Highlights in this report:
- Crop growth stages and condition report
- Soybean leaf defoliators, what is out there?
Corn Growth Stages and Condition (County-wide report, not sectioned by region)
April and May planted corn is in the blister to late milk growth stage across the county with some corn on sandy soils in the Platte River valley reaching the dent stage already (drought hastens maturity, Figures 1). June replanted corn is V17 to R1 (silking) northeast of the Elkhorn River near Uehling. (Figure 2). We will have favorable weather for pollination on replanted corn, but the heat units needed to get this crop to maturity before the average first hard frost is becoming more of a concern with below normal temperatures predicted the rest of the growing season. Irrigated corn conditions ranges from poor (June waterlogged soils) to excellent (well-drained fields with sufficient nitrogen). Overall, irrigated corn is in good to excellent condition with ears filling out nicely to the tip and having weather conditions for an extended grain fill period for higher kernel weight (Figures 3). In dryland corn, the cool weather and lower crop water use has been a salvation during a very dry 5 week period for most across the area (Figure 4). Significant rainfall fell on August 2nd in the northeast part of the county with some reports over 1.2 inches. As I mentioned in a previous blog post on 2014 forecasted yields, cool daytime highs in July is the largest driver in dryland corn yield locally. Not uncommon for this time of year, but the dryland corn condition and yields have decreased slightly over the past two weeks.
Figure 1. Drought stressed corn already dented on sandy soils in the Platte River bottom.
Figure 2. Replanted corn starting to tassel west of Uehling.
Figure 3. Irrigated corn ear filled out to the tip in the Platte River Valley.
Figure 4. Dryland corn ear in the Elkhorn River bottom filled out nicely.
Soybean Growth Stages and Condition (County-wide report, not sectioned by region)
Irrigated soybean ranged from fair to excellent condition with most in good to excellent condition (Figure 5). Dryland soybeans are at a critical growth stage, R5 or beginning seed, for yield determination. Soybeans at R5.5 (Figure 6) have finished flowering and reached maximum height, thus yield compensation with favorable weather is limited by genetic ability to increase seed size. Replanted soybeans in June have reached R3 or the beginning pod stage (Figure 7). Dryland soybeans are in fair to good condition. Dryland soybean yield potential has been limited over the past two weeks during the pod setting and early seed fill stages. Soybeans have been changing their leaf orientation or flipping their leaves to the silver-green underside (Figure 8) to slow down photosynthesis and conserve water during some of the warmer and less humid days lately. As most know, dryland soybean yield is most affected by August rainfall over any other single weather parameter, so we still have time to catch some more rains for a good soybean crop.
Figure 5. This irrigated soybeans field in the Platte River valley is in excellent condition.
Figure 6. This soybean field is at the R5.5 growth stage and is done blooming and setting pods.
Figure 7. Replanted soybeans setting pods (R3 growth stage) near Dead Timber Recreation Area.
Figure 8. Soybean leaves changing orientation to to reflect more light, slow photosynthesis, and thus reduce water use under slight drought conditions.
Soybean leaf defoliators
It is that time of year when it seems like every insect wants a bite of your soybean crop. The soybean leaf defoliators I saw during the tour included grasshoppers (Figure 9), bean leaf beetles (Figure 10), grape colaspis adults (Figure 11), thistle caterpillars (Figure 12), and green cloverworms (Figure 13). The northern half of the county seemed to have more pressure from these defoliators than the southern half. Some soybean fields had up to 5-10% defoliation, but most had less than 5%, which is well below thresholds for spraying defoliators. A nice 3-page guide to Managing Soybean Defoliators covers the catch-all defoliation level recommendations, how to scout for defoliation, and reference pictures for what 5, 10, 20, 30, and 40% defoliation look like. As I mentioned before, most fields I saw had <10% defoliation. If defoliation is 20% and some pods are being chewed on, control of defoliators may be warranted.
Figure 9. Differential grasshopper is one of several species than can be found in fields.
Figure 10. Bean leaf beetle (can be other colors, i.e. tan, orange, etc.).
Figure 11. Adult Grape Colaspis.
Figure 12. Thistle caterpillar near Uehling, NE in a replanted soybean field.
Figure 13. Green cloverworm in a soybean field near Snyder.
Crop Tech Cafe – Fremont, NE
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