Storms: Planning for more than just your chips

 

It may seem early to start thinking about downy mildew or some of those other nasty fungal pathogens that are sure to be coming our way soon. However, as storm systems make their way up the Eastern Seaboard they usually bring spores with them from diseased fields all along the coast. In addition to transporting spores to our province they usually provide ideal conditions for fungi to colonize plants as these systems often bring with them sustained wet, cool, and humid conditions.

Downy mildew was positively identified in New Jersey last week and while it doesn’t look like storm Bret and the newly developing storm Cindy will be tracking over Nova Scotia anymore, it’s important to monitor systems coming up the Eastern Seaboard to correctly time preventative fungicide sprays and other IPM techniques such as trapping and scouting for new pests and ensuring physical barriers such as insect netting are in place as needed.

Over the last 2 years downy mildew has become a serious problem for cucurbit growers here as it is devastating when it gets a foothold in your field. Over the last 2 years both of the first confirmed occurrences in Nova Scotia happened in August, however, we need to be prepared for earlier occurrences as it is only one storm system away once it is detected along the eastern U.S coast. Along with fungal spores, these systems can bring with them novel insect pests to be mindful of as well.

Please reach out to your commodity support specialists if you have any disease or pest concerns!

Click here for excellent information on effective disease management, fundamentals of fungicides, herbicides and using weather stations for decision making on your farm

here for more information on downy mildew in Nova Scotia

Tim

Cucurbit Downy Mildew was detected in New Jersey on June 13th, 2023

The first incidence of Cucurbit Downy Mildew was detected in New Jersey, United States on June 13th, 2023. Previously (in 2021 and 2022) Clade II has been detected in Nova Scotia, in the Annapolis Valley region, which predominantly infects cucumbers and cantaloupes. Clade I, which affects watermelon, pumpkin, squash, and zucchini has not yet been detected, but monitoring should still be undertaken in these crops on the chance that it does make an appearance.

It is important that growers remain vigilant and scout their fields regularly for this disease, as spores may be blown into the province by storm systems in the United States. We are not recommending protectant fungicides at this point in time, but strongly recommend weekly scouting for disease.  Downy mildew may be identified initially as water-soaked lesions that appear on the top side of the leaf, which may first appear on any region of the canopy. The most ideal time to identify these lesions are during or right after a heavy dew. The centre of the lesion initially appears chlorotic or yellow before eventually the tissue dies, becoming brown or necrotic (Fig 1 and 2). This disease is very fast spreading, the lesions will continue to spread across the canopy, and quickly kill the entire plant if left unchecked.  When conditions are humid, a “downy growth” may be observed on the underside of the initial water-soaked lesions. These symptoms may first appear before lesions on the upper leaf. This growth is particularly apparent in the morning, after a period of wet weather or dew formation.

Growers must stay vigilant, scout often, and report any positive findings they may see.

 

Figure 1: Chlorotic lesions associated with downy mildew infection on cucurbits.

Figure 2: Necrotic lesions associated with downy mildew infection on cucurbits.

If you suspect downy mildew in your field, please contact Dustin MacLean, the Field Plant Pathologist at dustinmaclean@perennia.ca or 902 324-9623.

 

 

Posted by Dustin Maclean, Horticulturalist and Field Plant Pathologist with Perennia

Whats New with Biological Control?

  2021 has seen a lot of new and exciting things in the world of IPM with some of the tools available to producers for managing pest populations. Please find a quick summary of some of these new developments below with their corresponding contact information – this is a list of curated material from various sources, credit must be given where credit is due!

1)Introducing Anystis, the new generalist predator in our toolbox

 Anystis is a new generalist predator which was discovered and trialed by Vineland Research and Innovation Centre. This predator has shown control over thrips and spider mites as well as suppression of aphid populations. Not only that, but it also preys on Echinothrips and mealybugs, which currently do not have effective options when it comes to biological control agents! Not only that, but Anystis is compatible with other commonly used biocontrol agents, meaning less stress about adjusting your current regimes and more success overall when it comes to targeting your problematic pests. 

The use of Anystis has been validated in commercial greenhouse trials on gerbera and sweet pepper in Ontario, and further supported by promising results generated through recent trials at Niagara College for use in cannabis to control aphids. The predator has been transferred to Applied Bio-nomics Ltd for scaling up the rearing system and commercialization, and have a limited number of mites available for growers to try.

For more information on Anystis, contact Rose Buitenhuis, PhD Senior Research Scientist, Biological Control at Vineland Research.

 

2)Slow-release method of nematodes

The current application of beneficial nematodes is limited to sprenches, or drenches, across the surface of the growing media. The biggest targets for beneficial nematodes are the larvae of fungus gnats and western flower thrips, as well as onion thrips pupae. While the product is quite effective, the current application method to the crop sees a few technical difficulties. These drenches/sprenches are not the most effective when it comes to penetrating deeper into the growing mix, and they must be applied on a weekly basis. Not only that, but the current methods of distribution sees a very poor storage capacity – all must be distributed at once, which leaves the small producers in a bit of a financial pinch!

E-Nema is a new tech company based in Germany. They have come out with a slow-release method for these beneficial nematodes which tackles some of the difficulties associated with the existing system. These look similar to tapioca pearls, and are designed to be incorporated into the growing mix before planting. Then, over time, they will slowly release nematodes through the entirety of your growing container. These pearls are very safe, and do not contain any harmful chemicals. In addition to that, they store quite well, which is a win for smaller producers who may not need massive volumes to be distributed all at once. The reintroduction and inoculation of low doses of nematodes has proven to be more effective than coming in hot and heavy with one dose during the cycle, and this technology allows just that! 

BioBee will be the distributer for this new product, so be sure to keep your eyes peeled for that! I want to give a huge shoutout to the Cannabis Cultivation & Science Podcast for keeping up with the biocontrol world and spreading the word on cool innovations like this one!

3)New rearing methodology for Phytoseiulus persimilus

Our old reliable predatory mite is coming at us new and improved! BioBee has re-evaluated their current rearing methods for persimilis and has landed on a product that addresses some of the downfalls to the original release system. The original system sees that the predators are reared on spider mites, meaning they come out of their sachets starved and ready to tackle some serious spider mites. While that works well in heavily infested crops, it doesn’t bode well for the low pest pressure grow room, or the preventative release strategy either. This new product raises the predators on mite eggs, meaning that each sachet will come with a variety of life stages, and each sachet will have a long-life span overall as these different stages progress towards adulthood. These sachets can see up to 12 days to release the contents, giving you almost 2 weeks of release from one purchase. The new food source sees that these mites are not as hungry as they would be when raised on spider mites. This means they have time to establish in the crop, as well as hunt down those low density mites that are scattered through the room. Not only that, but there is no carrier mixed in with these predators. This is a huge win for producers of heavily-trichomed crops, as their plants will no longer be littered with pesky lingering carrier bits.

Figure 1. An image of persimilis predating on a two-spotted spider mite. Photo credit: Biotactics Inc. 

This new persimilis can also be purchased in bottle form. But grower be warned! It was interestingly noted that these predators are not their characteristic red colour when you receive them from the insectary. That colour develops on the persimilis as they start feeding on spider mites. This acts as an added bonus when it comes to your scouting efforts. If you note which predators have transitioned from milky to red, you can get a sense of the pest pressure in the space and how effective your release was at managing the spider mite population.

I want to give a huge shoutout to the Cannabis Cultivation & Science Podcast for keeping up with the biocontrol world and spreading the word on cool innovations like this one!

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Posted by: Talia Plaskett

Cucurbit downy mildew!!!

Fig 1. Heavily infected cucumbers.

ALERT!  Downy mildew has been found in Cucurbit fields throughout Kings County!  

We are lucky here in Nova Scotia, we do not usually get downy mildew in our Cucurbit fields.  This disease is catastrophic - it can take out a field in a matter of days (Fig. 1).  It affects all Cucurbits: melons, watermelons, cucumbers, pumpkins, and squash.  It can very quickly breed fungicide resistance so rotating FRAC groups and following the label closely is key to management.  

Fig. 2. Downy mildew
sporulating on the
underside of a cucumber
leaf.  Sporangia can vary in
colour from light grey to
deep purple with a downy
appearance.

Monday's cool, drizzly weather has been perfect downy breeding conditions.  Abundant sporangia are produced if humidity is at 100% for 6 hours with temperature between 15-20˚C (Fig. 2). These sporangia are wind blown or splashed onto susceptible host tissue and germinate if leaves are wet for at least 2 hours at 20-25˚C.  Spores can also be carried on your tools, clothes and hands so DO NOT move from infected fields to healthy fields. Spores do not last indefinitely on non-host surfaces, for example exposing spores to sunlight for 4.5 hours kills 63% of the spores.  Spores can survive where there is moisture, for example on wet clothes or farm equipment, but needs living plant tissue to survive for any length of time.  It does not overwinter in our region.  This infection likely blew in from the Southern US.  

Fig. 3a. Early downy infection on
cucumber, leaf surface.

Pale green or yellow spots can be seen on the upper leaf surface as an early sign of infection.  These spots later turn brown and spread.  The spots are typically bound by leaf veins giving it a bit of an angular appearance, especially in cucumbers.  As the lesions spread, the whole leaf will turn brown and look like it's been zapped by frost.  

If downy mildew develops in fields nearby, but not in yours, use weekly rotations of Manzate + Zampro (FRAC group 40, 45) or Manzate +Torrent 400 SC (FRAC Group 21).  If downy mildew is present in your field, apply Phostrol (FRAC Group 33) or Orondis Ultra (FRAC Group 49, 40).  

For organic growers, if you have downy, use copper.  If you don’t have it, Serenade Opti (44), Serifel (BM02– cucumber only) with a liberal dose of prayer.

Fig 3b.  Underside of cucumber leaf.

For all pesticides, be sure to read the label carefully, and follow exactly.  If the label differs from what you read here, always follow the label.  Up-to-date labels can be found here.  

Do you know about Perennia's Pest Management Guides?  Every year we update pest management options for the major crops in Nova Scotia.  A complete listing can be found here (click on Vegetable Crops for the drop down menu).

Fig. 4a. Older lesions of downy
mildew on cucumber leaf surface

Fig 4b. Advanced downy mildew
infection, underside of cucumber leaf.

Fig 5. For contrast, this is powdery
mildew on squash. Powdery mildew
sprays are NOT effective against
downy mildew.