Midwest Vegetable Guide - 2022 - 58

Weed Management Strategies
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 betweenrow,
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.
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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
Midwest Veg Guide 2022
Midwest Vegetable Guide - 2022

Table of Contents for the Digital Edition of Midwest Vegetable Guide - 2022
