Vegetable Diseases

Vegetable Diseases

Part of Ep. 1906 Grow Local, Eat Local

If you grow vegetables, you need to be on the lookout for diseases that can affect your crops - not only for this season, but next year as well.  Plant pathologist Brian Hudelson teaches us how to identify problems, and what to do to prevent them from happening again next year.

Premiere date: Jul 13, 2011

TRANSCRIPT+
Wisc Gardener Transcript: 

Shelley Ryan:

Now that we've got you all excited about planting vegetables, whether it's in a community garden or your own backyard, now it's time to talk about the down side. I'm with UW-Extension plant pathologist Brian Huddleson to talk diseases. You're favorite subject.

 

Brian Huddleson:

My favorite subject, that's right. We're here in a local Madison backyard home garden. We're seeing basically the results of what we see in a lot of gardens, which is a lot of crowding that tends to create conditions that are really favorable for a lot of diseases to develop.

 

Shelley Ryan:

We have small spaces, sometimes we have to use them.

 

Brian Huddleson:

We have to use them efficiently and that can be a problem from the disease point of view.

 

Shelley Ryan:

What are we looking at? We should mention this is a late-season garden.

 

Brian Huddleson:

That's right.

 

Shelley Ryan:

So it's too late to do anything now.

 

Brian Huddleson:

So what we're going to emphasize is what you watch for, how to identify the diseases. Then what we're going to try to do this fall and next spring to prevent these diseases from being a problem next year.

 

Shelley Ryan:

The first step is to know what it is.

 

Brian Huddleson:

That's right. What we're dealing with here on this poor tomato plant, is a Septoria Leaf Spot, which is probably the most common of the leaf diseases that we see on homegrown tomatoes in backyard settings. It's a fungal disease and it causes these little tiny circular spots, very bleached in the center with kind of a dark ring around the edge.

 

Shelley Ryan:

Even the browning here, too?

 

Brian Huddleson:

Yeah, that's caused by the fact that you get so many infections in a leaf that the leaf tissue just collapses.

 

Shelley Ryan:

It dies.

 

Brian Huddleson:

It dies basically, and the fungus is producing spores here and reinfecting the plant. Usually where this comes from initially is if you have old little bits of plant tomato debris from last year. It's coming up out of that plant debris. Spores are coming up. It moves from the bottom of the plant up, and by the end of the season you typically end up with a plant with no leaves. Usually the stems are still there, fruits are still there, but you don't have any leaves left.

 

Shelley Ryan:

Is it killing the plant or affecting production?

 

Brian Huddleson:

It's affecting production. Smaller fruits, fewer fruits that sort of thing.

 

Shelley Ryan:

We still need to do something about it, because it is affecting production.

 

Brian Huddleson:

Right, and what we normally recommend is good fall clean up to try to get rid of as much of this contaminated debris as possible. Next year, do good rotation and move your tomatoes to another area of the yard.

 

Shelley Ryan:

Somewhere else.

 

Brian Huddleson:

What I would suggest to keep these spores from moving up from the soil would be to mulch. That provides a physical barrier, just to prevent those spores from getting up out of the soil. Then definitely, you may want to prune your plants a little bit to open up the canopy to provide better air flow, because you don't the plants to get wet and stay wet.

 

Shelley Ryan:

Actually, more space you might get more production from less plants.

 

Brian Huddleson:

Very true. The other thing you have to be careful with, is don't overhead irrigate. Don't use your sprinkler to water. You want to use a soaker that goes at the base to get that moisture into the ground rather than onto the leaves.

 

Shelley Ryan:

The other disease I'm hearing a lot about is late blight. What does it look like?

 

Brian Huddleson:

It could look very similar to this. But typically what you see is a more lethal disease. It will kill the plants, oftentimes within about three to seven, to ten days. It's very, very quick. It oftentimes moves in from the top of the plant and works its way down. Those spores are coming in, usually, from another location, not locally in the garden.

 

Shelley Ryan:

You can actually see that on the fruit, too?

 

Brian Huddleson:

You will see it on the fruit. What you see with late blight on fruit is usually a fairly large-size infected area. It is usually leathery and brown. It has kind of a wavy pattern, like growth rings of a tree, around the edge that are very, very distinctive.

 

Shelley Ryan:

That's not what you've got in your hands.

 

Brian Huddleson:

It's not what I have here. I found another little fruit rot in this particular garden.

 

Shelley Ryan:

Oh, wonderful. This is called Anthracnose Fruit Rot. You can see very discrete circular areas that are sunken. As they age, they get this black discoloration in the center. That's the fungus producing spores again.

 

Shelley Ryan:

So, whether it's Late Blight or Anthracnose here, can we eat them?

 

Brian Huddleson:

I would not recommend that. It's not recommended to eat any infected fruit.

 

Shelley Ryan:

Again, good fall cleanup, crop rotation, mulch, and no overhead watering.

 

Brian Huddleson:

Definitely, for preventing this sort of disease on tomatoes.

 

Shelley Ryan:

Now we're moving to one that's fairly new that you're real excited about.

 

Brian Huddleson:

Yeah, we first saw this disease in 2010. This is what is called Basil Downy Mildew. You notice as you come up to this plant, that it's very yellow.

 

Shelley Ryan:

I thought it was just a variety.

 

Brian Huddleson:

No, this is due to the disease. The leaves are very cupped, and if you flip over the leaves, you can see all of this kind of grey powdery material. That's actually the pathogen producing the spores.

 

Shelley Ryan:

Can I eat it?

 

Brian Huddleson:

I would not recommend that. There's even green stuff on here that I might typically recommend, but that even on the back on some of the green leaves you can see that the fungus is already present. I would be inclined just at this point to leave this plant alone.

 

Shelley Ryan:

Oh, no pesto for me!

 

Brian Huddleson:

Unfortunately, no.

 

Shelley Ryan:

What do we do about this?

 

Brian Huddleson:

Again, I would recommend no overhead watering, thinning of plants, good spacing, so you get good airflow. That will help prevent this disease. There are also fungicide treatments. You can get copper containing products that would be labeled for vegetables that you could potentially use as a preventative for this disease. You put them on before you see the symptoms.

 

Shelley Ryan:

So, if we see it this year, plan ahead for next year.

 

Brian Huddleson:

Plan ahead for next year, that's right.

 

Shelley Ryan:

We'll have more information on our Website, and we have a link to your Website.

 

Brian Huddleson:

That's right, and we have a lot of fact sheets on diseases like these and others, as well, that you might see in your vegetable garden.

 

Shelley Ryan:

Let's go look at one more that's one of your favorites.

 

Brian Huddleson:

My favorite diseases, that's right. This is a Powdery Mildew, which is a very common disease on cucurbits, so cucumbers, squash, pumpkins, that sort of crop.

 

Shelley Ryan:

Sure, but usually I see it like all over the plant, Brian.

 

Brian Huddleson:

Yes, this is a light case. Normally it can get severe enough it will cause a lot of leaves to brown.

 

Shelley Ryan:

What do we do about it?

 

Brian Huddleson:

This is definitely a disease that you can deal with if you have good plant spacing and get good air flow.

 

Shelley Ryan:

You have a recipe for a solution, and we will have that on our Website, too.

 

Brian Huddleson:

It's a spray treatment that you can use as a preventive treatment.

 

Shelley Ryan:

It's back to, basically, our list of what we need to do when we see these things this year, what we do next year.

 

Brian Huddleson:

Good fall clean up. You want to rotate your crops. You want to space them properly. Good mulching techniques. And then finally, don't overhead water.

 

Shelley Ryan:

Okay, thanks, Brian.

 

Brian Huddleson:

You're Welcome.

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