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Plant-Parasitic Nematodes in South Australian Horticulture, With

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Plant-Parasitic Nematodes in South Australian Horticulture, With WAITE INSTITUTE AUSTRAIIAN PLAIIT-PANASITIC NEMATODES IN SOUIH ON HORTICULIURE. WITTI PARTICUI'AR UVIPIIASIS STIIBBY ROOT by G.R. Stirling, B.Ag.Sc. (ttons') laetaiae South Australian Department of Agriculturet Loxton Research Centre Loxton. DePartnent of Plant Patholoryt l^Iaite Agricultural Research Institute' UniversitY of Adelaid'e ' A thesis subnitted. for the degree of M'Ag'Sc' UniversitY of Àdelaid'e Novenberr 1974 3.4"6 Host range 62 J.4.6.1 Weecl hoets 62 t.4.6o2 Native hosts 6t 1.4.6,, Addítional host range info:mation 6S 1.4"T Control 66 1.4.7,1 Control of p. lobatus on m¡.rsery peach trees 66 ,.4.7.2 Control of p. Iobatus on nursery citrus trees General Discussfon 1.4.8 7o ,"5 Paæat¡ichodonrs minor 72 Population fluctuations 1.5.1 on peach trees 72 A diseàse s¡mdrorne 1.5.2 of onÍons 74 1.5.2.1 A field survey 74 palhogenicity 1.5.2.2 of p. mÍnor to onions B2 1.5.2.1 Relationship between numbers of P. minor a,nd plant size B1 1.5.2.4 Nenaticide application B5 i.5.2.5 General Diecussion B9 1.5.2.6 A disease d.istribution pattern following peach trees 9o t.6 Trichodorus roxtoni (ttenatotta: Doryrainida) a new specÍes of stubby root nematode from south Austraria 9t 4. ACKNO}ft&DGEil'IENTS 95 5. APPENÐICES 96 6. BIBI.,IoGRAPIIT 107 TABLE OF CONTENTS Page SUMMÂRY 1 a TNTRODUCTION 1 20 THE OCCURRENCE OF NEIVIATODES ON HORTICULTIIRAI AN} VEGETABI,E CROPS IN SOUTH AUSTRAIIA 6 2.1 Peach 6 2.2 Vine 11 2.3 citnrg 1t 2"4 Nurseries 15 2.5 Tonato 18 2.6 onion 1g 2.7 General discussion 20 , STUBBY ROOT ÑflVIATODES AND SOUTH AUSTRÀLIAN HORT]CULTURE 2) 1.1 Literature review 2t 3.2 Collection, extraction and storage of samples j1 1.1 Root growth of peach trees J4 1.4 Paratrichod.orrrs l-obatus )t 5.4.1 Population fluctuations in peach nurseries 17 1.4.2 Vertical distribution in the soil 42 1.4.1 Relationship of tree size to p. l_obatus numbers 45 1.4.4 Effect of temperature on population increase 46 1.4.5 Pathogenicity 5o 1.4.5.1 Field symptoms 50 1"4"5.2 Glasshouse experiments 51 ,,4"5"1 Laboratory studies 57 1"4"5.4 Discussion 60 this thesÍs contains no rnaterÍaI which has been accepted for the anard. of a:\y other d.egree or d.iploma in any University and no material previously published or written by another person, except when due reference is nad.e in the text. signed 'SUMMARY surveys were u¡d-ertaken to deter¡nine the occurrence of plant-parasitic nematod'es in south Austrariats peach, vÍne and citrus orchards, tomato and onion crope, and hortlcultural nurseries. Root-knot nern¡tod.es (Uetoidogyne sp.) were widespread and. economically inport,ant in pea,ch orchard.s, vine_ ya^rd's a¡rd' tonato crops, and were a najor problem in nurseries. The stubby root nematodee paratrlchod.orus foÞtos- and p. nirìor frequently occurred_. P. minor was common on peach, vine, citrus, tonato and onion, and generally occurred' in nore tha^r¡ half the sa.urprea processed from a particular crop, nhile robatus P. lras present in zo-tq" of sampree from rnost crops. Nearly arl citrus orchards, and more tha¡r one-third of Riverland vineyard.s, were infested with cit:rrs nematode (Tylenchurus senipenetrans), but the nenatod,e clitl not occu.r in nurseries" The verti".ì ¿i"t"ibution of P. lobatus in peach orchard.s was simil-ar to that of root distrÍbution. Both nematode numbe¡s a¡rd root weights were highest at a depth of 1! crn. Grasshouse experinents showed that the optimum tenperature for populatÍon increase of p. r-obatus on peach was in the range 25-tooc' rn peach nurseries, P. robatus popurati-ons increased rapidry to a maxi'mum at the end' of the treesr first ercason of growilr, u.ruL then declined. 0n removal of the peach trees, populations were maÍntained on volrrnteer weed.s. A sipgtifica¡rt negative correlation (r = -0. 129) was obtained between the height of nursery peach trees and. numbers of p lobatus associated. wi th those trees. Many weed.s were shorm to be hosts of p. lobatus, but the nenatod.e was alr¡o found. in soil near native plants in virgin scrubla¡rd. synptons probably caused' by P. l-obatus were observed in peach, apricot and citrus nu¡series, a.nd' the nenatod-e was shovm to be pathogenic to citrus a¡d apri- cot, a'nd to feed' on peaoh roots. The fumigant DBcp proved. ineffective in controlling P. Ìobatus on peach, but excel-Ient control- was obtained. on citms using the non-volatil-e nenaticide phenaniphos. There were indicat- ions that the p. control of lobatus on nurs ery citrus trees inproved root growth. ?' mi'nor was shor+n to be associated with a disease of onions which occu¡red mainly when onions llere groÌrn after removal of a horticul-tural cropo rn the field, seedlings were stunted and yellow, with dead leaf tips and' severely stunted' roots. order plants had. abnornally branched root sys- tems' Higher nu'nbers of P. ninor occurred. around the roots of stunted plants tha¡r near healthier prants in the sa^ne fie1d., and. a pathogenicity test showed that the nematod.e severely stunted onion roots. Trichod.orus l_oxtoni t a new species of stubby root nematod.e fron peach a¡¡d citnrs orchard'e at loxton is described. The nematod.e has some charac- ters typical of genus paratrichodorus the and others typical of the genus Trichodoms eensu stricto. WAITE II.,IST|TUTE 1 LIBRARY 1. INTRODUCTION There are fou¡ main centres of horticultural production in South Australia (fig:ure 1b). A r,ritie range of crops are SEovrn in a¡rd. near Adelaitte, inoludlng apples, cherrfeer g?apevines, alnonds and a variety of vegetables. An extensive vine growing region exísts in the Barossa VaIìey, while horticulture in the South East has become increasingly inportant with recent developments in the viticultr¡ral and. vegetable industries. The major part of the state's horticultu¡e is centred. along its largest wateruay - the River Murray (figure 1c). About 22'OOO hectares are irrigated fron the river, with the najor crops being grapevinesr cítrrrsr peaches, apricotst pears, almond.s a,nd vegetables, particularly tonatoes, onions and pumpkins. The River Munay flows thror:gh Ern area with rainfal-l and temperatures characteristic of inla¡rcl, serni-desert areas. Average annual rainfall varj-es from 21O nm in the north to 280 nm in the south. The average su¡nmer is long and wa*rrn to hot (nean claily narclnun tenperatures generall,y exceed 26oC for five nonths of the year, November to March ínclusive). Winters are relat- ívely mild ( the lowest nea¡¡ claily ninimum tenperature is about !oC, bei.ng recorded in July). RainfaÌI, soil tenperatute, air temperature and. sunshine data for Loxton ca¡r be seen in Figuree 2a arß' 2b. Alor:g the river, the most domina¡rt land forms are a series of round.ed.t east-west orientated, dÍscontinuous, aeolian clepoeited parallel sandhillst with flats and. depressions in between. The soils of the sandhills consj.st mainly of d.eep coarse red.d.ish sand.s, occasionally grading to loany sa¡ds. The flats consist of relatively shallow (10 crn - JO cn deep) red.dlsh sand.s, sa^¡dy clay loamb, Ioa.uy sa¡rds or sandy loams overlying line rubble or ca1- crete" Soil in the depressions tends to be more clayey. In atldition there are areas of river terraces used nainly for viticulturer with deep red.dish grey clay soils. (fotter et aI 1971, trrretherby 1971). 2. Most of South Australia's i:rigated. horticulture is concentrated. along the River lfurray fron the Victorian bord.er to Morgan, i-n areas known coll-ec- tively as the Riverla¡rd.. Other irrigation occrl-rs further up the river in Victoria and New South l¡'Iafes. The nearect ie an area around Milclura known as Sunraysia. It has sinila¡ soile a¡rd clinate to the Riverlandr but a smal- ler ra.nge of crops, being restricted largely to vines and cit:rrs. Althor:gh there is virtual-Iy no recorded infornation on plant-parasitic nematod.es in South Australia¡r horticulture, nenatodes are widely recognised as inportant pests. Their significance is particularly noticeable in the warm, irrigated sarrdy soils of the Riverland., where root-knot nematod.es (Meloid.o¡n'ne spp.) axe a major problen on mar\y crops, Other plant-parasitic nematodes occur on horticultural crops in South Australia, but Iittle is knorrn of their clistribution and economic importartce. This thesis is presented. in two parts. The work reported. in the first part was aimed at ad,d.Íng to our linited. knowledge of the d.istribution of nematod.es in South Australian horticultural crops, In the second. part there is particular enphasis on the distribution, ecology and economic importa¡ce of stubby root nematod.es (Trichodqlus spp. and Paratrichodorus spp.) a group of nenatocles that have rarely been studied in relatj.on to Australian horticulture. Most of the work was done in the Riverfand area because of its inporta¡rce in rel-ation to the rest of the state's horticulture. Figure 1a. AustralÍa 1b. South Australia, showing its four nain centres of norticu-ltural prod.uction. 'lc. The River Murray, South Australia.
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