Search

Regional Update: July 10 – July 18, 2023

July 18, 2023 10:27 PM
Blog Post

Over the last week much needed rain was received, but it also unfortunately brought along wind and hail to some parts of the state. Other hot topics coming in from fields across the state this past week included corn rootworm, soybean gall midge, phytophthora in soybeans, tar spot, gray leaf spot, and weed control issues. Read on for more specifics about what Iowa State University Extension and Outreach Field Agronomists have seeing or had questions about around the state in the last week.  

Northwest Iowa

Category: 

Keep an Eye out for Soybean Defoliators

July 12, 2023
Graphic explaining soybean defoliation.

When it comes to soybean, one of the most common types of injury is defoliation from insects. This damage can be easily detected in the canopy by observing holes in the leaves or along leaf margins as insects with chewing mouthparts consume leaf tissue. The insects most responsible for defoliation are bean leaf beetles, Japanese beetles, and grasshoppers. There are numerous caterpillars that also cause soybean defoliation, including green cloverworm, soybean looper and alfalfa caterpillar.

Crop: 

Don’t jump to early treatment with grasshoppers

July 6, 2023 2:34 PM
Blog Post

Although some parts of Iowa have been catching up with moisture deficits, many areas continue to be in severe drought. Drought stress combined with high temperatures is good news for field crop pests like grasshoppers and spider mites. We’ve been getting reports of high grasshopper numbers around the state this year. If your area is hot and dry, consider scouting fields now and throughout August.

Insect activity update

June 21, 2019 9:25 AM
Blog Post

I was a speaker at the ISU Northern Research Farm field day near Kanawha yesterday. So many questions about thistle caterpillar and soybean gall midge. I also saw some feeding injury to vegetative corn. Here are some pictures:

Stink bug injury in corn.
I saw a few stink bug nymphs. I think this is the result of their feeding last week. Note the yellow halo around the holes. 

Scouting guidelines for soybean defoliators

June 17, 2019 12:23 PM
Blog Post

The most effective way to make treatments decisions for pests with chewing mouthparts (e.g., Japanese beetle, bean leaf beetle, caterpillars, and grasshoppers) is to estimate defoliation. I’m a “lumper” and don’t try too hard to distinguish feeding by species. Replicated data over multiple growing regions consistently shows economic thresholds for soybean are 30% in the vegetative stages and 20% in the reproductive stages. This threshold applies to the entire field.

Japanese Beetles Get a Slow Start to 2019

June 17, 2019
2019 degree day map for Japanese beetle.

Several reports from ISU Field Agronomists have indicated Japanese beetles are emerging in southern Iowa. The emergence is about 7-10 days behind the last few years, due to slowly accumulating degree days in 2019. Literature shows Japanese beetle adults need about 1,030 growing degree days (base 50°F) to complete development and will continue emergence until around 2,150 degree days. Based on accumulating degree-day temperatures in 2019, Japanese beetle adults should be active in some areas of southern Iowa this week (Figure 1).

Crops: 

Potpourri of caterpillars in Iowa

June 14, 2019 9:42 AM
Blog Post

I’ve been hearing about and seeing a variety of caterpillars in seedling crops this week. In soybean, you notice thistle caterpillars feeding and making webbed cavities from the leaves. They can be easy to find in early-vegetative soybean but rarely build up to economic populations. Read more about thistle caterpillars in this ICM News article

Don’t mistake this look-alike chafer

June 14, 2018 3:46 PM
Blog Post

 


This week, I’ve had a number of people tell me they spotted Japanese beetle. I was initially surprised, because I track degree days to predict adult emergence every summer and it seemed a bit early. According to the ISU Agronomy Mesonet, adults could be emerging in southern Iowa and I would expect adult emergence in central Iowa next week. See my recent ICM News article showing a degree-day map for 2018.


Japanese Beetle Adults Emerge in Southern Iowa

June 14, 2018
degree day map for Japanese beetle

Japanese beetle is an invasive insect that feeds on corn and soybean plus many other plants. This pest has been in Iowa since 1994 but its distribution in field crops is considered sporadic around the state. Statewide populations in field crops have been variable since 2014 and it is unclear if pressure will be significant this year. Several reports around Iowa indicated high numbers of grubs within fields, but it is not clear if they were Japanese beetle or another closely-related species. Adult emergence well before corn silking is noteworthy.


Crops: 

Pages