Does it ever seem like just when you’ve mastered your farm management plan, something changes and you have to rethink your strategy? Chris Streit, technical sales agronomist with DuPont Crop Protection in northern Illinois, says he sees this all too often with his growers. “It’s hard to stay on top of changing conditions and technologies. That can make decision-making difficult,” explains Streit. To help guide crop production decisions for 2017, he shares answers to common questions below.

1.  How do I know if I have herbicide-resistant weeds?

Working with an integrated team can be the key to a successful growing season. Every member of a growers’ farm team should understand the bigger picture of the operation and how one product selection affects another. DuPont can help develop a full-year crop protection plan.

It’s not easy to identify herbicide-resistant weeds based on field observations alone. If a herbicide fails to control a weed that is normally susceptible to the rate of herbicide you applied, you may have a resistant weed population, especially if adjacent weeds are effectively controlled. To confirm resistance, submit suspect weed samples for testing. Purdue University offers testing on seeds or leaves of waterhemp, Palmer amaranth and giant ragweed for resistance to ALS, glyphosate and PPO herbicides.

Illinois has seen an increase in glyphosate-resistant weed populations, particularly in waterhemp, marestail and Palmer amaranth. Southern Illinois University and the University of Illinois reported PPO inhibitor resistant populations of Palmer amaranth in Cahokia and Collinsville, Illinois, fields in 2016. Although the frequency of PPO-resistance seems low at this point, Palmer amaranth’s ability to evolve quickly could mean control problems for growers in the near future.

While resistant weed populations are increasing, many herbicide failures are due to factors other than resistance. Application factors, including time of day, environmental conditions, application practices and insufficient herbicide coverage can all contribute to herbicide failure.

2.  How can I reduce the spread of resistant weed populations?

Get into the habit of using best management practices to help control the spread of resistant weeds. Scout fields early and regularly throughout the season and take note of weed species. Herbicides are most effective when weeds are small and growing quickly, so a timely application is important. If appropriate, a post harvest burndown herbicide application to control winter annual weeds will help ensure fields are clean for planting.

Diversifying your herbicide strategy makes it more difficult for weeds to develop resistance. Use multiple modes of action and tank-mix grass and broadleaf herbicides for broad-spectrum weed control.

Layering residual herbicides extends the period of weed control. A study by the University of Minnesota reported that control of glyphosate-resistant waterhemp dropped sharply by late June when using a preemergence herbicide alone. In contrast, layering a preemergence herbicide with a residual postemergence application provided 90 to 95% control of glyphosate-resistant waterhemp through September. Always use full application rates and follow label instructions for effective weed control.

Preventive and cultural practices, such as keeping ditches and field borders free of weeds, cleaning harvest and tillage equipment between fields, rotating crops, and planting in narrow rows to increase crop competition, can all help control the spread of resistant weed populations.

3.  Do I need to use fungicides?

Agronomists get this question every year, and the answer depends on the season. The short answer is that you should use a fungicide if disease pressure is high enough to reduce yields. To help you make the decision, take into account disease severity, number of plants infected, future weather conditions expected, and how susceptible your hybrids and varieties are to disease. Scouting for disease early and often can help you stay ahead of disease progression and time your fungicide application for the maximum return on investment.

Iowa Soybean Association On-Farm Network trials over a nine-year period showed that corn yields increased an average of 5.2 bushels per acre after a fungicide application. During high disease years, the average increase rose to 8.4 bushels per acre.

Fungicide applications also help maintain stalk integrity late in the season. When plants are stressed by disease, photosynthesis and sugar production are reduced. To continue filling grain, the plant compensates by remobilizing sugars from the stalk. That is why stalks sometimes become soft late in the season during grain fill. When weather delays harvest, a mid-season fungicide application can help ensure your crop will still be standing when you’re able to run the combine. Growers who saw corn standability issues this year could benefit from a fungicide application if choosing similar hybrids next year.

4.  What will disease pressure be like next season?

While it’s hard to predict future disease issues, there are clues that can help you prepare. Most growers know that many diseases, particularly fungal pathogens, overwinter in soil. Late-season rains and high humidity brought diseases to Illinois fields this year. It will be important to monitor conditions in 2017 since pathogen levels in soil may be high.

Growers often believe a cold winter will mean less disease next year, but that isn’t necessarily true. Fungal spores have evolved to adapt to harsh conditions. They can be insulated by soil, plant residue and snow, allowing them to survive extreme winter temperatures. Don’t rely solely on winter conditions to set expectations for disease pressure next year.

The best indication of what disease pressure might be like next season is to review field history, cultural practices, and hybrid and variety choices. These factors, combined with in-season weather conditions, are better indicators of what you can expect for disease pressure the following season.

Diseases thrive in fields with reduced tillage and no crop rotation. Reduce plant residue in fields, manage weeds and rotate crops to help reduce disease problems. Find disease management strategies here.

Scout fields throughout the season for signs of disease, since environmental conditions and disease pressure can change quickly. Insects are also vectors for disease, so controlling them can help reduce disease. Be prepared to apply fungicides if diseases like gray leaf spot or northern corn leaf blight threaten yields. DuPont Aproach® Prima fungicide delivers two modes of action for effective disease control in corn and soybeans.

5.  How can I get the most from my input dollars?

Understand your fields and identify the main trouble areas you need to address. Every grower has different input needs and costs. Consult with your trusted agronomic advisor to help you make input decisions.

Choose suppliers who allow you to buy chemical and seed products early to bundle savings. You’ll also benefit by matching your seed genetics with the appropriate crop protection program. The DuPont^™ TruChoice® Early Pay Multiplier program allows you to multiply your savings upfront for the purchase of seed and crop protection products.

One area where you shouldn’t cut corners is weed control. You’ll likely end up paying more in the long run with reduced yields and less harvest efficiency.

If your equipment is set up with precision agriculture technology, use it. Work with your agronomist to develop a prescription for planting populations and fertilizer and crop protection applications. This allows you to focus input dollars on the acres that have the highest potential for top-end yield.

You can find region specific crop protection information at the Seed to Harvest Resource Center.

TruChoice^® program terms and conditions apply.

Always read and follow all label directions.

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