The wheat crop continues to grow rapidly in the cool moist conditions and is 5-10 days ahead of normal in general. Following up on last week’s report, by the time sprayers are able to be back in the field, the weed stage and competition from the crop canopy will likely negate herbicide use in most situations.
These weather conditions favour disease growth and although current disease levels remain low in most fields this can change quickly. Septoria leaf spot and powdery mildew are the most common diseases present currently and primarily still situated in the lower canopy. Last week leaf rust was found in Bruce County as well as wheat spindle streak mosaic virus was confirmed in Essex County. With the rapid growth of the crop and favourable weather conditions , it is important to continue scouting to determine if fungal disease infection is progressing up the plant (especially on susceptible varieties) and if a fungicide application is needed. With the rapid growth of the crop, scouting for effectively timing fungicide applications is critical. Crop growth stage, climatic conditions, variety susceptibility, presence of or anticipation of disease are all considerations that go into the decision if and whether a fungicide application is needed.
Stipe rust at very low levels was found in one field in Essex County last week on a susceptible variety. The infection was mid canopy which considering the recent storm systems would suggest spore movement into Ontario from the Midwest US and not overwintering. Unfortunately, weather conditions favor further stripe rust development and spread. As was seen last year, there are large differences in variety susceptibility to the disease. Check with your seed supplier and the Ontario OCCC performance trials for specific variety ratings (www.gocereals.ca). All wheat growers should be scouting for stripe rust (Figure 1) and based on last years’ experience, a preventative fungicide applied to susceptible varieties was beneficial and a good integrated wheat disease management strategy. Fields planted with susceptible varieties should be sprayed while those with planted to tolerant varieties need to regularly scouted from now until heading to assess stripe rust risk. Refer to the following article for more information on how to manage stripe.
Figure 1. Stripe Rust vs Common Rust Symptoms on Wheat
Very little progress has been made in corn planting as wet weather continues to delay field work. Impatience is building! But the consequences of getting on fields too quickly can be significant. Everyone is fixated on the importance of early planting date. What is forgotten is the statement “given field conditions that are fit for planting” which should precede any mention of early planting date! Figure 2 below from shows a gradual reduction in yield potential with time. This assumes all other stresses being similar throughout the season.
Figure 2. Corn yield potential by planting date at 3 locations in Ontario, 2006-2009 (OMAFRA/University of Guelph).
Figure 3 is a summary of Ontario average corn yields and the dates at which 90% of the corn crop was planted. This suggests that even with delayed planting, there is still good yield potentia possible given that the crop is planted in good conditions.
Figure 3. Average Provincial Corn Yield by Year and Date at Which 90% of Crop Was Planted (OMAFRA)
Dr. Joe Lauer’s from the University of Wisconsin has studied the impact of planting date on corn yield back to the early 90’s. Table 1 illustrates the variability in optimum planting date and the seasonality that occurs in the amount and timing of yield loss potential associated with missing the optimal planting date. There is usually a solid two weeks following the annual optimal planting date when 95% of yield potential can be achieved. Additionally looking at the right 3 columns of table 1 and the slope of the line in Figure 1, the loss in yield potential is gradual as you get beyond the 95% of yield potential date, and then gets faster as you are more than 20 days beyond the optimal planting date.
Table 1. Corn grain yield response of full-season hybrids (104-108 d RM) to planting date at Arlington, WI. Dr. Joe Lauer, University of Wisconsin (http://wisccorn.blogspot.ca/2013/04/B031.html )
The fitness of the soil for planting is always the most important consideration, and then planting date. Dr. Fred Below of the University of Illinois suggests that there are 7 important components of production that contribute to yield optimization in corn (Table 2). Dr. Below’s work states that while the factors in the table interact, the higher the factor is on the list, the more influence it exerts on achieving yield potential.
Weather is the biggest factor and we can’t control it but we can to some degree manage around it. If you compromise the crop right from the start, its ability to buffer against other weather and stress extremes will be compromised. Plant by soil conditions, not the calendar.
Table 2. The Seven Wonders of the Corn Yield World. Values presented in bushels/acre as well as percentage of the total (260 bushels/acre). Dr. Fred Below, Univ. of Illinois (http://cropphysiology.cropsci.illinois.edu/research/seven_wonders.html )
If there is only a small window to plant, it’s best to plant first and apply nitrogen afterwards provided you have the means to do so.
When planters start rolling, some may try and get ahead by speeding up planting. Unless your planter is setup for it and the field conditions can take it, you are likely not helping yourself. Cutting corners on planting pays no dividends. The continued cool forecast means we have not lost much heat with the seed still in the bag. Last week Wednesday to yesterday we achieved only 10-20 CHU across the province. It takes 180 CHUs from planning to emergence. Be patient and do it right!
While a few acres of beans have been seeded, field conditions have not allowed for large scale seeding. Early planting is less critical to yield for soybeans than corn. Soybeans planted in mid-May often have the highest yield potential. Something to consider while waiting to get back in the field is seed size. Soybean seed size tends to be large this year and this has implications for planting equipment. Ensure that your equipment is setup to deliver whole seed effectively to the ground. A split seed will not survive. Soybean seed supply is tight in many zones so ensure you have your needs confirmed. Last year’s weather hurt seed quality resulting in a lower volume of high quality seed being available. Trying to switch corn acres to beans as the planting season condenses may be difficult.