High tunnels have the potential to provide specialty crop growers with the ability to extend the growing season and moderate the environment with respect to soil moisture and temperature. This can translate to increased income from increased marketable yields and improved produce quality. High tunnels play an important role in the local food system of Kentucky. As of 2022, there are over 1,500 high tunnel across Kentucky. As more growers adopt high tunnel production, new challenges are observed. Because of the valuable infrastructure and the season extension they provide to specialty crops, high tunnels are intensively cropped (more so than open fields), often with very little crop rotation. Regular sanitation is often not practiced. Because of the intensive cropping and lack of rotation, plant-parasitic nematodes, specifically the root-knot nematode, may become an increasing issue in high tunnel soils. Root-knot nematodes invade plant roots and cause root galling. This impairs root function which causes reduced water and nutrient uptake. Root-knot nematodes have a very wide host range, including nearly all vegetable crops. They can significantly impact yield and thus, profit margins for the grower.

The two most common species of root-knot nematode in vegetable production are Meloidogyne hapla (Northern root-knot nematode) and Meloidogyne incognita (Southern root-knot nematode). Although, root-knot nematode has been observed on crops in Kentucky before, it was unknown how prevalent this plant-parasite was across the state and what species are present and where. It was previously thought that root-knot nematode was not an issue in Kentucky. Aboveground symptoms can often be confused with nutrient deficiencies, water stress, or other diseases. It is only by examining the roots or soil that one can confirm the presence of root-knot nematode.

In 2019, Extension Vegetable Specialist Rachel Rudolph received a Specialty Crop Block Grant from the Kentucky Department of Agriculture and United States Department of Agriculture that provided funding for a statewide census for root-knot nematode. Along with her graduate student, she has sample 27 Kentucky counties and 49 farms to date. Of the 27 counties sampled, root-knot nematode was observed in 23. Southern root-knot nematode was confirmed via molecular diagnosis on 23 farms while Northern root-knot nematode was confirmed on 17 farms. Several farms had both species present at the same time. Given Kentucky’s transitional climate zone, this is not completely unexpected. 

Farms are chosen based off the presence of a high tunnel and growers are briefly surveyed on their knowledge and understanding of root-knot nematodes, the age of the high tunnel, and the cropping history. The majority of growers have limited awareness of this plant parasite or how to manage it. Most of the growers were unaware their soil contained root-knot nematode. Although in some cases, the nematode could be endemic, there is a large possibility that it was transferred by unsanitized equipment or tools. After sampling, Dr. Rudolph communicates the results to county agents and growers along with guidance and recommendations. If no root-knot nematodes were observed, it is important that growers understand how to prevent its introduction onto their farm. If root-knot nematode is observed on a farm, Dr. Rudolph provides guidance based on the species identified and further guidance on preventing the spread or movement to other parts of the farm. Recommendations include sanitation of equipment, utilizing resistant plant cultivars including grafted rootstock, cover cropping, and possible chemical control options. Dr. Rudolph’s lab is also researching other alternative management options. 

The root-know nematode census will continue through the summer of 2022 and results will be shared with agents and growers at the annual Fruit and Vegetable conference in Bowling Green, KY in early 2023. Results will also be published in a peer-reviewed journal.