Hops are in full reproduction growth mode, sending side arms out full of burrs that will soon be lupulin-filled cones. Early harvested varieties in Nebraska, such as Centennial and Willamette, have already developed cones, though their readiness for harvest is still a few weeks away. We are at a critical point in the season to take the necessary precautions to prevent advances of insect pests and diseases as cone development continues full force.
What should I be doing at this time in my hop yard?
You should be scouting at a minimum 1-2 times per week, walking your yard in different routes each visit, and if manageable, walking your entire yard each time. Identify pests and their economic thresholds, and treat accordingly.
You should be implementing cultural practices to encourage air movement and reduce disease and competition.
- Remove weeds in the hop rows to reduce competition for water and nutrients, and to help reduce disease pressure and increase air movement.
- Defoliation of lower leaves by mechanical hand stripping or application of AIM EC + crop oil should be done to remove the bottom 2-3 feet of leaves and excess shoots. Be sure stems are woody before chemical defoliation. Apply at a rate of 2-3.2 fluid oz/A to basal 18 inches of plants. When making additional applications, allow 14 days between applications. With harvest approaching, be aware of any chemical’s pre-harvest interval (PHI). AIM has a 7 day PHI.
What is happening in hop yards across Nebraska?
Downy mildew: Recent rain events, cooler temperatures, overcast days, and sitting water has been the perfect recipe for increased downy mildew presence. You should be making regular applications of fungicides, rotating modes of action to decrease chances of resistance development. With burr and cone development, it is especially critical to prevent downy mildew infections.
Fusarium canker: Storms and wind events coupled with loose coir on trellises have and continue to cause breakage of bines around the base of the hop crown. Fusarium is a fungus that thrives in wet soils and has been known to cause minor issues in hop yards in Eastern Nebraska. Ensuring your trellis and coir is tight will help reduce instances of fusarium damage in your hop yard.
Question mark caterpillars: A new potentially problematic pest to hops in Nebraska (but has been recorded elsewhere) is the question mark caterpillar, Polygonia interrogationis. The damage is similar to that of Japanese beetles, with the potential of completely defoliating plants in a matter of days.
Japanese beetles: Japanese beetles continue to wage war against hops in the Eastern part of the state. Applications of bifenthrin appear to keep them at bay for 5 or so days. We are continuing to monitor changes in populations as the season progresses.
Minimal presence of twospotted spider mites (TSSM), potato leaf hoppers, grasshoppers and hop aphids are being reported at this time. It is important to scout regularly for these pests and treat when economic thresholds are reached. TSSM (threshold for treatment = 6-10/leaf) and hop aphids can potentially be quite detrimental and cause total yield loss in worse case scenarios.
Leaf mottling and other leaf discolorations are being reported by growers, indicating hop mosaic virus and potentially other viruses. Confirmed infections appeared in hop yards across the state are likely caused by infected plants at establishment. Be aware as you seek to expand your current hop yard or establish a new hop yard that the industry is unregulated in most states including Nebraska, and sources stating “propagation from virus-free mother stock,” “guaranteed virus free stock,” etc. does not guarantee anything. Be aware of spreading the virus among plants in known infected hop yards as well. If you have questions about reliable sources for hop plants, please contact me directly. You may find my contact information here. For testing, submit samples to the Plant and Pest Diagnostic Clinic at UNL. For directions on submitting samples, please visit: https://cropwatch.unl.edu/plantdisease/pest-samples.
To learn more about managing pests at this time of the season and what you should be doing to prepare for harvest, join UNL Extension & the Nebraska Hop Growers Association for a field day on July 21st at Oak Creek Hops in Kearney, NE, 10 am – noon, followed by a tour and discussion with the brewer at Thunderhead Brewing Co. (201 F Ave, Axtell, NE 68924). RSVP by emailing email@example.com or by selecting “going” on the facebook event here so that we have enough food and materials.