NORTHERN "AG" EXPOSURE

by Mark Miller
Rolette County Extension Agent

Published 8-13-01 Turtle Mountain Star

Green Seed Problems

Cutting too early with high temperatures and rapid drying can lead to excessive green seed count. Two percent or less green seed is currently the allowable limit. Any higher than the 2 percent and market discounts can occur. The key to curing the crop is moisture. The enzyme responsible for clearing the chlorophyll requires moisture. Therefore, seed moisture is critical. If the stems and seeds dry too rapidly after swathing, then chlorophyll can be fixed. Leaving canola in the swath longer can help eliminate some green seed problems or potential. A rain will also help reduce green count in canola. Once the moisture content of seed is 20 percent,chlorophyll will begin to be moved out. In some cases however, when swathed too green in hot weather the chlorophyll will not be reduced to any great extent. Cool temperatures and light frosts in August and September slow the enzyme activity that breaks down chlorophyll. Frosts from 32 to 33 degrees F disrupts that system, more specifically it can reverse it and restart the synthesis process. This is very sensitive in the seed development stage, and the window is very narrow. This can cause differences between adjacent fields that are only days apart in maturity, or differ in uniformity of maturity. Even canola swathed four to six days before a frost will retain relatively high levels of chlorophyll.Thin stand counts can result in plant with more branching and more variability in seed maturity and are more likely to have immature seed at swathing.  Late seeded canola may be impacted by all these situations. When looking at uneven stands, its suggested that one do a count early on the ratio of early emerged canola which is bolting or starting to flower and  the late emerged flush of young more immature plants. If one knows the ratio of early to late emerged canola plants, a better decision can be made as to how soon to swath or wait until the later crop catches up. If the stand is on 20-25% early and 75-80% late, then waiting to cut later may be the best strategy to reduce the amount of green seed. Two years of NDSU research has shown that at 0-5 seed color at swathing time resulted in 3.5 percent green seed content which is higher than the 2% allowed in the market place before a discount will occur.

Approximately 180 lbs/A of yield gain was noted when swathing was delayed to the 15-20 percent seed color change. Another sign of canola being very near the swathing stage is the natural yellowing and senescence of leaves and leaf drop. When canola plants consist only of stems, stem branches and pods, it is probably very near the optimum time for swathing. Canola should be allowed to cure and ripen from ten to 14 days in the swath before combining. If combined too early, the chance if increased green seed in the harvested crop is much greater.

“Be in a hurry to swath on time and prevent shattering, but take your time in moving the combine in the field to ensure maximum drying, maturation and quality of your harvested canola.”

WHAT ARE THE WHITE-COLORED BUTTERFLIES FLYING AROUND?

WILL THEY FEED ON MY CROPS?

The beautiful white butterflies flying around are the Cabbage Butterfly, Clouded Sulphur, and Alfalfa Butterfly (more yellowish than white)! The Cabbage Butterfly prefers to feed on cabbage, broccoli, kale and other rassicae plants. So, one could find it in canola. Fortunately, most of the canola is being swathed within the next few weeks. Clouded Sulphurs feed on clovers, sweet clovers, and alfalfa; where as the Alfalfa Butterfly prefers alfalfa, but can feed on clovers and other legumes. Normally, these butterflies are not pests in forage-legume crops grown in this area. The larvae or caterpillars of the Clouded Sulphur and Alfalfa Butterfly are velvety green caterpillars with a double lateral strip (white on top of red). The caterpillar of the Cabbage butterfly is green with a white lateral strip. These butterflies will NOT FEED on most of the our later crops – flax, sunflower, and small grains.

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Updated by August 23, 2001 Shelley Armstrong Webmaster