rrECI-INICAL PROG.RESS REPORT NO.. 139 SEPTEMBER 1963

HAWAII AGRICUI-JTURAL EXPERIMENT STATION'COLLEGE OF TROPICAL AGRICULTURE

UNIVERSITY OF HAWAIIHonolulu, Hawaii

Studies on the ControlofRoot-Knot and Reniform Nematodes

with Soil Fumigation in Hawaii

O. V. Holtzmann* and M. Ishii**

INTRODUCTION

Root-knot (Meloidogyne spp.) and reniform (Rotylenchulus reniformisLind Ford and Oliveira) nematodes attack a wide range of crops in Hawaii(3, 4). Year-round production of many vegetable crops is frequent ly possiblebec a us e of a nl0derate wint.er climate. Presently, although chemical controlof nematodes in I-Iawaii is being practiced by so~e growers, little is under­stood as to the factors which affect the efficacy of the soil fumigation.

l'he objectives of these studies were: (I) to determine the relativeeffect of nematocides on root-knot and reniform nematod'es in the field, and(2) to determine whether fumigation in a particular growing season had aneffect on crop yield.

MATERIALS ·AND METHODS

Field and Soil Preparation': The fields selected for these tests werelocated at the Poamoho Experimental Farm of the Hawaii AgriculturalExperiment Station. These fields are used by the Horticulture Department

*Dr. o. v. Holtzmann is Assistant Plant Pathologist at the Hawaii Agricultural Exp eriment

Station.

**Dr. M. Ishii is Associate Plant Pathologist at the Hawaii Agricultural Experiment Station.

of the H:Af:S for testing nematode -resistance to breeding lines ' of tonulLo a ndlima beans , l'he constant recropping of .s us cept ib le plants assured "~l rela­tively high population of root-knot and reniforni nern~t()des. Very fe'w ofother plant-paras iti c nematode forms were present. The soil wa s a low hurnielatosol of the .Wah~iawa series.

Soil preparation was made by .s ubso i l i ng and discing 1 rnonth beforefumigation. Plots were disced and harrowed just prior to treatment.

P lot Design: The experimental design was a rand om i ze d cornpletebl ockv .e ach treatment was replicated 8 times. Each treatment plot consistedof treating a strip 3 feet wide and 10 ' feet long centered on a row. Rowswere spaced 4 f:eet apart. Three-foo't-w ide . untreated buffer zones wereleft between each plot in the row and on the ends of each row.

Treatmetits rt Tests 1 and 2 were designed to compare c ornmer c ia Isources and rates or" application 'of nematocides for root-knot and re niforrnnematode control. All treatments were made 4 weeks prior to planting. Intest 2 there was also included a postplant treatment which was made 2months after planting, 6 inches to each side of the row. Liquid formulationswere injected into the soil with a McC lean F'umigun at a depth of -6 incheson the center and 12 inches to either side of the center of each treatrne ntrow. Nematocides applied in this manner .were: 1,3-dichloropropene, 100%(Te lone}; 2. ethy lene dibromide, 83% by .' weight (EDS); 2 1,2-dibrolno-3­chloropropane, 67,.5% by weight (DBCP); 3 and chloropi.crin. 2

Weighed qu~ntities of 85%. Mylone (3~'5-dimethyltetrahydro-l,3,5, .2H­thiad iaz ine-Zvth ione )" were spread ' by hand on the 3-foot-wide plot on therow. It was mixed ' into the soil by rototillering twice. Measured vo lume s ofVapam (sodium N';~e:thyldithiocarbamatedihydrate) was mixed with adequatewater to distribute the chemical over the 3-foot-wide ' plot. Each of theseplots was rototil le d twice. After treatment 'with chloropicrin, Mylone, andVapam the soil was thoroughly wetted; .

Methyl bromide (98%. methyl bromide 'a nd 2% chloropicrin)2 wasapplied in the 30-sq.-ft.-wide plot under a 2-mil polyethylene cover. rrheplastic cover was .removed after 2 days. Soil temperatures at a 6-inch depthfor tests 1 and 2 ·were 68 0 and.75° F, respectively.

IThe use of any chemicals in this test does not constitute a recommendation of the product

or its manufacturer by the' Hawaii -Agr i cultu ra l Experiment Station or its personnel • .

2Telone, EDB, chloropicrin, and methyl bromide were supplied by Dow Chemical Co-, San

Francisco, Ca l ifornia,

3DB C P was supplied by Shell Development Co., Modesto, Ca l if orn ia ,

4My}one was supplied by Union · Carbide Chemical Co., New York, N. Y~

2

Four weeks after application of chemicals, the plots were seeded with

Fordhook variety of lima bean, which is susceptible to both root-knot and ·reniform nematodes. Subsequent cultural practices were those reco·mmendedby the Hawaii Cooperative Extension Service for .lima bean culture. F'urrowirrigation was employed during the course of these studies.

Nematode Extractions and [Ieterminations : Profile soil samples weretaken in the rhizosphere to a depth of 6 inches in each plot. A compositeplot sample ·c ons is t e d of at least 10 subsamples. Samples were taken 3weeks after fumigation and at harvest. The nematodes were recovered fromthe soil by Anderson's modified Baermann funnel technique (1). tlowever, a40-cc soil sample was processed instead of 100 c c . Nematode counts weremade after re laxing.

Root-knot ·index was based on an average evaluation of at least 10 rootsysterns per plot: 0 == clean, 1 == few srna ll galls, 2 == slightly galled, 3 =moderately galled, 4= heavily galled, 5=:severely galled .

Ilarvest: Beans were picked biweekly and weighed. Only marketablebeans were corisidered.

EXPERIMENTAL RESULTS

Test 1: This test encompassed the period fr·om March 14, 1958 toAugust 6, 1958. F'umigants in general reduced root-knot and reniformnematode populations. There was an apparent inverse relationship betweenthe root-knot index and bean yield. A high index reading was associat edw ith a low yie ld and vice versa. The results s umrnar iz e d in table 1 showthat treatments EDB (96 lb /acre) , methyl bromide , DBCP (68 lb/acrc),Te lone (400 lb/acre), and EDB (48 Ib/acre) gave · yields s ign ifica nt lybetter at the 1% level than the untreated che cks , However, there was nodegree of high significan ce between the treatments EDB (96 lb/acrc),methyl bromide, DBCP (68 lb/acre), Telone (400 lb/acre) , EDS (48 lb/a cre),Te lone (200 lb/acre), chloropicrin, or DBep (34 lb/acre).

Test 2: This test encompassed the period from September 16, 1958 toFebruary 9, 1959. Nematocidal a ct ivity of the chemicals was similar to thatobserved in test 1. Table 2 shows that to a degree the inverse relationshipbetween yield and root-knot index is in evidence. No significance i·s foundbetween the y'ie lds in any of the treatments.

D.ISCUSSION

All the . chemicals tested were relatively effective in reducing theinitial soil population of both root-knot and rcnifonn ncma t odes . tIowcv er,the nematocidal effect of DBCP is less in the initial kill of the reniformnematode than it is with the root-knot nematode. 'The reduction in bean

yield in these tests is probably due to .the root-knot rather than to the reni­form nematode infestation. Although the F'ordhook lima bean j is susceptibleto both root-knot and reniform nematodes, the reniform nematodes did notshow a high degree of parasitism on the roots.

Bean ' yields were significantly increased in the treatments EDB(96 Ib/acre), methy I bromide, Telone (400 Ib/acre), and EOB (48 lb/acre)in the summer-harvested test (test 1), whereas no significance was de­termined between the yields of the treatments in the winter-harvested test(test 2). The yield of the untreated check in the winter test outyielded thatof the summer test despite the fact that the roots of the beans in the winterwere more heavi ly ga l le d with root-knot nematodes. Th is yield variance maybe because of the low occurrence of environmental stresses during thewinter, i.e., high temperature and low moist.ure which accentuates theadverse effect on yields of root-knot infested plants (2).

The bean roots in comparative OBCP treatments were less heavilygalled in the winter test than in the summer test. This may be because ofthe lower soil ternpcrature s which prevailed during the fall and winter grow­ing season. OSCP has a lower vapor pressure than does E.DB or Telone,.thus is able to act nematocidally over a longer period of time.

REFERENCES

1. Anderson, E . .1., and I. Yanagihara.1955. A method for estimating .numbers of motile . nematodes In largenumbers of soil samples. Phytopathology 45(4): 238-239.

2. Christie, J. R.1959. Plant Nematodes-Their Bionomics and Control. AgriculturalExper'irnent Stations, University of Florida, C;ainesville, I~'lorida. 256 pp.

3. Linford, M. B., and F'rancis Yap.1940. Some host plants of the reniform nematode In Hawaii. Proc.HelminthoI. Soc. Wa~hington, D.C. 7·: 42-44.

4. Oliveira, Juliette M.1940. Plant-parasitic and free-living nematodes in JIawaii. Bernice P.

·Bis hop Museum, Occasional Papers 15(29): 361-373.

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WARNING

The chemicals used in this test should be considered dangerous. Themanufacturers' recommendations for handling should be strictly adhered to.F'urther, the United States Department of Health, Education and Welfareunder the provisions of the Pest ic ide Chemicals Amendment to the FederalFood, Drug, and Cosmetic Act has established criteria to govetn the use ofeach chemical to which clearance for use has been given. Growers. shouldalways check the current status of any pesticide with their county agent 01'

the local U.S.l1.·E.W., F'ood and Drug Administration representative, beforeuSIng.

UNIVERSITY OF HAWAIICOLLEGE OF TROPICAL AGRICULTURE

HAWAII AGRICULTURAL EXPERIMENT STATIONHONOLULU, HAWAII

THOMAS H. HAMILTONPresident of the University

",ORTON M. ROSENBERG·Dean of the College and

Director of the Experiment Station

~. DONALD SHE . ANAssociate Director of the Experiment Station