A few thoughts on disease in seed crops

We grow quite a bit of our own seed, but our farm still buys seed from other seed companies. The high disease pressure that we face in our hot and humid climate keeps us from producing high quality seed for seed crops.  In some cases, the crop actually succumbs before producing any seed. More often, seed vigor and germination is simply compromised – adequate for homesteading purposes but dangerous for a commercial operation. And there is always the chance that the seed might become a disease vector for future crops. Still we haven’t given up on all these tricky crops. In many cases we have managed to prevail and produce seed we’re happy with.

These are some of the things that have done to improve disease control:

Plant spacing: Give crops more room for air circulation. My previous post on plant density began this reflection on disease management.

Row orientation: Planting rows parallel to the direction of the wind promotes air circulation and dries out plants. This usually means planting rows on an East-West axis.

Crop selection: It is easier to simply grow the types of crops that do it better in your climate. The easiest crops in Eastern Canada are those packed in nice protective containers:

– Seed protected in juicy wet fruit: Solanaceae (tomatoes and company) and Cucurbits (cukes, zukes, squashes and melons)

– Seed protected in dry seedpods: beans and peas, and Crucifers

Naked seeds of other crops (lettuce, beets, carrots, and oh so many others) are exposed to the humidity in the air and more disease prone.

Variety Selection: There is as much difference in disease resistance between varieties of the same crop as there are between different crop species. If you really want to grow a disease prone crop species, trial a number of varieties and choose those that fare best.

Climate Protection: It is possible to modify your climate to create a dryer seed-growing environment. Tunnels and other protective structures will keep plants free of precipitation. Be aware that this won’t eliminate all the ambient humidity.

Lettuce under Tunnel

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Lettuce under Tunnel
Lettuce Gone to Seed under Tunnel

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Lettuce Gone to Seed under Tunnel

Crop Rotation: Crop rotation is the only way to ensure you aren’t planting into an already disease infested location.

Crop Protection Products: Organic certification does condone the use of some products to control fungal and bacterial diseases (notably copper based sprays). These do work and can salvage a seed crop. But Organic systems work best when you rethink your whole farm system as a first line of disease control and keep sprays (even if they’re organic) as a backup.

So, if you’re having problems with a seed crop, you can reorient  your crop rows, adjust your planting density or improve your crop rotation. You can also trial different varieties and experiment with crop protection. As a last resort, you can use crop protection products. BUT  until you’ve figured out a system that works, only grow small amounts of a trouble crop. 

Of course, disease is only one thing that makes a difference. Coming soon: when to plant to make sure your seed crop matures in time.

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