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Hawaii Institute of Tropical Agriculture and Human Resources College of Tropical Agriculture and Human Resources, University of Hawaii INFORMATION TEXT SERIES 020 Burrouuing Nematodes: fl Menace To Hauuaii Nurseries O. V. Holtzmann, A. P. Martinez and W. J. Apt NOTE: As part of a structural reorganization, the Hawaii Cooperative Extension Service and the Hawaii Agricultural Experiment Station have been merged administratively under the name HAW AII INSTITUTE OF TRO PICAL A G RIC U L­ TURE AN D HUM AN RESOURCES, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Issued in furtherance of Cooperative Extension work. Acts of May 8 and June 30, 1914, in cooperation with the U.S. De­ partment of Agriculture. Noel P. Kefford, Director and Dean, Cooperative Extension Service, College of Tropical Agricul­ ture and Human Resources, University of Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity Employer providing programs and services to the citizens of Hawaii without regard to race, color, national origin or sex. INFORMATION TEXT SERIES 020-05/84 (700) THE AUTHORS Oliver V. Hotlzmann is a Professor in Plant Pathology, College of Tropical Agriculture and Human Re­ sources, University of Hawaii. Albert P. Martinez is a Specialist in Plant Pathology, College of Tropical Agriculture and Human Re­ sources, University of Hawaii. Walter J. Apt is a Professor in Plant Pathology, College of Tropical Agriculture and Human Resources, University of Hawaii. BURROWING NEMATODES: A MENACE TO HAWAII NURSERIES O. V. Holtzmann, A. P. Martinez and W. J. Apt The burrowing nematode (BN) (Radopholus slmlI Is) Is without a doubt the most serious, Individual pest with which growers of export ornamentals have to contend. Its presence In a nursery may mean either the rejection and destruction of a valuable consignment of plants to the Mainland and/or the expensive and laborious process of trying to locate the source of contamination In the nursery. The subsequent eradication of Infected plants and the disinfestation of the area Is not easily accomplished. The best way to avoid a BN problem Is startin g clean and staying clean. Of course th is Is so easy to say and so hard to accomplish. The pitfalls for contamination of a nursery with BN are many, so the location of the problem area Is often very difficult to accomplish. In order to have control of nursery sanitation one must know the possible sources of BN contamination and those Improper cultural practices which could aid in the spread of the contamination within the nursery once established. Burrowing nematodes are already recognized a major problem in Hawaii's banana and anthurium Industries and to a much lesser extent In commercial edible ginger. SOURCES OF BURROWING NEMATODE CONTAMINATION: The ways that nematodes can enter a nursery are many and often their entry Is peculiar to the specific oprations of a given nursery, some of the ways that nematodes Infest a nursery site are: 1. infecting plants on the site before the nursery was establI shed; 2. brought In with Infected or Infested plants; 3. brought In with contaminated planting media. Hapu from hawallan tree ferns used In potting media Is suspected of being a source of the BN. However, hawailan tree ferns are not known to be host for the BN. Therefore If the BN is coming In with hapu It Is the result of the harvest of other BN hosts along with the tree fern or from the logs coming In contact of Infested soil during the harvesting operation. A less probable source Is cinder contamination from Infected plants growing In or near the cinder mines. Page 1 4. Contaminated vegetative seed pieces, pots, or wood previously used for benches or other nursery operations. 5. Contaminated water from open Irriga tio n ditches which receive run-off water from fie ld s or native areas (city water Is free of plant pa rasitic nematodes). Surface run-off water from surrounding areas. 6. Soil movement of any kind, whether for potting mix, landscaping or landfilling. Nematodes also can enter In soil and mud on shoes, hands, and clothes of nursery workers and visitors. Yes, they even enter on the paws and fur of dogs and cats (entry by birds and Insects are more Improbable). Mud and soil on treads of equipment tire s, on equipment accessories, on hand tools used outside. 7. Plants In and around the nursery such as bedding stock plants, landscape plants, native (herbaceous or woody), and adjacent cultivated or weed hosts are suspect. Burrowing nematodes may be found In most areas where bananas and wild gingers grow. They have been recovered from Infected banana plants In the remote Hanakaplal and Hanakoa valleys of Kauai, the east slopes of Haleakala on Maul and from run-off water from non-cultlvated areas above Walmanalo on Oahu. The nematode Is e asily Introduced Into new areas with Infected plant material. Subsequently It is disseminated In that area by surface run-off water, wild animals, and any other agent which can move plants or so il. By Itse lf, the nematode being less than a millimeter In length, moves relatively very short distances In Its life span of about a year. Since then the BN spread has been facilitated by various agents e.g. wild pigs and plant collectors of various kinds. Always be wary of "free" or purchased plants. Page 2 TYPES OF PLANT INJURY CAUSED BY BURROWING NEMATODES: Above-ground Symptoms: Above-ground symptoms of plants heavily Infected by BN are similar to those associated with general nutrient deficiency and chronic water stress. The appearance of the plant Is generally unthrifty, with some chlorosis, stunting and wilting at peak transplratlonal times of the day. Generally, environmental stress Is required for the symptoms to show, in fact, the greater the environmental stress, the more pronounced the symptoms. Therefore, one should not expect to see above-ground symptoms In potted ornamentals in the nursery caused by BN since normal cultural care should be adequate to minimize environmental stress. The BN does not enter above-ground parts. Below-ground Symptoms: Below-ground parts i.e., roots, rhizomes, corms and tubers may be Infected. The most Important effect in most plants Is the destruction of the feeder root system. Weakening of plant support occurs when fleshy root Is invaded and subsequently the nematode colonization of the root causes lesions to form which later rot and enlarge thus g ird lin g and weakening the root system. Sunken lesions may be seen in some corms and rhizomes. In general, root symptoms are not specific for the BN and may resemble those caused by root-rotting fungi. Since the nematode, feeding Internally In the root provide a wound, this area may be Invaded by other root parasites such as fungi and bacteria, some of which need a wound to enter. Thus the BN can either predispose plants to root rotting fungi or intensify existing root rots. LIFE CYCLE OF THE BURROWING NEMATODE: The BN is an obligate parasite, I.e., It requires a living host on which it can feed or It may die In 4-6 months. The adult female nematode Is approximately 0.75 mm long. The life cycle, from egg to egg can be completed In about 3 weeks, depending on an available host and favorable environment. Initially, a larval or adult nematode punctures tender root cells In the vicinity of the root hairs, near the tip of the roots. Puncturing and feeding In root cells Is accomplished by a hollow style t in Its head region. Hardened or corky roots are not invaded. The burrowing nematode gets its name from its habit of feeding in the fleshy cortical region of the root and migrating through the tissue. Lesions occur because as the female migrates she may deposit eggs along the way which hatch In 3-7 days. The larval nematodes go through several molts to become an adult and the life cycle process is repeated, thus the root becomes colonized and the breakdown of the root tissue Is first observed as tiny lineal lesions. These enlarge and coalesce with others to form cankers. Larval and adult nematodes may leave the root and migrate to other feeding sites. Identification of BN root lesions may require up to 9 days Incubation and/or examination with microscopes at 30-45x. Positive Identification of the BN may require an adult male or female at magnifications of up to lOOOx. Page 3 The BN has a wide host range, however, certain Identity Is complicated because of the existence of at least two races, the "banana race" and the "c itru s race", which are Indistinguishable by a microscope. The "citrus race" attacks both citrus and bananas and many other hosts, while the "banana race" Infects bananas and a number of other hosts, but not citrus. The host range of the "banana race" Is more restricted than that of the "citrus race". Spreading decline of citrus, caused by the "citrus race" Is one of the most Important diseases of c itru s In Florida, but has not as yet been found In California, or any of the Pacific Islands. Because of this Inability to readily distinguish between the two races, California has Imposed the very rigid quarantine restriction on a I I forms of R. slmlI Is. the Burrowing Nematode. Over 300 hosts of BN without regard to race have been reported worldwide. It has been recently reported that a population of BN Infecting Anthurlum from Hawaii was able to Infect Citrus aurantlcum (sour orange) In Florida and that the mating behavior of the Florida citrus race and the Hawaiian Anthurlum population was similar.

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