JUNE 19, 2024

• Crop Update
  • Soybean Herbicide Options (2024) →
  • Rolling in Soybeans →
  • Preliminary PLW Survey Results →
  • Fungicide Decisions in Peas →
  • Dry Bean Herbicide Options (2024) →
• Assessing Early-Season Weather Damage
• 2024 Pea Leaf Weevil Survey Results
• Iron Deficiency Chlorosis in Soybeans →
• Scouting for Pea Aphids and their Predators
• Regional Variety Trial Update
• MPSG’s On-Farm Network Trial Update
• Growth Staging Guides →
• Scouting Calendars →

Listen to the Bean Report:

Crop Update

• Recent warm temperatures have been a welcome change from an otherwise cool spring. As a result, crop stages have begun to advance more quickly. As of June 9, the majority of central and western Manitoba had received less than 90% of normal growing degree days and more than 150% of normal precipitation.
• Soybeans range from VC (unifoliate) to V2 (second trifoliate). As the summer solstice approaches and the change in daylength occurs, soybeans will be heading towards reproductive growth soon.
  • Weather has caused damage in fields – either from hail or high winds and sandblasting. Most fields are expected to recover.

    

  • Herbicide applications are ongoing when wind conditions are favourable . Soybean Herbicide Options (2024) →
  • Symptoms of Iron Deficiency Chlorosis (IDC) have begun in fields with more moisture, interacting with calcium carbonates, soluble salts, and nitrates in the soil to limit iron uptake.  IDC in Soybeans →
  • If planning on rolling post-emergence, target V1 on a warm day, during the warmest part of the day (+25°C). Check for signs of stem breakage behind the roller, especially as conditions change throughout the day. Rolling in soybeans →
• Field peas range from V6 (6 true leaf nodes) to V10 (10 true leaf nodes). Flower bud stages (R1) are nearing in some earlier-seeded fields.
  • In areas that have received more moisture, peas are yellowing around low spots and drains due to root rots and stress of saturated soil conditions.
  • In several fields, spotting has been observed on leaves in the lower canopy caused by spray applications or bacterial blight following environmental damage. Take note of these symptoms since their position in the lower canopy will be confusing when it’s time to make fungicide spray decisions. These symptoms will be easy to confuse with Mycosphaerella blight, which is the main target of fungicide applications. Find photos to tell them apart here →

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    At R1 (flower bud) stages, assess pea nodulation to ensure your inoculant was effective.

  • The spring 2024 pea leaf weevil survey is wrapping up. Preliminary PLW Survey Results → Pea leaf weevil populations were found to be lower than last year, with moderate populations found in northwestern Manitoba and lower populations in central Manitoba. Root nodules with signs of larvae feeding damage may be found when digging up plants at flowering and podding.
  • The first signs of pea aphids have been noted in a few fields. Pea aphids overwinter in Manitoba, so it is not surprising to see them earlier than other aphids that blow in (like soybean aphids). Natural enemies of pea aphids – including lady beetles and green lacewings – have been noted as well in these fields and are expected to keep aphid populations low for the time being.
• Dry beans range from VC (unifoliate) to V1 (second trifoliate).
  • Herbicide applications and inter-row cultivation operations are ongoing. Dry Bean Herbicide Options (2024) →
  • Saturated soils and sandblasting have been causing some emergence stress and damage.
• Faba beans range from V6 (6 true leaf nodes) to R1 (flower bud) with some fields with open flowers.
  • Leaf notching from pea leaf weevils is evident in most fields, as faba beans are a preferred food source.

Assessing Early-Season Weather Damage

Recent storms brought hail and high winds to several areas, causing early-season damage in several crops. Hail resulted in stem breakage, wounding and defoliation. Sandblasting from high winds has been evident as well, causing leaf tearing, bronzing of cotyledons and in some severe cases, shearing of stems.

If growing points remain intact, plants are expected to recover and continue to grow through the damage. A maturity delay may occur, depending on the severity of damage. In the cases of severe hail or sandblasting that broke stems below the cotyledon node, regrowth is not expected due to the loss of growing points.

In your fields, assess plant stand loss 5-7 days after the damaging weather event (hail, sandblasting, frost) to look for signs of regrowth. If the main growing point was damaged, look for signs of regrowth at the axillary buds (buds located where leaves meet the main stem).

Take plant counts to assess the remaining living stand to inform yield expectations moving forward. If plant stands are low but uniform across the field, it may make sense to keep that existing stand at this point in the season after considering all factors. Soybean plant stands as low as 80,000 pl/ac may still be expected to produce a successful crop. More information on soybean reseeding decisions →

Following weather damage, take extra consideration when it comes to weed control and management. The time it takes for the crop to achieve full canopy closure will likely be delayed, leaving more room for late-emerging weeds.

In terms of disease management, hail wounds will often scab over. Bacterial blight or occasionally northern stem canker have been noted to infect these wounds in soybeans. Often, the plant seals off the damaged tissue before these diseases take hold.

From 2015-2016, Iowa State University assessed whether or not fungicide applications following hail damage during vegetative crop stages would benefit plant recovery. In general, a fungicide application did not provide yield-increasing benefits after early-season hail when risk of foliar diseases was low. If you’re considering a fungicide application to manage a hail-damaged soybean crop, consider conducting an on-farm test to determine if that application did provide a benefit. MPSG’s On-Farm Network is here to support farmers in conducting these tests.

2024 Pea Leaf Weevil Survey Results

Pea crops are surveyed during early to mid-June for leaf notches caused by pea leaf weevils. While these characteristic leaf notches on the edges of pea and faba bean leaves are easy to notice, they do not cause yield loss. What does impact yield is the subsequent pea leaf weevil larvae below-ground that feed on root nodules of pea and faba bean plants, robbing them of their nitrogen.

Surveying for pea leaf weevils helps us monitor their populations and inform future seed treatment decisions in high population areas. Preliminary results have been compiled from 2024 survey data so far. This year, pea leaf weevil population levels are generally lower than previous years. Numbers are the greatest north of Riding Mountain National Park in the northwest.

Iron Deficiency Chlorosis in Soybeans

Up to V1, soybean cotyledons supply stored iron to the plant. Once that source is depleted, plants need to acidify their root zone to access iron in a plant-available form. Excess moisture, calcium carbonates, soluble salts and nitrates can all impact this.

If chlorosis is present early on and plants recover by the V5 to V6 stages, yield loss will be minimal. If symptoms persist beyond these stages, expect more significant yield loss. Research conducted in Manitoba has shown that for each 0.1 unit increase in IDC score, soybean yield is estimated to be reduced by 2.2 bu/ac, on average (range: 1.5 – 2.8 bu/ac).

More Information on Iron Deficiency Chlorosis in Soybeans →

Research: Iron Deficiency Chlorosis – Kristen MacMillan, MPSG’s Agronomist-in-Residence, Soybean and Pulse Agronomy Lab, University of Manitoba (2017-2022).

Scouting for Pea Aphids and their Predators

• Scout for pea aphids when 50-75% of the field is in early flower in late June to early July.
• Check five plant tips (top 8 inches) or conduct 10 sweeps at four locations within the field. Assess populations in different areas of the field, including field edges. Populations will likely be higher at field edges.
• The economic threshold for peas is 2-3 aphids/plant tip or 90-120 aphids/10 sweeps.
• If the threshold is reached, insecticide applications should be made at the early pod stage (when 50% of plants have produced young pods). Pod formation and elongation stages are the most sensitive to aphid feeding.
  • Insecticide Options for Pea Aphids (2024) →
• Natural enemies may reduce pea aphid populations. Scout for lady beetles and their larvae, lacewing larvae, hoverfly larvae, minute pirate bugs, damsel bugs, parasitic wasps that leave behind aphid mummies and fungal diseases that infect aphids.

Regional Variety Trial Update

Each year soybeans, dry beans, faba beans, field peas and lupins (new in 2023) are tested at multiple locations across Manitoba. The purpose of this testing is to provide independent, unbiased data to help farmers choose the best varieties suited to their farms. Results from previous years can be found here →

Soybeans 2024

• 58 herbicide-tolerant soybean varieties are being tested at long-season sites (St. Adolphe, Carman, Portage and Morris), with 41 of these also being tested in the early site locations (Stonewall, Arborg and Beausejour)
• 54 herbicide-tolerant soybean varieties are being tested at western sites (Hamiota, Souris, Cypress River, Melita and Dauphin), 33 of these are also being tested in Swan River
• 26 conventional soybean varieties are being tested at long-season sites (St. Adolphe, Carman, Portage and Morris), with 12 of these also being tested in the early site locations (Stonewall, Arborg, Beausejour)
• 7 conventional soybean varieties are being tested at western sites (Melita, Swan River and new in 2024 Souris)
• Of the varieties submitted to these regional trials, 63 have been sent for independent Phytophthora root rot field tolerance testing
• Soybean varieties are also grown at an IDC-prone site near Winnipeg to independently assess their tolerance to IDC

Pulses 2024

• 47 dry bean varieties are being tested on wide rows at Morden, Carman, Winkler and Portage. Market classes include pinto, black, navy, light red kidney, dark red kidney, white kidney, cranberry and great northern beans
• 22 pinto, black and navy bean varieties are being tested on narrow rows at Morden, Portage, Melita and Souris and 6 pinto and black varieties at Swan River
• 20 field pea varieties are being tested through MCVET at Morden, Stonewall, Roblin, Melita, Swan River, Holland, Carberry, Arborg, Souris and Hamiota
• 12 faba bean varieties are being tested at Dauphin, Morden and Swan River
• 12 lupin varieties are being tested at Melita, Carberry and, new in 2024, Roblin

MPSG’s On-Farm Network Update

Trials established at seeding are now complete, with the last seeding-timing trial established on June 14. The season got off to a good start with field pea trials starting the last week of April and into the first week of May. Generally, field pea trials were well established and are currently looking healthy.

Many soybean trials suffered from cool and wet spring soil conditions, resulting in delayed emergence while others had uniform emergence and are now progressing well. Unfortunately, some field pea, soybean and dry bean trials were cancelled due to farmers opting out as they were up against crop insurance deadlines. Other cancelled trials were simply switched out to different crops as farmers changed their seeding plans. The only dry bean trial (DBN01) seeded to date was established on June 9 and the first soybean biological trial has been established (June 13).

The OFN team has begun field scouting and data collection. So far, we’ve focused on peas with soil sampling for Aphanomyces, early-season plant counts, early-season nodule assessments, root rot ratings and pea leaf weevil predation (leaf notching) counts. We are playing around with five new weather stations where two are equipped with soil moisture and temperature probes and a new drone capable of multispectral imagery (e.g. NDVI).

Despite the challenging season, farmers are thinking that their established crops are worth protecting by investing in testing fungicides. The OFN team will soon be conducting pre-spray checklists on field peas and then soybeans in approximately two weeks. If the results show heavy disease pressure this may result in garnering more interest in fungicide trials.

Farmers lined up for pea fungicide trials are changing to 2 vs 1 application from planned 1 vs 0 treatments because of potentially high disease pressure. We expect to see more soybean fungicide trials added too due to current conditions.

Established On-Farm Network Trials
Crop Type	# of Trials	Trial Type
Peas	1	double vs. single inoculant
Peas	6	seeding rates
Peas	3	seed treatments
Soybeans	1	iron chelate product for IDC
Soybeans	12	seeding rates
Soybeans	1	single vs. no inoculant
Soybeans	3	double vs. single inoculant
Soybeans	6	row spacings
Dry Beans	1	nitrogen fertilizer rates

More trials to come with fungicide and biological products.

Have questions about our OFN program? Reach out to MPSG’s OFN Agronomist Chris with any questions: 204-751-0439 or chris@manitobapulse.ca.