Berry Crops: Introduction
Excerpt from 2010-2011 Chapter 14, Publication 75,
Guide to Weed Control, Order
this publication
Table
of Contents
- Cultural Weed Control in Berry Crops
- Perennial Weed Control
- Site Preparation
- Mulching
- Reducing Weed Pressure
- Rotating Herbicide Families
- Herbicide Application Timings
- Related Links
In April of 2009, the Ministry of Environment ammended the Pesticides
Act with the Cosmetic Pesticides Ban Act, 2008 and Ontario Regulation
63/09. Pesticides are now classified for sale and use under 11 different
classes. It should be noted that agriculture (e.g. nursery production)
is exempted. For more information on the legislation see the Ministry
of the Environment’s website at www.ontario.ca/pesticideban.
Cultural Weed Control in Berry Crops
A successful weed control program must integrate cultural and chemical
weed control practices. Growers cannot depend entirely on chemical weed
control in berry crops, since there is a limited spectrum of herbicides
registered for these crops.
Perennial Weed Control
It is important to identify and control perennial weeds in the preplanting
year. It is very difficult to control perennial weeds once a planting
is established because of crop sensitivity to some herbicides and since
it is not possible to clean cultivate in established berry crops.
The following perennial weeds present serious problems in these crops:
quackgrass, bindweed, vetch, wild grape, perennial nightshade, thistles,
ground-ivy (creeping charlie) and burdock. In strawberries, sheep sorrel,
toad flax and milkweed also present problems.
Systemic herbicides such as glyphosate (e.g. ROUNDUP) or amitrole (e.g.
AMITROL 240) should be applied to perennial weeds in the preplanting year.
Consult the product label and be sure to use the recommended rate for
the weed in question. Apply the herbicide at the proper stage of growth
of the weed, otherwise only temporary control will be achieved. Repeated
cultivation of some perennial weeds such as bindweed will also provide
control.
Site Preparation
A green manure crop such as perennial ryegrass or Sudan grass should
be established in the preplanting year following or in conjunction with
measures to control perennial weeds. This crop will provide competition
to reduce weed growth as well as improve the soil structure. Non-selective
herbicides can be applied before planting the green manure crop and before
plowing it under. Short residual selective herbicides such as 2,4-D may
be used with the green manure crop, but avoid using herbicides that leave
a soil residue that will carry over into the planting year. See Chapter
6, Preplant-Site Preparation Prior To Any Crop, page 81.
Mulching
For bramble and bush fruit, biodegradable plastic mulch could be used
for weed control in the planting strip. Straw mulch will also assist in
weed control beneath the plants or in the planting strip if it is applied
early in the season before the weed seeds germinate.
Use mulch that is free of weed seeds and ensure that enough nitrogen is
provided for the plants. The mulch should be pulled away from around the
plants for winter rodent protection.
For strawberries, use of straw mulch before weeds germinate can help
control weeds. Some growers are trying plasticulture as a way to improve
weed control.
Reducing Weed Pressure
Cultivation can provide weed control between the rows. In bramble and
bush fruit, a vigorous sod between the rows will prevent weeds from becoming
established. It is better to seed in a fescue sod rather than rely on
a natural sod composed of weed and grass species, because the weeds will
seed into the herbicide strip.
Prevent weeds from setting seed in adjacent uncropped areas by using
cultural or chemical weed control measures. Mowing at regular intervals
will prevent many weeds from flowering. Try to control weeds that escape
before they set seed, by cultural removal or chemical mowing. In some
situations, tools such as a weed whip may be of use. Mowers are available
which will cut close to the plants without injury. Mowing, however, will
not eliminate weed competition.
Rotating Herbicide Families
(See Table 4-6, Herbicide
Groupings in Ontario, page 65)
In perennial crops, rotation of herbicide families is important to minimize
the building up of seed from weed escapes, including triazine tolerant
weeds. Rotation will also help avoid an accumulation of herbicide residues
in the soil that may result in crop injury over a period of years and
may hinder replanting.
Herbicide Application Timings
Preplant (PP) Treatments
Preplant treatments are applied before the berry field is planted. Some
of these herbicides kill seedlings soon after germination while others
also kill weed seeds. Most herbicides used for these treatments must bethoroughly
incorporated into the soil by cultivation soon after application. Check
the label. Also see Preplant Weed Control, Preplant Site Preparation
Prior To Any Crop on page 81 for details of products, rates and remarks.
Preplant (PP) Weed and Cover Crop Control
Control cover crops and emerged weeds before planting berry crops. Refer
to Table 6-1. Non-Selective Herbicides Available for Preplant Site
Preparation, page 77. Alternatively, a grower may choose to kill the
cover crop and/or emerged weeds just before planting the berry crop and
either till the area or leave the seedbed untilled.
Preplant Incorporated (PPI)
Two incorporations at right angles operating at a depth of 10 cm using
a double disk (7–10 km/hr) or vibrating shank S-tine cultivator (10–13
km/hr) are required unless otherwise stated. Cultivation-type equipment
used for herbicide incorporation is known to spread perennial weeds to
previously uninfested areas. Special attention should be directed toward
machinery cleanliness, and/or treating fields with perennial weeds last.
Preemergence (PRE)
Rainfall at 15–20 mm within 7–10 days after application is necessary
to activate preemergence treatments. Shallow cultivation, rotary hoeing
or harrowing will control weed escapes and improve herbicide activity
in the absence of rainfall. These materials prevent emergence of many
weed seedlings without reducing crop stand. Apply immediately after seeding
or at least before the emergence of the crop. If these materials are applied
after weeds have emerged, kill is usually poor. Best results are obtained
with this method when conditions for weed seed germination are good.
Postemergence (POST)
These chemicals are applied after the berry crop is planted. Applied as
directed, the weeds can be killed without injury to the crop. Leaf stage
of the weeds is critical for good control. Smaller weeds are generally
easier to kill but there needs to be enough leaf surface to intercept
the herbicide. Apply according to recommended leaf stages. Crop stage
is important to optimize crop safety. Adjuvants will frequently improve
the weed control when used as directed. Weather or other conditions may
influence the optimum rate of adjuvant, see the product label for more
details. Always use appropriate drift management technology.
Inter-row Weeding
The herbicide is directed between the berry crop rows onto the emerged
weeds. The herbicide is used as a rescue operation where other methods
of weed control have failed. Use special low pressure (7–15 kPa)
applicators such as dribble bars or vibra jets equipped with shields to
prevent wetting the crop. See Stale Seedbed and Inter-Row Weeding,
page 82.
Wiper Applicators for Selective Weed Control
Wiper applicators (rope-wick, roller applicator or similar device) have
been extensively used with glyphosate (ROUNDUP). Check product labels
for use of this application technique with other herbicides.
Related Links
