Integrated Crop Management News
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Watch Soybean Aphid Numbers - NOW
By Jon Tollefson, Department of Entomology
Last week the conditions in Minnesota were very good for soybean aphid reproduction. With those conditions, the populations increased rapidly in many locations throughout Minnesota. We have been expecting 2008 soybean aphid populations to be lower as they were in 2004 and 2006, but the 2008 weather has not been exactly “typical.”
Reviewing Decision Thresholds for Pest Insect Control
By Jon Tollefson, Matt O’Neal, and Marlin Rice, Department of Entomology
Three tools need to be understood in order to make decisions regarding the control of insects found on crops: damage boundary, economic injury level, and the economic threshold. The existing values for these three variables are now being questioned with the increase value of Iowa’s row crops and the cost of controlling the pests. This article reviews the use of these tools in regards to soybean aphid control.
Two Soybean Aphid Field Resources Now Available
By Rich Pope, Department of Plant Pathology
Knowing how to manage and "speed scout" soybean aphids, just got easier, thanks to two new pocket-sized publications authored by Iowa State University Extension entomologists Marlin Rice and Matt O'Neal.
Preventative vs. Curative Fungicides
By Daren Mueller and Alison Robertson, Department of Plant Pathology
We have received several questions about selection of fungicides, especially with regards to deciding between “curative” and “preventative” fungicides. People want to know if they should be applying a strobilurin fungicide, triazole fungicide, or a premix of both.
More on Fungicide Application Questions
By XB Yang, Department of Plant Pathology
Near the end of July, a common time for fungicide applications, there are many questions about using fungicides to control soybean diseases. This article responds to questions producers are currently asking about soybean and corn fungicide use.
Here Come the Bean Leaf Beetles!
By Jon Tollefson and Marlin Rice, Department of Entomology
The bean leaf beetle overwinters as an adult that feeds on young soybeans in May and June. They lay eggs that produce the first generation, which attacks beans in July. The subsequent generation, the second, is of most concern when protecting the plant from the beetles feeding because it attacks the pods and beans as well as foliage.
Is that Common or Southern Rust Showing up in Iowa Fields?
By Alison Robertson, Department of Plant Pathology
Is that common or southern rust showing up in Iowa fields? Chances are it is common rust. It has probably been too cool and wet so far this growing season to see southern rust. Symptoms of the two rusts are very similar but there are subtle differences.
Unusual Foliar Diseases Showing up in Iowa Corn
By Alison Robertson, Department of Plant Pathology
Over the past week I have received emails, phone calls and samples of two leaf spots that occur in Iowa from time to time, Holcus leaf spot and Physoderma brown spot.
HOLCUS LEAF SPOT
Holcus leaf spot is caused by the bacterium Pseudomonas syringae. Symptoms are light tan (sometimes almost white), round to oval spots, which may appear water soaked at the margins or have a light brown border occur on the lower leaves (Figure 1 and 2).