After the harvest – protecting food from rats, mold, insects, fire, and bacteria

Preface. It’s hard enough to protect crops before a harvest. In New South Wales, Australia a plague of millions of mice has multiplied after a bumper grain harvest and eating whatever they can find. Mice can produce 500 offspring a season (Glover 2021).

Mice, rats, and other pests can get into the post-harvest storage buildings in the U.S. as well and exponentially increase.  These are gigantic grain elevators, some so huge they can store enough grain for most of the U.S. for weeks at a time. These silos are highly energy-intensive and far apart, requiring legions of trucks hauling grain long distances and again for distribution. In 2020, the largest grain bin in the U.S. is about to be built in Mason city, able to hold 2.2 million bushels of corn. It will be 155 feet high, and 165 feet wide.  It will be subsidized by a federal program to encourage higher ethanol blends (15%) in gasoline rather than the standard 10% today.

To prepare for energy descent, while there’s still energy we ought to think about when, where and with what materials we can build thousands of much smaller, widely distributed storage silos.  Before oil, grain elevators could be found about 7 miles apart, the distance a horse could travel in one day hauling a heavy load of grain.

Alice Friedemann  author of “Life After Fossil Fuels: A Reality Check on Alternative Energy“, 2021, Springer; “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer; Barriers to Making Algal Biofuels, and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Collapse Chronicles, Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report

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Grain storage in the news:

NPR. 2019. Meet the Granary Weevil, the Tiny Bug Who Resides in Our Pantries. “If you store grains in your pantry, you’ve probably openED a package or jar to find tiny bugs living inside. It’s no accident that they’ve made a home in your pantry — they’ve evolved along with humans. Grain insects cause the loss of 2 to 5% of harvested grains in developed countries. That number shoots up to 50% in less-developed countries. For most of history, humans had only the tools of creating dry environments and tightly sealed storage to fight pests. Today, we have insecticides, sophisticated packaging, and even an “Infestation Destroyer” that uses centrifugal force to fling insects to meet their high-impact deaths.”    Okay, but in the future we won’t have the energy or technology to do this, again, this needs to be planned for to help our grandchildren cope with the future.


Peter Golob, et. al. 2002. Crop Post-Harvest: Science and Technology. Volume 1 Principles and Practice. Volume 2 Durables. Volume 3 Perishables.  Blackwell Science.


This is a book review of Golob’s book.  After reading it, I found it amazing farmers can grow anything, since crops can be destroyed by drought, wildfire, flood, insects, birds, snails, rodents, fungi, bacteria, viruses, hail, frost, lack of vital nutrients, too much pesticide, and so on.

But that’s only half the story, the story most familiar to everyone.  You’d think that once the harvest is over, it’s time to relax and celebrate.  Yet the crop is still not safe from harm, wherever it is stored it’s still susceptible to all of the above, plus spoilage and silo explosions. Civilization exists because our ancestors figured out how to store grain for several years to make it through bad harvests.

Before fossil fuels initiated the Industrial Revolution, 90% of the population was rural, unlike now, where over 80% of us in the United States are urban.  Most people spent a good deal of time preserving perishable food like meat, vegetables, and fruit by drying them out, or with preservatives such as salt and alcohol.  Canning didn’t begin until the early 1800s when Napoleon began using canned food to feed his troops.

Most people in the world got, and still get, the majority of their calories and nutrition from long-lasting food, mainly grains and beans.

Brian Fagan, in The Little Ice Age 1300-1850, described how hard it was to store a harvest to last beyond one bad harvest and for the next planting, even if barns were stuffed to the eaves and local lords and religious foundations also stored crops. It was usually impossible to keep mice and rats away or prevent spoilage. During this period of climate change, crops failed often from blazing hot summers, excessive cold, or torrential rain. Two or more bad years in a row happened every ten years.

In the 20th century, post harvest food technology was developed and enormous granaries were built that can store grain for many years. These modern granaries keep rodents and other pests out. Durables are fumigated or sprayed with pesticides to kill insects at all stages of their life cycle. Grain elevators keep durables cool and dry, vastly extending their storage life.

Post harvest technology preserves food after harvest and before delivery. Although transportation isn’t part of the discussion, it’s important to mention that the main reason famines stopped was the invention of the railroad. Areas with good crops could send their surplus to regions where crops had failed.

The length of time and amount of durables that can be stored with fossil-fuel built and controlled food storage technology is amazing. This technology has also made food safer to eat. Fossil fuels allow produce just harvested from the field to be cooled immediately, and kept cool throughout the supply chain, which makes it possible for us to enjoy fresh food year round — often produce that’s come thousands of miles before reaching our plates.

Golob et al’s Crop Post-Harvest volumes 1-3 are heavy textbooks that provide an in-depth look at the continuing war to get perishables to market and to preserve food. Both the old methods, still used in developing countries, and the amazing energy-intensive modern technology we’ve developed, are explained in great detail.

Humans are now using nearly all of the arable, ranch, and forested land on the planet, so preserving as much harvested food for as long as possible is our main hope of increasing food supplies in the future.

Why does good food go bad?  How durables like grains and beans are destroyed.

High temperatures and moisture are the enemies of harvested crops.  In places with both grain can spoil in months.

Temperature affects how quickly insects, mites, fungus, and mycotoxins develop and germination qualities are lost.  The biological activity of insects, mites, fungi, and the grain itself doubles for every eighteen degree Fahrenheit rise in temperature.  At low temperatures, insect breeding stops.

It’s hard for insects and microorganisms to survive if there’s no water, so low moisture is critical as well.  This is why it’s so hard to preserve fresh food for a long time — fresh food has a very high water content, i.e. on average, the percent of water in apples is 84%, turnips 92%, pork 56%, Beef 58%, and fish 81% .

Damage and cleanliness

Produce that isn’t stored sterilely is bound to be degraded by some biological agent.  Damaged produce provides a point of entry for secondary pests and saprobic fungi.  Attack usually begins with one or a few species followed by the invasion of a broad range of non-specific microorganisms and secondary insect pests.  Primary pests can also lead to quality losses since some insects feed on the germ region of seed, leading to a loss of nutrition or viability if planted.

Infection after harvest often occurs at the site of wounds from insect feeding or mechanical injury during the harvest.  The main insect pests in stored food are Coleoptera (beetles) and Lepidoptera (moths), as well as diptera, psocoptera, and dictyoptera.  There are also some bacterial infections of stored foods that can be serious, poisonous even, especially for those who are old, young or sick.


There are over 200 species of rodents that damage crops while they’re growing, but rodents haven’t coevolved with grain storage long enough yet – only 40 species of rodents prey on food stores.  Rodents can eat 10% of their body weight every day.  They reproduce quickly, so if even two of the opposite sex get in, it won’t be long before exponential growth begins.  Rats live about a year, can get pregnant at 3 weeks with litters of four to eight, and reach adulthood in two to three months.  You’ve got to go for 100% rat mortality or they’ll quickly come back.  Rodents do even more damage by contamination with urine and feces than the food they eat.

Rodents can cause extensive damage to storage structures.  They almost impossible to keep out – they can climb smooth surfaces, walk along wires, ropes, electric cables, etc.  They’re also good at digging and tunneling, can gnaw through anything less than 5.5 on the Mohr hardness scale, i.e. lead, aluminum, tin, etc, so structures need to avoid edges rodents can get purchase on to gnaw.  Some species of rats can jump five feet high, squeeze through 1/5th of an inch cracks, and swim long distances.

Birds and Insects

Birds not only eat grain directly from bins, but they’ll peck bags open.  Twenty pigeons eat as much as a human does.  Birds contaminate food and spread pathogens like salmonella and zoonoses.

Insects not only eat grain, but can affect the quality and taste of grain, affect the ability of making dough, and ruin the flavor.  In the USA, some areas are more likely to succumb to insects than others.  The highest risk area are the southernmost states, the lowest risk area are the states of South & North Dakota, Montana, Minnesota, Iowa, Wisconsin, Michigan, Oregon, Washington, Idaho, and Montana.

In developing countries, termites can devour wood storage structures.

Fungi, mold, and microorganisms

Fungi flourish when moisture is over 22%.  They can cause blemishes, blights, discoloration, and even wreak revenge in the next generation, when the fungi-damaged seed produces a diseased plant or reduced germination rates.

Molds can produce toxic myco- and afla-toxins making them unsafe to eat and of poor quality.

If rodents, birds, insects, mites, fungi, and mold don’t harm the stored grain, then bacteria, viruses, yeasts, nematodes, anthracnose, blight, blotch, brown rot, canker, scab, dry rot, hyperplasia, hypertrophy, leaf spot, mildew, mould, mosaic virus, rust, smut, vascular disease, wet rot, soft rot, and toxins are still a peril.

And more…

In addition to all the pests and diseases, grain can suffer from mechanical damage at harvest, threshing, or any point thereafter — while being hauled to market, and careless handling at the market.

Grain can be damaged if drying is done incorrectly, or through temperature extremes at any point.  Moisture over 10-14% will lead to deterioration from fungi and biological degradation.

If grain is harvested too early, it will be green and therefore have high moisture content, causing it to rapidly deteriorate in storage.  If harvesting is too late, the mature grain may be attacked by insects and microorganisms, or cracked from repeated rain and dry weather, making it easier for microorganisms to attack in storage.

Fresh produce

However hard it is to store durables like grain and beans, it’s much easier than fruits or vegetables, which must be delivered to the consumer quickly, often within days.  The new, high-yield varieties of produce have higher nutrition, but they also have greater likelihood of spoilage in storage.   Lack of plant nutrients in the soil affects the quality at harvest and the ability of the produce to store.  Nitrogen may be good for growth, but it can lead to problems in some produce in storage.

For example, ideally lettuce is picked when the temperature is less than 60 degrees Fahrenheit and cooled within two hours.  If kept cool, it won’t spoil for nine and a half days.  But if lettuce is picked when it’s over 75 degrees Fahrenheit and isn’t cooled down until ten hours later, spoilage will begin in two and a half days.

Produce is pre-cooled by evaporative cooling, positive ventilation with ice banks, ice cooling, forced air cooling, hydro-cooling, and vacuum cooling.

Both durables (grains, legumes) and perishables are sprayed with chemicals to keep biota from attacking.

Fumigants can be essential to killing insects as well. Since Methyl Bromide causes ozone depletion, there’s a race on to invent a new fumigant, but this isn’t easy because there are so many essential properties. Fumigants must be a gas at room temperature, good at diffusing, kill all stages of pests, not be greatly heavier than air, and not leave harmful chemical residues. So other, costlier, methods of controlling insects are being tried, such as airtight storage, vacuums, and carbon dioxide atmospheres.

This is a very small subset of what’s covered in these three textbooks, which go in depth into the details of plant physiology, how to measure important storage parameters, detect pests, a long list of specific pests and the damage they do, how to build storage structures, manage pests, preserve food, the chemical structure of plants and oils, milling grains, trade and international agreements, applied research and dissemination, food systems, how food is preserved in developing countries, and much, much more.

Conclusion – Energy descent implications

If you’ve ever driven through the Midwest, you’ve seen enormous grain elevators from miles away.

These are built to protect against theft, rodents, birds, and insects.  They’re designed to keep the durables stored within as dry and cool as possible, by preventing cold humid air from getting into the grain at night and keeping the roof from getting so hot that condensation forms.

Climate change will make harvests far less assured in the future, with more years between successful harvests, as Brian Fagan describes in “The Little Ice Age”.  Research into how to store food after harvesting for long periods is essential to prepare for the double whammy of extreme weather and declining energy.

Long distance fresh produce will be the first to vanish from grocery store shelves as energy declines, but as Marion Nestle points out in “What to Eat”, the longer it takes food to reach market, the more nutrition is lost.  Locally produced produce is far healthier.

One solutions is to fund more research into low-energy, potentially manual post-harvest storage of durable crops ought to be increased.   Currently, modern storage technology is very energy intensive, and favors large farms over small farms because:

  • Small farms are expensive to include in horizontal and vertical supply chains
  • Small farms can’t meet as stringent quantity and quality demands as large firms supplying food to markets
  • Fruits and vegetables are hard for smaller or medium farms to deal with – they need special packing and refrigeration equipment to cool down the produce, transport it, and large growers can afford the computer-controlled deep irrigation systems, intense fertilizers and pesticides, and sophisticated packing plants to keep produce cool throughout the entire supply chain.
  • Small and medium farms don’t have the money to keep up with the latest research on hygiene, health, aesthetics, development, and marketing
  • The cost to build and operate high-tech storage structures is huge

Because agriculture, infrastructure, and western civilization are so dependent on fossil fuels, many writers have concluded the best way to lower suffering as energy declines, and to make as orderly and peaceful a transition as possible, is for millions of families to go back to land.  Clearly most families would prefer to be independent small farmers on their own land rather than poorly paid seasonal workers.

I hope, but doubt, there is funding for engineers and scientists to figure out the best ways to adapt existing infrastructure each step downward on the energy curve.  In the case of post-harvest technology, one puzzle that needs to be solved is how to continue using the enormous durable storage facilities we’ve built.  If long-term, it’s impossible to load half-mile-long 120-foot high grain elevators without fossil-fuel driven energy, then let’s start building smaller grain elevators and other post-harvest storage technology now, while the energy to do so still exists.


Glover E. 2021. The ground is just moving with thousands of mice: Australia hit by rodent plague. The Independent.

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2 Responses to After the harvest – protecting food from rats, mold, insects, fire, and bacteria

  1. zoe says:

    i hate to say it, but you are farting against thunder. i.e., you have no chance that this research is being/ ever will be, done in the public domain. but it was a very useful post to us believers who know that within the, probably, next 20 years, 80% of the population is going to be dead from starvation or, sooner, lack of water.

  2. Steve Bull says:

    I agree that taking advantage of surplus food production (surplus to immediate needs) is one of many ‘survival’ strategies that need greater consideration as we descend along the energy-contraction curve. I would also agree that we need to be focusing our ‘energies’ on small, local solutions and have to wonder what will be the future for those millions of sub/urban dwellers who have not only lost the skills/knowledge to feed themselves but have paved over a lot of the agricultural land that will be needed to feed future populations. The vast majority of the current 7+ billion humans seem to have painted themselves into a corner…