Iowa Field Reports: Much Needed Rains Alleviate Crop Stress

    The hot and dry conditions last week resulted in many fields showing signs of stress. Thankfully, a much-needed rain fell across a good part of the state late last week and on Sunday evening. Unfortunately, most of NW Iowa seemed to miss out on the rain.

    With the much-needed rain, there was also some wind, hail, and tornado damage reported. In addition to the dry conditions and storm damage, herbicide injury (carryover and drift) and sulfur deficiency in corn were common issues or questions received by ISU Extension field agronomists.

    Read on to see what’s happening in different regions across the state.

    Northwest Iowa

    Joel DeJong (Region 1): “In the NW corner of Iowa rainfall was hit or miss last week – and for most, it was a miss. Mid-week delivered a rainfall along the extreme eastern edge of the region I serve, but it brought hail with it. Some fields in eastern Ida County were significantly injured. Weekend rainfall was spotty, at best.

    “Southern counties fared better than northern counties. Some cornfields continue to roll, even on the cooler days. Several comments about slow soybean growth have been heard. Carryover symptoms can be found in some fields, also slowing beans. Herbicide drift injury calls are increasing.

    “Alfalfa tonnage for the first crop was quite good, but the second crop appears short. Pastures are quite brown. Unwatered lawns have been dormant for about three weeks in the drier areas, which is a good indicator to me about pasture growth. With recent rainfall patterns and lower subsoil moisture levels, it is hard for many to be optimistic about yield chances for corn in this region at the present time.”

    Paul Kassel (Region 2): “The continued dry weather is the major concern for the area.  Corn fields continue to show the effects of moisture stress – often early in the day. Soybean fields that are non-Roundup Ready Xtend varieties are showing the effects of dicamba drift.  Soybean plants are exhibiting cupped leaves, the source of this dicamba drift is likely from dicamba applications to corn fields.

    “The recent hot and windy weather likely created conditions that favored the volatilization of dicamba from those corn fields. There is also some carryover injury to some soybean fields from last year’s application of Topramezone or Impact/Armezon herbicides.  These injury symptoms are often also complicated with the effects of dry soils and iron deficiency chlorosis.”

    North Central Iowa

    Angie Rieck-Hinz (Region 3): “Scattered rains were welcomed across NC Iowa this past week, but while we had several chances of rain, we did not receive much in terms of amounts.  Rainfall varied from 0.84 inches at Rockwell City to 0.19 inches at Northwood (Iowa Environmental Mesonet).

    “High winds reported on Sunday, June 20 flattened corn in some areas, but reports state the corn is starting to stand up. Corn is V9 to V10, and most was rolling by mid-morning every day last week. Soybeans are V4 to V5 and remain short. All soybean fields I visited last week were flowering so I would call them R1.

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    “Iron deficiency chlorosis started making an appearance last week in our calcareous soils.  Do not confuse this annual interveinal chlorosis for herbicide injury.  Soybean aphids have been reported in central Iowa, but I have not seen any soybean aphids, spider mites or soybean gall midges to date.

    “I am seeing a lot of grasshopper nymphs which is not surprising given our dry conditions. Grasshopper nymph damage is characterized by irregular feeding that cause ragged edges on leaves and sometimes holes. Pastures continue to deteriorate. Phone calls this past week have consisted of herbicide carryover concerns, drift issues from corn to soybeans, over-spray of corn fields by neighbors, and dicamba off-target movement.”

    Northeast Iowa

    Terry Basol (Region 4): “Most of the corn and soybeans in NE Iowa range from the V6 to V9 and the V3 to R1 growth stage respectively, depending on planting date. As shown in the picture, soybeans are entering the R1 stage of development (one open flower at any node on the main stem).

    “For the most part, field operations for corn are finished. POST herbicide applications for soybeans are finishing up. Much of the area received some rainfall on Sunday, June 20, ranging from about 0.3 to over an inch in isolated areas. Ken Pecinovsky, NE IA research farm superintendent, reported receiving 0.47 inch the farm gauge.

    Josh Michel (Region 5): “Most of NE Iowa has finally received some much-needed rain. Combined precipitation from last Thursday and Sunday evening has resulted in most of the area receiving around 1 to 1.5 inches of precipitation. This, along with some cooler night temperatures will hopefully bring some relief to heat and drought stressed crops.

    “Corn is generally around V6 to V7 and continues to grow quickly despite showing signs of heat stress. Nitrogen sidedressing and POST herbicide applications are continuing throughout most of the region. Soybeans are generally around V4 and have also been showing signs of heat stress. There continues to be some concern that alfalfa second crop regrowth may be slower than normal, but recent rainfall should provide some relief.

    “Oats continue to look good, with estimates of up to 50 percent headed out. Pastures are also showing signs of heat stress from warm temperatures and a lack of soil moisture. Recent field calls and questions have centered around alfalfa and small grains management, POST herbicide applications, pesticide drift complaints, and questions pertaining to heat stress on crops.”

    Southwest Iowa

    Aaron Saeugling (Region 10): “Much needed rainfall fell over most portions of SW Iowa the past week.   Crop conditions look good considering the lack of subsoil moisture.  Unwelcome hail and isolated wind damage reported in portions of Montgomery, Adair, and Union counties.  Corn is rapidly growing after the rainfall and is in the V8 to V10 growth stages, soybeans have begun to flower while most soybeans are V3 to V4.

    “Herbicide injury and drift calls are common reports.  Most corn herbicide has been applied while soybean herbicides are now being applied. At this point very little insect damage has been reported, I expect insect activity to increase with typically summer weather patterns. Hay and pasture conditions continue to deteriorate with the hot dry weather, we will soon know if the last rainfall will help conditions.”

    East Central, Southeast, and South Central Iowa  

    Rebecca Vittetoe (Region 8): “With the hot and dry conditions last week, the crops were really starting to show signs of stress. It was not uncommon to see corn leaves rolling by mid-morning in places. Forage growth has really slowed, and pastures are doing dormant. Thankfully we did receive some much-needed rain late last week and again Sunday evening.

    “Rainfall totals ranged from around 0.25 inch to 3 plus inches in areas. Unfortunately, with the rain came some severe weather including some wind, hail, and even tornado damage. The hail damage ranged in severity from minimal to significant.

    “Corn is mainly around the V8 to V10 growth stage and soybeans range from about V4 to R2. Sulfur deficiency symptoms in corn, corn nematode, weed ID, and herbicide drift were common calls and field visits last week.”

    Virgil Schmitt (Region 9): “Rainfall during the last week in the counties I cover was generally less than 0.1 inch of rain along Highway 30 to over 3 inches in the Burlington area. In general, temperatures during the last week in the counties I cover were 1 – 3 degrees above normal. Corn is V9 +/- one collar and soybeans are generally about V4 to R2.

    “Oats are heading out. Sulfur deficiency symptoms in corn were very common last week. Moisture stress in corn is common along and north of Interstate 80. Also, I saw my first Japanese beetle of the season. Calls last week centered mostly around sulfur deficiency symptoms in corn, weed ID, and herbicide drift.”

    Clarabell Knapp (Region 11): “Over the past week, the area received multiple rainstorms, some producing a few pockets of hail and high winds. The amount of rain received varied greatly during each shower but the average total for the week in most areas was around 1.5 to 2 inches. Most corn fields are around the V10 stage, while early planted soybean fields have been seen flowering and later planted fields are around the V5/V6 stage.

    “Oats continue to look good and are over 50 percent headed out. The alfalfa and pasture ground have been slow for regrowth with the heat and lack of moisture at the beginning of the week but will be looking to benefit from the rain that was received. Most field calls have been directed towards weed control and identification, pesticide applications, and crop health.”




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