The dreaded lance nematode is a microscopic roundworm that feeds both outside of (ectoparasitic) and inside (endoparasitic) turfgrass roots. Also known as the crown-headed lance nematode, this organism can infest creeping bentgrass and bermudagrass putting
greens, which leads to a decline in turf quality and function, especially during periods of drought and heat stress. Turfgrasses aren’t alone, as plant parasitic nematodes are responsible for over $157 billion annually in crop loss globally
The botanical species name for lance is: Hoplolaimus galeatus (Cobb, 1913) Thorne, 1935. Hoplolaimus means weapon, and galeatus means helmet-shaped. But who are Cobb and Thorne? They are the “authority” or person(s) who named the species.
Nathan Cobb, Ph.D., (1859-1932) is considered the “father of nematology” for his pioneering work with nematode taxonomy. Gerald Thorne, Ph.D., (1890-1975) worked under Cobb and wrote the classic “Principles of Nematology” textbook
Derek Settle, Ph.D., studied the lance nematode as a doctoral student at Kansas State University in Manhattan, Kan. He wanted to learn more about their population densities and seasonal fluctuations in turfgrass root zones, so he monitored lance populations
in a creeping bentgrass putting green. Sites and conditions (or treatments) were: four cultivars (Penncross, Crenshaw, L-93 and Providence), two mowing heights (0.125 or 0.157 inches [3.175 or 3.988 millimeters]), and two irrigation water amounts
(1.2 or 2.4 inches [30.5 or 61.0 millimeters] per week.
The test site root zone was 98% sand with 2.1% organic matter and pH of 7.3 and naturally infested with lance. All treatments were arranged in a representative experimental design with three replications. Lance populations were intensively measured every
month from July 2001 to October 2003, by collecting soil cores of 0.5-inch (1.3-centimeter) diameter × 2-inch (5.1-centimeter) depth and utilizing the sugar-flotation centrifuge method for nematode extraction and then microscopic identification.
Lance nematodes collected were classified as juveniles or adults (male or female).
What did Settle— as a young, ambitious graduate student — find? For creeping bentgrass putting greens, lance populations tend to increase from late spring into the summer, peak about midsummer, decline in late summer, increase again by midautumn,
then decline later in autumn going into the winter. Lance populations in the root zone are density-dependent, meaning they tend to aggregate or “clump” together and do not uniformly disperse throughout a sand root zone.
For creeping bentgrass putting greens, a good time to collect soil samples and monitor for lance populations is during May or June, prior to their midsummer peak. Keep in mind, those samples would only reveal lance adults, especially the females that
feed on root surfaces. Because most lance juveniles are migratory and feed inside the root, they are nearly impossible to uncover from soil samples and nearly impossible to control with a contact nematicide.
Within the same putting green, sample from an area showing signs of wilt and poor roots and compare with a sample from a healthy area. This is the best way to determine any negative effects from lance and doesn’t depend on damage thresholds, because
the weakest greens are most likely to suffer damage, while the healthiest greens may be tolerant of even the highest lance populations.
What about creeping bentgrass cultivars, mowing height or irrigation? Lance populations were similar in all sites and conditions, so those cultural practices tested didn’t affect lance populations. Unfortunately, lance nematodes are not effectively
controlled by current nematicides. Therefore, cultural practices that promote healthy rooting and alleviate abiotic stress are recommended — for example, mitigating midday wilt stress by hand watering, using soil surfactants for root zone moisture
management, raising mowing heights, rolling instead of mowing, avoiding excessive equipment wear in areas such as clean-up laps, and alleviating concentrated foot traffic by golfers via regular rotation of pin placement.
Settle is senior director of turfgrass programs at the Chicago District Golf Association (Lemont, Ill.). When he’s not chasing nematodes or tweeting nematode photos as @turfdom, he’s chasing his French bulldogs, Ralph and Leo.
Source: Settle, D.M., J.D. Fry, T.C. Todd and N.A. Tisserat. 2006. Populations dynamics of the lance nematode (Hoplolaimus galeatus) in creeping bentgrass. Plant Disease 90(1):44-50 (https://doi.org/10.1094/PD-90-0044).
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 21-year member of GCSAA.