MP481 Controlling Nematodes on Golf Courses DIVISION OF AGRICULTURE RESEARCH & EXTENSION University of Arkansas System University of Arkansas, United States Department of Agriculture, and County Governments Cooperating Authors TERRY KIRKPATRICK, Ph.D., is professor - nematologist and RONNIE BATEMAN is program a ssociate - pest management at the Southwest Research and Extension Center in Hope. TERRY SPURLOCK, Ph.D., is assistant professor - plant pathologist at the Southeast Research and Extension Center in Monticello. DAVID MOSELEY is a program technician in Crop, Soil, and Environmental Science at the University of Arkansas in Fayetteville. They are faculty of the University of Arkansas System Division of Agriculture. AARON PATTON, Ph.D., is an associate professor - agronomy at Purdue University in West Lafayette, Indiana. Controlling Nematodes on Golf Courses Nematodes are important months for warm- season grasses). (Meloidogyne spp.) nematodes, all economic pests of golf courses in In addition to direct damage, damaging turf nematodes, belong Arkansas. These pests are particu­ nematodes may also enhance turf to this class. larly problematic in golf course damage by fungal pathogens and putting greens. Nematodes are increase the level of damage that A second class of parasitic microscopic, unsegmented is caused. Soil fungal pathogens nematodes has an odontostyle roundworms, 1/300 to 1/3 inch that are known to form disease rather than a stomatostyle type in length (10) (Figure 1), which complexes with nematodes stylet (Figure 3). The odontostyle live in the soil and can parasitize include Fusarium and Rhizoctonia stylet has flanges at the base many crops including turfgrasses. and oomycetes in the genus rather than knobs and a larger Pythium. Control methods for lumen (opening). Needle and Although most nematodes are nematodes, including preventa­ dagger nematodes belong to this actually beneficial and feed on tive and curative measures, are class. This larger lumen is signifi­ fungi, bacteria and insects or help discussed later in this publication. cant because it is large enough in breaking down organic matter, Diseases caused by fungi and to allow viruses such as the there are a few species that oomycetes may be managed with St. Augustine Decline virus to be parasitize turfgrasses and cause fungicide applications. ingested by the nematode and damage, especially in sandy soils. transmitted from infected plants All plant-parasitic nematodes There are two general classes to healthy plants. have a stylet (Figure 1), which is of nematodes differentiated a protruding, needle-like mouth- primarily by the shape of their part used to feed on plant cells. stylets. The most common class Nematodes feed on turfgrass has a stomatostyle, which is a roots and are most abundant hollow spear with distinct knobs when the turfgrass is actively at the base (Figure 2). Sting growing (spring and fall for cool- (Belonolaimus spp.), lesion season grasses and the summer (Pratylenchus spp.) and root-knot Figure 2. Stomatostyle type stylet of a lesion nematode. Photo by C. Högger, Nemapix Vol. 2 Figure 3. Odontostyle type stylet Figure 1. Schematic drawing of a plant-parasitic nematode. of a dagger nematode. Adapted from N. A. Cobb, Nemapix Vol. 2 Photo by T. Vrain, Nemapix Vol. 2 3 Life Cycle Sting nematodes are large and life cycle. Root-knot nematodes have a long, slender stylet. Feed­ (Meloidogyne spp.) are sedentary There are six stages in the ing by only a few sting nematodes endoparasites. Lance nematodes nematode life cycle including can result in root systems that (Hoplolaimus spp.) are semi­ an egg stage, four immature have a stubby appearance and in endoparasitic in turf (Figure 4). (juvenile) stages and the adult. the absence of root hairs. With The four juvenile stages allow the severe infestations, plants may nematode to increase in size (in show little or no new root devel­ some species to change shape) opment during spring and sum­ and are similar to the larval mer. Because sting nematodes stages found in insects. Nema­ require soil with an 80 percent or todes are aquatic animals and greater sand content, putting require water to survive. They greens, particularly those estab­ live and move in the soil water lished according to USGA specifi­ film that surrounds soil particles. cations, are ideal environments Soil type, particularly sand for nematode damage. Figure 4. Semi-endoparasitic lance nematode feeding on a plant root. content, has a major impact on Endoparasites actually enter Photo by U. Zunke, Nemapix Vol. 2 the ability of nematodes to move, roots to feed and reproduce. infect roots and reproduce. For There are two types of endo­ most nematodes that are a parasitic nematodes – migratory Symptoms problem in turf, well-drained and sedentary. Migratory and Signs sandy soils with soil moisture at endoparasitic nematodes, such as or near field capacity are opti­ the lesion nematode Pratylenchus In turfgrasses, there are few mum for nematodes to flourish. spp., can enter and move through definitive symptoms or signs For this reason, nematodes are roots, feeding as they go, and for consistent diagnosis of a most problematic on highly can leave and reenter the root at nematode problem. Generally, maintained putting greens and will. Sedentary endoparasitic symptoms of nematode damage sand-capped tees and fairways. nematodes enter the root either are similar to those of other pest partially (semi-endoparasitic) problems, nutritional deficiencies Feeding Habits or fully as juveniles and create or environmental stresses a permanent feeding site, where (Figures 5 and 6). However, Nematodes feed as either they remain for the rest of their greens or fairways where there ectoparasites or endoparasites. Ectoparasitic nematodes spend their entire life cycle outside the host roots, feeding and reproduc­ ing in the soil surrounding the root system. Many ectoparasites cause only limited damage to roots by their feeding, thus a relatively high population density of these nematodes is required to cause appreciable turf damage. An exception, however, is the sting nematode (Belonolaimus), which is the most economically damaging Figure 5. Typical nematode damage: irregular-shaped areas without nematode pest of turf. distinct border including yellow, stunted turf that is thin and not responsive to fertilizer or irrigation. Photo courtesy of N. Walker 4 Important Nematodes in Turfgrass Sting Nematodes Sting nematodes are more damaging to turfgrass than any other nematode species (6). Sting nematodes can grow to 3 milli­ meters long and can complete Figure 6. Mild symptoms from nematode infection can appear similar their life cycle in 18 to 24 days. to many other plant stresses including drought, nutrient deficiencies, In Arkansas, sting nematodes are pH problems and other common symptoms seen in damaged turf. found in golf courses, particularly in putting greens and sand- are irregular areas in the turf insecticides and fertilizers. capped tees or fairways. Sting without distinct borders, areas Aboveground symptoms do not nematodes generally feed at the of yellow, stunted plants, areas of typically occur until injury to the root tip causing roots to cease wilting and thin, weedy turf turfgrass root system is well growing and the turf to exhibit could indicate a nematode advanced (10), and since the root symptoms of nutrient and water problem. Actual signs of nema­ system is damaged by nematode deficiencies. As a result, these tode infection such as root galls feeding causing a reduction in areas could be overirrigated and due to root-knot nematodes or root hairs, turfgrasses may not overfertilized in an attempt to get the presence of cysts attached to readily respond to applications of a response from the turf (11, 13). roots may sometimes be evident, fertilizer or irrigation. Addition­ Symptoms of sting nematode but a soil sample assayed by a ally, turf may be unresponsive to damage can include wilt, stunted nematology laboratory will gen­ applications of fungicides and growth, nutrient deficiency, irreg­ erally be required for an accurate insecticides since these products ular patches and added growth diagnosis of a nematode problem. will not control nematodes. Once of weeds such as prostrate spurge nematode populations reach a (Figure 8). Turf areas with heavy An additional symptom of critical threshold, turfgrass death sting nematode infestations can nematode damage is a lack of can occur (Figure 7). response to irrigation, fungicides, be completely killed. ~- . .-,' ... e -:-· Figure 7. Once nematode populations reach a critical Figure 8. TifEagle putting green showing symptoms of threshold, turfgrass death can occur, as seen in this sting nematode damage. zoysiagrass lawn. 5 Lance Nematodes yellowing, dying and poorly important nematode in many Lance nematodes are rooted turf (Figures 10 and 11). agronomic and horticultural migratory semi-endoparasites It is difficult to diagnose lance crops. Several species of root- (Figure 9). Adults can grow to nematode damage by observing knot nematodes are damaging to 1 mm long. Lance nematodes are symptoms since the symptoms turfgrass. A sign of root-knot the most common nematode are similar to other stresses, nematodes is root gall formation problem nationwide because including insect damage, disease, in response to their infection they are adapted to many soil drought and nutrient deficiency. (Figure 12). Although galls can be environments. Generally, damage easily observed on the roots of thresholds are higher than for most crops, they can be difficult sting nematodes, but since lance to see on turfgrass roots. Roots nematodes can feed and repro­ may look normal on the outside, duce on a wider variety of soil but galls can be seen if the root is types, damage can be found dissected longitudinally. Symp­ extensively in native soil fair­ toms of root-knot nematodes can ways and tees in addition to include darkened, rotted roots, older putting greens with higher chlorotic areas of turf and limited organic matter. Lance nematodes response to fertilizer, fungicide generally affect warm-season or irrigation. Figure 9. Female lance nematode grasses.