East Lansing, Michigan —European corn borer, a pest of concern for Michigan corn producers for decades, caused substantial damage this past growing season to the Great Lakes Region’s re-emerging hop industry.


With a value of $618 million 2017, according to the USDA, the Michigan hop industry has been on an upward swing for the last several years, fulfilling a desire to provide locally grown hops to an even more profitable craft beer movement. From 2016 to 2018, hop acreages have increased by 150 percent. But just like any other crop, the growth in hop acreages does not mean the plants are immune to pest pressure and damage, as was shown by the surprise arrival and swift damage done to a significant portion of the region’s hop farms by ECB in 2019. While the hop crop in the U.S. is diversified enough to keep output of hit brews on pace, the damaging event was very impactful this year, and something to be aware of for growers in the Michigan and the Great Lakes region as a whole.


ECB damage was observed at low levels in many Michigan hopyards in 2019, but severe damage occurred on a total of between 15 and 20 acres and illustrated the potential threat the insect poses. Erin Lizotte, an Integrated Pest Management (IPM) Educator at Michigan State University, said this is uncommon for the state’s hop industry, as the pest had previously been present at minimal amounts, discounting the need for monitoring or preparation.


However, in 2019, Michigan experienced large amounts of precipitation in the spring before the traditional crop planting season began. Because of the delayed planting as a result of precipitation, corn farmers were not able to plant at times typical for the season, resulting in later seeding and in some cases, no crops in lieu of prevent-plant acres. Typically, ECB females look for corn, their preferred host, during the growing season when they are ready to lay their eggs. However, due to later maturing corn and slower temperature increases, female ECB used hops as an alternative egg-laying site. ECB actually has a broad host range that includes hops in its native Europe.


“Originally in Europe, hops were one of the hosts in the European Corn Borers’ natural range, so the name can be misleading because it implies that the insect only affects corn,” Lizotte said. “But, it actually affects a myriad of species: hops, soybeans, bell peppers and even some of the weed species. So, ECB has a pretty broad host range.”


Though not normally a hops pest of concern throughout Michigan, the damage caused by ECB in the 2019 hops crop was too extensive to be minimized. In hops, ECB females lay their eggs on top of plant leaves, the larvae emerge from the eggs and briefly feed on the plants exterior before boring into the bine (stem), side arms, and leaf petioles where they continue to feed. The foliar feeding that occurs has a minimal impact on the plant, but the feeding damage to the main stems, side arms and petioles damages the tissues that move water and nutrients, effectively starving the plant. Once larvae are present inside the hop plant, pesticides are ineffective because the insects are physically protected by the plant, thus larvae can continue feeding and damage continues until they pupate. Because the infestation was not discovered until the plants began collapsing due to internal feeding damage, suppressing ECB populations to preserve yield wasn’t an option in 2019. Lizotte says growers and specialists are now monitoring the situation and looking for solutions and methods of prevention for the next season. One such method is scouting and trapping techniques, as well as weather modeling to predict pest emergence. Lizotte explained that this will make it possible to assess population levels and determine the economical need for pesticides in the future, as well as optimize the application timing.


As for whether or not this year’s ECB damage will raise the price of beer in Michigan, Lizotte said there is no need to worry. There is enough supply of hops in the global market to offset any potential losses.


However, Lizotte said that while the recent infestation and damage to the region’s hops isn’t enough to drastically hurt consumers at the tap, the circumstances that left hop growers vulnerable is something to monitor in the future. Despite this year’s positive outlook, this is an example of how climate change continues to have an impact on the way all crops are grown throughout the North Central region.


“Even though it’s small scale perennial crops, changing weather affects what we can produce from year to year,” Lizotte said.


Delayed planting is just one of the impacts of climate change that will continue to impact crop production. Shifting weather patterns in Michigan trend towards hotter, wetter conditions and will continue to produce a shifting pest landscape for crop producers, including hops. Of course, changing weather is not just an issue in the Great Lakes Region, the Pacific Northwest experienced a damaging pest incident in 1997 when the disease “powdery mildew” caused farmers to abandon over 800 hectares of hops (approximately 2,000 acres). With such large amounts of damage, the diversity of the amount of beer that could be made and sold in the U.S. (the diverse flavors in India Pale Ales, Ambers, Lagers, Stouts, etc.) was put at risk. This spurred an increase in regional production outside the northwest, including Michigan, potentially minimizing the impact of regional weather-related conditions impacting the supply of hops.


The North Central IPM Center is here to help

The Great Lakes Hops Working Group (Great Lake Hops) has been a large contributor and producer of hop management resources. Funded through the North Central Integrated Pest Management Center (NCIPMC), the Hops Working Group has dramatically changed the landscape of hop agriculture in the states such as Colorado, Iowa, Wisconsin, Michigan, Ohio and California since 2009. The Great Lakes Hop Working Group has helped encourage hop production outside the Pacific Northwest by promoting small and independent hop growers as the demand for hops continues to rise. GLHWG delves into greenhouse, post harvest, horticulture, crop management and internal needs for the Midwest through Integrated Pest Management (IPM).


The Working Groups program is one of two competitive grant programs offered by the NCIPMC. This program supports collaboration among diverse groups and backgrounds to address a regional IPM priority. These groups also help the NCIPMC accomplish its goals with improving health, environmental and economic conditions in pest management circumstances. The North Central Integrated Pest Management Center is one of four National IPM Centers, serving stakeholders in the U.S. and abroad.