Issue No. 4, Article 8/April 20, 2007
Field activity is still limited by wet soil conditions throughout the region. Anhydrous ammonia application, tillage, and dry fertilizer application are occurring in some areas but not on a wide scale. Dave Feltes, IPM extension educator, caught 7 black cutworm moths on April 13 in Whiteside County. Winter annuals such as henbit and chickweed have become more apparent in soybean stubble throughout the region.
Jim Morrison, crop systems extension educator, reports that much of the alfalfa in northwest Illinois has a "brown cast" due to early April cold temperatures, but in most fields new growth is evident from the axillary stem buds and crown buds. Plants are expected to survive, but first harvest will be delayed due to the cold injury. Wheat is exhibiting brown leaves as well due to the cold weather; plant survival is expected to be good, though, throughout most of the region.
The dates and topics have been set for the 2007 Crops Training Center programs at the Northern Illinois Agronomy Research Center at Shabbona: June 8, Corn/Soybean Disease Update; June 28, Corn/Soybean Insect Update; August 8, Weed Competition/Corn and Soybean Plant Disease Update. All programs are from 9:00 am to noon. Preregistration is required; contact Greg Clark, Whiteside County Extension Unit, 815-772-4075, firstname.lastname@example.org.
Health of the wheat and alfalfa crops continues to be the major concern. Wheat condition varies throughout the region, with some fields obviously dead, some relatively uninjured, and the vast majority somewhere in between. The farther south one travels the more significant the degree of injury, because the wheat was more advanced in its stage of development. The greatest field-to-field variability seems to exist in the corridor bordered by IL Route 16 on the north and IL Route 50 on the south. South of Route 50 the situation deteriorates more markedly. In many cases, the leaf tissue and upper canopy aren't exhibiting a great deal of injury, but the lower stem tissue has been damaged around 1 to 2 inches above the ground. Assessing the level of damage both within and between fields has been complicated by the cool and cloudy conditions immediately following the freeze. These weather conditions have tended to mask the level of injury that may be present. As sunshine and warm temperatures return, damage in fields will become much more apparent.
Alfalfa recovery has been very slow, and the presence of alfalfa weevils isn't helping the situation. Where axillary regrowth is present, stems are damaged badly enough that severe lodging is apt to occur. Unfortunately, field conditions have been too wet up to this point to harvest and salvage most fields.
There's nothing like a day or two of sunshine and nice temperatures to improve one's perspective. Across the region, folks are noting considerable variation in the degree of damage to the wheat crop. Depending on the plant's growth stage when the cold weather occurred, levels of damage range from slight to serious. Most plants that were at Feekes 7 or beyond show damage to the lower stem. This portion of the plant has been weakened, and in many cases it may not support the plant to maturity. Mike Roegge, crops systems educator in Adams-Brown Counties, suggests that 99% of the crop he has examined is healthy beyond some upper leaf desiccation. Producers are continuing to find bird cherry oat aphids in the wheat.
Alfalfa fields are also variable depending on the quality of the stand and the conditions going into the cold weather. Stems in some fields were killed back to the soil line, while in others only the top 4 or 5 inches were killed. With regrowth occurring from both the crowns and buds along the stem, there will be uneven development across fields for the first cutting. Alfalfa weevil larvae are resuming activity in the southern part of the region. Some third instars were killed by the cold, and first instars are still present.
There were reports of intense black cutworm captures late last week in three locations. Degree days will be tracked from this point forward to help predict cutting dates.