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| March 23 | |
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What a dreary day! It has been raining on and off all daylong. But the
wheat doesn’t mind. The temperatures have been warm this week, but last week they
were about normal for March. The wheat is growing well and starting to cover the soil, so
there isn’t much soil exposed. In fact, with all that growth some farmers might be
tempted to let cattle graze the wheat, especially when
wheat prices (the price farmers are paid for each bushel of wheat they produce) are low. Do you notice anything funny about how the wheat looks in our area? Is it my imagination or does the wheat appear to be uneven with some yellowish spots? Do you see that yellow spot in the foreground of the picture? I think we have a problem! Let’s look a little closer.
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What’s the first thing you notice about this spot? The plants don’t have a healthy green appearance, in fact the leaves are yellowish. The next thing you might notice is the yellowish plants are stunted compared to the green plants around the spot. You might think these plants don’t have enough nitrogen fertilizer (nitrogen deficiency), but we saw the Spra Coupe apply nitrogen in February. This is an example of a disease called Barley Yellow Dwarf. Let’s look a little closer at some plants. |
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The plants are stunted. The leaves are yellowish, but some leaves are
purple. These are classic symptoms of Barley Yellow
Dwarf. This disease is caused by a virus, but the virus is carried by aphids, such as
greenbugs and bird cherry-oat aphids. When the aphids feed on the wheat, they inject the
virus into the plants and that causes the disease symptoms. This is a widespread problem this year, because we had such a warm fall and aphids seemed to be everywhere.
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The wheat in our area between the red flags isn’t showing any
symptoms of Barley Yellow Dwarf. It doesn’t appear to have grown very much, maybe an
inch or two. But you can see how much the wheat has grown over the past month by clicking here. The plants are continuing to form new
tillers (stems). Let’s look at the tillers.
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Here’s a closeup of the tillers. You can see small and large tillers. We are still trying to find that first node or joint on the stem. That will tell us the growing point (head) is above the soil surface and moving up the stem. We will be able to see the first node about one to three inches up the stem (from the soil surface). I don’t see anything, do you? Some tillers are pretty big. I think we should take a tiller and cut the stem with a knife to see if we can find the growing point. |
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The stem has been cut and you can see the white area on the left is the root system. As you look to the right, there is an area (in the middle of the picture) that appears to be hollow and then to the far right there is a spear-like structure. The growing point or head is the whitish area at the tip of the "spear". We don’t see a node or joint yet, but this is a stage that we look for because the growing point or head has moved about one inch from the crown area of the root system (This picture was taken with a camera mounted to a dissecting microscope.). This stage is called the hollow stem stage. It is important for farmers to recognize this stage because if cattle are grazing the wheat, they should be removed from the wheat if it is going to be harvested for grain. Otherwise, if cattle continue to graze the wheat, the grain yields will be reduced. |
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I found a larger stem that didn’t have a node yet and wondered where its growing point was. I took this picture with my camera without the aid of a dissecting microscope, but you can see that the growing point is about three inches from the crown area. I’m amazed this stem doesn’t have a node yet! It won’t be long now and most of the larger stems will be jointed. |
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