The Cropwalker - Volume 3 Issue 24

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Crop Conditions

Weather most areas are dry and could use a rain. Some areas (Parts of Huron, Perth, Oxford) have great growing conditions. The short-term weather is predicting hot and dry. The long-term weather predictions for the summer are near normal or a bit above for rainfall and same for temperature. Winter wheat – continues to fill. Earliest fields really turning colour. Some areas are dry and will hold back yields. Spotty army worm continues. Not a pandemic. Corn Looks amazing where soil moisture is adequate. Some areas could use a rain. Soybeans have seen a lot of issues this past week with herbicide interactions. (see below) This will be the last week to spray any herbicide that must not be applied when soybeans are flowering. Stands reseeded due to insect feeding or crusting look to be a great improvement over what had been there initially. Forages second growth is coming good where there is adequate moisture. Aphids are at very high levels. Eastern Ontario is dry and leaf hoppers are staring to show in numbers requiring control.  Spring cereals are heading. If you have not applied a fungicide yet now is the time. See the list below of which fungicides you can use. Recommendation is not to use a strobi of spring cereals once they head out. Some fields are showing Cereal Leaf Beetle and Cereal Aphid feeding. Joanna Follings of OMAFRA confirmed my observation this week that spring oats are more prone to attracting Cereal Leaf Beetle and Cereal Aphids than spring barley. Weed control BASF has advised that the window for spraying dicamba is closed.

Articles

Herbicide damage/effects on soybeans

More has shown up last week. The effect is on the unifoliate and first trifoliate. These symptoms should not go beyond the first trifoliate in most cases. However, there is at least one field that plants do not seem to be growing out of it. There is suspected carry over from herbicides applied last year. Areas of fields with overlap are showing symptoms that normally do not show up when herbicides are over lapped. Many herbicides have a two-fold safety factor built into their rate. Overall, I don’t think it will affect provincial yield. Some individual fields may be affected. The issue is the soybean plant was not able to metabolize/break down herbicides in the normal manner. This is because of either cold conditions, dry soil, or major temperature swings. We have seen it before when you get daily temperatures swing by 20 C plants are not able to metabolize certain herbicides. Historically, it has been corn that has this problem, especially with group two herbicides. This year there are a lot of herbicides causing the effect. If you sprayed and the emerging seedling sat in a soil area of a high concentration of herbicide, this was taken up by the plant. In some fields the cold weather resulted in soybeans sitting in this herbicide layer for a while. Normally a rain would move the herbicide down and dilute the area that caused problems this year. There are a lot of herbicides that have been used and are showing effects on soybeans. Sandy soils with less organic matter are worse. Metribuzin (Sencor/Tricor) is showing bronzing and necrotic tissue at leaf edges.

Insect alert

Wet weather favours diseases and hot weather favours insects. You must be alert for armyworm. The first sighted were probably from the first flight. A further flight will bring more. The adult moths are blow in every year from the south. But check fields where you have seen them before. Wind patterns tend to be similar from year to year. So, if winds brought them to a certain field another year check those fields. In wheat fields they will be feeding on the heads. They normally feed in the evening or early morning and then bury into the ground during the day. Sometimes you will see birds hovering over a grain field. They are probably eating the armyworms. They will soon move to spring grain or corn. Watch perimeters of these fields.

Cereal Leaf Beetle should be finished feeding in most fields. Adults can move to corn fields where they will do some but minimal leaf feeding. Then they are gone for another year.

Bird cherry aphid is at threshold levels in some fields. We seldom have numbers high enough to warrant control of this insect. Use the APHID APP, insert link, to share.

Potato leaf hopper numbers are building. They can be extremely harmful to new alfalfa seedings. If they hold back a new seeding it sometimes appear as if that field never does really well the following year. A strategy is to check new seedings after first cut and established stands after second cut. The rate of dimethoate is 170 ml/ac. For the same insect in edible beans the rate is 280-404 ml/ac. Matador is also registered to control potato leaf hoppers in alfalfa and edible beans. CHECK THE LABEL

Potato Leaf Hopper in Alfalfa and Edible Beans

Generally, leaf hoppers start to show visible damage on edible beans and alfalfa around first of July. Last couple of years they have been showing up earlier. If you have dry conditions you are apt to have leaf hopper damage. You can sweep and look for symptoms but by that point it is too late. Some growers who have this insect many years will spray once the regrowth gets 2-3” of new growth. Product of choice is dimethoate sold as Cygon/Laygon/Dimethoate 480.

Aphids in Alfalfa Are common every year. This year they seem to be more abundant. Threshold is 40-75 per stem. If you are spraying for leaf hoppers with dimethoate, this will have some control of aphids.

Soybean aphids

Be on the lookout. Current hot dry weather is the signal that they may be active. I do not expect high enough levels to warrant control but watch and see what develops. Hopefully the high level of beneficials in some of the other crops will keep them in check.

Fusarium or Take all

These two pictures show the difference between Fusarium and Take all. Fusarium will infect individual kernels while Take all affects the whole head.

Fungicides for Spring Grain in Head

Products that are safe include Caramba, Folicur, Proline, Prosaro, Propiconazole or Tilt. These are all triazoles. You should not spray the strobilurins (strobis) on cereals that are in head. Main disease you will want to control in Oats is Crown Rust. In Barley it could be a number. Could be spot blotch, net blotch, scald or Septoria

Question - Did I spray my Reflex too early? There is less ragweed plant visible now compared to when I had scouted the field.

Answer - No, usually in most situations it is sprayed too late. Applications timing decisions are made based upon weed stage, not weed density. Weed density determines if it is economical to spray or not. In this situation the pre-emerge may have pulled down some of the initial population you had saw when you did the first scout. The weeds that escaped and their stage should determine when you should spray. If you had waited for more to come, then that initial flush would have been too big for the Reflex. There is unlikely to be another flush because the herbicide was activated enough to pull down plants beyond the seeding (cotyledon) stage and would have controlled any that would have just emerged. Secondly, the Reflex does have some residual activity, and is rated an 8 in the US when sold as a pre-emerge herbicide.

White mould in soybeans

Current weather suggests that mould should not be a problem. BUT If you believe we will have normal rainfall this summer start thinking about white mould. Make a strategy for fields that are most likely to develop mould. In fact, go through all your fields and decide which fields are most apt to get mould. Here are the factors in order of importance

1 Field history. Was there mould before.

2 Variety. Some varieties are relatively tolerant like S03 W4. Longer season varieties tend to be more prone to mould

3 Tillage. No till has lower probability

3) Planting date. Earlier planting dates more apt to have mould. Some will say other way around. From my experience when you plant early there appears to be enough dew to get the disease going. Also, may be a function of the spore production. Maybe by the time later plantings start to flower the apothecia that have produced the spores are done producing.

4) In my area if we have fog in late June/early to mid-July, it is a strong indication that we should be spraying for white mould.

Products to control White Mould in Soybeans (v2)

Last week we had suggestions from BASF and Corteva. Here is Bayer’s recommendations

Spray Stratego Pro at 0.23 L/ac or 30 acres per jug at R1-R5 for suppression. Best spray time for mould control is R 1.5

Propulse at 300 ml/ac at 20% bloom followed by a second application in 7-14 days.

What Volunteer Corn/Graminicides Products are Available?

Please note that if tank mixing with group 2s (i.e. Classic), or group 14's (Reflex/Blazer), we did not account for any antagonism, or tank-mix-ability.

Manganese Deficiency in Soybeans

If you are in an area prone to it, you may have started to see visual symptoms already, means it is time to spray it. In severe cases you will have to spray twice (or more). Manganese applied to foliage does not move within the plant. Hence why you must apply it a second time or subsequent times each time you see visual deficiency. Previous applications do not move to new growth, you may have to spray multiple times at lower rates on soils prone to deficiency, rather than 1 large rate at once.

Available Manganese Products in Ontario for Soybeans (and other crops)

Question - Did I spray my Reflex too early? There is less ragweed plant visible now compared to when I had scouted the field.

Answer - No, usually in most situations it is sprayed too late. Applications timing decisions are made based upon weed stage, not weed density. Weed density determines if it is economical to spray or not. In this situation the pre-emerge may have pulled down some of the initial population you had saw when you did the first scout. The weeds that escaped and their stage should determine when you should spray. If you had waited for more to come, then that initial flush would have been too big for the Reflex. There is unlikely to be another flush because the herbicide was activated enough to pull down plants beyond the seeding (cotyledon) stage and would have controlled any that would have just emerged. Secondly, the Reflex does have some residual activity, and is rated an 8 in the US when sold as a pre-emerge herbicide. I haven't done the math to confirm the same rates of active are being applied.

Xarvio Field Manager– Scouting/Crop Staging Application

If you haven’t gave BASF’s Xarvio Field Manager a test drive, it might be worth a look. BASF has waived any fees for the 2020 growing season and it can forecast crop and disease development in canola, corn, soybeans and winter wheat. It also has a weather and spray forecast along with radar component. Once you have entered the respective information, it will alert when a fungicide application may be necessary at the appropriate crop stage (i.e. white mould in soybeans). There is both a web browser (i.e. Google Chrome) and an app version. When you do a field inspection, there is a location to update the actual crop stage vs. forecasted crop stage. After a fungicide application is made, update the app with the date product and rate, so that it can reset the disease model, and alert if additional applications are required. A few screenshots below.

Nitrogen Response in Corn

Source Side Factors

C: N Ratio – Previous Crop

The winter of 2020 meant very little decomposition for materials spread on the soil, causing nitrogen immobilization on fields following crops with heavy residue.

C:N Ratio – Manure History

Significant amounts of residual nitrogen results in faster residue cycling versus those without manure or organic materials applied.

Soil Organic Matter

Determines the size of the pool available to mineralize.

Soil Temperature

Determines rate of mineralization of organic matter, crop residues and manure sources.

Commercial Fertilizer Applied

Increases the size of available pool for residue decomposition and plant available nitrogen

N-Losses – Volatilization/Leaching/Denitrification/Immobilization

Areas most prone to largest amount of loss are knolls, less moisture and more air movement = Volatilization, risk of leaching or erosion due to water movement. Next biggest area at risk of N losses are water holding depressions for denitrification. These areas capture water and cause the soil to be fully saturated, driving out all the oxygen. See above on C:N ratios for immobilization.

Sink Side Factors

Number of plants

More plants mean more plant material removing nitrogen (with other nutrients) and water from the soil

Sunlight

More sunlight means more photosynthesis activity, which means more ATP, which means more starch product, which means more yield (eventually).

Water

Plants with adequate nutrition can have sink size limited by available water. Mobile nutrient uptake into the plant is primarily driven by transpiration. As the plant pulls water from areas deeper in the soil profile, it will have to run more water to cool itself, but there are also less nutrients in the water it is pulling into the plant. (one of many reasons you get Boron deficiency in dry weather).

"I don’t think people purposely go down the wrong path. I just think that they’re unaware. Blind spots mean that they’re blind spots. You have no idea. You’re totally surprised when all a sudden you see something that you never saw before. And one of the greatest things we could do for others is to come alongside them and help them with those areas."

- John Maxwell