NEMATODES A new problem?


turfgrass managers due to their very real ability to cause


severe and lasting damage to turf


DR KATE ENTWISTLE of the Turf Disease Centre looks at the group of nematodes that are referred to as plant parasitic nematodes. These are of greatest concern for


NEMATODES are an abundant and extremely diverse group of microscopic unsegmented roundworms that can be found virtually everywhere across the planet. Some nematodes live on dead and decaying organic matter and these saprophytic nematodes provide an important and beneficial role in recycling nutrients. Large populations of these nematodes can be found in healthy turfgrass rootzones and they pose no threat to the health of the sward. In addition, there are so-called entomopathogenic nematodes (which feed on insect larvae) which are also beneficial and which provide us with a viable option for biological control of certain turfgrass pests. There are products


currently available, in both the professional and amateur markets, which contain different beneficial entomopathogenic


nematodes and which allow for the management of insect pests including chafers and leatherjackets. However, it is the group of nematodes that are referred to as plant parasitic nematodes that are of greatest concern for turfgrass managers due to their very real ability to cause severe and lasting damage to turf.


ALTHOUGH we are aware of several different plant parasitic nematodes that have the ability to cause damage to cool-season turfgrasses, arguably the most important are those in the Genus Meloidogyne, the root-knot nematodes.


Meloidogyne species


Female root-knot nematodes are known to be sedentary


endoparasites. This means that once the immature females enter the plant root from the surrounding rootzone, they move to a suitable feeding site within the root tissues and remain at the same location, feeding, becoming mature and producing eggs for their entire life. The female nematode causes the deformity of the root cells that results in the obvious swellings or galls that characterise their damage. Once mature, the female root-knot nematode produces an egg mass that is


positioned on the outside of the root. The eggs release second-stage juvenile nematodes in to the rootzone and these juveniles move through the rootzone until they find a suitable root to infect. The nematodes undergo four moults as they enlarge and mature in to adults and the final stages of development take place inside the roots. The adult males leave the root tissue and become migratory, joining the juveniles in the rootzone and leaving the mature females to feed within the root cells. Under ideal conditions the life cycle can be completed in about one month with females producing between 500 and 1000 eggs. As a group, the root-knot nematodes feed on over 3000 plant species worldwide (Shurtleff & Averre III, 2000) and several species within this group are able to colonise and feed from the roots of amenity turfgrasses. We have been aware of their potential to cause damage to warm- season turf for many years but, until recently, they were not considered to be a problem on any cool-season turfgrass. A detailed


investigation, which took place over several years, eventually confirmed a new species of root-knot


nematode causing damaging symptoms on creeping bentgrass putting greens across the UK and Ireland. What follows is a summary of the work that was completed in the four years of investigation that finally confirmed nematodes as potential pests of cool-season turfgrass.


I BECAME involved in this investigation at the end of 2000 when Mark Hunt (Headland Amenity Limited) contacted me and showed me photographs of damage that he had seen on golf courses across the UK and Ireland during the previous three years. The symptoms were those of 0.3 - 0.5 m diameter circles or patches of yellowed plants across the majority of the putting surface on affected greens. Between 1997 and 2000, Mark had sent numerous turf sample for independent analysis to try to identify the cause of the damage and in every case, the result of the analysis was Rhizoctonia cerealis, the fungus responsible for the disease known as yellow patch (cool-weather brown patch). Although the appearance of the symptoms appeared to support the diagnosis, some details of the problem didn’t make any sense. The fungal disease yellow patch develops under cool, wet conditions and although these symptoms always started to develop following torrential rainfall in April, they remained throughout the summer and autumn months and only disappeared during October/November. Put another way, although the symptoms on the golf greens


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64