Why do we need pest management?

posted in: Science | 2

Bt cottonEverybody needs to eat. Agriculture is the cornerstone of civilization, and by 2100 we’ll need to be a lot better at agriculture because there may be as many as 11 billion people on this planet. Unfortunately, agriculture is also extremely inefficient. For every 100 lbs of food which could potentially be harvested, only about 30 lbs is used by consumers. Some of this is waste, but a lot of this is pest damage.

This is the main challenge for an agricultural scientist: Of 100 lbs of food grown around the world, 70 lbs of it is lost along the way on average. Of those 70 lbs, 35 lbs of that is lost in the field before harvest. If every farmer stopped all pest control measures, that number would increase to 70 lbs of food lost before harvest. Without any additional increases in efficiency between field and table, we would need to increase the amount of land used for agriculture by 30%…or by 136 million acres.

Our biggest animal competitors for food, fiber and shelter are insects. Insects attack food products at various points in the production chain. The examples which spring most readily to mind are those which attack plants in the field, but insects also attack food while it’s being stored. On average, pest and disease losses in the field are between 20 and 40% depending on the crop. In storage, 10-15% of the crop can be lost to pests and the value of the harvest can be dropped by up to 50% due to loss of quality. Complete losses of some crops aren’t uncommon either. Insect infestation also leads to other problems by encouraging the growth of mold that produces aflatoxins, so the losses due to infestation can lead to larger losses due to a loss of quality. While this secondary problem might sound minor, aflatoxins are among the most carcinogenic substances known and are thus one of the biggest and most persistent public health challenges.

Damage to raspberry by D. suzukii. Arrows indicate maggots. Image from here.
Damage to raspberry by D. suzukii. Arrows indicate maggots.
Image from here.

To give one very specific example…you might have noticed the increase price and decreased quality of summer berries this year. That’s because a recent invasive species, Drosophila suzukii, has been scaling its way up the eastern United States. Although it has been in Hawaii since the late 1980’s, by 2010 the fly had been spotted in North and South Carolina, Louisana and Utah in addition to Michigan and Wisconsin. D. suzukii deposits its eggs in summer berries like blueberries, raspberries, and blackberries. The maggots eat the flesh of the fruit, but seem to leave unnoticeable damage until the berry is broken into which exposes many the little wriggling maggots. As you can imagine, this makes the fruit unmarketable. In 2008 alone this fly was responsible for $500 million worth of damage, and some farmers lost 80% of their crop. It’s possible that other countries will refuse to buy our fruit out of fear of accidentally introducing this pest, so there are economic consequences beyond yield loss. In order to protect the livelihoods of these farmers, someone has to figure out how to manage this pest and lots of research has gone into understanding it’s basic biology.

Agricultural scientists work towards solving these problems by developing better tools for controlling insects. In some cases, insects can be controlled by making the environment really tough to live in through the use of biological controls. In some cases, this isn’t a feasible option and insects need to be controlled through other means. If we didn’t control insects, we would have to choose between widespread starvation, exorbitant food prices, or increased environmental destruction…and this is not a choice anybody wants to make.

This post is a modified version of a post written by Joe Ballenger and Nancy Miorelli which originally appeared on Ask an Entomologist titled Why do Entomologists Kill Insects? A Non-Taxonomist’s Perspective.

If you’re curious about insect biology, you can submit a question for the Ask an Entomologist blog here.

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Joe Ballenger is an entomologist who works in the biotech industry as a contractor. In his spare time, he helps answer questions about bugs at Ask an Entomologist.https://askentomologists.wordpress.com/

  • André

    Many thanks for this post. Most useful.

    My impression is that the world is not paying sufficient attention to losses to pests (i.e. Production that is achievable but does not materialize in the output). When you read FAO’s page on Food Loss and Food Waste (http://www.fao.org/food-loss-and-food-waste/en/), you may wonder whether the problem is understood, or even identified.

    FAO also has a –nicely made as usual – brochure on the Global initiative on food loss and waste reduction (http://www.fao.org/3/a-i4068e.pdf). The chapter « The impacts of food loss and waste are multifaceted » starts with: « Food loss and waste have negative environmental impacts because of the water, land, energy and other natural resources used to produce food that no one consumes. » I would have thought that FAO – whose full name includes the word « food » – would have started with a reference to the lost opportunities to feed the (currently) 7+ billion.

    But, may be, this is understood in another silo of the FAO structure.

    This seems to be good reading :

    « Crop losses to pests », E.-C. Oerke

    http://www.nrel.colostate.edu/ftp/conant/SLM-proprietary/Oerke_2006.pdf

  • Mike

    “This is the main challenge for an agricultural scientist: Of 100 lbs of food grown around the world, 70 lbs of it is lost along the way on average. Of those 70 lbs, 35 lbs of that is lost in the field before harvest. If every farmer stopped all pest control measures, that number would increase to 70 lbs of food lost before harvest.”

    I’m not sure the math works out here.

    If 70 lbs are lost with pesticide use, the lost before harvest accounts for 35 lbs of that, and if removing pesticides increases the lost before harvest value to 70 lbs, then what happens to to other 35 lbs not lost before harvest? If that number remains the same (i.e., 35), we are losing more than we are producing (70 + 35 = 105 > 100, impossible scenario) or that number is also affected by pesticides, but in a positive way (i.e., removing pesticides decreases our food waste/loss during and/or after harvest).