Why is ecology important to agriculture? Ask the Plataspids.

Before moving to the southern US, I lived in Iowa. If there’s one thing Iowa’s known for, it’s known for our row crops. Everywhere in the summer is green and pretty and filled with all sorts of farmland and not much visible biodiversity outside of that.
If you live in certain areas of the south, it’s really actually very similar. There are lots of rowcrops… peanuts and soybeans instead of corn and soybeans but still a similar concept. Lots of crops. Everything’s green and pretty without a whole lot of biodiversity. There’s one other major difference, though…lots of areas look like this:

Image courtesy of Wikipedia Commons

The green curtain draped over everything? Kudzu.
Kudzu was a vine originally planted to control erosion which grew out of control. It grows quickly, is hard to kill and covers everything with a green blanket and crowds everything out by keeping sunlight from reaching the plants. The trees under that green carpet are all dead.
So… how can things get worse?
Simple, really… just introduce something which lives on kudzu.

In 2009, a graduate student at the University of Georgia’s department of entomology found a very odd insect which resembled a beetle, but wasn’t. It had sucking mouthparts and a bunch of other features which landed it in a group of insects called the Heteroptera. The problem is that the insect wasn’t able to be identified with any of the keys available for the US. It was a new family which hadn’t been recorded in the New World before. The insect was eventually identified by another group of researchers as belonging to the family Plataspidae, and the species found was Megacopta cribraria, which lives on Kudzu but also on beans.
Megacopta species are known pests of various beans, including soybeans. From a recent review of Megacopta biology:

A number of authors report that Megacopta spp. are pests of soybeans. Soybean yield loss ranged from 1-50% depending on density of the bugs. The reported pest status ranges from minor to severe. As an introduced species, this bug appears to have potential to be a pest of legume crops in the United States.

They also invade houses during the fall while looking for a place to overwinter and can be smelled from some distance away, so they’re an urban pest as well.

The pest status of this species isn’t really certain; experimental crops infested with the species showed no apparent damage, I can’t find any information about thresholds for this species in particular and a lot of the information out there seems to be for the genus level and not this particular species so I can’t tell how well it’s been studied in it’s native range. There just simply isn’t enough information at this time to say if it’ll be apocalyptic, a flash-in-the-pan concern or something in between which is dependent on region, weather and/or biotype.
However, it’s considered a pest species in most of it’s range and this still presents a serious potential problem for soybean growers in the south because we now have a species that quickly reproduces, can grow to huge populations and which has a refuge which quite literally covers the entire south.
ResearchBlogging.orgD. R. Suiter,1 J. E. Eger, Jr.,2 W. A. Gardner, R. C. Kemerait,3 J. N. All,4 P. M. Roberts,5 J. K. Greene,6 L. M. Ames,, & G. D. Buntin, T. M. Jenkins, and G. K. Douce5 (2010). Discovery and Distribution of Megacopta cribraria (Hemiptera: Heteroptera: Plataspidae) in Northeast Georgia Journal of Integrated Pest Management

Joe Ballenger

Written by Joe Ballenger

Joe Ballenger is an agricultural scientist studying weed control at the University of Wyoming. He has a Masters degree in Entomology. He co-founded the successful Ask an Entomologist project!. In his spare time, he likes to cook and climb.

4 comments

  1. Do you know if the insects also prey on peanut plants? All three (kudsu, soy, and peanuts) are in the Fabaceae family and soy and beans are in the same subfamily so it seems that peanuts aren’t safe either. That’s not good at all. These bugs are really nasty looking too – kinda of like soft ticks which have to be some of the most disgusting creatures out there. Yuck.
    Kudzu itself is pretty horrible. I’ve seen whole valleys swallowed by the stuff, with trees and everything else dying under its shade. I wonder how it affects wildlife – can deer or other animals eat it? I’ve heard that it can be fed to cows. If it turns out to be a reservoir for a soybean and peanut pest I wonder if efforts to destroy kudzu will be stepped up.
    Wow. Way more questions than answers here, but thanks very much for the information! I’ve never really thought about how the local ecology could affect agriculture before, but this is an excellent example.

  2. This post was basically the culmination of me reading about Plataspids for about a day or so. I’ve been hearing about them all semester but not in a whole lot of detail.
    I’m not sure if they can feed on peanuts or so…most of the literature out there focuses on beans and such. I’m guessing that peanuts aren’t grown in a whole lot of regions where they’re a problem.
    I don’t know how kudzu affects mamallian wildlife and I haven’t read anything about insect fauna, but I can tell you that while sweeping kudzu the only things I’ve ever found are things which don’t actually eat plants and were probably only on there incidentally.
    I just got done compiling my insect collection, and here’s what I found while sweeping kudzu:
    Lauxaniidae, larvae live in decomposing plant matter, couldn’t find info on what they or the adults fed on (probably saprobes)
    Aedes albopictus, adults ectoparasitic, larvae acquatic
    Megacopta criberia, discussed above
    Dolichopodidae, adults predatory and found on essentially everything, larvae aquatic
    Coccinellidae, larvae and adults generally predatory
    Calliphoridae and Sarcophagidae, larvae and adults generally saprophagous but with some parasitoid species as well
    And that’s about it. With the exception of the Plataspids, nothing was really super abundant. The area around my apartment looks just like the picture above and there are plenty of deer, but I’ve never seen them eating.
    As for local environment affecting ecology, I think this might be an artifact of our different training. Entomologists are taught to look at famland as an environment with very low biodiversity and are taught in great detail about the interactions of it’s inhabitants.
    There’s another far less subtle example of local environment affecting agriculture, and that’s local pollination. Native pollinators are responsible for quite a bit of the pollination of crops in the US, about $3 billion or so.
    Here’s a link to The Xerces Society, a group which studies native pollinators with the intention of conserving them. Spend awhile reading about their projects. I think you’ll find their work really interesting.

  3. Joe,
    there is a considerable literature on invasive species. Typically, a new organism will arrive, establish small populations (or die out), then remain at very low levels with no one noticing its presence, until it reaches a threshold, when presto, its suddenly everywhere.
    Lots of agricultural and biological scientists, farmers, politicians and economists often pay scant regard to the ecological implications of their practices, often because they are so focused on their area of expertise that they fail to see the broader implications, or recognise them when they occur.
    A good place to start (and sorry for the Antipodean bias) is the Invasive Species Council – lots of good links.
    GM

  4. Human interference in the nature leaves ineffaceable traces. Let´s take as an example forest monocultures. They are all around us and their order and greenness tingles all hearts. These days we can hardly find a natural forest in Europe. How surprising that a stronger wind throws all of the trees down and a light snow calamity ends up in a complete catastrophe. Once balance in the nature is shattered, its “immunity” is shaken as well.

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