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Funded Project |
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Funding Program:
Regional IPM Competitive Grants - Northeastern |
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Project Title:
Identifying Field-specific Characteristics that Lead to Successful Postemergence Weed Management in Corn |
Project Directors (PDs):
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Lead State: PA Lead Organization: Pennsylvania State University |
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Cooperating State(s):
Delaware, New Jersey |
| Extension Funding: $55,167 |
| Research Funding: $114,494 |
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Start Date: Jul-01-2000 End Date: Jul-14-2003 |
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Pests Involved: weeds |
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Site/Commodity: corn |
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Summary:
Postemergent applications of herbicides are increasingly important for managing weeds in com. Postemergence (POST) strategies can target specific weed species, stage of growth, and can be based on weed severity by adjusting rate and application timing. In addition, a total POST approach can reduce the number of trips across the field and can be environmentally positive, compared to using soil-applied herbicides. However, the risk of poor weed control and reduced crop yield is generally considered greater with a POST approach compared with a soil-applied approach. A single or one-pass nonresidual POST application offers a greater risk of failure compared with soil applied or multi-pass POST herbicide programs. Therefore, this strategy has not been widely accepted in corn production systems. However, previous experience by both university scientists and farmers suggests that one-pass POST programs can succeed in some situations. Identifying field specific characteristics that lead to successful POST weed management in corn is the focus of this project.
The proposed research and education activities in this proposal will be conducted at multiple locations in the Mid-Atlantic Region. The primary goal of the work outlined in this proposal is to develop a Decision Guide that will help growers assess their potential for eliminating soil applied herbicides, while relying on postemergence control of weeds in corn. In order to accomplish this goal, four objectives have been identified. The proposed research will specifically determine the effect of tillage system on rate and duration of weed species emergence at locations in Delaware, New Jersey, and Pennsylvania. A weed emergence model will be developed in this process. Secondly, we will examine the effect of weed severity and POST timing on weed control and corn grain yield at these locations. Thirdly, the extension portion of the project, we will demonstrate the impact of varying management, soil type, climate, and weed infestation on POST weed control and corn grain yield, and lastly, a decision guide will be developed to help assess the relative importance of field parameters (weed species severity, tillage system, soil characteristics, planting date, herbicide program, and climatic conditions) for successful POST weed control without soil residual herbicides. It is intended that the decision guide will be easily accessed in electronic or paper format. In this process, we will demonstrate and extend weed management guidelines along with the Decision Guide through outreach education activities. The proposed project includes scientists and extension personnel from three northeastern states. County agents will play an integral part in this project. The results of this research and extension project will help growers save money, reduce their reliance on soil residual herbicides such as atrazine, and thus help preserve water quality, and promote IPM practices that base weed management on pest species and severity. Problem, Background and Justification Rationale. This proposal addresses issues specifically mentioned in the Northeastern Regional IPM Program Priorities. Corn is the most widely grown agronomic crop in the northeastern region of the US. To date, corn producers have not used a total postemergence (POST) herbicide program in corn. Greater reliance on total POST treatments will allow producers to more fully implement an integrated pest management approach by tailoring a weed management tactic to the emerged weed community rather than using prophylactic tactics. The ability to recommend a total POST herbicide program in corn will allow producers to reduce or eliminate soil-applied herbicides that have the greatest potential to move into water sources; use herbicides that are less likely to leach into groundwater supplies; and possibly reduce the overall amount of herbicides used by-producers. This research will be applicable to a wide range of farmers in the Northeastern Region. Current situation. In the United States, 95% of the corn and soybean acreage is treated with herbicides each year (Burnside 1993) and greater than 200 million pounds of herbicide active ingredient is used annually in corn and soybean production. Most Northeast farmers rely heavily on soil applied residual herbicides for weed management in corn (Anonymous 1997; Hancock 1998). Atrazine and other triazines and the chloroacetamide herbicides including metolachlor and acetochlor account for the majority of corn herbicides applied in the Northeast Region as well as throughout the Corn Belt (Anonymous 1997). Certain soil residual herbicides have been continually examined and criticized as potential environmental threats to water quality (Baker 1985; Wu et al. 1983). In addition, soil applied residual herbicides are often considered less suited than POST herbicides for developing more integrated weed management programs based on weed species and threshold density. This project will assess the potential success of foliar or POST control of weeds in corn based on field specific characteristics. We believe that soil residual herbicides are not always necessary for the management of weeds in corn. Postemergence weed control. The potential for successful POST weed control in corn has improved with the introduction of herbicide resistant crops (HRCs). Prior to their introduction, few options existed for managing both grasses and broadleaves after corn emergence. Use of non-selective herbicides in HRCs can provide cost effective weed control, increase the flexibility of crop rotations, improve crop yields, and also offer compatibility with minimum tillage systems (Wilcut et al. 1997). In these proposed experiments, glyphosate resistant corn will be used along with the herbicide glyphosate. Glyphosate resistant corn allows for the use of this nonselective herbicide for control of most weeds postemergence. Glyphosate's positive environmental profile makes it an excellent candidate for weed management in corn. Although glyphosate will be used in these experiments, a number of effective herbicides are available today for POST control in corn for both HRC and conventional corn hybrids (Curran et al. 1999). Weed interference in corn. The corn grower has some control over weed interference by choosing the time and method of weed control. If a grower adopts total POST weed control, the time of herbicide application is important to ensure successful weed control and to prevent crop yield loss. Studies examining the relationship between weed density and corn yield have been conducted for a number of weed species (partial list includes: Beckett et al. 1988; Camacho et al. 1990; Cardina et al. 1995; DeFelice et al. 1988; Knezevic et al. 1994; Moolani et al. 1964; Scholes et al. 1995; Wilson and Westra 1991; and Zanin and Sauin 1988). Much of the previous duration of interference research in corn examined single weed species and used hand pulling and hoeing to remove weeds by a certain period of time after corn and weed emergence (DeFelice et al. 1988; Knake and Slife 1969; Moolani et al. 1964). A limited number of critical weed-free period studies on corn have been conducted with mixed weed species in the United States and Canada (Carey and Kells 1995; Hall et al. 1992; Zimdahl 1988). Researchers in Canada investigated early-season competition from mixed weed infestations on corn yield in seven experiments (Hall et al. 1992). Weed density was strongly correlated with the critical period, with sites having high weed populations generally having shorter critical periods than sites with low to moderate infestations (Hall et al. 1992). More recently, interference research has examined the use of selective herbicides such as nicosulfuron for weed removal (Carey and Kells 1995). In a Michigan study, a combination of nicosulfuron plus bromoxynil prevented reductions in corn yield when applied to weeds 10 cm or less in height (Carey and Kells 1995). Corn yield and weed control was more variable if this combination was applied to weeds 15 to 20 cm tall. Penn State research looking at one-pass application timing of glyphosate in glyphosate resistant corn determined that application to 15 cm weeds or about 4 weeks after planting provided the most consistent weed control (Voight et al. 2000). Similar experiments were conducted at 22 sites in the North Central region during 1998 (Loux et al. 1998). The critical period ranged from 10 to 30 cm tall giant foxtail, with a 15 cm height being the most common stage where yield losses were first observed. The differences between the Penn State and North Central Region experiments demonstrate the importance of region specific data to more accurately estimate the influence of weed species and severity on critical weed-free period. The results of these studies illustrate the complexity of crop-weed interactions. The time at which weeds begin to impact yields is influenced by many factors with both weed density and early season soil moisture availability perhaps the most important. Because few competition experiments have been conducted in the Northeast or included common weed species found in the mid-Atlantic region, accurate critical period information is lacking for this region. None of the studies cited in this review were conducted on coastal plain soils, which have limited water-holding capacity. Objective 2 in this proposal will help identify; the critical period for one-pass POST application at multiple locations in the mid-Atlantic region, including water-limiting soils. Seed bank effects. Many weed species typically emerge during certain periods of the year (Ogg and Dawson 1984; Roberts and Boddrell 1983). This period of emergence is influenced by several factors including seed dormancy status and soil environmental conditions (Baskin and Baskin, 1985; Bouwmeester and Karssen 1989). Temperature broadly influences time of germination and is the basis for generally categorizing some plants as summer or winter annuals (Egley and Williams 1991). More recently, field experiments have been conducted across the Corn Belt measuring weed seed bank emergence along with daily values for air and soil temperature and precipitation (Forcella et al. 1997). Variation among site-years for some species could be attributed to microclimate variables thought to induce secondary dormancy. Objectives: Research Objectives: 1. Determine the effect of soil disturbance on weed species emergence rate and duration and develop a predictive model for weed emergence - This experiment will help define weed emergence periods for common annual weeds in the Northeast. These data will be used to develop a weed emergence model, which in turn. will support a decision guide that will help predict the success of total POST weed control programs. This study will be conducted in years two and three. 2. Determine the effect of weed density on single-pass POST weed control and corn grain yield. - This experiment will help determine the impact of weed density and weed control timing on corn grain yield with a single POST application of a non-residual herbicide. These data will be used to develop a decision guide that will help predict the success of total POST weed control programs based on critical application period to avoid yield loss. This objective will be conducted in years two and three. Extension Objectives: 3. Evaluate the effectiveness of a total POST weed control program over a broad range of conditions. -This study will be conducted over three states in a range of conditions to identify characteristics for success and/or failure. This objective will be conducted in years one and two. 4. Develop a decision guide for the probability of a successful total POST herbicide program in corn and need for residual herbicide(s) at a given location. A user-friendly decision guide, which incorporates data from the previous three objectives. To be conducted throughout the three years. |
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