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Dorchester County, Md.,
Extension Agent Betsy Gallagher takes soil samples as part of
a SARE-funded project seeking to reduce root-damaging nematodes
in potatoes and soybeans. |
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Geographic Adaptability: The cultural
practices described in this publication were evaluated for nematode
control in field and small plot studies in Maryland. The practices
described in this fact sheet should be effective in mid-Atlantic vegetable
crop production systems where the southern root-knot nematode is the
most important root-knot species and where growing season and crop
rotations are similar to Maryland’s Eastern Shore.
Introduction
Growers of vegetable crops in the mid-Atlantic have typically used
nematicides to control root knot nematodes (RKN) and root-lesion
nematodes. The loss of many nematicides from the market due to environmental
concerns and constraints of use, such as the length of the period
when crops cannot be planted following application for currently
labeled fumigant nematicides, have focused attention on the development
of alternative methods for managing plant parasitic nematodes.
This publication discusses the use of non-host crops, sorghum sudangrass
and castor bean grown as cover crops, RKN-resistant crops, and the
application of poultry litter (PL) and PL compost to manage RKN
and root-lesion nematode. These methods can be used in vegetable
production systems to reduce build-up of nematodes over time, to
lengthen the interval between nematicide applications and to provide
a non-chemical management approach for organic growers. Examples
of different cultural practices for managing RKN and root-lesion
nematodes are shown in Table 1.
The southern RKN and root-lesion nematode are prevalent in Maryland
and Delaware and cause severe damage in areas with sandy soils.
The southern RKN damages a wide variety of crops grown throughout
the mid-Atlantic region including soybeans and tobacco, and vegetables
such as sweet potatoes, tomatoes, potatoes, cucumber and green beans.
Fields cropped repeatedly to these crops have experienced significant
losses due to RKN. Corn and wheat, common crops in the region, are
reproductive hosts for RKN.
Root-lesion nematode also has caused severe damage on potato and
cucumber, although yield losses due to root-lesion nematode are
highly variable and influenced by environmental conditions. In addition,
when the fungus Verticillium dahliae is present with root-lesion
nematode, potato early dying disease occurs.
Symptoms of plant damage due to nematode activity may initially
appear similar to lack of or improper fertilization, too little
or too much water, improper soil pH, poor soil, or other environmental
factors. Irregular patches in the field with poor plant growth (sickly
growth, wilting, yellowing, stunting and premature plant aging)
can range from a few feet to hundreds of feet across. Losses due
to nematodes may be more prevalent than is currently known
Growers who use nematicides to control root-knot and root-lesion
nematode on potatoes and cucumbers incur large expenses. For example,
25% of the pickling cucumber acreage in Maryland and Delaware was
fumigated in 1998, a typical year.
Maryland potato growers met in the fall of 1999 and expressed interest
in alternative strategies such as cover crops, non-host rotation
crops and poultry manure for managing parasitic nematodes in the
potato cropping system. The research and management tactics described
in this publication were developed as a result of that meeting.
Suppressive cover crops and nematode-resistant rotation crops have
been reported to significantly reduce nematode populations in agricultural
soils in trials conducted in other regions of the U.S.
Poultry litter (a mixture of poultry manure and pine shaving bedding)
and composted poultry litter also have been used as an organic soil
amendment to suppress root-knot nematodes and provide an alternative
to nematicides. The breakdown of poultry litter (PL) or PL compost
stimulates microbial activity in the soil that suppresses nematode
damage and reduces population densities.
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