Utilizing potential weed pressures to improve efficiency of weed management programs

Currently, Iowa farmers have no convenient method for reliably determining weed pressures in a field. It is difficult to establish an efficient weed management program without a realistic estimate of weed pressure. As a result, many farmers may apply more herbicides than are necessary to achieve adequate weed control. This practice may result in excessive production costs or degradation of the environment due to erosion or overuse of herbicides

Fomesafen Carryover to Corn

ISU Extension and Outreach Field Agronomists continue to receive calls regarding fomesafen carryover injury to rotational corn. There are several factors resulting in this injury: 1) continued problems with waterhemp result in late-season applications, 2) fomesafen is relatively persistent, and 3) many areas of Iowa received less than average late-season rainfall in 2017. In most cases, this carryover injury has been limited to relatively small sprayer overlap areas, though some fields are showing injury on a more widespread area

Managing Winter Annual Weeds this Spring

After another relatively wet fall, late harvest season, and mild winter, early weed management may be important this spring for those who have persistent issues with winter annuals such as field pennycress and horseweed/marestail in no-till. Winter annuals resume growth soon after the arrival of warm temperatures, so as soon as fields are fit, the weeds will be susceptible to spray

Effect of Residual Herbicides on Cover Crop Establishment

The interest in cover crops has increased recently due to the benefits they can provide to the corn-soybean cropping system. The use of residual herbicides has increased at the same time, and the potential impact these herbicides may have on establishing cover crops is an important consideration

Managing Residual Herbicides with Cover Crops

A common question when incorporating cover crops into a production system is, will the cover crop interfere with the performance of residual herbicides included with the burndown treatment? This article will discuss the fate of residual herbicides applied to crop residue and living cover crops, and how this may influence herbicide effectiveness

Fall Weed Control in Pastures

Fall is one of the best times for managing perennial and biennial weeds found in pastures or other areas maintained in perennial grass. As perennials prepare for the upcoming winter they move energy reserves from shoots to their perennial vegetative reproductive structures (e.g. rhizomes, perennial rootstocks). Systemic herbicides applied at this time are translocated along with the energy reserves to the reproductive structures, therefore providing more consistent control than applications made at most other times of the year

Harvest Considerations to Reduce Weed Seed Movement

Harvest is just around the corner for many Iowa farmers and now is a good time to consider options to reduce movement of weed seed between fields with harvest equipment. While we may not think of it during harvest time, combines are extremely effective at transporting seed from field to field. A few precautions leading up to harvest and during harvest can help manage any escaped problem weeds

Scout Now for Palmer Amaranth

Now is a great time to scout for Palmer amaranth (Amaranthus palmeri) in Iowa cropfields. As of late 2018, this species had been identified in over half of Iowa’s 99 counties.While new identifications have waned since the widespread introductions in 2016, Palmeramaranth is a species to watch out for in virtually any Iowa crop field. A native of theAmerican southwest, Palmer amaranth is more competitive than common waterhemp(Amaranthus tuberculatus), a pigweed native to Iowa. Both species are known for fastdevelopment of herbicide resistance, prolific seed production (\u3e500,000 seeds/plantpossible), and prolonged emergence

Survey of Herbicide-Resistant Waterhemp in Iowa Corn and Soybean Fields

The escalating spread of herbicide-resistant weed populations has become a production challenge in the corn-soybean based cropping system of the Midwest. With the evolution of weed resistance to major herbicide groups used in corn and soybean, we have a limited number of herbicide options left, which is even more disconcerting as no new herbicide site of action has been discovered in the past three decades. A new site of action coming to the marketplace in the next 5-8 years would also be a rare event

Preemergence Herbicide Application Timings: Pros and Cons

Preemergence herbicides are the foundation of herbicide-based weed management systems, and effective use of these products is essential to protect crop yields and reduce selection pressure for herbicide resistant weeds. In a perfect world, applying preemergence herbicides immediately after planting would provide the greatest likelihood of maximum performance, but equipment and labor availability limit many farms from using this approach. This article will provide a brief overview of the pros and cons of different application strategie