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Updated: November 5, 2024

Organic Weed Management in Weeds

Weed management is more challenging in organic crops and accounts for a large portion of production costs. As such, managing weeds is a major economic constraint to the organic vegetable industry, and comparisons of weed communities between conventional and organic farming systems consistently demonstrate higher weed levels in organic systems.
Updated: November 5, 2024

Branching Out - Winter 2022

Read some "parting thoughts" from Extension Forester Jonathan Kays prior to his retirement. Our regular features include the "Woodland Wildlife Spotlight," "Invasives in Your Woodland," plus the events calendar, the Brain Tickler challenge, and the News and Notes section.
Screenshot of Jonathan Kays on Voice of America
Updated: November 5, 2024

Minimizing Combine Weed-Seed Movement

Harvest is fast approaching for grain producers; some of which have already begun shelling corn in recent days. Though this time of year often marks the end of the season, some decisions we make at harvest have lasting effects on subsequent growing seasons; one of which is weed control. If weeds are allowed to mature and set-seed, harvest equipment can be highly effective at retaining, and transporting weed seeds from field to field, as well as dispersing weed seeds across the field, further increasing the weed seed bank.
Photo: Kondinin Group Research Report www.farmingahead.au.
Updated: November 5, 2024

Keys to Identifying Palmer Amaranth and Waterhemp (FS-2023-0653)

Pigweeds are annual weeds that can cause significant problems for Maryland farmers. Palmer amaranth and waterhemp are two pigweeds that are especially troublesome, and have been designated as noxious weeds by the Maryland Department of Agriculture. Therefore, it is required that these two species be actively managed to prevent their spread and resulting negative impacts on Maryland agriculture. To the untrained eye, Palmer amaranth and waterhemp can appear similar to each other and to other pigweed species. However they can be easily distinguished from one another by looking at some key botanical characteristics. Becoming familiar with these species allows for earlier detection, and as a result, improved management practices. Authors: Kurt Vollmer, Ph.D., and Ben Beale; Title: Keys to Identifying Palmer Amaranth and Waterhemp (FS-2023-0653)
Updated: November 5, 2024

Evaluating Biosolarization as a Weed Management Tactic in Organic Vegetables

Biosolarization, akin to solarization, is a soil disinfection technique but involves the addition of organic amendments before the passive solar heating process. As the damp soil warms, organic materials break down, releasing allelochemicals and other biotoxic compounds briefly into the soil. Read more about "Evaluating Biosolarization as a Weed management Tactic in Organic Vegetables."
Updated: November 5, 2024

Thoughts on the Control of Palmer Amaranth in Organic Systems

An article on the control of Palmer amaranth in organic systems that will discuss the biology, Palmer amaranth weaknesses, management considerations, early detection, and elimination, managing populations in organic systems, considering cultural techniques/growing practices that are less conducive to palmer amaranth, strategic tillage, cultivation, and crop rotation/fallowing.
Updated: November 1, 2024

Herbicide Spray Tank Check Charts for Corn and Soybean

As planting gets underway, it is important to stay on top of our most troublesome weeds. In particular, marestail/horseweed, common ragweed, and Palmer amaranth. Below are two new charts to help determine the type of products to be included in the tank mix to best manage these weeds in corn and soybean.
Updated: November 1, 2024

Time to Pull Palmer Amaranth

Lately, I have seen several fields with Palmer amaranth flowers (Figure 1). It is imperative that these plants be managed before harvest (Palmer amaranth is listed as a noxious weed in Maryland and Delaware). At this point, mowing or herbicides will not improve yield nor prevent Palmer from germinating next year. Plants need to be physically removed from fields. Palmer amaranth has both male and female flowers on separate plants (Figure 2), and focus should be placed on removing the seed-producing females first. A single female can produce approximately 600,000 seeds per plant, and these seeds can remain viable for six years. Palmer seed matures within 2 weeks of flowering and if left unchecked, a single plant can infest an entire field within a few years (Figure 3). 
Figure 1. Palmer amaranth emerging through a soybean canopy. Image: k. Vollmer, University of Maryland
Updated: November 1, 2024

Spring-Seeded Grass Cover Crops in Watermelon Production

Commercially acceptable weed control is difficult to achieve in plasticulture vegetables even with pre- and post-emergent herbicide applications. These applications often do not provide season long weed control between rows. Moreover, several weed species have become resistant to commonly used postemergence herbicides, including common ragweed and pigweed species. Cover crops are an additional tool that could be successfully integrated into a weed management program.
Figure 1. Tractor-Mounted shielded sprayer used for cover crop termination.
Updated: November 1, 2024

Options for Postemergence Common Ragweed Control in Enlist E3 Soybean

In Maryland, populations of common ragweed have developed resistance to three herbicide groups, Group 9 (glyphosate), Group 2 (FirstRate, Synchrony), and Group 14 (Flexstar, Valor). These herbicide-resistant populations limit options for effective postemergence control. Even though alternative herbicides are available, control can be inconsistent when applied to common ragweed plants exceeding 4” tall (Figure 1). 
Figure 1. Common ragweed pants exceeding optimal spray height.