Category Archives: ONveg in The Grower

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)
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.

Samples requested for clubroot survey

By Travis Cranmer, Vegetable Crops Specialist

First appeared in ONvegetables in The Grower, April 2017.

Clubroot, caused by the soil-borne pathogen Plasmodiophora brassicae can cause yellowing, stunting, wilting and club-like roots on susceptible Brassica species including broccoli, cabbage, canola and cauliflower. Clubroot causes an estimated yield loss of 10-15% in Brassica crops worldwide and in severely infested fields a 30-100% yield loss can occur. There are different races of clubroot known as pathotypes and the resistance of many cultivars is pathotype dependent.

severe clubbing, six weeks after seeding
Figure 1. Pak choy with severe clubbing, six weeks after seeding.

Continue reading Samples requested for clubroot survey

Three Problem Weeds for Asparagus

The website, Ontario CropIPM, contains the full range of pest management information from many vegetable crops, including asparagus. Many users do not realize that it is also home to weed galleries, herbicide injury information and critical weed control period information. The following three problem weeds for asparagus are excerpts from the weeds and herbicides section of Ontario CropIPM. Continue scrolling for the best control options for each of the problem weeds. Continue reading Three Problem Weeds for Asparagus

Sprayer Math for Banded Applications

Jason Deveau, Application Technology Specialist, OMAFRA

Banding allows producers to save on chemical costs, reduce the potential for wasted spray and to make targeted applications, where they are most effective. Banding can be particularly useful in fungicide applications on small seedlings or transplants.  For the mechanics (and mathematics) of banding, read more at sprayers101

Sprayer Math for Banded Applications

The Potential for Spread of Phytophthora Blight of Cucurbits and Peppers in Irrigation Water

Excerpts taken from ONvegetables in the Grower, April 2014. A full pdf version of this article is available at 2014_Infosheet_Phytophthora-in-irrigation-water

Phytophthora blight (Phytophthora capsici) is a serious and complicated disease of peppers and cucurbit crops. Under the appropriate environmental conditions, infections can quickly spread and completely destroy a crop in a matter of days.

Dr. Mary Hausbeck, Michigan State University, conducted an extensive study on the presence and potential impact of phytophthora in irrigation water sources. The study did indicate that irrigation from surface water is a potential source of phytophthora infection in cucurbit and pepper crops.

Figures 1-3. Peppers (L), Crown Rot (C), "Powdered Sugar" Spores (R)

Continue reading The Potential for Spread of Phytophthora Blight of Cucurbits and Peppers in Irrigation Water

The next level of herbicide resistance – cross resistance

From ONvegetables in The Grower, February 2014

Kristen Obeid, Weed Management Program Lead (Horticulture), OMAF/MRA

Herbicide resistant weed populations are now found throughout Ontario. The number of resistant species and areas affected by resistance continues to increase. Herbicides are the most heavily relied upon weed control method for many growers because they are both cost effective and simple, which has resulted in high selection pressure for herbicide resistance in populations of weed species. Continue reading The next level of herbicide resistance – cross resistance

Managing wash water to protect your farm stream

From ONvegetables in The Grower, February 2014

By Deanna Nemeth, Nutrient Management Program Lead (Horticulture)/ OMAF and MRA

Fruit and vegetable producers have been looking for low cost methods to manage wash waters. When you are washing fruit and vegetables, the physical characteristics of the washwater varies depending on your operation. Characteristics can range from potable water used to rinse fruit and vegetables prior to packaging; to washwater high in soil sediments from rinsing soil from root vegetables or peel from scrubbing vegetable before packaging and marketing. Both the liquid and solid waste streams must be managed to protect water quality in and around the farm. Continue reading Managing wash water to protect your farm stream

Pest of the Month – Bacterial Spot of Pumpkins and Squash

From ONvegetables in The Grower, February 2014

Identification: Currently, bacterial leaf spot (Xanthomonas cucurbitacae) is not commonly found in Ontario.  However, it is known to cause serious pumpkin crop losses in the Mid-western United States.  Leaf lesions are dark and very small with yellow margins (figure 1).  As the disease progresses they coalesce to form large necrotic areas.  They are easily confused with several other foliar diseases including angular leaf spot.

Bacterial Spot Leaf Lesions
Bacterial Spot Leaf Lesions

Fruit lesions are circular in shape, small and slightly sunken.  They often have a dark brown border (figure 2).  As the lesions enlarge in size (up to 12 mm in diameter) they crack and become scab-like.  Infected fruit often develop soft, watery rots in the field or in storage and collapse quite quickly.

Bacterial Spot Fruit Lesions

Biology: Bacterial spot survives in crop residue.  It is also seed-borne.  It can tolerate high mid-summer temperatures.  It spreads quickly within the field.

Management Notes: Use disease-free, certified seed.  Follow a 2-3 year rotation away from all cucurbit crops.  The bacteria are easily spread by splashing rain or irrigation and by machinery.  Avoid working in the field when the foliage is wet.

Pest of the Month – White Mould in Snap Beans

From ONvegetables in The Grower, December 2013

Beans are susceptible to white mould infections during flowering and early pod-set.  Small, circular, water-soaked lesions develop on the pods of infected flowers, or where fallen petals become caught in the lower canopy or leaf axils.

Infected tissues later develop a dense, cottony, white fungal growth.  Leaves of severely infected plants will eventually turn yellow and fall off.  Sclerotia (hard, black, irregular-shaped fruiting bodies) form in the branches, stems and pods of infected plants (Figure 1).

White mould over-winters mycelium in infected crop residue and as buried sclerotia.  The sclerotia will survive for up to five years in soil and crop residue. Continue reading Pest of the Month – White Mould in Snap Beans

Disease Innoculum, the Gift That Keeps on Giving

From ONvegetables in The Grower, December 2013

Some years the weather patterns just work against us.  Cool temperatures, intermittent rains and prolonged, heavy dews spell paradise for many crop diseases. Under these conditions, many vegetable crops are impacted by diseases such as mildew, scab, fusarium, anthracnose, phytophthora, etc…, despite a well-managed crop and the timely use of fungicides.

What type of impact do last year’s diseases have on next year’s crop?  In part, it will depend on the weather we get next year.  However, rotation is also an important factor. Continue reading Disease Innoculum, the Gift That Keeps on Giving