In part 1 of this series, I discussed the history of genetic modification in insects as pest control. We’ve been creating insect GMOs for the purposes of controlling pests for awhile. If you bombard insects with radiation, it can kill rapidly reproducing cells. High doses of radiation can also damage the DNA in quickly reproducing gamete producing cells to the point where it can’t be read, creating severe mutations that stop important proteins from being made. In other words, sperm are produced, but they aren’t healthy. If female flies mate with one of these males, she won’t produce any offspring. If this happens enough on a large scale, the population plummets because females aren’t producing viable offspring.
This technique has been used for years in various disciplines from medicine to agriculture. There’s always room for improvement, and this is no exception.
Vector borne diseases (VBDs) are generally pretty bad. Yellow fever, the disease which stopped the Panama canal dead in it’s tracks, makes your liver fail and turns you yellow… hence the name. Malaria is caused by a parasite which ruptures blood cells in unison. African trypanosomiasis makes you go to sleep and then die. Dengue fever lays you up in bed for six months in some of the worst agony imaginable. Hell, even veterinary VBDs are horrifying… outbreaks of rift valley fever usually present with random farm animal abortions.
In 2008, malaria alone killed 708,000 to over a million people, most of them young children in sub-Saharan Africa, and an estimated 190 to 311 million cases of malaria occurred worldwide, according to the CDC. Diseases like malaria, may actually work to keep poor regions poor. Control methods often do not reach the poorest people due to high cost… vector borne diseases tend to be diseases of poverty.
Check out this video made as a public service announcement in 1943 by Disney. Some of the control methods have changed, such as specific chemicals, but not that much.
So… what can be done to help save lives in regions with VBD problems? We can vaccinate, in those few cases where vaccines have been developed, and we can kill the vectors, but vector control efforts can be expensive. Education and awareness is great, too… let the locals know what the potential harm is and send them on search and destroy missions to remove insect breeding grounds.
But… and this is the cool part… we’ve got a new tool in our arsenal.
In Part 1 of Pest Control, I discussed what a pest was and how they were divided into categories as well as how those categories overlap. Identifying pests and how they cause damage is only one part of the puzzle. There’s another part of the puzzle that comes along when you start treating the crops and when talking about pesticides, it’s one that’s the most frequently overlooked. Economics need to be taken into account when treating crops because, believe it or not, going easy on the pesticides can actually be beneficial to farmers.
The latest paradigm for pest control in agricultural situations is called ‘integrated pest management’, which I’ll refer to as IPM from here on out. It takes an economical approach to pest management by sampling pests, looking at how they damage crops and what numbers of a pest are sufficient to damage a set of crops. This is much better than randomly spraying pesticides at anything which looks like it might be eating your crops because it takes into account how much money you’ll spend and save on treatments. It also encourages a conservative use of pesticides which not only lessens a pest’s exposure to pesticides and selection pressure for pesticide resistance but also lowers the amount of pesticides sprayed in the field. Although not all farmers use IPM (although most figures I see are well over 50%), it’s the best way to deal with pests because you know roughly how much money you’re saving by treating versus spraying randomly and you limit the amount of pesticides you spray on your fields.
Since I’m the resident entomologist on Biofortified, and because the main pests in almost all agricultural systems are insects it only makes sense for me to write something about pests and how they’re managed in agricultural situations. My role here on Biofortified is to write about the basic biology of pests, but I will be discussing management from time to time.
To say that insects are pests would be far too simplistic because of their sheer diversity. The two families of parasitoid wasps I’ve been discussing, the Braconids and Ichneumonids consist of about 180,000 species together. If you want something to compare this to, there are roughly 10,000 mammalian species. There are a lot of insects around us, and they all have different ecological roles.
While some insects feed on crops, others feed exclusively on other insects which makes them the enemies of our enemies and thus…our friends. Even in a monoculture system, there are interactions between pest animals, their environment and people. Understanding these interactions is key to understanding things like why we need pesticides or why your town is inundated with ladybugs every year.
In Polydnaviruses, Nature’s GMOs, I explained how polydnaviruses disabled host immune defenses through genetic modification. A post after that, I discussed how polydnaviruses use modified insect proteins to interfere with these systems.
So if you’re a biologically-minded person, there’s one question you should be asking yourself. It’s a rather important question because it’s answer could shed light on what makes these wasps species-specific, and this is essential for any biocontrol project.
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