TABLE CONTENTS

Evaluation of Millet and Rapeseed as Rotation or Green Manure Crops to
Control Nematodes in Orchard Replant Sites
Halbrendt. J.M. (1), J.A. LaMondia (2) & I.A. Zasada (3)
(1) The Pennsylvania State University, Department of Plant Pathology, Fruit Research and Extension Center,
Biglerville, PA 17307-0330 USA (2) Connecticut Agricultural Experiment Station, Windsor, CT (3) USDA-
ARS, Beltsville, MD 20705
Four annual crops including Canadian forage pearl millet (Pennisetum glaucum) hybrid 101,
velvetbean (Mucuna spp. ), rapeseed (Brassica napus) cv. Dwarf Essex, and buckwheat
(Fagopyrum spp.) were evaluated as rotation or green manure crops for suppression of dagger
(Xiphinema americanum) and lesion (Pratylenchus spp) nematodes. Two sets of field plots
(3 m × 3 m) were established in Pennsylvania and one in Connecticut, four replications per
treatment were arranged in a randomized complete block design. All plots were planted with
seed from the same seed lot to eliminate variability. Nematode population levels were
determined three times for each treatment in each set of plots; pre-plant, end of season and
three weeks after the crops were incorporated as green manure. Canadian forage pearl millet
suppressed lesion nematodes but was a good host for dagger nematodes. Dwarf Essex
rapeseed reduced populations of dagger nematodes only after incorporation as green manure
but did not suppress lesion nematode populations. All sites had similar results although the
dagger nematode data was not statistically different at one location in Pennsylvania.
Buckwheat was included as a susceptible control and the data showed that it was a good host
for both lesion and dagger nematodes. Velvetbean has been reported to have nematicidal
activity but our results showed that the variety used in these experiments appeared to be a
good host for both lesion and dagger nematodes and was not nematicidal as a green manure.
Many old orchard sites are infested with lesion and dagger nematodes and both nematodes
have the potential to cause problems on young trees in replant sites. Rotation crops offer an
environmentally friendly alternative to chemicals for nematode control but as this research
demonstrates, it is important to know which nematodes are present and what effect a rotation
crop may have on the population.
In vitro Screening of Nematicidal Activity of Volatile Fatty Acids in Liquid
Hog Manure to Pratylenchus penetrans and Caenorhabditis elegans
Mahran, A. (1,3), M. Tenuta (1), M. Hanson (2) & F. Daayf (3)
(1)Department of Soil Science; (2) Department of Environment and Geography; (3) Department of Plant
Science, University of Manitoba, Winnipeg MB Canada R3T 2N2
Application of acidified liquid hog manure (LHM) in microplots and field studies reduced the
total numbers of plant parasitic nematodes and lesion nematodes below threshold levels.
Previous reports indicated that short-chain volatile fatty acids (VFAs), products of the
bacterial anaerobic fermentation of the LHM, were responsible for the suppression of the
microsclerotia of the wilt fungus Verticillium dahliae in potato fields. Those reports
prompted us to examine whether these VFAs might have the same effect on lesion
nematodes, Pratylenchus penetrans, which interacts synergistically with V. dahliae leading to
Early Dying Syndrome of potatoes. We have also examined their effects on the model
nematode Caenorhabditis elegans. Acute toxicity tests (bioassays) were conducted to: (1)
Compare the sensitivity of P. penetrans and C. elegans to the VFAs, (2) Screen the VFAs
(acetic, propionic, butyric, isobutyric valeric, isovaleric and caproic acids) in the LHM based
5 th International Congress of Nematology, 2008 280