Agronomy Update – September 11

Hi everyone,

A little shower overnight for most of the Island was again welcome, but more is needed in most communities.  Most readings I’ve seen show between 2 and 6 mm, with the highest I’ve seen being 7.5 mm in Tyne Valley and Lot 16.  The forecast does not look that favourable in terms of rain next week, but it also appears to be staying warm enough to avoid early frost (knock on wood) for the next couple of weeks.  With a very active hurricane season this year, I’m sure the forecasts will change unexpectedly.  Hopefully we can get the right amount of moisture to finish off the crop this month.

Potatoes are now being dug in eastern PEI for table and chip and in the O’Leary area for chips.  Generally, growers I’ve talked to have been surprised with the yields they are getting given the dry summer weather.  Some of these potatoes went in the ground two weeks earlier than normal, so a fuller canopy in June may have helped to offset some of the yield limitations of drought.

Dealing with Early Dying:

Of course, this is a bad year for Potato Early Dying (PED) or Verticillium wilt around the province.  For susceptible varieties, the extreme lack of moisture in July/August provided the right conditions for Verticillium and nematodes to “clog up the plumbing” in the potato plants and cause significant wilting and leaf necrosis/chlorosis.  In many cases, this seemed to worsen after a big rainfall, as the plants moved out of “survival mode” but then couldn’t uptake enough water due to Verticillium compromising the internal water transport in the plant.

So, it’s too late to do anything about fields afflicted with early dying this year; however, it’s the right time to record which of your fields (or parts of fields) seeming to be suffering the most and doing some soil testing to assess how you might be able to lessen the impact of Verticillium and nematodes in future years.  The Potato Quality Institute (PQI) offers diagnostic testing for root lesion nematodes and Verticillium here in Charlottetown.  I would recommend taking samples this fall (before ground freeze) in order to have enough information to make management decisions starting next year.

In my experience, most potato fields that have a long history of potatoes in a three year rotation (or less) have a significant amount of Verticillium spores present.  Verticillium spores can live a long time in fields and can be hosted by more than just potatoes.  On the other hand, root lesion nematode numbers tend to vary more from field to field and are heavily dependent on what you have in rotation.

A few quick points regarding the effect of rotation crops on Verticillium and root lesion nematodes:

  • Most crops can host root lesion nematodes; however, some are much more preferred hosts (ie. potato, corn, soybean, red clover) than others (ie. barley, oats).
  • The only crop we’ve seen that is a complete non-host to root lesion nematodes – and causes numbers to go down – is forage pearl millet.  For high nematode fields, this is a great option.
  • Grass species (ie. barley, wheat, ryegrass, timothy, etc) do not appear to host/multiply Verticillium.  Broadleaf species (ie. potato, soybean, red clover) are the primary targets for Verticillium.
  • Sorghum sudangrass has been shown in some studies to reduce the amount of Verticillium and/or improves the ability of other soil microbes to out-compete Verticillium.  We are still working to confirm those studies in PEI, but it has been associated with reducing the symptoms of early dying.
  • Local data from the past number have years appears to show that red clover is a major host of both root lesion nematodes and Verticillium.
  • Other options for battling early dying include biofumigation with mustard, Velum Prime to kill root lesion nematodes, and Elatus for control of Verticillium.  I have seen better local research numbers for the first two of these options.

Long story short:  get your fields tested to know how big of a problem you are facing, and then adjust your crop rotation to address issues you may have.  Feel free to reach out to me to discuss how to do the sampling, interpreting your test results, and looking at rotation options.


Pest/Disease Update:

  • Spore Collection with Air Spore has concluded for the majority of participating farms.  Only 5 farms are still getting spore trap results.
  • No late blight spores have been found to-date in PEI, NB or Maine this season.
  • Early blight spores have now been largely non-existent for a couple of weeks.
  • Bortrytis (grey mold) spores are high in certain areas and appear to be higher in PEI than in New Brunswick.
  • Lots of fields are not effectively dead due to the lack of rain, while others (seed, table) have been topkilled in recent days.
  • Scab is certainly an issue in certain varieties/fields.  Also hearing about increased wireworm damage on early digs this year over the past couple of years.


Looking Ahead to Harvest:

A few things to think about as we move closer to the harvest season:

  • Safety should always be your #1 priority.  Ensure that all staff have proper footwear, proper protective equipment, and proper safety training in advance of harvest.
  • Disinfection should also be a high priority for all farms.  Any equipment coming on to your farm should be thoroughly cleaned/disinfected before use.
  • For any potatoes harvested before October 15th (assuming a normal fall), consider using a fall cover crop.  There are so many advantages to having a cover crop on your field, even if it only had a limited window for growth.  Make sure you have your cover crop seed lined up now.
  • If you are growing some of the newer varieties (ie. Dakota Russet, Clearwater Russet, Mountain Gem), you will need to pay extra attention to potato handling.  Many of these varieties are more susceptible to bruising/cracking than Russet Burbanks.  Make sure your equipment has necessary guards/let-downs in place and minimize drop heights everywhere.

Finally, Morgan and I will be getting into gear on fall sampling right away.  We have a lot of potato fields to sample as well as soil sampling to do for a number of projects.  If you have a field in a trial with us, please give one of a call before harvesting/plowing/seeding to ensure that we can collect all necessary samples in time!

I am still looking for some growers interested in doing fall hilling with a cover crop this month – give me a call to discuss.