Corn Detasseling

This is the season for corn. Corn is great to eat but it must be at least minimally processed from it's raw state in the field in order to be eaten by us humans.

Part of making corn plants edible for humans is detasseling. Detasseling is the process of removing the silky tassel from the corn so that it can be further processed for human consumption.


Machine Detasseling
Nearly all detasseling is done in two steps; the field will first be detasseled by machine and then detasseled manually. Machine detasseling is itself typically a two step process. Initially a detasseling machine called a "cutter" will go through the rows of corn to be detasseled and cut off the top portion of the plant. This is done to make the field more uniform so that a "puller" machine can come through the corn field a few days later and pull the tassel out of the plant by catching it between two rollers moving at a high rate of speed. This will remove a majority of the tassels.

Detasseling machines can typically only remove from 60 to 90 percent of the tassels in a seed corn field. This is far less than the 99.5 percent that need to be removed to produce the uniformity of seed desired by farmers. The main problems for the machines are that they are unable to adapt quickly to height differences in plants and they throw tassels into the air where they can become lodged in other corn plants and inadvertently allow pollination. It is desirable that the pulled tassel ends up on the ground to prevent this problem.



Manual Detasseling
Whether or not a field of seed corn is initially detasseled by machines, eventually people are employed to detassel the plants that the machines missed and to remove any tassels that the machines left in the leaves of other corn plants. This is done either by having "detasselers" walk through the corn field removing the tassels or by having detasselers ride though the corn field on a detasseler carrier. From eight to twelve detasselers are usually carried by each machine and these machines are typically employed when the corn is too tall to be detasseled from ground level.

Detasseling work is usually performed by teens; as such, it serves as a typical rite of passage in rural areas of the Corn Belt. (Byron 2002)(Gustafson 2003) For many teens in these areas it is their first job. Exact starting dates depend on the specific area of the country and the growing conditions of any given year. The detasseling "season" typically lasts from two to four weeks with work days varying from just a few hours to over 10 hours depending on the growing season. Wages for detasselers vary greatly depending on the seed corn company, the detasseling contractor, the experience of the detasseler and even the individual field conditions. Some detasselers earn minimum wage while others earn over $10.00 per hour. In addition to employing a large teenage workforce, some areas of the country employ migrant workers as detasselers.

Early 20th century

Detasseling was used in the late 1800s and early 1900s in the "ear-row" method of corn breeding. In this method alternating rows of corn are detasseled and the seed from the detasseled rows is saved for planting the following season. However, ear-row breeding did not result in large yield increases and was largely abandoned after a few years.(Wallace 1925, pp. 223)

Around 1910 experimental corn breeders became excited by the possibility of improving corn yields by crossing two high yielding varieties. Again, this was accomplished by planting the varieties in alternating rows and detasseling one of the varieties. This method of seed production also proved disappointing and was also abandoned.(Wallace 1925, pp. 224)

However, from this early work in cross breeding, developed the modern hybridization process where one inbred line of corn is crossed with another. In 1908, George Harrison Shull described heterosis, also known as hybrid vigor. Heterosis describes the tendency of the progeny of a specific cross to outperform both parents. In 1917 a process was developed that would make this hybridization commercially viable. In 1933 less than 1% of the corn produced in the United States way produced from hybrid seed; by 1944 over 83% was. (Copeland 1995, pp. 236) This hybrid seed is produced by crossing two inbred lines by planting a row of one inbred variety followed by several rows of a second variety. The tassels of the second variety were removed by hand so that the second variety could be pollinated by the first.

Late 20th century

Hybrid corn was detassled manually until the mid 1950's when a cytoplasm was discovered that would cause one of the inbred lines to be male sterile while the hybridized seed corn it produced would regain male fertility. This gene allowed seed corn companies to greatly reduce their labor costs by producing seed corn without the need for manual detasseling. By the mid 1960's nearly all seed corn was produced with this gene. (Basra 1999, pp. 52)

This situation was changed in 1971 with an outbreak of the fungus Southern Corn Leaf Blight. The cytoplasm used to produce male sterility was highly susceptible to this fungus. At the time approximately 90% of hybrid corn used in the United States contained this gene. (Smith 2004, pp. 601) About 15% of the corn crop was lost to infection and for the next few years male sterility was abandoned and nearly all seed corn was again detasseled manually. (Copeland 1995, pp. 238)

In the mid 1970's machines were developed to help reduce the large labor costs associated with manual detasseling and as a response to a shrinking rural teen labor force. In the 1980s male sterile varieties were reintroduced that were not susceptible to Southern Corn Leaf Blight, however the reliance on a single sterile variety seen in the 1960s has not been repeated. (Basra 1999, pp. 51-52)

Today corn hybridization is accomplished by a combination of machine and manual detasseling as well as male-sterile genes.
Courtesy of Wikipedia