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United States Department of Agriculture

Agricultural Research Service

Pollen: Nothing to Sneeze At

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Animated graphic of a sneezing flower. Pollen: More than a Sneeze.

Agricultural Research Service (ARS) palynologist (one who studies pollen) Gretchen D. Jones in College Station, Texas, thinks there is a strong connection between pollen and what an insect eats. That's valuable information because it can tell us a lot about how far an insect travels--and when it's best to spray crops, for example.

Photograph of an adult western corn rootworm searching for pollen on corn silk.Pollen appears as tiny grains in the male parts of flowering and cone-bearing plants. For some people, pollen means allergies. During the spring, for example, these people may start sneezing uncontrollably from the pollen of blooming flowers, grasses, and trees.

Allergies--sensitivity to certain substances--may be triggered by dust, mold spores, pollen, dandruff, hair and some foods. Asthma and hay Graphic of Dr. Watts, a scientist with a light bulb for a head. fever are allergies that often begin in childhood.

Some USDA scientists are studying pollen to track the movement and feeding habits of insects. Photo of an adult corn rootworm moth.Scientists examining moths and butterflies found that pollen "sticks" to various body parts (eyes, nose, antennae and legs). The corn earworm has been found to have pollen from the flowers of citrus, like oranges and grapefruit and honeysuckle, on its body parts. Pollen also has been found in the insect's digestive system after feeding on these plants.

Photograph of a citrus pollen grain.How far do insects migrate? Pollen can provide evidence of how far some insects travel. Pollen from Texas ebony and citrus was found on corn earworm moths captured in Oklahoma. Since these two plant species are not found in Oklahoma, the corn earworm moths must have eaten them in an area in Texas or Mexico and then traveled more than 500 miles to Oklahoma.

"Knowing that an insect migrates into a particular area is important for two main reasons," Dr. Jones explains. "First, it can help farmers avoid spraying their crops with pesticide before the insect has even arrived. Second, by knowing where the insect originally comes from, it's possible to fight the pest there, rather than wait until it has migrated into a crop field."

In either case, the information helps farmers use as little pesticide as possible.

Animated gif of a flying bee. Honey, made by honey bees, is an important food throughout the world. The raw materials of honey are pollen and nectar (pronounced "NECK-tar"). Pollen is the bee's source of protein, and nectar is its source of carbohydrate.

Changes in climate can be determined by studying pollen taken from the soil of lakes. Pollen falls onto the soil and into lakes throughout the year. Each year, another layer of pollen is added to the pre-existing layer. As the vegetation changes, so does the pollen that's deposited in the soil or lake. Climate changes can be determined by comparing the pollen found in the layers to the climate in which the pollen-producing plants grew.


Did you know that scientists can be detectives and
solve crimes by using pollen as evidence
?

Animated graphic that says "Search."During a European vacation along the Danube River in the Austrian capital of Vienna, a man disappeared, but his body could not be found. The police had no evidence to link a suspect with a possible crime until they searched the suspect's room and found a pair of boots with mud still attached to the soles. The mud was examined and found to contain pollen from modern spruce and willow.

Based on the pollen evidence, only one area where the suspect must have walked was pinpointed. Only one location, a small area 20 kilometers north of Vienna along the Danube Valley, had soils that contained the precise mixture of pollen in the mud. When confronted with the evidence, the suspect confessed his crime and showed the police where he had killed the victim and buried the body.

Today, the country of New Zealand leads the world in the use of forensic palynology (the study of pollen) and the acceptance of this type of evidence in courts of law.

-- By Linda McGraw, formerly, Agricultural Research Service, Information Staff


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Last Modified: 2/14/2011
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