid is available under the brand names of Enide and Dymid, and a 1966 comparison showed the two formulations to be equal in herbicidal activity when applied with dinoseb at cracking, Table 7. Diphenamid has good activity against annual grasses and some broadleaf weeds, such as carpetweed, pigweed, and Florida purslane. It will not control Florida beggarweed, cocklebur, or sicklepod. In general, rates greater than 2 pounds per acre have been required to give acceptable late season control. In 1968, per acre rates as high as 6 pounds dinoseb plus 8 pounds diphenamid did not cause injury to peanuts. Falone (2,4-DEP) and sesone are phenoxy-type herbicides that have preemergence activity resulting from their transformation to 2,4-D in the soil after a period of microbiological, activity. Soil moisture is often a critical factor in performance of these herbicides. Once converted to 2,4-D the herbicides are active against weeds, but they are also subject to leaching or further breakdown in the soil. This accounts for the relatively short period of weed control they provide. Falone and sesone have activity against both grass and broadleaf weeds, but because of TABLE 7. COMPARISON OF FORMULATIONS AND RATES OF DIPHENAMID IN COMBINATION PEANUTS WITH DINOSEB FOR WEED CONTROL IN Stand count' 17 4 26 4 116 11 15 20 9 Weed control and injury ratings Herbicide, rate/acre 1966 Dinoseb ± dymid, 1.5 + 2.0 lb._ Dinoseb + dymid, 3.0 + 4.0 lb.Dinoseb ± enide, 1.5 + 2.0 lb.-Dinoseb + enide, 3.0 + 4.0 PausGasBodefEry Weeds Grasses' Lt Broadleaf weeds' al ae Ery injury 3 Crop Lt Yield, ons lb.-- Ch eck -- ----- - - --- --- -- --- -- 105 97 99 101 89 154 182 159 147 11 9 11 3 65 13 2 2 6 85 94 92 95 0 85 96 100 95 98 96 96 96 0 36 95 90 95 92 96 91 95 0 81 87 81 80 35 70 80 75 0 25 57 56 67 0 0 0 0 0 2,142 2,024 1,797 2,161 1,543 1967 Dinoseb + enide, 1.5 + 2.0lb.-Dinoseb + enide, 1.5 ± 4.0 lb. Dinoseb + enide, 3.0 + 2.0lb.-----------Dinoseb + enide, 3.0 ± 4.0 lb. Check----162-------------2-------------Dinoseb +enide, 1.5 +2.0'lb. -------Dinoseb ± enide, 3.0 + 4.0 lb.------Check ---------- 162 194 189 207 25 12 5 142 379 90 25 427 0 100 100 0 0 0 70 0 0 100 100 0 0 0 42 0 0 0 0 0 0 0 1,206 1,506 1,315 1,488 1,089 2,050 1,942 - _---------------- 1968 Dinoseb + enide, 1.5 ± Dinoseb ± enide, 3.0 + Dinoseb ± enide, 4.5 ± Dinoseb + enide, 6.0 + Check -- 0 010 2 2.0 lb. 4.0 lb. 6.0 lb. 8.0 lb. - - - - - - - - - - 118 108 156 166 184 116 129 107 105- 130 76 10 1 947 132 169 115 1,068 74 14 9 3 134 37 18 25 970 --- 45 95 100 100 0 72 76 60 0 ____ ____ __ ____ 30 29 0 0 50 80 100 100 0 92 97 97 0 0 0 0 ------- m 1969 Dinoseb ± enide, 1.5 ± 2.0 lb. Dinoseb + enide, 3.0 + 4.0 lb. Dinoseb + C h eck enide, 4.5 6.0 lb.- - - - - - - - - - - - - - - - ---- + 'Number of plants per 80 feet of row on 12-inch band. '0= no control; 100 - complete control. 41 0 32 7 32 15 0 0 0 no injury; 100 - complete kill. 4Pod weight of unshelled peanuts per acre. 0 z -- -- - TABLE 8. COMPARISON OF 2,4-DEP AND SESONE IN COMBINATION WITH DINOSEB AT CRACKING TIME FOR WEED CONTROL IN PEANUTS Stand count' 5 1 76 89 Weed control and injury ratings Yield, pounds4 1,416 1,779 1,543 1,270 1,896 2,695 1,506 1,942 1,861 1,761 1,543, 1,875 1,752 1,520 - 0 Herbicide, rate/acre Peanuts - - Grasses2 Weeds Grass Broadleaf Early Late 33 48 Broadleaf weeds' Late Early 93 95 0 100 Crop injury2 Early Late 0 0 0 25 z fl 0 m ,T, 1966 C - h - e - k- - -. - - - - - - - --- -- - -- - - - Dinoseb Dinoseb ± + 2,4-DEP, 1.5~ + 3.0 3.0 lb.----2,4-DEP, 4.5 + lb.----- 25 95 108 12 53 48 Check-----1967 88 199 64 10 116 17 0 100 0 20 0 40 30 40 0 m ± 2,4-DEP, 1.5 + 2.0 lb.----Dinoseb ± 2,4-DEP, 1.5 ± 3.0 lb. Dinoseb ± 2,4-DEP, 3.0 + 2.0 Dinoseb 32 lb. - 200 180 Dinoseb + 2,4-DEP, 3.0 + 3.0 lb.----Check ---------------------------1968 _----- 186 5 2 0 142 9 2 2 426 100 100 100 0 30 35 72 0 100 100 100 0 43 60 83 0 207 0 0 0 0 0 0 m m z .Q mI Dinoseb Dinoseb C heck 1969 ± sesone, 1.5 + 3.0 lb + sesone, 4.5 + 3.0 lb. ------------------ ----- 100 106 88 13 11 64 150 109 3 3 116 18 54 87 87 0 82 54 40 58 0 59 27 95 96 0 99 92 0 ------ 45 66 0 42 40 0 0 0 0 0 30 0 0- af Dinoseb ± 2,4-DEP, 1.5 + 2.0 lb. Dinoseb + 2,4-DEP, ---- 1.5 + 3.0 lb. - 126 - 0 5 0 100 Check--Dinoseb Dinoseb ± sesone, 1.5 + 2.0 lb. ± sesone, 3.0 + 4.0 lb.-------Dinoseb ± sesone, 4.5 + 6.0 lb.C h e c k ----- ---------- --- -- --- -- ---- -- 105 -- 1,068 970 -- --- 0 -40 0 --- --- -- -- -- - - --- -- -0 40 40 0 0 0 0-0-0-- - --- --- --- '0 2 0 = no control; 100 = complete control. = no injury; 100 = complete kill. ' Number of plants per 80 feet of row on 12-inch band. 4Pod weight of unshelled peanuts per acre. 18 ALABAMA AGRICULTURAL EXPERIMENT STATION short residual only the highest rate of dinoseb plus 2,4-DEP showed appreciable control late in the 1966 and 1967 seasons, Table 8. Naptalam has in some experiments extended the length of weed control when applied with dinoseb. Although these herbicides (diphenamid, 2,4-DEP, naptalam, and sesone) are usually applied in combination with dinoseb, there are some conditions where application of one of these alone might be used. Under dry conditions where there are no weed seedlings present, the producer wanting to use the residual herbicide can apply it without the dinoseb. However, with these current residual herbicides, if moisture is limited to the point of inhibiting weed germination, then in all probability there would be too little moisture for best results with sesone, 2,4-DEP, naptalam, or diphenamid. Nitralin In 1968, season-long grass control was obtained with nitralin applied at rates as low as 0.25 pound per acre, Table 9. However, in the same year broadleaf weed control was poor with rates as high as 1 pound. A 1.5 or 3.0 pound per acre rate of dinoseb applied at cracking time over 1 pound of nitralin preplant considerably improved late season control of broadleaf weeds. In 1967, nitralin gave only fair grass control at the lower rates, but 1 pound per acre gave good grass control throughout the growing season. A cracking-time application of dinoseb did not improve the final grass or broadleaf weed control rating. Alachlor Alachlor (Lasso) has given acceptable control of such annual grasses as crabgrass, goosegrass, and crowfootgrass, Table 10. Grass control was essentially complete for the entire 1967 season at rates as low as 1 pound per acre. In 1968, however, plots receiving up to 2 pounds per acre were grassy, and only fair season-long control was obtained with as much as 4 pounds. Alachlor failed to control broadleaf weeds such as tall morningglory, sicklepod, and Florida beggarweed at rates that were adequate for grass control. Effective against Florida purslane and pigweed, alachlor provides some control during the early part of the season of resistant weeds such as Florida beggarweed. Experiments in 1969 substantiated those of 1967 and 1968. Grass control was acceptable at all rates, and there was consider- TABLE 9. INFLUENCE OF NITRALIN AND VARIOUS COMBINATIONS OF NITRALIN OF PEANUTS + DINOSEB ON WEED CONTROL, INJURY, AND YIELD m Herbicide, rate /acre 1967 Nitralin (PPI), 0.25lb.Nitralin (PPI), 0.37 lb. Nitralin (PPI), 0.50 lb. Nitralin (PPI), 0.75 lb. Nitralin (PPI), 1.00 lb. Nitralin (PPI) + dinoseb (CR), 0.5 1.5 lb. Nitralin (PPI) + dlnoseb (CR), 0.5 - 3.0 lb. Peaut StandOMIATOSOFIIRAI ARIU CasBodfPEarl Weeds .1 C1. 1 count' AN Weed control and injury ratings ae al Lt ar Broadleaf weeds' Erl Lte T*T Lt pounds 4 0 Grasses' Lt aly Crop injury' aepun' Yield,PausGasBodefEry z 0 0 m 193 180 178 191 190 183 187 199 130 140 118 120 113 129 44 37 20 17 5 31 23 166I 13 4 1 1 0 1,819 81 63 60 36 15 64 15 342 64 71 18 46 24 20 81 74 92 92 96 86 88 0 97 97 98 99 100 100 37 40 70 72 97 4,790 62 0 90 98 95 97 98 98 82 71 83 83 93 91 88 0 100 97 100 100 100 100 17 15 52 30 75 53 68 0 0 0 0 0 0 17 27 0 0 2,323 0 0 0 0 0 0 1,815 1,787 2,123 2,686 o + 2,314 2,141 1,801 2,159, 2,032 1,422 2,268 2,105 2,221 1,871 2 Check --- - - - - - - - - - - 1968 Nitralin (PPI), o 0 0 0 0 0 0 0 2 0 10 7 7 0 z C HI Nitralin (PPI), 0.50 lb. _-------. Nitralin (PPI), 0.75 lb._-------_ Nitralin (PPI), 1.00 lb. Nitralin (PPI) + dinoseb (CR). 1.0± 1.50 lb.. Nitralin (PPI) + dinoseb (CR), 1.0 + 3.00 lb..C eck h 0.25 lb. ----- ------ 10 26 52 30 70 72 0 0 0 0 0 22 0 0 --------------------lb. ------------lb.----- -------lb.------------- 131 2 358 0 0 0 1969 Nitralin, 0.25 Nitralin, 0.50 Nitralin, 0.75 123 5 11 14 112 3 91 20 42 Nitralin, 1.00 lb. _-----------13 6 79 Nitralin, 2.00 lb.---- -------97 7 13 C h eck -- - - - - - - - - - - - - - - - - - - 704 109 279 'Number of plants per 80 feet of row on 12-inch band. ' 0 - no control; 100= complete control. 97 0 99 95 86 97 74 7 99 95 15 96 74 93 99 92 15 96 99 99 30 99 90 99 99 12 0 0 0 12 '0 no injury; 100 complete kill. 4Pod weight of unshelled peanuts per acre. i..a TABLE 10. INFLUENCE OF ALACHLOR ON WEED CONTROL, INJURY, AND YIELD OF PEANUTS Stand count' Weeds Weed control and injury ratings Grasses' Lt Broadleaf weeds2 Erl Lte aly Crop injury' aepuns Herbicide, rate /acre Yield,PausGasBodefEry 1967 Alachlor(pre), 1.0 Alachlor(pre), 1.5 Alachlor(pre), 2.0 lb._----lb. - lb.------ -- ---- - - Alachlor(pre), 3.0 lb._----Alachlor(pre), 4.0 lb.-----______ 187 Check------------ ------41 384 0 1968 Alachlor, 1.0 lb-.--------------------------187 474 218 100 Alachlor, 1.5 lb--.---------_-164 582 172 100 Alachlor, 2.0 Alachlor, 3.0 183 180 166 161 166 0 0 0 0 1 29 30 21 7 8 100 100 100 100 100 100 98 100 100 98 0 20 0 0 20 56 66 75 88 96 0 95 97 100 100 27 52 62 71 81 0 0 0 0 0 0 0 0 0 0 0 1,497 1,325 1,606 1,606 1,569 1,436 0 Alacblor, 4.0 Check___________________ 1969 Alachlor(pre), 2.0 lb. Alachlor(pre), 3.0 lb. Alachlor(pre), 4.0 lb. C heck --------------- lb.------------------lb.------------------lb._.______________________ 214 173 588 17 68 30 100 100 148 1 ___________________________ 161 2,658 38 691 208 100 0 96 91 76 0 69 100 0 73 10 0 52 92 0 0 0 0 o o 1,767 1,713 1,695 1,851 1,996 1,871 I- c -----107 - 42 -----121 ______ 109 - 119 5 12 9 6 73 95 279 704 12 91 96 95 12 99, 0 86 91 92 0 97 97 85 0 45 65 52 -I C 12 91 98 95 12 1969 Alachlor', 2.0 lb. ------------------------ 74 22 39 Alachlor, 3.0 lb. ----------------------- 93 65 59 Alachlor, 4.0 lb.----------------------- 62 22 37 Check--------------------------109 279 704 l~h~Nume of plant pe 80 feet ofrwon1-nc 2 3 ad 0 2 2 25 0 0 --- - 0 ----- 0 - no control; 100 - complete control. 0= no injury; 100 - complete kill. Pod weight of unshelled peanuts per acre. Applied preplant and incorporated with a disk harrow. z PERFORMANCE OF HERBICIDES IN PEANUTS 21 able broadleaf control. The broadleaf weeds in the 1969 experimental area were predominantly the susceptible ones, Florida purslane, and pigweed. Comparison of preemergence with preplant incorporated applications of alachlor in 1969 indicated either no effect or slight reductions in control with incorporation. Similar control of annual grasses was obtained with 3 and 4 pounds per acre of alachlor. Two pounds per acre applied preemergence appeared slightly less effective than the same amount applied preplant. Late season broadleaf control with the preplant applications was inferior to that obtained with preemergence applications. In experiments involving other crops, preplant applications of alachlor have been slightly less effective than preemergence applications. Although stands of Texas panicum were not uniform in the experimental areas, available evidence indicates somewhat less than commercial control of this annual grass. Combinations of alachlor and dinoseb applied at cracking time have also looked promising, Table 11. Excellent season-long control of grasses and broadleaf weeds was obtained with this combination of herbicides at rates of 3 pounds each per acre. DCPA DCPA is a relatively old herbicide and has been widely used in cotton, gardens, and lawns. Evaluations made in 1967 and 1969 indicate that peanuts have considerable tolerance to DCPA, Table 12. Early season control of annual grasses have been acceptable with rates as low as 4 pounds per acre, but 8 pounds were required for late season grass control. DCPA has poor activity against many of the most troublesome broadleaf weeds in peanuts. SUMMARY Although herbicides are used on over 80 per cent of the peanut acreage in Alabama, many weed control problems remain to be solved. The preplant incorporated herbicides benefin and vernolate are excellent grass herbicides. Vernolate is weak on Texas panicum. Nutsedge is not controlled at all with benefin or nitralin, but they control most of the annual grasses. Herbicides such as diphenamid, naptalam, 2,4-DEP, or sesone, applied either preemergence, postemergence, or cracking time, TABLE 11. COMPARISON OF COMBINATIONS OF ALACHLOR AND DINOSEB AT CRACKING TIME FOR WEED CONTROL IN PEA~NUTS, 1969 Stand count" Herbicide, Weed control and injury ratings Earlyrse" Late 93 62 Bodefwes Early rate/acre 118 Crass Broadleaf Wed 96 31 Late Early rpijr' Late 2 2 0 0 pounds' 1,597 1,551 2,478 1,520 YedPeanuts Alachlor + dinoseb, 1.5 + 1.5 lb. Alachlor + dinoseb, 2.0 + 2.0 lb._ Alachlor 1 ± dinoseb, 3.0-1-+ 3.0 C h e ck ------------------------ ------------------------------- lb.- 116 124 63 48 25 14 90 97 0 72 92 0 - 98 92 0 71 61 0 15 0 0 97 96 0 feet of row on 12-inch band. Number of plants per '0 - no control; 100 = complete control. TABLE 12. RATES OF 80 105 1,068 970 complete kill. no injury; 100 Pod weight of unshelled peanuts per acre. 0 I- ' Herbicide, DCPA FOR PREEMERGENCE WEED CONTROL IN PEANUTS Weeds Weed control and injury ratings Crop injury' Broadleaf weeds' Grasses' Early Late Early Late Early Late Stand count 1 rate/acre 210 180 207 113 PausGrass Broadleaf pons 1,751 1,615 1,630 Yield, n C C 1967 DCPA, 4.0 DCPA, 8.0 lb.Check------- -1969 DCPA, lb.- 6 1 142 26 260 130 533 143 100 100 0 81 60 95 0 52 79 21 37 o 0 0 0 0 0 0 0 0 96 92 94 0 22 34 54 m DCPA, DCPA, 4. 0 lb.- 6.0 lb.- 111 110 24 10 453 187 94 97 77 96 96 DCPA, 12.0 lb.Check .-------- IIV~ CCVIV UIU~~V~ I U~VI 1 2 8.0 lb.- 131 106 2 133 63 194 96 0 92 0 96 0 89 0 1,606 1,425 1,643 1,595 1,597 m Z -I LA Number of plants per 80 feet of row on 12-inch band. 0 no control; 100 - complete control. 0 no injury; 100 complete kill. Pod weight of unshelled peanuts per acre. 0I Z PERFORMANCE OF HERBICIDES IN PEANUTS 23 PERFORMANCE OF H:ERBICIDES IN PEANUTS 2 are used with mixed levels of success. Results are often excellent, especially if moisture conditions are favorable. Under dry conditions weed control with these compounds leaves a great deal to be desired. Dinoseb is still considered a standard herbicide for weed control in peanuts. It is economical and effective if applied at the proper rate and weeds and peanuts are at the right stage of growth. Its weakness is that results are often short lived. Application in hot weather causes foliage burn, although this usually does not reduce yield. Experimental herbicides such as alachlor offer some promise of more consistent weed control when applied preemergence or at cracking time with dinoseb. The major weed problem remaining is the control of largeseeded broadleaf weeds, such as morningglory, sicklepod, cocklebur, and Florida beggarweed. At present there are no herbicides being evaluated which offer a panacea to the peanut growers' weed problem. LIST OF HERBICIDES MENTIONED Common name Alachlor Benefin DCPA Dinoseb Diphenamid Naptalam Nitralin Sesone . Trade name Chemical name 2'-chloro-2,6-diethyl-N-methoxy Lasso Balan Dacthal Dow Premerge or methylacetanilide N-butyl-N-ethyl-a,a,a,-trifluoro-2,6-di= nitro-p-toluidine dimethyl tetrachloroterephthalate 2-se c-butyl-4, 6-dinitrophenol N,N-dimethyl-2,2-diphenylacetamide N-1-naphthylphthalamic acid 4- (methylsulfonyl) -2,6-dinitro-N,Ndipropylanaline 2- (2,4-dichlorophenoxy) ethyl sodium sulfate Sinox PB Enide or Dymid Alanap Planavin Sesone Vernam Vernolate 2,4-DEP S-propyl dipropyithiocarhamate tris [2- (2,4-dichiorophenoxy) ethyl] phosphite Falone AGRICULTURAL EXPERIMENT STATION SYSTEM OF ALABAMA'S LAND-GRANT UNIVERSITY With an agricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Ala bama. Every citizen of , ©C 0 the State has a stake in this research program, since any advantage flom new and more economical ways of producing and handling farm products directly benefits the consuming public. is 0 0 m 0 C J Research Unit Identification 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. Tennessee Valley Substation, Belie Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Forestry Unit, Fayette County. Thorsby Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Talassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. Tuskegee Experiment Field, Tuskegee. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton Ornamental Horticulture Field Station, Spring Hill. Gulf Coast Substation, Fairhope.