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The Cropwalker - Volume 2 Issue 28

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Crop Conditions

Weather – Hot, rainy, hail in some areas, but generally mixed. Some areas have enough moisture, and some still very dry. Wheat – harvest continues slowly. Yields are 45-100 bu/ac. Too few fields off to get a trend. In Essex rains last week has slowed harvest. REPEAT THE CAUTION, when you can get wheat off, take it off.  Corn - could see some tassels this week in earliest fields. Still a lot of acres at 8-9 leaf, and, a way to go. Lots of variability. Some sulfur deficiency showing up as lighter green colour plants. Western bean cutworm numbers are still low in Ontario and Michigan. They are building in US Midwest.  Soybeans – earliest fields at pin bean stage, and a lot of fields in flower. Rain will help some fields; other fields are ripe for mould. Trace levels of aphids being found. Forages  leaf hoppers are abundant across Ontario. For fields that just had second cut leaf hopper control is important as well as new seedings. Spring cereals early seeded are turning colour. Hot weather is not conducive to high yields.

Picture 1 - 1 soybean aphid on a trifoliate.


What is your tissue sample telling you?

Last year a co-worker had a grower pull a few tissue samples of their soybeans; they were trying to pin-point a few issues they were having in the field. The tissue results came back low in Nitrogen and Zinc. Seems odd for a plant that is supposed to produce its own N requirements. After figuring out the soil had plenty of zinc, and it wasn’t first year soybeans, I suggested that they soil test for soybean cyst nematode. Results came back positive. If you are getting back tissue samples low in nutrients, and have high soil test results, keep testing or looking, it may lead to something else.

What would I do about diseases in my corn this year?

If I was in the area that had high DON levels last year, or am growing corn for on farm feed, the number one priority is to spray to control DON. That means spraying one of Headline AMP plus increase the Caramba rate to give DON suppression and leaf disease control, or Proline which has activity on DON and other corn leaf diseases. Syngenta has a new product called Miravis (meer a vis). I attended a session on this new product. It includes a new active, not just old chemistry with a new name. Miravis control leaf diseases as well as reduces DON. They have a limited amount of product for 2019 (soft launch). Try to get your hands on some. They are planning to sell it in the DON areas of last year, but your supplier may be able to get some if you are outside this area. We are coming to a point that we may have to spray corn twice just as we spray wheat twice. One spray for leaf diseases and one spray for DON control. Currently that is out of the question, so I would spray once at silking to brown silk to control DON and leaf diseases. If I was not worried about DON, I would spray with another fungicide to control leaf diseases. The table points out the various products and diseases they control.

Table 1 - Summary of Ontario Corn Fungicides

Spraying Insects in Alfalfa

Associate professor Bob Fulkerson did some high yield forage research in the 70’s. He looked at varieties, fertility, seeding rate and controlling insects. The only thing that consistently gave a yield increase was spraying for insects in July. I would imagine if Bob was around now, he would also say that spraying to control diseases also increases yields.

Table 2 - Potato Leaf Hopper Thresholds in Alfalfa

Damaged Alfalfa Regrowing

A number of alfalfa fields are having alfalfa seemingly come back to life. If you look at the arrow on these roots you will see why. There are basal buds on the alfalfa roots that have started to regrow. The main root is rotted but there are some of these buds that are still alive. They will give regrowth but as in this picture there is significant rot in the crowns. Get what you can from these fields this year and then kill them off this fall.

Picture 2 - Alfalfa regrowth on damaged crown

Should I foliar apply Boron to my corn?

Boron is primarily taken up by corn plants via mass-flow, meaning it needs to be in the soil solution for uptake. If you do apply boron, for instance with your tassel or silking fungicide, it will be too late to improve the situation if you are limited, as Boron can impact pollination via tassel formation. As well, boron is not mobile within the plant, when applied in a foliar application. Soil-applied applications are best for this nutrient.

More thoughts on spraying corn silage for DON

Overheard a comment that spraying corn silage for DON reduction is not beneficial since fungicides will not control fusarium in corn stalks. True, they are not labelled for this. But since grain makes up 50% of silage and if you can reduce DON by 50% in grain you are effectively reducing DON in corn silage by 25%

Spraying Corn Silage Keeps It Wetter

True. But in research trials it is only wetter by 1-2% moisture. When making corn silage this 1-2% is nothing. Typically, on most farms the issue is silage that is too dry because it dried down too fast, not that silage is too wet.

What would I do about diseases in soybeans this year?

Spraying for mould should start at around the pin bean stage which is R 2.5. R 2 is when there is an open flower at one of the two uppermost nodes. R 3 is when there are 3/16” pods at the 4 uppermost nodes. There is variation in the field so it is a judgement call. Most companies suggest you spray for mould at about R 2.5 and then again in 10-14 days (flowers at the top, and pin beans at the bottom. If you are just spraying for general leaf diseases and improved plant health spray at R 3. Timing for all products is based upon the flowering and podding of the main stem, not the branches. If there are no flowers present, you will have no impact on white mould.

Picture 3 - Soybean Staging Chart (OMAFRA)

White Mould Life Cycle

White mould spores are produced from sclerotia. These sclerotia can live in the soil for years. The spores need a nutrient rich material to start to grow. The dead blossoms are this source. The spores land on the blossoms, they fall and are caught in the leaf axils of the plant, and the mould continues to grow. The strategy for mould control is to cover the blossoms and the parts of the plant where the blossoms fall. It is impossible to get full protection against mould. New flowers and new plant growth mean there are areas not covered with fungicide. But the later flowers tend to be hung up higher in the plant and are not as big a concern as flowers that drop into the lower branches.

Should I spray for white mould?

There are several factors that help you decide. 1) Variety. Some varieties are more susceptible than others. Check your seed guide for a rating. 2) History of mould in a certain field. Previous mould disease increases risk of mould. 3) Tillage. No till beans have less mould than beans on fields that were worked. 3) Soil moisture. You need soil moisture to germinate the sclerotia that produce spores. If your soil is very dry in the top 1-2” there is a, low probability of mould. 4) Moisture in the canopy. This can be wet soil from rain, dew or high air humidity. If there is significant moisture on plants when you walk through them at 11:00 in the morning you have weather conditions favouring mould growth.  5) Row width. Narrow rows with less air movement can make mould worse. 6) Row direction. If planted in direction of prevailing winds, the foliage should dry out more. 7) Soil type/fertility – black muck or high organic matter soils can be hot spots, fields that get manure (especially pig or poultry) have strong canopies. Speaking with a trusted CCA his strategy for mould prevention is to spray either Acapela or Stratego Pro and then if worried about mould spray the other one 10-14 days later.

BASF Strategy - Fungicides for White Mould in Soybeans

If white mould is not a concern, then spray Priaxor first, if white mould has been an issue in the past, spray Cotegra first. More of a wait and see approach? Then spray Priaxor followed by Cotegra if weather conditions are conducive. All are BASF products.

Picture 4 - BASF's suggested strategy

Insect Watch

Alfalfa weevil are alive and well in many alfalfa fields. Take action now. Western Bean Cutworm – levels in Ohio are starting to pick up. Moth count in Ontario still very low. Thresholds for WBC are based upon egg counts, not moth flights. Moth flights provide an indication of when you should scout, not if you should spray. No economic response to spraying corn for WBC prior to tasseling. Spider mites while not a problem yet could start to show up this week. Do not expect to see them until the fence line vegetation starts to burn-off from drought stress, keep checking the outside of fields. If you find them there, you can slow their activity by spraying around the outside of fields, if you are late, you will have to spray the entire field.

Should I be controlling Volunteer Corn in Soybeans

Continue to see quite a bit of volunteer corn in my travels, much of it looks quite healthy. What is the yield impact if you decide to leave it? OMAFRA data suggests 1 volunteer corn plant per m2 is a yield loss of 4%, 5 volunteer corn plants per m2 is 15%.

I have a late flush of nightshade in my soybeans, will there be a yield impact?

OMAFRA data suggests that nightshade is quite competitive with soybeans. 14% yield impact at 1 plant per m2, and 40% at 5 plants per m2.

Reflex or Flexstar GT on Horsetail

Grower applied Reflex on his soybeans for a ragweed escape, also provided good suppression of horsetail. See picture below. (For RR soybeans, Reflex is available as a pre-mix of glyphosate and Reflex as Flexstar GT). Reflex is not registered for flowering soybeans.

Picture 5 - Reflex activity on Horsetail

I have dicamba injury on my soybeans, what is the expected yield penalty?

Not a straightforward answer to the question, but there are resources to help narrow down the possible yield penalty. In most situations, it will be a combination of % of visual injury, and growth stage that determines the yield impact.

Table 3 - Soybean injury by dicamba by plant stage

Purdue Factsheet WS-56

Differentiating 2,4-D and Dicamba Injury on Soybeans

Louisiana State University has developed an app that can calculate expected yield loss of dicamba injury. It is based upon severity and plant stage; you can find the app at the website below. Keep in mind it is based on maturity group 4.8 to 5.1 indeterminate soybeans. We grow maturity group 000.5 to 3.0 in Ontario.

SoyD-YeLP (Soybean Dicamba - Yield Loss Prediction)

Soybean Injury and Loss Prediction Tool

Lastly, University of Wisconsin has an excellent resource on possible causes of dicamba injury, it can be found here;

University of Wiscosin - Dicamba Injury Factsheet

4 sources of Dicamba injury in soybeans

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