Effective control of plant health problems depends on knowing the cause. A wrong diagnosis can be expensive and damaging, such as spraying insecticides to control a fungus disease or applying fertilizer to crops stunted by virus.
Scientific advances have greatly improved pest identification. But many extension workers have yet to benefit, particularly in developing countries. Improving access to diagnostic laboratory services would help but wouldnât solve everything. Analysing disease samples is costly and takes time. Farmers need to act quickly when valuable crops are threatened â and thereâs no guarantee that a lab will identify the cause.
Extension workers and farmers can do much with simple methods that donât require fancy equipment and advanced degrees. Conan Doyleâs Sherlock Holmes didnât have DNA testing but still he solved perplexing crimes. He elegantly defined his method: Â âwhen you have eliminated the impossible, whatever remains, however improbable, must be the truth.â Being a good diagnostician made him a famous detective.
Diagnosis is as much elimination as identification, whether solving a crime or finding out why plants are dying. Agriculturists are like detectives. They eliminate the âimpossibleâ by assessing the evidence, most commonly the symptoms of the the sick plant. Field diagnosis â recognizing and interpreting symptoms â is fast and cheap. Itâs also a neglected technique, one that deserves more attention and better training.
I had worked for some years on tree health problems when a Bolivian farmer asked me to look at his tomatoes: âThereâs something wrong with them and Iâm not sure what it is.â I had a look, but couldnât make any useful suggestions.
My attempt at field diagnosis failed not only because I had little knowledge of tomato pests, but because I didnât think like a detective. Afterwards, I thought about how I could do better and share useful tips with others.
Field diagnosis is thinking with your eyes. You begin by observing symptoms, comparing sick plants with healthy ones, incorporating farmer observations and other available information. Doctors write case histories, combining observations of symptoms and patient information. Once you have the evidence, you review the âsuspectsâ or possible causes in your search for the truth, as Sherlock Holmes put it.
I was on a field trip with bacterial wilt specialists who eagerly photographed a wilting tomato plant at an agricultural research station. Many were laboratory scientists with few opportunities to visit the field. Our guide from the research station was puzzled, then amused, as he explained that plants had not been watered for a day. The scientists had failed to eliminate drought as a possible cause.
Itâs important to diagnose sick plants cautiously. Thereâs often more than one possible cause for particular symptoms, and you may be unfamiliar with a crop, as I was that day in Bolivia. I recommend a simple method for starting a field diagnosis, one that I teach to to extension agents and agronomists to help them narrow down the possible causes.
Participants examine symptoms from a variety of plants and have to decide whether the cause is A (abiotic cause), B (biotic cause) or C (confused â a gentle way of saying itâs OK not to know something). The result of the ABC test suggests the next step and can have a practical use. Why spray a pesticide if the cause of a plant health problem is abiotic?
The ABC test helps participants understand what they know about the meaning of symptoms. By comparing their decision with the correct answer, they learn more about field diagnosis and become better at giving good advice. The ABC test also helps the teacher identify the need for additional training and information.
Does field diagnosis reduce the need for lab diagnostics? No. Field diagnosis has its limitations. You canât always find the âsmoking gunâ or identify the exact cause from symptoms. Sometimes I use a bit of modern technology, speedy and low cost, to help me in the field. I email photos to colleagues. The mobile phone and computer are my Watson: even Sherlock Holmes didnât know all the answers.
Here is some excellent advice on how to write clearly, especially for smallholder farmers.
Steven Pinker writes charming books on language and on the mind, where he manages to explain complex ideas clearly. He is so well read that he branched out and wrote an optimistic book on violence, explaining that regardless of what most people think, the world is getting more peaceful, and Pinker has the numbers to show it.
In most of Pinkerâs books at one time or another he ridicules what he calls the Â âpuristsâ who correct other peopleâs English. The purists are often armed with false rules of English grammar.
So when I heard that Pinker had written a style book on proper English writing, The Sense of Style, I just had to read it. Here was a chance to hear the master turn his hand at a genre he usually criticized.
Pinker confesses that he loves style books and has read quite a few. Of all Pinkerâs insights into good writing, one really stands out: the curse of knowledge. As Pinker explains, when a person knows something, she assumes, unconsciously that other people know it as well. People who write extensively on one topic may unintentionally leave out so much background that the paper is nearly impossible to understand.
When people write papers for their colleagues, they compress complex ideas into short, dense words and phrases (e.g. airport people say âbird strikeâ when they mean that an airplane hit a bird). This jargon makes technical writing clear enough for disciplinary specialists, but difficult for the rest of us.
Sometimes a common word takes on a new, jargonized meaning. For example, a market is a concrete place where buyers and sellers come together, to offer food and tools for sale from little booths. But in economics jargon, a market is an abstraction for any arrangement of buying and selling. A âland marketâ or âa water marketâ is an imaginary space. When writing for farmers who have not taken Economics at university, it is better to say âyou can buy this product in a shopâ than to say âthe stuff is available in the market or in a shop.â
When my colleagues and I teach technical writing, we weed out most of the agronomistsâ jargon, so the text is clear for farmers. We are useful editors simply because we are not cursed with the knowledge that our trainees have.
The best cure for the curse of knowledge, as Pinker explains, is to ask someone else to read your paper. You can never get completely into the minds of your readers, but you can show them your paper and ask them to read it, and comment. This is an especially good way to find out what parts of your prose are confusing.
For a long time at Agro-Insight we have helped people write one page fact sheets for farmer. We share a draft version of the fact sheets with farmers. We call it a âfarmer peer reviewâ. We learn so much from these reviews that many of our earlier blogs come from these experiences.
Getting someone, anyone, to read a draft of your paper usually helps you to avoid at least some of the curse of knowledge, because as Pinker puts it, that personâs greatest advantage is that they are not you. Technical writing does not need to be dumbed down, just made clearer.
Bentley, J. and Boa, E. 2013. The snowman outline: fact sheets by extensionists for farmers. Development in Practice 23(3), 440-448. Read paper Â âș
Pinker, Steven 2014 The Sense of Style: The Thinking Personâs Guide to Writing in the 21st Century. New York: Viking. 359 pp.
An invention often has no Eureka moment, but slowly evolves in the minds of several people. The McCormick Farm of Walnut Grove, in Virginia, honors the creativity of young Cyrus H. McCormick, the son of a prosperous farmer who, in 1831, invented the McCormick reaper, a wheeled contraption, pulled by a horse that cut ripe grain ten times faster than workers with scythes.
Timing was crucial for the reaperâs success. In the early 1800s, white and black Americans were settling beyond the first range of mountains, which for two centuries had marked a boundary between them and the Native Americans. By the 1830s, settlers were flooding North America, harassing and dislodging the Native people. The reaper was crucial for working this sudden windfall of land.
As a pilgrim to Walnut Grove, I hesitated in the empty, gravel parking lot, admiring two handsome stone buildings on a rolling, tree-studded lawn. This educational shrine to invention is maintained by the Agricultural College of Virginia Tech, a state university. One of the two buildings is a large, restored and fully functional flour mill, powered by a water wheel. In its day the mill was state of the art.
Next door, in a simple shop with a forge and an anvil, Cyrus McCormick invented his reaper that revolutionized agriculture. And he did it on a remote farm, on the far side of the Blue Ridge Mountains.
People love stories of the lone genius, maybe because it feeds a heroic image of ourselves. So the stories often bend the facts.
On the second floor, above the McCormick family blacksmith shop, todayâs pilgrims find a wooden box which hides a loudspeaker. A sign invites visitors to push a wooden button and listen to a recorded lecture. There was no guide and the site was empty, on a gorgeous Saturday afternoon in June. Agriculture is not very sexy anymore.
The recorded talk told an orthodox tale of how Cyrus invented the reaper in 1831, when he was only 22 years old, after just 6 weeks of work. Cyrusâs father, Robert, had spent his lifetime trying to invent a reaper, but had just abandoned the project.Â Cyrus had help from a master blacksmith, an enslaved African American named Jo Anderson, but the invention was all Cyrusâs. That was the story.
There was something missing from this gospel. What was the fresh insight that sparked Cyrus into bringing his fatherâs design to life? How was Cyrusâs design better than his fatherâs?
Later I read up, and found that other key people had been completely written out of the story. A Scotsman named Patrick Bell had invented a reaper in 1828, but never patented it, and some of his hand-crafted reapers were exported to America. Obed Hussey of Ohio patented a reaper in 1833, which was similar to the McCormick design. Cyrus didnât patent his reaper until the following year, 1834, although he claimed to have invented it in 1831. Later, the US patent office would come down on the side of Hussey, and refuse to renew McCormickâs patent, even though Cyrus did have the young Abraham Lincoln on his legal team.
Inventions often come from several people who are linked together, in collaboration or competition. Or as the Spanish proverb says: âsuccess has many parentsâ (El Ă©xito tiene muchos padres).
The reaper did have many inventors: Bell, Hussey, Anderson and both of the McCormicks, at the very least. But that does not diminish the reaperâs significance as an innovation. The functioning reaper would flood European markets with American grain, depress grain prices and spark mass migration of peasants to the New World. The reaper also allowed an individual to produce enough grain to sell most of it and make serious money. Wealth could now be earned through cereals and other food crops, not just tobacco or cotton. Later, other inventors followed the example of the reaper, and created more handy farm machinery.
Cyrus was a poorly educated farm boy who exaggerated his own accomplishments. His real genius, though, was as a salesman and self-promoter. After âinventingâ the reaper, McCormick dedicated several years to the familyâs foundry business before coming back to the reaper, making one copy at a time with his younger brothers and the familyâs slaves in the farmâs blacksmith shop.
At first, sales were hard-won. Cyrus sold 2 reapers in 1841, seven in 1842, 29 in 1843, but 50 in 1844, when he went to what is now the Midwest of the USA, and saw its vast potential for agriculture. In 1847 McCormick moved to the newborn village of Chicago, built a factory, and in 1848 sold 800 reapers. He was soon selling them by the thousands.
Cyrus was not a mechanical genius, but he showed real ingenuity in business. Â Cyrus travelled the plains with blank order forms for reapers, offering live demonstrations. He sold the reaper on credit.Â He used mass production in his factory, published illustrated newspaper advertising to sell the reapers, and offered warranties for the reapers. He sent out travelling salesmen and shipped spare parts to customers on the newly emerging railroads.
Cyrus was ruthless, and dragged many an opponent into court, often all the way to the Supreme Court. He was a loudmouthed supporter of slavery. When his underpaid factory workers demonstrated, a dozen police and protesters were killed at the Haymarket Riots in Chicago on 3 and 4 May 1886. These murders are commemorated every May 1, as International Labor day, in most countries of the world, although not in the United States. Even Joseph Stalin, hypocritically mourned McCormickâs victims.
Cyrus McCormick, ever willing to elbow competitors out of his way, amassed a great fortune, transformed world agriculture and founded a company that eventually became International Harvester.
This story has two morals. Good inventions come not from a lone genius, but from the minds of several people, who may collaborate by stealing each otherâs ideas and then viciously driving the other out of business. Secondly, social innovation, finding new ways to organize people, may be as important as new hardware.
Boorstin, Daniel J. 1965 The Americans: The National Experience. New York: Vintage Books. 517 pp.
Cocoaâs natural range spreads from Central America to western Amazonia. For centuries, smallholder farmers had grown cocoa in the shade of other trees, so the story went. But thereâs no reason why cocoa canât be grown in full sun once the delicate young plants are established. Large-scale farmers shade their young cocoa with banana plants or fast-growing legume trees such as Inga, which are then removed after a few years.
Ecuador was my first experience with cocoa. I learned that shaded cocoa was âgood for biodiversityâ. The shade trees sheltered the birds on their flights between North and South America, but ornithologists were concerned about full-sun cocoa. Thereâs a lot of cocoa planted along the migration route. The debate between shaded and sunny cocoa sounded like a morality play, with traditional, small farms and their bird-friendly shade trees pitted against profiteering plantation agriculture.
The grant proposal said that not enough was known about shade tree health. Better knowledge of their pests and diseases would protect the trees, the birds and biodiversity. Win-win-win. The real story was not so simple.
Driving around the western lowlands of Ecuador, with Jeff Bentley and John Stonehouse, we soon realized that shade trees were astoundingly healthy. I had this uneasy feeling that we were studying a non-problem. We ploughed on, visiting 21 farms, interviewing the farmers at length about their shade trees. We wrote up our notes separately and the tree health specialist (me), agricultural anthropologist (Jeff) and entomologist (John) compared what weâd seen. Slowly some light emerged.
We asked farmers why they grew shade trees though this wasnât what we had set out to do. But I relaxed a little as I realised that weâd done what my colleague Harry Evans had called âwrong experiment, right resultsâ. We were looking at shade trees in a naĂŻve, but fresh way. Early in our farm visits we noticed that many of the trees growing amidst the cocoa could not possibly be for shade. Orange trees, a common âshadeâ tree, were barely taller than the cocoa. Coconut palms had small canopies that cast little shade.
Few of the shade trees were survivors from the remnant forest, contrary to a popular stereotype. Most were planted by the farmers, whose main concern was making the most of the land. They grew trees in between the cocoa because it was possible to do so, not because they provided shade. The other trees increased their income through sale of fruit and timber.
We quietly forgot about tree health. Our sponsors appeared happy with the results. At the end of the study we decided that âshade treeâ was the wrong label for the other plants that mingled with cacao. Shade was not their main function. Jeff suggested âneighbour treesâ instead and thatâs what we called them in our report.