WSU Whatcom County Extension

Integrated Pest Management for Raspberries

Nematodes...

Dagger Nematode (Xiphinema americanum and X. bakeri)

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

Insects and Invertebrates

 

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. The dagger nematode and some related species are vectors of Tomato ringspot virus (ToRSV). Virus transmission by dagger nematodes produces symptoms on leaves such as yellowing of veins, mosaic, and malformation of the plant. In the absence of ToRSV, dagger nematodes can cause stubby roots and dwarfing. Plants infected with root-lesion nematodes are dwarfed, off-color and grow poorly. Symptoms are most often observed on fruiting canes. Dead roots or lesions may be on roots with injury being more severe on small feeder roots. Yields may be reduced when nematode populations reach high levels.

 

Identification

Both dagger and root-lesion nematodes are microscopic and have a wormlike shape. Root-lesion nematodes migrate within the roots and between soil and root tissue, whereas the dagger nematodes stay outsides of the roots, feeding on root tips.

 

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 after harvest is finished (August to October).  Because root lesion nematodes (Pratylenchus penetrans) are found within the actual roots as well as in the soil, it is important to collect both soil and roots when evaluating them. 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 blocks, partitioning fields by soil type, stand vigor, drainage, and crop history.  Prior to planting a field, use a soil core to take a minimum of 20 deep soil cores (1 foot) to represent a block no larger than 5 acres. Sample established plantings in the plant row or hill and within 12-15” of the crowns. Collect samples systematically in each block. It is recommended to walk a “W” pattern throughout the block.

Diagnostic sampling. Sample should be a composite of ten soil cores scattered throughout ten plants in the sample area. Try to take at least two samples from each field, comparing good versus poor areas if possible. Sample around unhealthy plants as well as healthy plants for a comparison. Soil cores should be collected in the plant row or hill within 12-15” of the crowns. Be aware of where drip tape is located when sampling. Using a shovel and pruning shears, collect a handful of soil and feeder roots from the top foot of each plant sampled. Roots and soil can be placed together in a plastic bag and shipped to the lab for analysis.

 

Thresholds and Management

Time of sampling will influence nematode densities, thus effecting threshold decisions. Laboratories may use different extraction methods and therefore may have different nematode recover efficacy. It is important to develop confidence in a lab and relate lab results with your field experience.

Due to the migratory habits of root lesion nematodes, sampling roots in addition to soil can provide a more complete picture of the situation. There have been cases when soil populations are low, but roots are quite heavily infested. This is most likely to occur under very dry soil conditions. Dagger nematodes, if present, are usually found at much lower densities and seem to be associated with declining, low vigor fields.

The ability of a nematode population to cause damage to raspberry will depend on plant age, variety, soil type, other plant pests and diseases, nematode complexes, management inputs, and etc.  Examples of soil nematode population densities that might warrant treatment are:


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.

 

Root lesion nematode populations from root tissue in northwest Washington have been reported as high as 2,000 nematodes/gram of root tissue.

Currently, there are no post-plant nematicides registered for use on raspberry that effectively reduce nematode populations.  Plant-parasitic nematodes are most effectively controlled with chemical fumigation before raspberries are planted.

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

Secondary content using h2 tag.

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 h3 tag

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., Suite 201, Bellingham, WA 98225 (360) 778-5800 whatcom@wsu.edu