A blog about science and religion from the viewpoint of a biology student in a state that's pretty much not on the map.

Thursday, September 25, 2008

Environmentally Friendly Pest Control: The Vedalia Beetle and Cryptochaetum iceryae

Biological control is exactly what it sounds like in a nutshell...that is, the practice of using organisms to control organisms. It's cheap and effective quite a bit of the time. Biological control depends on the density of the pests to be effective. The more dense the pest population, the easier time that whatever control organism used (predator, parasite, pathogen, etc.) will have finding it's victim. We have quite a few exotic pests that reach incredible population densities quickly such as the soybean aphid, the gyspy moth and the fire ant. All of these are susceptable to biological control (and I'll be working on articles detailing methods to control them with bacteria, nematodes, parasitic flies, wasps and ants at a later date ;)). However to explore biological control fully in context, we first need to go back to the beginning. The very first case where biological controls were investigated, implimented and showed results. We must also investigate a spectacular failure. We'll do both in the coming weeks.

Agriculture has always been important to the US economy. I live in Iowa and my hometown is surrounded by countless miles of cornfeilds. Currently, I really do live next to a cornfeild. Many of my classmates grew up on farms. Agriculture isn't just a cornerstone of the US economy, it's a cornerstone of the world's economy. After all, we need food to live.

Unfortunately for us, many insects love agriculture as well. And why wouldn't they-we grow big plants and pump as many nutrients into them as we possibly can. There aren't a whole lot of insects that can substist in an environment such as farms that almost completely dissapear every year and begin anew the following year. So most insects aren't actually pest species. However, there are about 600 (out of a few million or so) which become regular problems in the US.

Some of the most major pests are in the Homoptera. These insects have mouthparts which peirce the plant and suck sap out of it. Aphids are an example. It's not exactly the damage which most people associate with insects...most people think of insect damage as the skeletonization and bite marks we associate with japanese beetles or catterpillars. The damage isn't exactly dramatic or even obvious, but large numbers of these insects will remove enough nutrients to stunt growth and reduce yields.

So...back to agriculture. Back to the olden days of the 1850s. The California gold rush really helped to populate California. However, as the gold mines stopped producing people switched to agriculture. They experimented with nearly everything, including pesticides in an era when pesticide development was still in it's infancy.

Unfortunately as mentioned earlier, when you start growing large amounts of crops insects aren't far behind at all. And due to the fact of international trades, sometimes we have pests show up and we have no clue where they came from. These are the worst types of pests because many native pest levels are controlled by so-called natural enemies. Things like predators and parasitoids.

The specific pest which showed up was a bad one. Not just pain-in-the-ass bad...I'm talking large, prolific, armored and potentially apocalyptic for the then-fledgling citrus industry in California. The pest was called Icerya purchasi. It's a kind of scale insect...kind of like an aphid, but not.

Like an aphid, scale insects have the sucking mouthparts and damage plants in a similar manner. Unlike aphids, they're hermaphrodites...but they self-fertilize so males aren't really neccessary. The adults have a thick, waxy covering which can make control with pesticides difficult. Their young are mobile and the adults are sedentary. The young, known as crawlers, look for a nice place to hunker down and suck sap. The adults keep producing crawlers who can then spread by wind or by crawling from tree to tree.

The scale insects were devastating and threatened to wipe out the California citrus industry in it's entirety because they were so difficult to control. By this time, many entomologists were well aware of the fact that many of our pests were exotic. As far back as the late 1850s, Asa Fitch and Benjamin Walsh suggested using natural enemies to control exotic pests, however they weren't exactly vocal about the practice.

Charles Valentine Riley, a student of Walsh's was the Chief of the Division of Entomology at the USDA. He wasn't exactly a popular figure because of his aggressiveness and ambition. He traveled quite a bit, taking frequent trips to Europe which resulted in congress passing appropriations legislation to prohibit him from traveling.

So you need to find a solution to the exotic pest threatening the extinction of an entire industry, but you can't travel because you can't get the $2,000 to fund your expedition. What do you do?

Well, first you need some ecology 101. You need to know where to look and what to look for. Everything has parasites. Usually multiple parasites. Everything. Grasshoppers are parasitized by nematodes and tachnid flies. Aphids are commonly parasitized by parasitic hymenopterans. However, most parasites/parasitoids are pretty specific; they have evolved to feed on either one species or a narrow range of species. There are also predators that eat a narrow range of insects. Ladybird beetles (Coleoptera: Coccinellidae) are an example. But if you want to find these guys, you need to look for them in their native habitat because that's where these types of relationships will evolve. Many of our exotic pests here in America are not native to our country. They evolved elsewhere, got imported and then began to spread. C.V. Riley was almost certian I. purchasi came from either Australia or New Zealand because it was described in 1878 feeding on Acacia (yay taxonomy-I'm currently eyeing taxonomy as my feild of study...either that or insect evolution).'ve hit the books and you know that the populations of this pest are kept in check by natural enemies. You need to get around this whole travel thing. How do you do it?

Well, you ask help from the people you're trying to help. In that day and age, the citrus growers were wealthy, powerful and understandably desperate. Riley knew that he would need about $2,000 for his venture-and back in the day, this wasn't a small sum of money. But thankfully when rich people are desperate, they'll do almost anything to keep their lifestyles intact.

The fruit growers adopted a resolution in favor of sending someone of Riley's choosing to Australia to look for predators and parasitoids. They put pressure on their representatives, who used an international exposition in Melbourne as a way around the troublesome appropriations legislation.

Riley sent Alfred Koeble to look for I. purchasi in it's natural habitat and he eventually found two promising natural enemies-a tachnid fly called Cryptochaetum iceryae as well as a coccenelid which we now know as Rodolia cardinalis that fed exclusively on I. purchasi.

Back in those days, overnight USPS shipping didn't exist. I can tell you from experience (I raise tarantulas) that you should expect casualties when shipping things over long distances even when you're only using overnight to three day shipping. Most invertebrate dealers won't guarantee three day shipping. In this instance we're not talking about a three day journey on an airplane, we're talking about a cross-ocean voyage on a ship. Koeble constructed mini-insectaries on the deck of the ship and housed citrus trees infested with I. purchasi with the vedalia beetles to get them across.

Koeble sent about 12,000 of the tachnids and only 129 R. cardinalis. The tachnid flies proved to be less effective in controlling the beetles everywhere except in cooler climates. R. cardinalis, however turned out to be a voracious and effective predator. Those 129 specimens turned into about ten thousand, and then exploded to millions within a few years. Imports of citrus out of California nearly tripled, from 700 carloads per year at the peak of the infestation to 2,000 carloads per year. Not too bad for $1500.

To this day, the beetles and flies still do a pretty good job of keeping I. purchasi in check despite the fact they're competitors. The flies don't parasitize the beetles and the beetles don't eat scales infested with flies. The immature stages of C. iceryae are resistant to cold weather, which means they become active sooner. This also means that they can control I. purchasi in places like coastal California, where the vedalia beetle doesn't go through as many generations in a year due to the cooler temperatures. In the hot desert areas, the vedalia beetle is the dominant predator and in interior areas like Riverside, the vedalia beetle and C. iceryae switch off between spring and summer with the fly being the dominant natural enemy during the cooler parts of the year and the vedalia beetle being dominant during the warmer seasons.

L E Caltagirone, R L Doutt (1989). The History of the Vedalia Beetle Importation to California and its Impact on the Development of Biological Control Annual Review of Entomology, 34 (1), 1-16 DOI: 10.1146/annurev.en.34.010189.000245

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Wednesday, September 24, 2008

A lot of shit to get in for a couple ball pythons...

...I sincerely hope the tarantulas were rare.

Exotic pet smuggling is a problem for both hobbiests and environmentalists. Some of the worst ecological disasters result from introduced species of plants and animals. The people who regulate shipping into and out of countries know this, and this type of thing gives a bad rap to people like me who love to keep spiders.

I do keep spiders. I have about 50 or so. The species on my profile is called Phlogellius vulpinus (I believe it's now synomized with Selenocosmia vulpina, but I don't keep up on my taxonomy as well as I should). It's incredibly rare...less than 10 were in the whole US the last time I checked so that gives you an idea of what my collection is like.

I only buy captive bred. And there's a huge movement within the hobby for captive breeding programs for most species. Nowadays, mature adults are only imported a few times and then bred until it becomes uneconomical to import full grown adults.

Unfortunately, it looks like this package was headed for Sydney, Austraillia. Even though they have some of the coolest animals on the planet...pretty much everything endemic (including the spider in my profile pic). Unfortunately, this is a continent that has been hit hard in the past by introduced species and any action they'll take is pretty much justified in my eyes.

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Friday, September 19, 2008

Just checking in...

Hey...I know I said I was going to be gone for awhile, but I just wanted to log in and make sure everything's posting OK. Looks like it is, so I'll just be on my way after a quck update.

My tests went OK. I don't think either went spectacular, but that's to be expected for the first tests. I have two more next (not this coming) Tuesday.

I also have a paper about the biocontrol of the Uji fly (Exorista bombycis -it's a tachinid parasitoid that attacks silkworms) with hyperparasitic hymenopteran parasitoids (hyperparasitic = noms parasitoids). Unfortunately, I can't find any info on host searching or specificity (although they use M. domestica pupae to rear them in the laboratory) in two of the species currently being investigated. I still haven't exhausted all avenues of approach, though. Still need to search the databases for more recent information than I might be able to find on google scholar.

It's really at times like this that I really wish ID were a legitimate science. I can't find any information on how these specific hymenopterans find their hosts and it would be totally awesome if I could just write a paper on that using the standard ID argument from ignorance.

I mean, really. If we don't know how they identify, locate and determine if that host is of suitable size or has already been parasitized...can't we just assume that they're guided there by lesbian faeries? I mean...really. Think about the implications for biological control. ID would totally revolutionize the field.

There are, however other things I could write about so it's not like the assignment is in danger. I just happen to love hyperparasitoids so I just wanted to do a paper on them as a challenge to myself. Expect me to post it when it's done...sometime around the 30th.

Anyways...a few things I thought were kind of interesting happened in the past few days. Every year, we have these guys who come and hand out bibles in areas of the ISU campus where the areas of highest traffic are. They don't preach fire and brimstone and don't disturb anything because they really don't talk to anyone. They just kind of take up space. They're not anything like Tom Short so I don't have a quarrel with them...other than taking up space.

However despite their misguided attempts to convert the heathen masses, they did actually have an idea that I can get behind 100%. Surprising, I know. But true, nonetheless.

I saw this right outside the building where they hold the lecture for the evolution course:


You know...atheists and christians disagree on quite a bit. Apparently, we both agree that religious texts should be recycled. Global warming and all.

I gave religion up about the same time I stopped believing in Santa. Many of the people I went to high school with stopped believing in their respective deities when they stepped outside their families and started learning about the world. Who knows...when I become a professor, I might even keep one of these babies in my office for shits and giggles.

Anyways, after those guys had allowed people to fill our trashcans with bright green bibles the political fundies came about. Election season is right around the corner and they want you to vote, damnit.

Unfortunately, they're a bit smarter than the bible thumpers. Come about noon, there comes out a bevy of beautiful women holding clipboards. They sidle up to you, flash their killer smile, talk politics and ask you if you've registered to vote.

Needless to say, I've registered to vote five times this week. Once as a republican, twice as a democrat and twice more as an independent. And I don't even live in Ames.

Bible thumpers, take note.

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Thursday, September 18, 2008

Youtube Gems: Katy Rose

I have a science post coming up on Friday, thanks to the 'schedule post' function so I figured I'd do a music post this week.

This song is called Catch My Fall by Katie Rose and you can find the lyrics here.

The clips in the background are from the movie Thirteen which is about a young teenage girl (played by Evan Rachel Wood) who discovers drugs, sex, crime and numerous other bad things through the help of the 'popular girl'. It's a coming-of-age clique story, but it's the fucked-up version which shows the things you'll never see in a Lindsay Lohan film. It deals with drug addiction, depression and shows cutting as well as a handful of other things I remember seeing a couple of my friends going through back in my early high school days. The movie deals with it's themes bluntly and honestly without trying to glorify or euphamize anything which happens during the course of the movie.

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Friday, September 12, 2008

I guess the honeymoon is much for the afterglow.

So after an entire summer of waiting, I have my first round of tests this week. And another custody battle to go through.

So my next week is going to be a blur of bugs, chemistry, ecology, lawyers and dealing with all sorts of people I don't really want to see.

Anyways, I have a post scheduled to post on 9/21 and I've decided to start doing a weekly Best of Youtube post when I don't have a science related post to offer. So you'll have plenty of bug related shiny objects to keep you occupied until I return.

The first Best of Youtube, a video from the documentary Planet Earth about a parasitic fungus called Cordyceps.

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Tuesday, September 9, 2008

Larry Fafarman, AIG, The ICR and Poe's Law

The idiocy of creationists and people like the Discovery institute never fails to amaze me. Or amuse me.

I mean, they've peddled the same bullshit for decades without ever realizing that their arguments are, in fact bullshit.

Of course, they cover it up with dishonesty, bad arguments (specified complexity, anyone?) and just ad-hoc reasoning in general.

Of course, one of the most prevalent things that I've noticed is that they'll take any excuse to attribute their own faults to athiests.

The latest example is Larry Fafarman. You'll be familiar with him if you post over at scienceblogs. He's a persistant pest in the blogs of anyone who writes about evolution.

Anyways, it seems that Fafarman doesn't realize that The Onion is a fake newspaper that runs satirical articles.

He cites an article where athiests supposedly flocked to a stain that beared a resemblance to Charles Darwin. The article is meant at ridecule, but people frequently flock to the images of the Virgin Mary, Jesus and such. Rank hypocrisy.

It's bad enough that Answers in Genesis seems to think that every bigfoot hoax is proof against evolution. Even the ICR falls for things like April fools jokes.

The reason they do this is because they're simply not interested in honest debate. When they do actually participate in one, they generally get crushed under the weight of the evidence.

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Friday, September 5, 2008

Ever wondered what happens when an insect sheds?

Quite a bit of what I blog about is going to come from my entomology class notes. To me, blogging is a way to help me understand various papers by forcing me to read them and then regurgitate the information in a form that's easy for people to understand. This is no different.

Before I go into all the hormoney goodness that is the moulting process, first we need to understand exactly an insect grows and how it's body is set up.

An insect is covered in a shell called an exoskeleton. It doesn't look like it, but insects are basically wearing suits of armor. All the time. It's actually pretty cool, and it's great protection. In some cases, especially ironclad beetles but sometimes velvet ants, entomologists actually have to drill holes in the insect before pinning it.

The whole exoskeleton thing is great...but there's a problem. It's too damn good. The insect actually can't grow because the exoskeleton can't expand with the insect. The insect solves this problem by changing it's clothes. Here's an example. A larval cicada looks something like this:


Photobucket Yes...the pictures suck. I know. Blackberry needs to make a cellphone camera with a macro function.

So what, exactly is this exoskeleton made of? It's a polymer, kind of like plastic (but not). It's made of proteins and chitin. The insect's epidermis ('skin'), only a few cells thick, sits beneath it and is more or less attatched to it.

So...what makes that little bug turn into one of those things which scream for ladies at the tops of trees?

Well first specialized cells in the brain, called neurosecretory cells secrete a substanced called 'brain hormone'. The brain hormone then circulates in the insect's bloodstream, where it ends up in a gland at the front of the thorax (prothoracic gland). This gland then secretes another hormone called ecdysone (ecdysis=moulting). Ecdysone is the hormone that directs the various activities related to moulting.

The cells in the epidermis start rapidly dividing in response to ecdysone and becomes closely packed. The exoskeleton then seperates from the epidermis in a process called apolysis. At this point, a substance called moulting fluid is produced.

Moulting fluid contains all sorts of proteases and chitinases (protease=noms proteins, chitinase=noms chitin) which digest almost all of the old cuticle. The digested cuticle is then reabsorbed and recycled by the insect.

While the old cuticle is being digested, the new cuticle starts growing. There are several layers that are formed, but the important thing is that the outer layer is resistant to enzymes. When everything from the old cuticle is absorbed and when the new cuticle is complete, the insect actually sheds it's skin.

The whole thing is initiated by a hormone called eclosion hormone which is secreted by the brain. When the insect moults depends on the species. Some insects just moult when they find a nice, cozy place and some moult at specific times of days. Either way, the actual process is pretty similar through all insects.

The insect swallows air or water and raises it's blood pressure and this causes the exoskeleton to split along already weakened lines. The insect just kind of squeezes out, usually head and thorax first. After this happens, the insect expands it's cuticle by again swallowing air or water and using blood pressure to expand the cuticle. At this time, the cuticle is pale and soft and the insect is vulnerable. It soons hardens and becomes pigmented again. This process is controlled by another hormone called bursicon.

These hormones, and others are sometimes used in pest control. I'm sure I'll eventually write a post about those hormones, as well.

Here's what that little bug turns into, by the way:



Here's a time lapse video of the same thing:

Pedigo, Larry P., Rice, Marlin E. (2009). Entomology and Pest Management (6th ed). New Jersey: Pearson Education

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