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Weed Management Research Project Abstracts |
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Triazine-Resistant Lambsquarters |
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Abstracts:
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A survey of triazine resistant common lambsquarters on Pennsylvania farms. 2001.
M. A. Bravo and W. S. Curran. Proc. NEWSS 55:18. Common lambsquarters (Chenopodium album L.) is a major weed problem in Pennsylvania (PA) cropping systems. Triazine resistant common lambsquarters was discovered in the early 1970s and is today considered to be prevalent on many PA farms. A survey sent to county agents and crop consultants provided a pool of farms known to have common lambsquarters present in their fields. Nineteen counties were selected for a survey. Soil samples were collected from three fields on each of three to four farms from each county. Field histories of herbicide use, crop rotation, and tillage practices were documented for each field. Soil samples from each field were divided into three trays, placed in the greenhouse and provided a 12 hr photoperiod and ample moisture to allow weed seed germination. Trays were thinned of all seedlings other than Chenopodium, Ambrosia, and Amaranthus (pigweed) species. Following emergence, seedling weeds in each tray were counted and sprayed with either 1 or 5 lb ai/A atrazine when they had one or more true leaves and were at least 1 inch tall. An untreated check was included. Ten to 12 days after application, plants were counted again and classified as either alive (resistant) or dead (susceptible). A plant of each species from each field that survived the 5 lb/A rate was allowed to flower for species identification. The experiment was repeated. Most Chenopodium plants grown to maturity were identified as Chenopodium album. Samples from 58 farms contained viable nondormant common lambsquarters seed. On average, common lambsquarters were 81% resistant to both rates across all samples. Of the 58 farms, common lambsquarters from 4 farms were 9% or less triazine-susceptible, while common lambsquarters from 34 farms were greater than 90% triazine-resistant. The remaining farms contained a mixed population of susceptible and resistant common lambsquarters. Samples from 52 farms contained viable nondormant pigweed seed. On average, pigweed was 32% resistant to both rates across all samples. Of the 52 farms, pigweeds from 23 farms were 1% or less triazine-susceptible, while pigweeds from 3 farms were 100% triazine-resistant. The remaining farms contained a mixed population of susceptible and resistant pigweed. Common lambsquarters and pigweed were found together in fields from 52 farms. Surprisingly, many fields that contained triazine-resistant common lambsquarters contained triazine-susceptible pigweed. A few fields had the same level of resistance or susceptibility in both species. Mexicantea (Chenopodium ambrosioides L.), spreading orach (Atriplex patula L.), halberdleaf orach (Atriplex patula L. var. hastata (L) Gray.), spiny amaranth (Amaranthus spinosus L.) and common ragweed (Ambrosia artemisiifolia L.) were found in a few samples and all were 100% triazine-susceptible. Pigweed species grown to maturity were identified as redroot pigweed (Amaranthus retroflexus L.), smooth pigweed (Amaranthus hybridus L.) and Powell amaranth (Amaranthus powellii S. Wats.). Several pigweed plants exhibited vegetative and floral characteristics that varied from classical descriptions of these three pigweed species. Impact of glyphosate timing and corn row spacing for common lambsquarters control in Roundup Ready corn. 2000. K. Handwerk, M. A. Bravo, and W. S. Curran. Proc. NEWSS 54:45. Two separate studies were conducted in 1998 and repeated in 1999 that investigated the effect of glyphosate application rate and timing and row spacing on the control of common lambsquarters (Chenopodium album L.) in Roundup Ready corn. Two sites were chosen in Centre County, PA and the two studies repeated at these sites. All plots were planted on the same day and treated preemergence with a broadcast application of fluthiamide (FOE-5043) at 0.6 lb ai/A for annual grass control. In the rate and timing experiment, glyphosate was applied at 0.5, 0.75, and 1.0 lb ai /A at four application times ranging from 3 to 7 weeks after planting (WAP) (POST 1-4). In the row spacing experiment, glyphosate was applied at 0.5 and 1.0 lb/A to corn planted in 15 and 30 inch spaced rows at two application times ranging from 3 to 6 WAP (EPOST & LPOST). Common lambsquarters percent control, density and biomass were measured. A total of four experiments were conducted each year for two seasons. Each treatment was replicated four times in each experiment. In the rate and timing experiment application timing was significant for common lambsquarters control at both locations and for both years. In two of these locations, control of common lambsquarters was greater as application was delayed, especially in 1998. At one location, common lambsquarters control was reduced in the POST 4 application because of larger weeds and interference of the spray pattern by larger corn. Application rate was significant in only one of the four locations, where common lambsquarters control increased with increasing rate. In general glyphosate provided good to excellent common lambsquarters control regardless of rate and timing. In the row spacing study, glyphosate generally provided good to excellent common lambsquarters control regardless of rate, timing or row spacing. In one location, control was reduced in the 0.5 lb/A LPOST narrow row corn treatment. This was probably due to poor spray coverage caused by interference of corn planted in 15 inch rows. These two studies show that glyphosate provides good control of common lambsquarters in Roundup Ready corn. Application timing can influence control, while corn row spacing was not an important consideration in these experiments. The Control of Common Lambsquarters in Corn with Four Soil-Applied Herbicides. 1999. . M.A. Bravo and W.S. Curran. Abstr. NEWSS 53:27. Common lambsquarters (Chenopodium album) occurs frequently in agronomic cropping systems. In Pennsylvania, triazine resistant and susceptible common lambsquarters can be found in corn fields. Several new corn herbicides may prove effective as preemergence herbicides in the control of triazine resistant and susceptible common lambsquarters in corn. Field and greenhouse studies examined the performance of four herbicides on the control of common lambsquarters in 1998. The herbicide field performance trials compared three rates (1/3x, 2/3x, 1x) of flumetsulam, isoxaflutole, pendimethalin, and rimsulfuron as a preemergence treatment. A single rate of atrazine was used to determine triazine resistance. The field experiment had four replications conducted at two locations in Centre County. The soil type at both locations was a silty clay loam with less than 3% organic matter. Common lambsquarters control was evaluated through visual estimates of control, weed densities and by harvesting above ground weed biomass in August. The greenhouse herbicide performance screen compared the same herbicides at 1/6, 1/3, and 2/3x rates. Weed density and biomass measurements were taken three weeks after application. The greenhouse experiment had four replications and was repeated. Rainfall during the 1998 growing season approached the seasonal average. However, following the application of the preemergence herbicides, almost three weeks passed without appreciable rainfall. This lack of rainfall reduced the performance of all the herbicides. At the Irvin location, common lambsquarters appeared to be a mixed population of triazine resistant and triazine susceptible. Three weeks after application pendimethalin, flumetsulam, atrazine, isoxaflutole, and rimsulfuron provided 81%, 61%, 59%, 58%, and 8% control based on lambsquarters density. By mid July, common lambsquarters control (based on density) was less than 50% with all herbicides. By the end of August, pendimethalin, isoxaflutole, atrazine, flumetsulam, and rimsulfuron provided 66%, 50%, 43% 35% and 2% control of common lambsquarters according to above-ground biomass. At the Hort location, common lambsquarters appeared to be triazine susceptible. Three weeks after application atrazine, isoxaflutole, rimsulfuron, pendimethalin, and flumetsulam provided 100%, 82%, 64%, 60%, and 25% control based on weed density. By mid July, control with atrazine was near perfect, isoxaflutole provided 81% control, and all other treatments were less than 50% based on weed density. Weed biomass in August indicated atrazine, isoxaflutole, pendimethalin, rimsulfuron, and flumetsulam provided 99%, 75%, 52%, 34%, and 8% control of common lambsquarters. The preliminary analysis of the greenhouse experiment suggests that ample moisture greatly improves the performance of all herbicides. The greenhouse experiment showed that isoxaflutole, flumetsulam, and pendimethalin were similar and provided good common lambsquarters control. Rimsulfuron was less effective than the other three herbicides, especially at lower than the full rate. In summary, pendimethalin and isoxaflutole provided the best control of common lambsquarters across locations. Atrazine was better than all other herbicides on triazine susceptible common lambsquarters. Rimsulfuron was the least effective common herbicide for common lambsquarters control in both the field and greenhouse experiments. Effectiveness of Five Foliar Corn Herbicides on Controlling Triazine-Resistant and Susceptible Common Lambsquarters (Chenopodium album L.) 1998.. W. S. Curran* and E. L. Werner. WSSA Abstr. 38:11. Five herbicides were applied postemergence at three rates in 1994 and 1995 to triazine-resistant (TR) and susceptible (TS) common lambsquarters in corn. Herbicide treatments included bentazon, bromoxynil, dicamba, pyridate, and 2,4-D (dimethylamine). Each herbicide was applied at three rates ranging from the full rate (1X) to one-quarter (1/4X) the full rate. In greenhouse research, the same five herbicides were applied at six different rates to TR and TS common lambsquarters. In both the field and greenhouse experiments, weed control and weed biomass were recorded. In 1994, dicamba, pyridate, and bromoxynil were more effective than bentazon or 2,4-D at reducing common lambsquarters biomass. In 1995, all five herbicides were equally effective at reducing common lambsquarters biomass. Increasing herbicide rate had a greater reduction in common lambsquarters growth with all herbicides in 1994 compared to 1995. In 1994, although no difference in susceptibility was detected between the TR and TS biotypes in terms of percent control, the TR biotype biomass was reduced more than the TS biotype with every herbicide except dicamba and 2,4-D. In 1995, bromoxynil, bentazon, and dicamba reduced TR common lambsquarters biomass more than the TS biotype. In the greenhouse, dicamba provided the best overall control, while bromoxynil and bentazon provided the least. Herbicide susceptibility differences were less in the greenhouse than in the field experiments between TR and TS common lambsquarters. Common lambsquarters control with 2,4-D and pyridate was better on average for the TR biotype than the TS. The other herbicides produced more similar results. These data suggest that differences in performance may exist between common lambsquarters biotypes for several non-triazine foliar-applied herbicides. Herbicide Susceptibility and Control of Common Lambsquarters in Corn. 1995. W. S. Curran and R. J. Parks. Proc. NEWSS 49:93. Previous research by these authors and others suggests the potential for differential susceptibility of triazine-resistant (TR) and susceptible (TS) weed biotypes to non-triazine herbicides. Differential fitness and herbicide susceptibility of TR weeds from their susceptible counterparts could afford alternative control strategies in field crops. Field and greenhouse experiments evaluated the susceptibility and control of resistant and susceptible common lambsquarters (Chenopodium album L.) to reduced rates of several foliar applied corn herbicides. Greenhouse experiments examined foliar applied bentazon, bromoxynil, dicamba, pyridate and thifensulfuron. Field studies included the above herbicides, but excluded thifensulfuron and included 2,4-D. Herbicide rates for the field study included 0.25X, 0.5X, and 1X the manufacturer's suggested use rate for each herbicide. A single rate of atrazine was included in both the greenhouse and field experiments. In the greenhouse, atrazine had little effect on the growth of the resistant biotype, while it reduced the susceptible one up to 68%. Although differences were small, the resistant biotype displayed greater sensitivity to bentazon, bromoxynil and dicamba than the susceptible one. The two biotypes responded similarly to pyridate and thifensulfuron. In field experiments, atrazine provided excellent (96%) control of the TS biotype and no control of TR common lambsquarters. Performance of the other herbicides was similar for the two common lambsquarters biotypes and regardless of triazine susceptibility, all five non-triazines were effective at the highest rates and less competent at reduced rates. Dicamba was the most consistent herbicide for common lambsquarters control at the rates evaluated. This research suggests that differential herbicide susceptibility due to triazine resistance may be present in common lambsquarters. Although slight differences in lambsquarters susceptibility may exist with some herbicides, successful control programs depend mostly on herbicide rate selection and timely accurate application. Control of Triazine Resistant and Susceptible Common Lambsquarters (Chenopodium album L.) with Several Foliar Herbicides. 1995. W. S. Curran and R. J. Parks. WSSA Abstracts 35:326. Previous research by these authors and others suggests the potential for differential susceptibility of triazine-resistant (TR) and susceptible (TS) weed biotypes to non-triazine herbicides. Differential fitness and herbicide susceptibility of TR weeds from their susceptible counterparts could afford alternative control strategies in field crops. Field and greenhouse experiments evaluated the susceptibility and control of resistant and susceptible common lambsquarters to reduced rates of several foliar applied corn herbicides. Field studies were conducted at four locations in Pennsylvania over a two-year period. Bromoxynil, dicamba, and thifensulfuron in combination with atrazine and cultivation were evaluated for the control of TR and TS common lambsquarters. Weed seed was collected from field experiment locations and assayed in the greenhouse for differences in herbicide susceptibility. In field experiments, weed control was better in cultivated plots than non-cultivated, and atrazine improved the level of control only if TS weeds were present. The lowest rates of bromoxynil and dicamba (1/4X) gave acceptable common lambsquarters control at all locations regardless of triazine susceptibility. The low rate of thifensulfuron (1/2X) was only acceptable in combination with cultivation. In greenhouse experiments, biotypes were similarly sensitive to bromoxynil and dicamba, while one TR biotype was slightly less sensitive to thifensulfuron. This research suggests that differential herbicide susceptibility due to triazine resistance varies in common lambsquarters and although slight differences may exist, successful reduced rate herbicide programs depend more on timely and accurate application. Common Lambsquarters (Chenopodium album) Control in Corn (Zea mays) with Postemergence Herbicides and Cultivation. 1995. R. J. Parks, W. S. Curran, G. W. Roth, N. L. Hartwig, and D. D. Calvin. Weed Technol. 9:728-735. Greenhouse studies assessed the susceptibility of three common lambsquarters biotypes to foliar-applied bromoxynil, dicamba, and thifensulfuron. Field studies evaluated the effectiveness of the same herbicides in conjunction with atrazine and row cultivation for the control of common lambsquarters in corn. In the field, bromoxynil was applied at 140, 280, and 420 g/ha, dicamba at 140, 280, and 560 g/ha, and thifensulfuron at 2.3, and 4 g/ha. In the greenhouse, bromoxynil and thifensulfuron reduced common lambsquarters growth by at least 55%, while dicamba reduced growth 45% or less. Two of the three biotypes were resistant to atrazine. In the field, weed control was up to 70% better in cultivated plots than in noncultivated plots. Cultivation sometimes promoted additional weed emergence, but later emerging weeds rarely reached reproductive maturity. Atrazine improved the level of weed control only if triazine-susceptible weeds were present. The lowest rates of bromoxynil and dicamba (140 g/ha) controlled common lambsquarters 85% or greater even without cultivation, whereas control with the low rate of thifensulfuron (2 g/ha) was acceptable (greater than 85%) 8 wk after planting only in combination with cultivation. Combinations of reduced herbicide rates and mechanical cultivation provided effective, alternative control strategies for both triazine-resistant and susceptible common lambsquarters. Herbicide Susceptibility and Biological Fitness of Triazine-Resistant and Susceptible Common Lambsquarters (Chenopodium Album) 1994. R. J. Parks, W. S. Curran, G. W. Roth, N. L. Hartwig and D. D. Calvin. Proc. NEWSS 48:23. Biological fitness and negative cross-resistance to other herbicides may be an important factor in managing triazine-resistant common lambsquarters (Chenopodium album L.). Greenhouse experiments examined the sensitivity of a resistant and a susceptible biotype to foliar-applied bentazon, bromoxynil, dicamba, pyridate, and thifensulfuron. The noncompetitive vigor of triazine-resistant and a susceptible common lambsquarters also was compared by growing plants in individual containers and harvesting them periodically throughout their vegetative period and at reproductive maturity. In the herbicide susceptibility study, 11 kg ai ha-1 atrazine had no effect on the growth of the resistant biotype, while it reduced susceptible common lambsquarters biomass one up to 68%. Estimated I50 values indicated the resistant biotype exhibited between 36 and 79% greater susceptibility to bentazon, bromoxynil, dicamba, and pyridate than did the susceptible one, while both responded similarly to thifensulfuron. In growth studies, the susceptible biotype achieved greater height, leaf area, and plant dry weight than did the resistant population for the majority of harvest dates; however, values equalized between biotypes as the plants reached maturity. These experiments suggest that alternative management programs that exploit reduced fitness and increased herbicide susceptibility in triazine-resistant common lambsquarters could be developed. However, further studies are needed to determine whether these results have application for the management of triazine-resistant weeds in the field. |
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