While the story of the "haves" and "have nots" continues across the state, some areas in NW did finally get some much-needed rain early this week. And unfortunately, the Zearing area in Central Iowa also had some hail damage. Some of the observations or questions coming in from the field this last week have been on or have included: spider mites, new counties in Iowa found to have soybean gall midge, soybean aphids, tar spot, SDS, and potato leafhoppers. Read on for more specifics of what’s happening around the state.
Joel DeJong (Region 1): “A week ago, the northern part of the region I serve received a much needed rainfall. However, the driest part of the region missed most of that event. The good news, on Monday most of the area that was missed a week ago received an inch or better. For some fields along the western edge of the state it might be too late – in fact, several have been chopped for silage already. Most fields will still benefit greatly from this precipitation event. In the drier regions spider mite populations have been increasing. Cooler weather and moisture might help crash these populations; we hope. Along the Minnesota border and increase in soybean aphid populations has been reported. A reminder, if treating those pests’ insecticide pre-harvest intervals need to be considered, and once soybeans reach the R6 stage the chance of recovering your investment goes down considerably.”
North Central Iowa
Angie Rieck-Hinz (Region 3): “ It continues to be the “haves” and “have nots” across the 8 counties I serve, at least in terms of rainfall. Parts of Humboldt, Webster, Hamilton and Wright got some much-needed rain on Monday, August 15, although more is needed. Parts of southern Hardin County into northern Story County experienced a downburst with hail that caused significant crop damage around Zearing in a storm that passed through on Thursday, August 11th. Crop conditions are highly variable across the area. I am receiving more and more reports of tar spot in my northern counties where there has been significant more moisture, but the majority of photos shared with me still indicate low severity. However, there are some fields with a higher degree of severity so take some time to evaluate your hybrid ratings to make defensive choices for next year. I have also received scattered reports of aphids in corn. There are no treatment thresholds for aphids in corn, but this ICM article offers points to consider. Gray leaf spot and northern corn leaf blight are also present. Sudden death syndrome is starting to make an appearance in soybean fields.”
Josh Michel (Region 5): “Over the past week, most of NE Iowa received anywhere from 1 to 1.5 inches of rainfall, with isolated heavier amounts of 2 inches in parts of Allamakee, Clayton and Winneshiek counties. Most of the corn in NE Iowa is currently at R3 to R4. I continue to receive calls about corn rootworm and disease management as we’re seeing increased pressure of tar spot and gray leaf spot. Soybeans are mostly at R3 to R4, as pod are continuing to develop. Leaf defoliation and late-season waterhemp emergence continue to be the main issues. I’ve also heard of some SDS and soybean aphids starting to show up in a few areas. Most of oats have been harvested, and I’d expect any remaining fields to be harvested this week pending favorable weather. Alfalfa harvest continues across the region, as farmers continue to scout for grasshoppers and potato leafhoppers. Most of my field calls over the past week have consisted of alfalfa pests and scouting, soybean aphids and defoliation, small grains and forage management, weed management in pastures and CRP fields, and managing corn and soybean diseases.”
Meaghan Anderson (Region 7): “Most of central Iowa received some much needed rain over the last week, but it didn’t come in large amounts (mostly <1”), so the crop stress and lack of moisture continues across much of this area. A small area in Story and Hardin counties received significant hail with some rainfall last Thursday afternoon and some crops in that area suffered significant leaf tissue loss, stalk bruising, and ear/pod bruising. We’ll have a hail meeting in Zearing, IA at 10 a.m. on August 17 to talk about the crop damage (see flyer: crop_damage_meeting_-_zearing.pdf). Corn is primarily in the dough (R4) growth stage and soybeans are primarily in the late R4 to early R5 growth stage across central Iowa. Twospotted spider mites, aphids, corn rootworm beetles, and grasshoppers are still familiar sights in corn fields, but disease pressure remains low. Twospotted spider mites are present in some soybean fields but the cooler temperatures and moisture should help keep them from spreading rapidly. Soybean gall midge was recently spotted in soybean in both Polk and Warren counties; these videos can help scouts determine what to look for. Crops are continuing to show stress from lack of moisture, especially in lighter soils, compacted soils, or areas where nitrogen loss was high earlier this spring; the recent rains will help but we could use some more to finish out these crops!”
East Central, Southeast, and South-Central Iowa
Rebecca Vittetoe (Region 8): “It’s the same song in EC Iowa when it comes to the "haves" and "have nots" with rainfall over the last week, with my more northern counties receiving more rain than my southern counties. Poweshiek, Marion, Mahaska, and Keokuk counties (or parts of them) are classified as a severe drought (D2) on the U.S. Drought Monitor. Corn is R4-R5 and a lot of soybeans fields are now at R5. Crop conditions are variable across the area. In the areas that have been catching rain, the crops look really good and in the drier areas things look tough. Additionally, in the drier areas, spider mites are more common, but hopefully the cooler conditions will help to slow them down. Other pests or diseases noted in fields this past week include corn aphids, soybean aphids (more my northern counties), corn rootworms, potato leafhoppers in alfalfa, tar spot, and late season weed escapes. Questions this past week have mainly been on corn rootworms, spider mites, late season weed escapes, and nitrate concerns for silage in the dry areas.”
Virgil Schmitt (Region 9): “Rainfall last week in the counties I cover was 0.5 inch or less except there was as much as 1.0 inch along the Highway 30 corridor. Areas roughly south of Highway 92 are listed as DO (abnormally dry) except that western Henry County and much of Lee County are listed as D1 (moderate drought) on the August 9 Drought Monitor. In general, temperatures during the last week in the counties I cover were one to three degrees below normal. Most corn is R4-R5 and looks good to excellent except for areas showing drought stress. There are low levels of gray leaf spot in some fields and tar spot can be found here and there. Most soybeans are at R4 and also look good to excellent except for areas showing drought stress. Again, disease levels are very low. Japanese beetles continue to be found in all of the counties I cover. Potato leafhoppers continue to be present in alfalfa and there are winged grasshopper adults in grassy areas. Phone calls, emails, and field visits last week mostly involved insect feeding on soybeans and waterhemp management in soybeans.”
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