WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Nematodes

Dagger Nematode (Xiphinema americanum)
Root-lesion Nematode (Pratylenchus penetrans and P. crenatus)

Insects & Invertebrates

 

Dagger Nematode

 

Symptoms

Nematode damage can occur without above ground symptoms, though a gradual decline in yield over a period of years often indicates a problem. Virus transmission by dagger nematodes produce symptoms on leaves such as yellowing of veins, mosaic, and malformation of the plant. Poor growth and yellowish foliage are symptoms of root-lesion nematode. Yields may be reduced when nematode populations reach high levels.

 

Identification

Both dagger and root-lesion nematodes are microscopic and have a wormlike shape. They are found only in the soil.

 

Life History

Dagger nematodes have the life stages of egg, juvenile and adult. Juvenile stages are smaller than the adult stage. They reproduce once per year, live four or five years and reach highest population levels in undisturbed areas and in zones within soil where oxygen is most plentiful. Dagger nematodes are migratory ectoparasites; they do not enter plant tissue and instead feed on root cells from the outside, piercing cells to feed on the interior. Root-lesion nematodes are migratory endoparasites; they tunnel into the root to feed and return back to the soil.

 

Monitoring

Scouting should be done in two ways: monitoring the plants, and sampling the soil.

Plants should be inspected throughout the growing season to identify weak stands and plants that have been infected with tomato ringspot virus through nematode transmission.

Soil sampling for nematodes should be done in late summer to early fall (September to October).  This allows time to decide on treatment and to apply a pre-plant fumigation if needed. Soil samples should be done using a standard soil sampler.  Two types of sampling can be done: predictive and diagnostic.  Samples should be taken, placed in a plastic bag, labeled, chilled and immediately delivered to the lab for testing.

Predictive sampling. This is done to determine areas that may have nematode problems.  Sample the field in 2-5 acres blocks, partitioning fields by soil type, stand vigor, drainage, and crop history.  Take 20 core samples, 6-8” deep, in each block. Sample systematically in each block.  Sample established plantings in the plant row or hill and within 12-15” of the crowns.

Diagnostic sampling. Sample around the margin of areas with severely weakened plants to determine if nematodes are the cause of the symptoms.  Adjacent areas with healthy plants should also be sampled.  Collect 8-12 soil and root samples in each area.

Different laboratories use different extraction methods so developing confidence in a lab and relating lab results with field experience is essential.  Time of sampling will influence nematode densities.

 

Thresholds and Management

Thresholds are influenced by age of plant, variety, soil type, and other pest pressures.  Some guidelines from McElroy indicate the following thresholds:

Nematode Type
Planting Age
Threshold
Lesion nematode
New planting
500 per pint soil
Lesion nematode
Established planting
1000-4000 per pint soil
Dagger (X. bakeri)
New planting
100 per pint soil
Dagger (X. americanum)
Any
Zero tolerance when Tomato
Ringspot virus is present

Before planting, chemical treatment can be made. In an established planting, plants in the infested area should be removed and a spot fumigation can be made. Plant virus tested, certified stock.

The use of soil solarization (using clear plastic over soil during the summer to heat the soil to a high temperature) has been used with some efficacy in the season before planting.

 

Resources

ATTRA, Nematodes: Alternative Controls
http://www.attra.org/attra-pub/nematode.html

Michigan State University, Michigan Blueberry Facts, Nematodes
http://www.blueberries.msu.edu/nematodes.htm

Oregon State University Extension, An Online Guide to Plant Disease Control, Root Lesion Nematodes
http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=184

Oregon State University Extension, An Online Guide to Plant Disease Control, Dagger Nematodes
http://plant-disease.ippc.orst.edu/ShowDisease.aspx?RecordID=183

 

Secondary content using h2 tag. Column 2

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

Heading using the h3tag

Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • (360) 778-5800 • whatcom@wsu.edu