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Monday, May 17, 2021

Managing Nematodes to Reduce the Impact of Early Dying Complex

A rotary hoe in a field.
Potato field

Figure 1. Potato field.

At first appearance, early dying complex in potatoes is seemingly inexplicable. The plants were thriving, and then they were dying. At that point, a grower has no options. Nematodes along with several diseases, including; early blight, brown spot, white mold, and botrytis, contribute to and can worsen the early dying complex (EDC). Nematodes play a significant role in the EDC.

There are several species of nematodes in Canada that can have a negative impact on yield and/or quality of a potato crop. Not all nematode species are present in all potato growing regions. The nematodes with the most economic importance to potatoes are the root lesion nematodes.

There are two species of root lesion nematodes, Pratylenchus neglectus and Pratylenchus penetrans. P. neglectus is present across all regions. A recent survey of Western Canada potato fields, conducted by Dr. Mario Tenuta at the University of Manitoba, showed that P. neglectus was present in 30% of the fields surveyed. In some regions of the West, populations exceeded 2,000 nematodes per kilogram of soil, which is a sufficiently high enough population to reduce yields. P. penetrans is present in Ontario, Quebec, the Maritimes, and British Columbia. This nematode is associated with and interacts with Verticillium wilt. Verticillium wilt is considered a barometer for the amount of early die complex in any given field. There are two theories of how these nematodes interact in the EDC that are generally accepted by the industry. One theory is that the root lesion nematode creates wounds on the roots allowing for entry of the pathogen. The other accepted means of interaction is that the root lesion nematodes change the physiology of the potato plant rendering it more susceptible to the disease. Regardless of which means of interaction you adhere to, it takes very few of these nematodes to make the Verticillium wilt a bigger problem compared to the absence of P. penetrans. If you have fields with this nematode control measures should be considered.

Root knot nematodes, Meloidogyne spp., are not a widespread problem in potato regions. They have more of an impact on tuber quality than on yield reduction. The cyst nematodes (Globodera spp.) are a quarantinable pest that have only been confirmed to be present in two provinces. Lastly, the stubby-root nematode (Trichodorus and Paratrichodorus), although not common, transmits Tobacco Rattle Virus resulting in brown threads/flecking, referred to as “spraing”, throughout the tuber making them non-marketable. This nematode is quite often associated with corn production.

As mentioned earlier the early dying complex (EDC) is caused by a fungus called Verticillium but is made worse by several other diseases and the root lesion nematode. Once EDC is established in a field and root lesion nematodes (Pratylenchus) are confirmed to be present control measures should be considered. There are several management tools that can be utilized; choose a variety more tolerant to Verticillium, if possible stretch your rotation so that potatoes are grown less frequently on that field, incorporate green manures and/or biofumigants, use of a chemical fumigant will reduce both nematode and Verticillium populations and lastly, the use of Velum® Prime nematicide in-furrow to suppress nematode populations is a good short term and sustainable option.

Velum® Prime nematicide applied in-furrow is a very different nematode treatment compared to using a chemical fumigant. Whereas fumigants sterilize the soil, removing beneficial organisms as well as pests, Velum® Prime nematicide only targets nematodes and leaves the beneficial organisms alone. There is an added benefit to using Velum® Prime nematicide in-furrow; it is also registered for the suppression of the diseases early blight and black dot. These two diseases play a major role in increasing early dying of the potato crop.

The Payoff with Velum ® Prime Nematicide: Higher Yield Potential and Improved Quality

The overall benefit of using Velum® Prime is the Return on Investment (ROI). Bayer has consistently shown the value of Velum® Prime by capturing yield data in both small plot research trials and large-scale field demonstrations. The most recent set of field scale demonstrations was conducted in 2020. Eighteen fields, across Canada, received a treatment of Velum® Prime nematicide in-furrow to compliment not replace their standard practice. The trial was conducted on part of the field and yield comparisons were made versus the grower’s normal or standard practice. The average increase in yield of the 18 trials was 20 cwt/acre which resulted in a very good average ROI of $203 per acre* (based on the 2020 SRP for Velum Prime and an average price of $13/cwt).

Whichever direction a grower takes, the goal is efficient, effective nematode management to protect potato roots and increase yield and quality.

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Performance may vary from location to location and from year to year, as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible and should consider the impacts of these conditions on the grower’s fields.

Velum® is a registered trademark of Bayer Group. Used under license. Bayer CropScience Inc. is a member of CropLife Canada. ©2021 Bayer Group. All rights reserved. xx72_S1