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Michigan hop pest report week of May 23, 2024

Michigan hopyards are entering a critical pest management period for key insect pests and diseases. Scout regularly and thoroughly.

In the field
For a hop production update from around the state, please see the hop crop report for May 23, 2024.

With the early warm up and ample rain, many growers are fighting an uphill battle against weeds, particularly those not using reemergence herbicides. Additionally, the fast warmup made it tough to get early glyphosate applications before hop bines developed and greened. Grass weeds need to be treated when small for optimal control. Some growers use various forms of cultivation to suppress weeds. Refer to the Michigan Hop Management Guide for weed control options.

The following section contains information on fungicide-based disease management. In all instances, it is important to manage fungicide resistance and avoid applying similar products back-to-back. This is particularly important with site-specific systemic fungicides.

  • Do not make more than three applications per season of the same Fungicide Resistance Action Committee (FRAC) code, regardless of if it is allowable based on the label.
  • Do not make two consecutive applications of the same FRAC code.
  • Rotate with unrelated fungicides in a different FRAC code that have efficacy on the target pathogen.

Downy mildew
Downy mildew infection symptoms are visible in some yards. Downy mildew is caused by the fungus-like organism Pseudoperonospora humuli and is a significant disease of hop in Michigan, potentially causing substantial yield and quality losses. This disease affects cones, and foliage and can become systemic; in extreme cases, the crown may die. Cool and damp weather during the spring provide ideal growth conditions for the pathogen. Disease severity is dependent on cultivar, environmental conditions and management programs. Growers should focus on proactive management strategies, including 1) sourcing clean planting stock, 2) clean crown management in the spring, 3) scouting regularly and 4) utilizing a preventative fungicide program.


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