Where are we now: Joe

Hi, I’m Joe!

For those of who are new to AaE, let me introduce myself.

I’m Joe Ballenger. I’m a single dad, and I really like to climb when I’m not working.

My background is physiology. Specifically, I’ve done a lot of genetics and physiology, and I look at the nuts and bolts of how things work. In the past, I studied insect viruses, I’ve looked for proteins which kill insects, and now I’ve changed tracks and I’m using these skills to look at how weeds hurt crops.

So how does that work?

What’s Joe Doing Now?

Shade Avoidance1

Joe’s currently studying shade avoidance. When plants are exposed to certian kinds of light reflected off other plants, they grow in a way that’s kind of bad for crops (right in both cases) because they put more resources into stems than yeild.

This year has also been a big year for me, as well. I decided to leave my job in industry, and not only go to grad school, but study a whole new group of pests.

There’s actually a lot of cool stuff going on in the field of weed science. New herbicides are hard to make, and as a result, herbicide resistance is…kind of a problem.

 

In the field of weed science, we’ve got to figure out how weeds work. More importantly, we’ve got to understand how plants fight each other so we can understand how weeds damage crops.

You’d think this is obvious. That yield loss due to weeds is from competition to nutrients, right?

So…it turns out that crops can never really recover from weed damage, and we don’t know why.

So, first, let’s talk about how plants damage each other when they fight. It all boils down to a simple equation:

W+P+N+A+S+Y+E = Lost Yield

W: Competition for water. Some plants are just better at getting water than others.
P: Competition for photosynthetically active light, which we should probably call shading.
N: Competition for nutrients. Some plants are better than crops at grabbing the things they need.
A: Allelopathy. Plants will actually produce poisons which kill other plants. This is really hard to prove in the field, though.
S: Shade Avoidance. Light reflected from other plants will cause crops to invest in growing taller, instead of putting resources into yield. This is what I’ll be talking about for most of this post.
Y: Plants need other critters, symbiotes, to help them get more nutrients. These are probably disrupted during plant fights, but we don’t know for sure. Or whether it’s a problem. It’s probably a thing, so I add it because I think it’s worth looking into.
E: Everything else we don’t know about.

Shade Avoidance

20190104_142759

I’m using, like, so many 5-gallon buckets.

My PhD project is to start ranking various parts of the WPNASYE equation, because we’re eventually going to have to start breeding plants to become resistant to weeds. It’s pretty reasonable to think that some of these are going to have a bigger impact than others, and that they’d interact in pretty weird ways.

So we decided to start with shade avoidance; yield loss from reflected light. It’s really hard to keep plants growing close together from reflecting light at one another. So if we can understand how light reflected from other plants influences growth, and how that growth influences yield, then we can use that to compare to other aspects of competition.

You can think of that reflected light as a kind of a waste product…almost a kind of poop. Plants absorb certain types of light while they’re photosynthesizing, and the light that’s reflected from other plants has a high amount of what we call far-red light which is almost invisible to our eyes.

20190516_090149

Yeah, we can just lift these suckers right out of the bags. Real weed control isn’t that easy, though.

We started by doing an experiment which more or less simulated weeds sprouting and weeds being removed at various points in the season. It turns out that Kentucky bluegrass grows really well on top of trash bags, so we grew discs of grass around the beets so they’d reflect light without growing roots.

To make a long story short, it turns out that shade avoidance is responsible for roughly 30% of yield loss.

Oh, and it turns out that the yield never recovers. Even after simulated weed control.

Right, so, let’s back up a little bit.

Weed Control

SizeComp

This is the kind of difference we’re talking about, visually speaking. These beets were planted at the same time, in field studies, with the one on the right grown around grass similarly to the plastic bag method. 30% is…actually a lot.

We’ve known for awhile that you can’t fertilize or irrigate your way out of weed damage. Lots of systems are irrigated, we use a lot of fertilizer on crops…so if these were the biggest issues, we’d be able to water and fertilize our way out of weed damage.

In 2009, a group of scientists led by Eric Page published a paper which implied that there was something really weird going on with corn. If corn plants sprouted with weeds surrounding them, they were always just kind of…small. It’s really hard to grow corn in this kind of experiment all the way through to harvest, though..so they couldn’t get yield data.

Wyoming is a big sugarbeet producing state, and sugarbeets produce about a third of the table sugar that’s used around the world. It’s also hard to get really good weed control in sugarbeets. They can get hurt by a lot of herbicides, and there’s a lot of weed resistance. This is a system where our tools are really limited. Sugarbeets are a great system for looking at weed damage, because we can grow them in buckets to roughly the same size we see them in the field.

So if weeds stick around until the plants have two leaves, sugarbeets lose one-third (30%!) of their yield right off the bat. If the weeds sprout after that point, they lose 7% of the yield. That 7% is potentially recoverable, but that 30% is gone permanently.

Shade Avoidance Root

This is the data from the first paper Joe participated in. On the left, is us simulating weed removal. On the right, is us simulating weed sprouting. The labels (GDD) are a measure of temperature accumulation over time; the field season started at 0 and the typical harvest happens at 1200.

This shows us something that’s kind of…shocking for a few reasons.

See, the entire idea behind weed control is that the plants will recover if we do weed control. If a grower doesn’t do weed control, and ends up losing a third of their yield…that changes A LOT of economic calculations. Probably means a lot for invasion ecology modeling, too.

There’s also a plant biology consideration here. It’s always been assumed that the plants will grow out of the shade avoidance growth pattern, eventually. The fact that this is fixed so early is…we don’t really understand it. Since getting these results in sugarbeets, we’ve been working on confirming this in a third species.

So it looks like there’s actually two shade avoidance responses, and the one we didn’t know about appears to be the more important one if we’re interested in crop yields. We also don’t know how this fixed pathway interacts with things like flowering time, or immune function.

There’s just…a lot of things we don’t understand about plant biology right now, and weed science is currently doing a lot of really cool science right now.

The Bottom Line

My background is in genetics, which means there’s a lot of things I can do. I’m an entomologist, and I’ll still be writing about insects. However, I’m also a virologist. And an ecologist. Now, I’m a plant biologist as well.

Eventually, we’re gonna have to breed plants to become resistant to weeds just like we do with insects. Every time we’ve considered breeding for this trait, the papers have always come down to plant architecture. Turns out…that’s really not that important. Not as important as what happens early in the plant’s life, anyways.

There’s a lot of issues with herbicides in the media, some which are accurate and some of which aren’t. At the end of the day, though, if we can’t keep up with the pace of plant evolution, we’re probably on our last generation of herbicides.

It’s a cool project; one which challenges me and lets me develop a different set of skills.

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