Report on the Agricultural Experiment Stations, 1952 Page: 59
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RESEARCH ON USEFUL AND DESTRUCTIVE INSECTS 59
of principles first established in fundamental research at the agricultural
experiment stations, and out of close collaboration between station
entomologists and scientists of the chemical industries. Combined
with the new equipment and methods of mechanized crop production,
chemical insect control methods have become striking examples
of advances currently being made in farm technology.
Studies on the nature of useful insects have been continued. These
have led to improved practices under which some insects are used to
control other insects or mites. For example, insects known as dusty
wings are encouraged to feed on mites that attack citrus orchards.
New facts are also coming to light with regard to the use of honey
bees as pollinizers for grassland legumes. Examples of results from
such research are here presented.
Honey Bees Increase Grassland Legume Seed Yields
Research on honey bees and legumes at a number of the State experiment
stations points to a need for increasing honey bee populations
in fields of legumes during bloom to insure good pollination for seed
production. Bees were found to be essential for good seed crops of
several legumes in studies made by the Oregon station. Crimson
clover to which bees had access produced 6,917 seeds from 100 heads
compared with 508 seeds from 100 heads when bees were excludedmore
than 13 times as many. Hairy vetch with bees made 390 seeds
and without bees 118 seeds from an equal number of pods. No seed
was produced by red clover and birdsfoot trefoil unless bees were available
The Iowa station determined the relation of distance from beehives
to pollination of red clover by honey bees. During two seasons the
number of seed set declined as distance from the hives increased. Seed
yield in the clover field maintained a relatively high level as far as
500 feet away in one year and as far as 350 feet away the next year.
At these distances pollination dropped to a definitely lower level, and
from there on declined gradually. The results indicate that under
Iowa conditions hives of bees should be placed throughout clover fields
in groups 600 to 900 feet apart, and half that far from the edge of the
field, for maximum pollination and seed set.
In its research on the pollination of sweetclover the Texas station
obtained an average yield of 130 pounds of seed per acre in cages
from which bees were excluded in an experimental field of second-year
Madrid sweetclover. Sweetclover varieties apparently are self-fertile
to a certain extent. Adjoining cages in which bees were enclosed
averaged nearly double this amount, although bees confined in cages
do not work in a normal manner. Adjacent open plats, with approximately
two-thirds of a hive of bees per acre, averaged three times the
seed yield obtained from cages without bees. An experimental field
of second-year Evergeen sweetclover yielded 33 pounds of seed per
acre in cages from which bees were excluded. Adjoining cages provided
with bees averaged 2.5 times this amount. Open field plats, with
slightly less than one hive of bees per acre, averaged 3.5 times the
yield of the check plats.
Research on the pollination of Ladino clover by the South Carolina
station revealed that in screened cages from which pollinating insects
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1952, book, January 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5990/m1/61/: accessed March 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.