Great American Media Services

2022 Midwest Vegetable Guide

Issue link:

Contents of this Issue


Page 57 of 291

Weed Management Strategies 58 Midwest Veg Guide 2022 Pre-plant, or pre-crop emergence weeds. After bed preparation, shallow cultivation tools including rotary hoes and flextine cultivators can be used to uproot small weeds including those that have germinated but not yet emerged from the ground (white thread stage). These tools can be used prior to planting to drain weed seeds from the top 1-2" of soil without bringing new seeds to the soil surface (see stale seed bed above). For large-seeded vegetable crops such as sweet corn, snap beans or cucurbits, flextine cultivators may also be used after planting but before crop emergence. Weeds after crop emergence. Many cultivation tools are available, and are generally categorized as either between- row, near-row, or in-row tools, based on the zone they target. The flextine cultivator mentioned above can also be used after crops have emerged and are firmly anchored (1-2 leaf growth stage), scratching the soil of between- and in-row areas uprooting and burying weeds at their white-thread stage. Between-row weeds. Removing weeds between crop rows is relatively easy, and there are several options available. Between row tools include various row-crop cultivators equipped with knives and sweeps that are capable of killing larger weeds. These tools may also be used to throw soil into the crop row at later crop growth stages, burying small weed seedlings. Other between-row tools include basket weeders (e.g. Buddingh or Tilmor) and rolling cultivators (e.g. Lilliston or Hillside). Basket weeders are designed to work close to the crop row, throwing minimal soil while uprooting small weeds. They require level soil that is relatively stone free. Rolling cultivators are more aggressive tools that are equipped with sets of toothed discs (spider gangs) that can be easily adjusted to accommodate different levels of desired soil disturbance and angles. They are particularly useful on edges of beds and in situations where crop or cover crop residue would interfere with less forgiving knives or sweeps. Near-row weeds. Tools such as side knives (sometimes referred to as beet knives or tender plant hoes) or cutaway disks are designed to disturb soil near the row without disturbing the crop, leaving a 1.5-3" band of undisturbed soil centered on the crop row. Success with these tools requires straight rows, and attention to precise steering and depth control. To best accomplish this, they should be mounted on parallel linkage with gauge wheels and steered either on the belly of a cultivating tractor, or on a steerable toolbar. In-row weeds. Weeds in the row are the most challenging to manage without disturbing the crop. This zone may be managed by burying small weeds by throwing soil into the row using sweeps, hilling disks or ridgers. Alternatively, specialized in-row tools such as finger weeders or torsion weeders may be used to reach into the crop row and uproot small weeds. In all cases, a size difference between the crop and weed is essential for success. As with near-row tools, these tools also require investments in depth control and steering for optimal performance. In some vegetable crops, such as asparagus, mowing can be an effective weed management tool. Mowing can prevent weed seed production and kill upright weeds, reducing competition. Mowing must be carefully timed to eliminate perennial, biennial, or annual weeds that would compete strongly in vegetables because of their upright growth habits. Timely, repeated mowing also helps deplete the food reserves (root systems) of perennial weeds. Mechanical control has many limitations that must be considered when designing weed management systems. Because mechanical management relies on relatively dry soil, a rainy period may prevent the use of mechanical weed management options and lead to severe weed competition. Relying entirely on mechanical practices to manage weeds is labor intensive, and many growers will use herbicides combined with nonchemical approaches to control especially difficult weeds. Some of these difficult-to-control weeds include wild proso millet in sweet corn, Canada thistle, hemp dogbane, field bindweed, quackgrass, and johnsongrass. Newly introduced problem weeds often show up in scattered patches along headlands and field borders. These are best controlled or eradicated with herbicides before large areas are infested. Cover Crops for Biological Weed Suppression One biological system that has potential in the Midwest is the use of cover crops to suppress weed development. Cover crops can reduce weed pressure in a variety of ways: they can compete with weeds to reduce weed seed production, release allelochemicals that suppress weed seed germination and growth, or produce residue that acts as a mulch to suppress weed growth. Successful cover cropping for weed suppression in vegetables requires use of competitive species that match the season and soil type. Summer cover crops with good weed suppressive ability include sorghum-sudangrass and buckwheat. Cool season cover crops like oats and oilseed radish can effectively suppress weeds beginning in late summer through the fall before winter killing in most areas of the Midwest. Winter cover crops such as winter rye or hairy vetch may provide weed suppression during the winter as well as a weed suppressive mulch if allowed to grow through early spring. One cover crop system that works well in parts of the Midwest for some large-seeded vegetable crops like pumpkins involves growing winter rye as a weed suppressive mulch. Winter rye is planted in late summer or early fall and overwinters. In the spring, the rye is killed two weeks prior to planting the desired crop. Rye can be killed using herbicides, or, once it has reached the reproductive stage, by mowing, or rolling and crimping. The rye is left as a mulch on the soil surface, and the crop is no-till planted. The system can provide early season control of many annual weeds, but generally this requires a thick uniform stand that is at least 4

Articles in this issue

Archives of this issue

view archives of Great American Media Services - 2022 Midwest Vegetable Guide