Reducing Weeds in Berry Crops:
In March, we talked about 3 things to do before you plant your next berry
field to reduce weed problems - site selection, crop rotation and preplant
cleanup. In May, we focused on things to do at planting time- stale seedbed
technique, switching to plasticulture, banding fertilizer and using trickle
irrigation. This month, let's look at things to do throughout the growing
- Manage field edges: Many problem weeds in berries
like thistles, dandelions, and groundsel move in from field edges. Did
you know that a weed growing in the small area of soil outside of your
crop may produce 10 to 150x more seeds than a weed growing in the crop
canopy? Plan some time each month to either mow weeds before they flower
and seed, or use a directed flaming or burndown herbicide on all edges
of fields. Ditches beside your fields may also be a source of weeds,
but herbicide options will be limited if water is present - physically
removing weeds may be required.
- Spot treatments: Many weed problems start in patches,
but once they spread through the field, you wish you had targeted the
spot where they started. Invest in some equipment dedicated to spot
treatments eg. a good hand sprayer, a wick wiper, a hand flamer and
a dripper, and charge them so they are ready to go. Plan the time to
walk your field in May, June and the fall, as well as any time weed
regrowth is ready for treatment. Most growers find satisfaction with
spot treatments, stopping weeds dead in their tracks.
- Chemical renovation: This technique has proven effective
in Ontario where common groundsel became the dominant weed problem.
After harvest, Gramoxone is directed between the rows to kill weeds
in the mulched area, as well as to narrow rows. Shields should be mounted
between each nozzle to prevent drift onto the crop row. After application,
renovation is completed as usual: rows are mowed down, fertilizer applied,
and herbicides applied, but no soil tillage is used. Chemical renovation
will drastically change the weed spectrum, so be aware that perennial
weeds may enjoy the undisturbed soil. Also, because no soil is thrown
up on the crown, this system may not be suitable where crown heaving
is a problem.
- Weed scouting: Most IPM scouts are trained to look
for insects and diseases, but additional scouting for weeds may pay
dividends. Scouts need to learn to identify weeds at cotyledon or young
stages, and should map each field showing weed locations and types.
Unknown weeds should be collected and identified. Weed scouting and
mapping can help identify sources of weeds (see Field Edges above),
and over the years, can help when planning your weed management strategies
In the next issue, I will focus on things you can do during the fall
to reduce weeds.
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