Category Archives: Weed Management

Tips for Broadleaf Weed Control in Pumpkins and Winter Squash

Originally published in ONvegetables in The Grower, April 2017

Even with the use of herbicides, broadleaf weed control in pumpkins and squash can be problematic. Product selection is key but timing and weather conditions are also important to the success or failure of a weed control program. Each of the broadleaf herbicides comes with its own strengths, weaknesses and risks.

As a general rule, the spectrum of weeds controlled can be increased by using tank-mixes. But, for pumpkins and squash, it is wise to limit the tank-mix to two products.  A three-way tank mix is risky from a crop safety standpoint; root damage, stunting, yellowing and/or burning may occur, especially under certain soil conditions.

All of the pre-emergence herbicides require soil moisture. The active ingredient is carried by the soil water into the germinating weed seedlings, causing them to die.  Under dry soil conditions, it is tempting to use overhead irrigation to “activate” the herbicides.  This is an inexact science.  Too much water can quickly move the herbicide band into the zone of the germinating crop roots, causing injury to the pumpkins or squash. Too little water may be insufficient to move the herbicide into the germinating weeds.

It becomes a gamble between loosing crop to herbicide damage or loosing yield to weed competition. Fortunately, both Dual II Magnum and Sandea can be used for early post emergence weed control.  Unfortunately, control of weeds such as lamb’s-quarters and pigweed is less effective with a post emergence spray.

Product: Command 360 ME (clomazone)
Timing:  after seeding but before crop and weed emergence.
Rate: 0.78-1.17 L/ha (0.31-0.47 L/acre) use the low rate on light, sandy loam soils; use the high rate on heavy soils.
Strengths: lamb’s-quarters, nightshades, ragweed, velvetleaf
Weaknesses: pigweeds.
Cautions: very sandy soils and/or certain varieties may be prone to crop injury, see label for details. Also refer to the label for rotational crop restrictions.

Product: Sandea (halosulfuron)
Timing(s): after planting and before soil cracking (direct seeded), before transplanting; do not transplant sooner than 7-days after application, OR post-emergence between the 3-5 true leaf stage or 14-days after transplanting[1]
Rate: 35-70 g/ha (14-28 g/acre). See the product label for specific rate information for direct seeded, transplanted, processing and fresh market pumpkins and squash.
Strengths: pigweeds, lady’s thumb, mustards
Weaknesses: lamb’s-quarters
Cautions: Under adverse growing conditions (dry or excessive moisture, cool weather, etc.) the maturity of the treated crop may be delayed which can influence harvest date, yield, and quality. Under dry soil conditions, apply 3 – 5 cm of sprinkler irrigation to settle the soil after planting and prior to application. Do not make a post emergence application if female blossoms are present on the plant; crop damage may occur to developing fruit.

[1] If using pre-emergence and post emergence applications of Sandea, allow for a minimum of 21 days between the two applications.

Product: Dual II Magnum (s-metolachlor/benxacor)
Timing:
pre-emergence or at the 1-2 leaf stage (direct seeded crops). Prior to transplanting or within 48 hours after transplanting (transplanted crops).
Rate: 1.15 L/ha (0.47 L/acre)
Strengths: annual grasses, nightshades, pigweeds
Weaknesses: lady’s-thumb, ragweed, velvetleaf
Cautions: risk of crop injury increases with cool and wet conditions. Foliar contact can increase the potential of crop injury. Note: research in Ontario has shown high levels of phytotoxicity when using Dual II Magnum on cucumber crops.  Use on cucumber crops is not recommended.

Use of Sandea Herbicide in Tomatoes, Vine Crops, and Peppers and Permit in Sweet Corn

Darren Robinson, Weed Researcher, Ridgetown Campus – University of Guelph

Sandea and Permit are Group 2 herbicides that are taken up by roots and shoots and are systemic in the plant.  The herbicides will translocate to the new growing tissues, and if applied to a sensitive crop or weed, it will cause stunting, chlorosis (yellowing) and may even delay maturity of sensitive species.  These herbicides are particularly useful for control of preemergence control of common lamb’s-quarters and postemergence control of yellow nutsedge.  They have also provided good control of common ragweed and redroot pigweed.  The labels should be consulted before use in all cases, and are available at http://www.uap.ca/products/products.htm.

Continue reading Use of Sandea Herbicide in Tomatoes, Vine Crops, and Peppers and Permit in Sweet Corn

Minor use label expansion granted for Reflex® herbicide for control of weeds on field cucumbers

J. Chaput, OMAF/MRA, Minor Use Coordinator, Guelph

The Pest Management Regulatory Agency (PMRA) recently announced the approval of a minor use label expansion for REFLEX® herbicide (fomesafen) for control and/or suppression of labeled weeds on field cucumbers in eastern Canada and British Columbia. Reflex® Herbicide was already labeled for management of weeds on soybeans, dry beans, lima beans and snap beans in Canada. Continue reading Minor use label expansion granted for Reflex® herbicide for control of weeds on field cucumbers

MINOR USE LABEL EXPANSION GRANTED FOR ASSURE® II HERBICIDE FOR WEED CONTROL ON CUCURBIT VEGETABLES IN CANADA

By Jim Chaput, Minor Use Coordinator, OMAFRA

The Pest Management Regulatory Agency (PMRA) recently announced the approval of a minor use registration for ASSURE® II (quizalofop-p-ethyl) Herbicide for control of labeled weeds on crop group 9, cucurbit vegetables in Canada. Crop group 9, cucurbit vegetables includes cucumbers, melons, squash, pumpkins and gourds. ASSURE® was already labeled for use on a wide range of Canadian major, specialty and minor crops. Continue reading MINOR USE LABEL EXPANSION GRANTED FOR ASSURE® II HERBICIDE FOR WEED CONTROL ON CUCURBIT VEGETABLES IN CANADA

Spraying Transplant Vegetable Row Middles – What are Your Options?

Written by: Kristen Callow, OMAFRA Weed Management Program Lead – Horticulture

There has been a lot of interest in spraying the row middles of vegetable transplant fields with herbicides using hooded sprayers.  Is this a good idea?  Well . . . it depends on the herbicide.  Some growers have questioned whether or not glyphosate can be sprayed.  This is not a labelled use and is definitely not a good idea.  Continue reading Spraying Transplant Vegetable Row Middles – What are Your Options?