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.
In Polydnaviruses: Nature’s GMOs, I wrote about how wasps use viruses to disable the immune defenses of their hosts. Braconid and ichneumonid wasps use a system that genetically modifies their hosts in order to shut their immune systems down.
So how does this all work?
A good system to use to describe how polydnavirus proteins work is the ankyrin/vankyrin pathways. It’s easy to visualize how they function and many other functions (Toll, Phenoloxidase silencing, etc) work in an indentical manner.
The wasps in the video below are most likely from the family Braconidae. These wasps make their living as parasitoids, growing within other animals and eventually eating them from the inside out. Their life starts as an egg which is laid in the caterpillar by a female. This egg may divide into many, many larvae which feed on the caterpillar from the inside by either eating the caterpillar’s fat body, it’s muscles or by drinking it’s hemolymph (which functions as blood). After they’ve completed their development, they simply exit the caterpillar by burrowing out of it and then pupate. A few weeks later, adult wasps emerge to fly away and look for other hosts.
So what makes Braconid (and Ichneumonid!) wasps so strange, and why am I writing about them on Biofortified?
Biofortified's volunteer authors are devoted to providing factual information and fostering discussion about agriculture, especially plant genetics and genetic engineering. The site is written by grad students, professors, and guest experts. Meet our authors on the Authors page.
Recent Comments