By: Tahera Sultana, Research Scientist, AAFC and Erica Pate, Fruit Crop Specialist, OMAFA
Published May 2023
Many plant-parasitic nematodes (PPNs) are pests to blueberries, feeding on or within the roots. This feeding reduces root volume and function, with above-ground symptoms including poor, weak areas of the field, slow-growing plants, and lower yields. In addition, nematodes can also vector viruses, including necrotic ringspot and tomato ringspot; which is always been a concern to any blueberry growers because of major yield loss. Nematode damage can be difficult to distinguish from other issues, such as fertility challenges, so soil samples need to be analyzed to accurately identify nematode pests. The occurrence of PPNs associated with blueberries has been assessed in some blueberry producing regions of North America but our knowledge of association of these nematodes in Southern Ontario is limited. Therefore, a study was conducted in year of 2019 to better understand the frequency of occurrence, prominent value (predominant species), and population density of plant-parasitic nematodes in selected blueberry orchards at Dr. Tahera Sultana’s lab on AAFC (Agriculture and Agri-Food Canada) facilities. 92% of samples from this initial survey were positive for at least one of the plant parasitic nematodes tested (Pratylenchus sp., Mesocriconema sp., Xiphinema sp., and Paratylenchus sp.). One of the major plant parasitic nematodes that we found was Dagger nematode (Xiphinema sp.), a well-known vector for several nepo-viruses, and presence of these viruses and nematode together can cause key decline in blueberry production.
Our initial data indicated that Southern Ontario region is witnessing an increase in the population of plant-parasitic nematodes associated with blueberry. Focusing the necessity, Tahera Sultana from AAFC and Erica Pate from OMAFRA have taken a long term action plan since 2021 with Berry Growers of Ontario to monitor different blueberry orchards within this region to characterize nematode associated with blueberry. In that aim, several orchards have been sampled in the year of 2021 and 2022. Soil samples were collected from each orchard followed a zigzag style from randomly selected plants. At least 5 cores of 2.5 cm X 25cm deep samples were collected around each plant (within 1 meter square diameter). Nematodes were extracted from 50gm of mixes cores of each samples by both Baermann pan extraction method and sugar centrifuge procedure.
In 2021, total 22 samples were collected from 7 counties within the time period from July to October. Plant parasitic nematodes in each sample were identified and counted using inverted microscope following morphological characteristics. While using Baermann Pan extraction method, PPNs were identified to genus and 82% of these samples were found positive for at least one of the plant parasitic nematodes tested. 69% samples were also came positive for at least one of the plant parasitic nematodes using sugar centrifuge procedure of nematode extraction. For both, most samples were positive for more than 2 of the nematodes tested (Pratylenchus sp., Mesocriconema sp., Xiphinema sp., Paratylenchus sp. and Tylenchorhynchus sp.).
2021 result summary:
- 50% of samples had root lesion nematodes (Pratylenchus sp.)
- 32% of samples have been found to contain ring nematodes (Mesocriconema sp.)
- 23% of samples had dagger nematodes (Xiphinema sp.)
- 5% of samples had pin nematodes (Paratylenchus sp.)
- Stunt nematode (Tlyenchorhynchus sp.) were not found in any of the samples
In 2022, total 10 set of samples have been collected from 3 different counties within Southern Ontario by the time period of May-June. Plant parasitic nematodes in each sample were identified and counted using inverted microscope following morphological characteristics as well. While using Baermann Pan extraction method, PPNs were identified to genus and 76% of these samples were found positive for at least one of the plant parasitic nematodes tested. 68% samples were also tested positive for at least one of the plant parasitic nematodes using sugar centrifuge procedure of nematode extraction. Similar to previous year, most samples were positive for 2 or more of the nematodes tested for with both extraction method.
2022 result summary to date:
- 60% of samples had root lesion nematodes (Pratylenchus sp.)
- 30% of samples had dagger nematodes (Xiphinema sp.)
- 50% of samples had pin nematodes (Paratylenchus sp.)
- No Ring (Mesocriconema sp.) or Stunt nematode (Tlyenchorhynchus sp.) were not found in any of the samples
Many of the samples over the last two years are very high in nematode count. This result stated that plant parasitic nematodes are a significant concern for Ontario blueberry growers. Presence of PPNs in growers orchard may lead to a major impact to blueberry plant’s health and susceptibility to other pathogens. However, not all the common plant parasitic nematodes have been tested in this study and sample numbers were also relatively low. Therefore, with one more year of the survey, a larger sampling will continue this spring and fall. Generating awareness among growers about the presence of plant-parasitic nematodes in their orchards and potential yield loss due to this issue is ongoing.
This survey will continue for its final year in 2023. Our goal at the end of this survey is to have a better understanding on the effect plant parasitic nematodes are having on Ontario blueberry production, and to identify what further research is needed to help manage this pest.
If any blueberry growers suspect nematodes are causing damage to their blueberries, or are interested in participating in the final year of this survey please contact Erica Pate (erica.pate@ontario.ca). The initial 2019 survey was voluntarily supported by AAFC researcher Dr. Tahera Sultana within her nematology lab at AAFC Vineland Station, and the current 2021-2023 project is funded in-part by the Berry Growers of Ontario.
Thanks to all participants in this survey to date.