Category Archives: Herbicides

Herbicide injury symptoms in tomatoes

Darren Robinson, University of Guelph, Ridgetown Campus; Janice LeBoeuf, OMAFRA, Ridgetown

Introduction

Herbicides are useful tools for the management of weeds.  The herbicides registered for use in tomatoes are selective in their activity, injuring or killing weeds while being safe to use on the crop. Crop injury may occur, generally when a crop is stressed beyond its ability to adequately deal with a herbicide application.  Injury due to herbicides can arise as a result of several factors, including weather-related stress, soil factors such as light soil texture and low soil organic matter, shallow planting and sensitive crop varieties.  The pages in this section contain information on herbicide injury for several products registered on tomatoes in Canada. Continue reading Herbicide injury symptoms in tomatoes

Resources on weed management

Kristen Obeid, OMAFRA Weed Specialist – Horticulture

Internet

weedinfo.caWeedinfo.ca: If you are trying to identify a weed, find the newest information on herbicide resistance and other emerging issues in weed management you need to visit weedinfo.ca.

Provincial Weed Page: http://www.omafra.gov.on.ca/english/crops/insects/weeds.html

Ontario Crop IPM: Know how and why it is important to scout and identify weeds, as well as diagnose herbicide injury. Continue reading Resources on 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.

Prowl® H2O Herbicide label expanded for control of labeled weeds on direct seeded green onions grown on muck soil

Jim Chaput, Minor Use Coordinator

The Pest Management Regulatory Agency (PMRA) recently announced the approval of an URMULE registration for Prowl® H2O Herbicide for control of labeled weeds on direct seeded, green (bunching) onions grown on muck soil in eastern Canada and British Columbia. Prowl® H2O Herbicide was already labeled for use on a number of crops in Canada for control of weeds. Continue reading Prowl® H2O Herbicide label expanded for control of labeled weeds on direct seeded green onions grown on muck soil

Spraying Dicamba in Canada

This is one to review and share! A very educational slide show from Jason at Sprayers101.com

There’s been unprecedented demand for information regarding the safe and effective application of the new dicmaba products registered in Canada in late 2016. In response, every extension agent, agrichemical rep and researcher with any know-how on the subject has spent the last year (or more) speaking at grower meetings. I, for one, am fairly certain…

via Spraying Dicamba in Canada — Sprayers 101

66th Annual Muck Vegetable Growers Conference

The 66th Annual Muck Vegetable Growers Conference will be held April 12-13 at the Bradford and District Memorial Community located at 125 Simcoe St., Bradford, ON. The conference is free and registration starts at 8:30. For more details please see:  http://www.uoguelph.ca/muckcrop/muckconference.html

Continue reading 66th Annual Muck Vegetable Growers Conference