Iowa Field Reports: Drought Persists, Disease Pressure Increases

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    Drought conditions persist in western Iowa and have expanded further into central and north central Iowa this week.

    Common issues reported by ISU Extension field agronomists this past week included poor grain fill and fast reproductive development in corn, increasing disease pressure in some corn fields, concerns regarding off-target movement of dicamba, and a variety of insect issues including corn rootworms, potato leafhoppers, Japanese beetles, twospotted spider mites, and white flies.

    Read on for more specifics for what’s happening in different regions across the state.

    Northwest Iowa

    Paul Kassel (Region 2): “Abnormally dry conditions, moderate drought and severe drought cover most of the area that I serve – according to the July 30 U.S. Drought monitor. The area of severe drought is mostly confined to Sac county.

    “Crop conditions have deteriorated because of this lack of rainfall. Many areas in Sac, Clay, Buena Vista and Palo Alto county are showing large areas of moisture stressed crops in fields that have deep, productive soils. Crop development is progressing rapidly.

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    “It is common to see corn in the R4/dough stage – which is about a week ahead of schedule. This increase in the rate of crop development may signal a response to the dry weather. This is also likely an indication of reduced dry matter accumulation and reduced crop yields.

    “Soybean aphids can be found in area fields, but they are at low levels. Farmers and agronomists are encouraged to keep checking fields for soybean aphids through the R6/full bean stage of soybean development.”

    North Central Iowa

    Angie Rieck-Hinz (Region 3): “Lack of precipitation is causing more area in NC Iowa to show up on the drought monitor.  Generally speaking rains were very spotty the week of July 27 through August with Humboldt reporting 0.2 inches and all other locations reporting lesser amounts if any rain. Isolated showers on Saturday, August 1st produced up to 0.3 inches between Gowrie and Callender.

    “Crop stress is starting to show up in Cerro Gordo and Worth counties as well.  Most corn is at R4 or dough, but occasionally I have found fields starting to dent or at R5 so we are pushing maturity with the high temperatures and lack of precipitation to assist with grain fill.

    “Soybeans are mostly R5 or beginning seed. There are a few reports of low-level soybean aphids.  Both corn and soybean disease pressure remains low.”

    Central Iowa

    Meaghan Anderson (Region 7): “Most of central Iowa got some much-needed rain in the last week, though much of Dallas, Polk, Jasper, Madison, and Warren counties received <0.5 inch. Corn is mostly R4 in the area, though I’ve noticed a handful of kernels beginning to dent in some fields.

    “In areas that have received more rainfall, corn looks mostly excellent but gray leaf spot pressure is increasing in some fields. Soybeans are primarily R4-early R5. Some waterhemp patches are beginning to show up in soybean fields. While most of my area is considered abnormally dry or in moderate drought, the most significantly affected area is western Boone County, western Dallas County and far NW Madison County.

    “Soybeans are beginning to show significant moisture stress and corn ear development and grain fill are extremely variable. Twospotted spider mites are prevalent in many fields in these counties.

    “Common phone calls this week were about off-target dicamba injury to soybeans, weed identification, fungicide application decisions, potato leafhoppers in alfalfa, and white flies in soybeans.

    East Central, Southeast, and South Central:

    Virgil Schmitt (Region 9): “Rainfall last week was generally less than 1.0 inch. In general, temperatures last week in the counties I cover and statewide were near normal. Most corn fields are at R3 – R4 and generally looking good, except for storm damaged fields. Gray leaf spot is increasing. Soybeans are mostly R3 – R4.

    “In general, they also look good, again except storm damaged fields. White flies are abundant in some fields. Corn rootworm trait failure (continuous corn), Japanese beetles, white flies, dealing with storm damage to crops, fungicide and/or insecticide applications, and dicamba drift were common topics of discussion last week.”

    Josh Michel (Region 11): “Scattered showers provided some relief to parts of SC and SE Iowa, with areas receiving anywhere from 0.25 to 1 inch of rain over the past week. Corn is generally R2 to R4, with many fields still looking good, despite limited rainfall. Symptoms of heat stress are still occurring in areas with poor soils.

    “Gray leaf spot continues to be found throughout the region, along with some minor reports of corn rootworm damage and southern rust. Soybeans are generally R3 to R5, and are also looking pretty good. The majority of my soybean field calls have centered around insect feeding and weed escapes, especially with soybeans planted on 30” rows.

    “Alfalfa continues to grow very slowly, with many reports of moderate to severe insect feeding, mostly due to potato leafhoppers and grasshoppers. Forages in pastures have been growing very slowly as well. Recent cooler temperatures and small amounts of precipitation are expected to slightly improve crop conditions.”




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