Erin Gunnink Troth and Dr. Carmen Murphy, Montana State University
The Regional Pulse Crop Diagnostic Lab (RPCDL) is located at Montana State University in Bozeman, Montana. Founded in 2014 it is the only laboratory exclusively dedicated to pulse crop pathogen diagnostics and provides testing services to all pulse-growing states in the U.S. The lab has several testing functions, including seed health testing for replanting purposes, export compliance, and soil testing for root rot and other soil-borne diseases. All test panels offered follow guidelines and protocols in accordance with the International Seed Testing Association (ISTA).
Seed Health Testing
Fungal plant pathogens are especially problematic when an infection of the crop culminates in the seed. Such seed-transmitted pathogens can then infect the germinating plant when contaminated seed is replanted, creating a two-pronged disease problem where pathogens arise from infested seed sources in addition to the environment, such as infected plant stubble in the area. The RPCDL offers a fungal assay, called our Ascochyta-Plus test, on seed lots intended for replanting to ensure the health of pulse crop seed. This conventional plating test looks for the pathogens causing Ascochyta blight (Didymella and Peyronellae spp.), gray mold (Botrytis cinerea), Anthracnose (Colletotrichum truncatum), white mold (Sclerotinia spp.), and Stemphylium blight (Stemphylium botryosum) on peas, chickpeas, and lentils.
In recent years, the RPCDL has conducted between 400 and 450 Ascochyta-Plus tests annually. Most of our Ascochyta-Plus tested seed lots have no pathogens detected; this varies depending on the year, but typically around 75% of the samples are clean (Table 1).
Table 1. (Left) Percentage of Ascochyta-Plus tested seed lots where no pathogen was detected and (right, italics) number of seed lots tested that year. Note: crop years are measured from harvest to harvest; i.e., crop year 2023 data are based on tests conducted from 8/1/2023 to 7/31/2024.
When pathogens are detected, Ascochyta blight-causing species are often the most common across all three crops. In most years, infestation levels are below 2% (Figure 1). Ascochyta infestation in a seed lot of less than 2% is typically safe to replant, although we always recommend using a fungicide seed treatment. Infestation levels of 2 to 5% are noteworthy and can cause problems if environmental conditions are conducive. When seed lot infestation reaches 5% or higher, applying a fungicide seed treatment is strongly recommended. A seed treatment will reduce the risk of seed-to-seedling transmission in addition to protecting seedlings from soilborne diseases and can reduce the need for foliar fungicide applications (and therefore costs!) later in the season. A list of seed treatment products labeled for the use of seedborne diseases of pulse crops is available on the Montana State University Extension Plant Pathology Resources website, which is updated regularly.
Figure 1. Mean percent infestation in chickpea, pea, and lentil seed lots where Ascochyta blight-causing pathogens are detected. The dashed horizontal lines marks the 2% infestation threshold.
Export testing
Another service the RPCDL offers is nematode export testing for phytosanitary compliance. This is typically done in conjunction with a seed lot screen for weed seeds that are prohibited by the importing country (i.e. The “India Quarantine” test conducted by the Montana State Seed Testing Lab). The nematodes included in the test are the stem and bulb nematode (Ditylenchus dipsaci), the potato rot nematode (D. destructor), and cyst nematodes (Heterodera spp.).
The demand for nematode export tests varies sharply based on geopolitical trends and tariffs in importing countries. In contrast, the number of Ascochyta-Plus tests do not fluctuate by more than 10% each year. Export conditions for lentil and dry pea have been very favorable in the most recent crop years (CY2023 to current) and to date the RPCDL has tested over 1,000 samples (with one sample representing between 1 and 5 rail) of pulses for nematode contamination for export compliance (Figure 2). This is more export testing than was conducted during crop years 2018 to 2022 combined.
Figure 2. Number of nematode export tests conducted per crop year.
*Status crop year 2024 as of 1/22/2025.
While nematode detections in seed lots are infrequent, they have considerable economic consequence for the exporter. In the current 2024 crop year, only 25 of the 600 samples tested (4.2%) were positive for the presence of a regulated nematode (D. dipsaci). While this detection rate may seem low, those 25 rail cars of pulses that cannot be certified for export represent considerable economic impact ; a single rail car can hold between 3000 -3600 bushels of seed, contingent on the seed and the company. Depending on the phytosanitary regulations in the importing country and on the contract between exporter and importer, a contaminated seed lot may be salvaged with a fumigation treatment, but this is not always possible or feasible.
Author Bios:
Erin Gunnink-Troth (M.S.) is the Manager of the Regional Pulse Crop Diagnostic Laboratory at Montana State University. She works in pulse seed health and plant diagnostics. Visit the RPCDL website to learn more about our testing capacities and for further references. Phone: (406)-994-7738 | Email: erin.troth@montana.edu.
Dr. Carmen Murphy is an Assistant Research Professor of Plant Pathology at the Regional Pulse Crop Diagnostic Lab and the McKelvy Extension Plant Pathology Lab at Montana State University. Her research is focused on the soilborne diseases of dry pea, lentil, and chickpea. 1911 W. Lincoln St, Marsh Labs, Lab 21, Bozeman, MT, 59717-3150. Phone: (406)-994-5162 | Email: carmenmurphy@montana.edu.