TABLE CONTENTS

TOPIC FIVE – PLANT-PARASITIC NEMATODES: SEEDS, LEAVES AND
STEMS
Seed- and Leaf-gall Nematode Infection of Eragrostis spp. Grasses in South
Africa and Evaluation of a Management Strategy
Bekker, S., H. Fourie & A.H. Mc Donald
Plant Protection Division, Nematology Unit, ARC – Grain Crops Institute, Private Bag X1251, Potchefstroom,
2520, South Africa
The presence of seed- and leaf-gall nematodes (Subanguina spp.) in seed of Eragrostis spp.
grass is currently of great economic concern to the local grass seed industry. The adverse
effect of these parasites on export as well as local markets since 2001 necessitated a survey in
the Eragrostis production areas of South Africa. Furthermore, a mechanical, commercially
viable technique for separating galled seed from uninfected seed was investigated. Eragrostis
seed samples were obtained from 13 localities and soaked in water for 48 hours at 25º C for
extraction of nematodes. To quantify the extent of seed- and leaf-gall nematode infestation,
population density, frequency of occurrence (%) and prominence values (PV) were
calculated. For identification purposes DNA fragments from these parasites were sequenced
using several nematode primers. Separation of galled seeds from uninfected seeds was done
for two separate nematode populations using three different aperture mesh sieves. Seed-and
leaf-gall nematodes were identified as S. weevilli, with PV and population densities ranging
from 0.1 to 205 in 1-g seed samples. With regard to sieving, the 250-µm mesh sieve
contained a significantly lower number of seed- and leaf-gall nematode individuals as well as
galls compared to the 600-µm and 500-µm mesh sieves for both populations. The unsieved
control, however, maintained a significantly higher number of seed- and leaf-gall nematode
individuals as well as galls than the three sieve treatments. Only one control strategy is not
adequate, but an integrated management approach needs to be developed to ensure that grass
consignments are free of seed- and gall leaf nematodes. Further research is in progress in an
attempt to assist producers and the grass seed industry to address the nematode problem.
Efficacy of Abamectin as a Seed Dressing for Control of the Stem
Nematode Ditylenchus dipsaci on Sugar Beet
Syeda , A., A.A. Dababat , V. Kunhold & R.A. Sikora
Soil-Ecosystem Phytopathology and Nematology, Institute of Crop Science and Resource Conservation INRES,
Department of Plant Health, University of Bonn; Nussallee 9; 53115 Bonn, Germany
The stem nematode is an extremely damaging parasite of sugar beet in many growing areas
of Europe. Control is complicated due to the lack of resistance and wide host range. Our
research focused on the non-fumigant nematicide, Abamectin = avermectin B1a, produced by
fermentation of the bacterium Streptomyces avermitilis. Abamectin is a very active
nematicide with low toxicity to humans and the environment. We evaluated the efficacy of
Abamectin as a seed treatment against D. dipsaci on sugar beet, Beta vulgaris. Greenhouse
experiments showed that Abamectin treated seed protected the young seedlings of sugar beet
from early D. dipsaci infection. The level of nematode penetration into the shoot of the
seedlings of two cultivars, susceptible and moderately resistant to the stem nematode, was
significantly reduced. There was no sign of phytotoxicity seen after treatment. In vitro
5 th International Congress of Nematology, 2008 213