Plant-parasitic nematodes in South Australian horticulture, with particular emphasis on stubby root nematodes

WAITE INSTITUTE

PLAIIT-PANASITIC ^NEMATODES

IN

SOUIH AUSTRAIIAN HORTICULIURE. WITTI PARTICUI'AR UVIPIIASIS ^ON

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}

J.4.6.1

^Weecl hoets

t.4.6o2 Native hosts

1.4.6,, Addítional host range info:mation

1.4"T

^Control

1.4.7,1 Control of p. lobatus on m¡.rsery

peach trees

,.4.7.2 Control of p. Iobatus on nursery citrus trees

1.4.8

General Discussfon

,"5

Paæat¡ichodonrs minor

1.5.1

Population

fluctuations

on peach trees

1.5.2

A diseàse s¡mdrorne

of

onÍons

1.5.2.1

^A

field

survey

1.5.2.2 palhogenicity of p.

mÍnor

to

onions

1.5.2.1 Relationship between numbers of P. minor a,nd plant size

1.5.2.4

Nenaticide

application

i.5.2.5

General Diecussion

1.5.2.6

A disease

d.istribution pattern following

peach trees

t.6

Trichodorus

roxtoni

(ttenatotta:

Doryrainida) a

^new specÍes

of

stubby

root

nematode

from

south

Austraria

4.

ACKNO}ft&DGEil'IENTS

5.

^APPENÐICES

62 62

6t

6S 66

66

7o 72 72 74 74 B2

B1 B5 B9

9o

95 9t

96

6.

BIBI.,IoGRAPIIT

107

TABLE OF CONTENTS

SUMMÂRY

TNTRODUCTION

THE OCCURRENCE OF NEIVIATODES ON HORTICULTIIRAI AN}

VEGETABI,E CROPS

IN

SOUTH AUSTRAIIA

2.1

Peach

2.2

Vine

2.3 citnrg 2"4

Nurseries

2.5

Tonato

2.6

onion

2.7

General discussion

STUBBY ROOT ÑflVIATODES AND SOUTH AUSTRÀLIAN HORT]CULTURE

1.1 Literature

review

3.2 Collection, extraction

and storage

of

^samples

1.1

^{Root growth}

of

peach trees

1.4

Paratrichod.orrrs l-obatus

5.4.1

Population

fluctuations in

peach nurseries

1.4.2 Vertical distribution in the soil

1.4.1 Relationship of tree size to p.

l_obatus numbers

1.4.4 Effect of

temperature on

population

increase

1.4.5

Pathogenicity

1.4.5.1 Field

^symptoms

1"4"5.2

Glasshouse experiments

,,4"5"1

Laboratory studies

1"4"5.4

^Discussion

Page

1a

1

20

,

6 6 11

1t

15 18 1g 20

2) 2t j1

J4

)t

17 42

45 46 5o 50 51 57 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 P.

robatus 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 control of p. 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 the

genus paratrichodorus _and

others typical of the

genus

Trichodoms eensu

stricto.