Crops throughout much of South Parkland continued to show improvement as a result of the mild temperature and the recent rainfall. Temperatures continue to be ideal for crops that are now well into the critical reproductive and filling stage of their development. Rainfall amounts mid-week and over the past weekend were variable ranging from trace amounts to 10-25 mm with higher amounts in thunderstorms. This rainfall was generally welcomed by most producers and should now be sufficient to carry most crops with the possible exception of soybeans through to maturity. Most livestock producers have now completed their hay harvest with only native and ditch hay remaining. The quality of this year’s crop continues to be well above average with overall yields still coming in at 75-80% of normal. Many producers have now begun looking at alternative feeds to help supplement this year’s winter feed supply.
Soybeans and Water Use and Growth Stage
All crops benefited from the most recent rainfall but none more so then this year’s soybean crop. Soybeans require significantly more water than wheat and canola especially late in the growing season. Water uptake by soybeans will peak 10-12 weeks after planting. In August, soybeans will take up approximate ¼ inch of water per day which is important for pod formation and seed fill. One of the ways soybeans resist heat and drought stress is by flipping their leaves over allowing the plant to reflect solar energy and reduces water loss.
Soybeans are now between R-3 (early pod) and R-5 (early seed). Once soybeans reach R-4 (full pod) they are past the halfway point of growth and will require 40-45 more frost-free days to reach R-7. From R-5, soybeans require 35-40 frost-free days. The period between R-4 and R-5 is the critical yield determining stage. Growing conditions during the next two weeks will be critical for soybeans. Between R-4 and R-5(70-75 days after planting), nitrogen fixation and nutrient uptake will peak. Stress during this time (lack of nutrients, water deficit) may reduce pod number and number of seeds per pod. The soybean plant will reach its maximum height, node number and leaf area during this period.
Trap counts over the past week continue to be at low levels with moth numbers now having peaked. Moth counts for much of South Parkland have been on the low side with no real hot spots in regards to moth numbers being noted. Scouting for bertha army worms should commence this week in order to get an indication of populations even though moth levels were low in traps as there is not a direct correlation between moth numbers and bertha larvae feeding. Initially most feeding will occur on the leaves prior to leaf drop. Populations of bertha armyworm can vary greatly between fields within a region so assumptions regarding a field cannot be made based on findings in nearby fields. The wide range in seeding dates may see moths migrate to later flowering fields so populations may vary widely even between neighboring fields. At $10 per bushel canola and control measures priced at $10 per acre, 17 bertha armyworm larvae/m2, are needed to cover the cost of the control measures.
Red Mites on Grasshoppers
Some have been asking about red mites seen on the wings of grasshoppers. These red mites on the grasshoppers are parasitic red mites (Eutrombidium locustarum). They feed on the blood (hemolymph) of grasshoppers and also prey on grasshopper eggs. Each female mite can lay up to 4,000 eggs allowing mite populations the potential to increase rapidly and substantially as grasshopper populations increase. Research in Montana has shown that these mites can reduce the survival and reproduction of grasshoppers.
Golden Rod Natures Indicator of GDD
Some of you may have noted that the native flowering plant Golden Rod is now well into flower in many roadside ditches. Typically Golden Rod will appear when we begin to see crop ripening and pod development in our cereals, oilseeds and pulses. When we look at the corresponding GDD necessary for Golden Rod to flower we find the number is somewhere between 900 – 1000 which is coincidentally where we have just recently surpassed.