6/18/18: Insects and Fungi

Mother nature was kind to us this week with some much needed rains over a broader area of our region with a forecast that sounds favorable for additional rain this coming week. That said, our crops still have some very good yield potential if mother nature continues to cooperate. This week should see the majority of the beans sprayed and we can hopefully put away our weed spraying for another season. But before we start patting ourselves on the back, we need to start looking at other potential threats to our crops, bugs and fungus. With all our heat units we have in the bank and if we can continue having periodic rains, many issues that normally occur later in the growing season could start happening earlier. We have a strong possibility of corn starting to tassel at, or soon after the 4th of July.

I will list some of the more common pests we need to be aware of going forward.

Corn Insects:

  • Japanese Beetle, normal time of attack for adults is from late June to harvest. We are starting to see them showing up around the area now.
  • Corn Earworm, normal time of attack is July to Harvest
  • Western Bean Cutworm, July to harvest, peak moth flight is mid-July
  • Armyworm, July to harvest

Obviously, there are economic thresholds for the physical damage that is caused by these pests, but also keep in mind that damage caused by the feeding will open the plant up to secondary symptoms such as funguses.

Corn Funguses

  • Anthracnose Leaf Blight and Stalk Rot. Ideal growing conditions are: warm, wet and humid conditions with stress from weather, insects and other diseases. Leaf blight stage is from April to July and Stalk rot phase from August to late October.
  • Ear Rots, Gibberella, Diplodia and Fusarium. All three favor wet, humid conditions especially around silking time and up to 3 weeks after silking. Generally best time to scout is Mid-August to harvest, however, could be a lot earlier this season.
  • Gray Leaf Spot, favors warm and humid with long dew periods. June to harvest.
  • Northern Corn Leaf Blight, moderate temps, with long dew periods. June to harvest

Bean Insects:

  • Mexican Bean Beetle, time of attack Mid-April to harvest (V1 to R7
  • Soybean Aphids, time of attack is June through August
  • Spider Mites: mid-May to September (V2-R7)

Bean Funguses:

  • Brown Spot: Early May to August, prolonged periods of leaf wetness and moderate temps, something we have not had a problem with this year.
  • Brown Stem Rot: Mid-July to early October, Cool wet weather during flowering.
  • Charcoal Rot: Mid-July to early October, root infection can occur early but hot, dry weather favors symptom expression in early reproductive stages.

There are numerous other diseases that occur in soybeans, but the point is with a little help, we can be looking at some pretty good crops. We need to be aware of the situation and determine if it makes economic sense on a case by case basis.

Hoping you all have a enjoyable and safe summer.

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