Highlighted items you may want to read more about in this week’s report:
- Soybean aphids reported, where at?
- Corn rootworm damage… have you checked your roots?
- What is a Grape Colaspis beetle?
- Corn and soybean weekly water use.
Platte River Valley (Fremont, Ames, North Bend)
Overall, corn is in poor to good condition and soybeans in fair to good condition, mostly steady from last week. Crop conditions deteriorated on some of the sandy ground along Hwy 30 since last week due to the lack of rainfall in July (only about 0.5″). Corn pollination is almost finished and some fields are in the blister stage, R2 (growth stages of corn). I grabbed a random ear and did notice a few pollination issues (Figure 2) but the ear was 16 rows around and 38 kernels long. Detasseling and irrigation season is in full swing this week throughout the valley. Gray leaf spot is still at low incidence and severity along with other fungal leaf diseases. Soybeans that were planted in early May are at the full pod growth stage, R4 (link to soybean growth stages). No soybean aphids were found in the fields that I stopped at.
Central Upland Flats and Maple Creek (Located north and south of the Maple Creek along the Webster Rd and Co Road N)
Corn is in fair to excellent condition and soybeans in good to excellent condition, holding steady from last week. Corn is at the R1-R2 stage. I did probe down and assess the soil moisture at the 1 ft, 2 ft, and 3 ft in a corn field that was silking. The moisture in the 1st and 2nd foot was hard to make a ribbon or ball out of, but the 3rd foot (Figure 3) still had decent moisture (I did found corn roots at this depth). Corn roots (Figure 5). continue to grow deeper after pollination through the blister stage (R2) and are capable of using a significant amount of moisture at the 4 ft depth. It is not uncommon for some corn hybrids to root 6-7 ft deep in our deep well-drained loess soils. Common rust incidence and severity has increased from last week (Figure 5), but severity is still low. Other corn leaf fungal diseases (Northern corn leaf blight, Gray leaf spot, Physoderma brown spot, common smut) are still at low severity. The amount of lesions (Figure 6) from Goss’s bacterial wilt has increased since last week. Most soybeans are in the beginning to full pod growth stage (R3-R4) without any presence of soybean aphids. Second cutting of alfalfa is mostly complete and bailing is on the docket (Figure 7).
Elkhorn River Bottom (Scribner, Hooper, Winslow, Nickerson)
Corn and soybean conditions ranged from poor to good, mostly steady from last week. I did see some male western corn rootworm beetles in this area. Growers need to be aware that resistance to the Cry3Bb1 protein (e.g. VT3P hybrids) has occurred in eastern Nebraska in previous years. Rotating away from corn for one year is a viable option. I did find root pruning (Figure 8) from corn rootworm and about two beetles per plant on a hybrid with the Cry3Bb1 protein this week. Also, some of the leaf defoliation we are seeing is not coming from grasshoppers, but the Grape Colaspis beetle (Figure 8) in fields around the county.
Northwest Rolling Hills/Pebble Creek (Snyder, Dodge)
The crops are in fair to excellent condition, steady from last week. Most corn is silking (R1) this week under warmer temperatures compared to the corn in the southern part of the county that pollinated last week. For the Soybean Management Field Days location south of Snyder, soybeans were at full pod stage, R4, and corn was silking, R1. Crop water use from July 14 to July 21 was 1.32” corn and 1.32” for soybeans. I applied the first irrigation treatment for the soybean irrigation study during the tour. Considering the time it takes for irrigation preparation and to irrigate the entire field (electricity shut off for 12 hrs), irrigation should be started when soils reach 65% percent of field capacity or 35% depleted to avoid crop stress. The first soybean aphid infestation was found this week near Dodge in a small spot, but with high populations (Figure 10). For more information on soybean aphid scouting and management, click on these hyperlinks. Also, try out the Aphid Speed Scout app.
North-central Sand Dunes/Cuming Creek (North of Scribner by Lone Tree and Dead Timber)
The crops are in poor to fair condition in this area, with some deterioration from drought stress. Sulfur (Figure 11) and nitrogen (Figure 12) deficiency continue to be issues this year in some spots. Herbicide applications on replanted soybeans were going on and most pivots have been repaired.
Northeast Rolling Hills/Logan and Clark Creek (Uehling)
Overall, crop conditions are very poor to fair, steady from last week. Replanted corn has reached the V10-V11 growth stage (Figure 13) and soybeans the V4-R1 growth stage (Figure 14). As I mentioned last week, late-emerging waterhemp has become a problem in some fields, which is too bad. Waterhemp plants can produce up over one millions seeds without competition and seed can survive about 4 years in soil seed bank. The 2014 Guide to Weed Management in Nebraska can be purchases for $10 at your local extension office. It a great resource to help starting planning next year’s herbicide program.
Agronomic matters to focus on this week are:
- Scout susceptible corn hybrids for leaf fungal diseases to assess need for fungicide applications
- Scout fields for weed escapes (possible herbicide resistance) and make changes to next year’s program
- Scout continuous corn acres for root damage and beetle pressure.
- Scout for soybean aphids and use the smart phone app, Aphid Speed Scout
Check in next week for the July 28th crop condition report for Dodge County.