Illinois Natural History Survey - University of Illinois

Children Conduct Biological Control Research


Fourth graders from Leal School in Urbana, IL., weigh gypsy moth larvae to determine if microsporidian disease affects weight gain.

The gypsy moths (Lymantria dispar) that are found in the United States originated in Europe. They were brought to North America in 1868 by Leopold Trouvelot, an amateur entomologist and astronomer, who planned to use them to produce silk. The moths escaped from his house in Medford, Massachusetts, then multiplied and began killing trees. Today, gypsy moths are found mainly in the northeastern states but they can also be found in Michigan, Ohio, Virginia, and sometimes Illinois.

The favorite foods of gypsy moth larvae are the leaves of oak, willow, aspen, and birch, but they will eat the leaves of many other trees. Gypsy moths have become serious pests in the forests of North America. Pesticides can be used to decrease the gypsy moth populations but pesticides may kill other harmless insects. Some scientists are focusing on the use of natural predators and pathogens to decrease the populations of gypsy moths. Some entomologists are testing microsporidia, a protozoan pathogen group, as a weapon against the gypsy moth.

Our fourth grade class at Leal School in Urbana, IL, was invited to perform an experiment with one kind of microsporidium that was found in gypsy moths in Slovakia but does not occur in gypsy moths in North America. We agreed to help. First, we visited the laboratory to learn about what we would be doing. We were going to help with an experiment to study microsporidia. Each week, a group of three or four students went to the laboratory to perform part of the experiment.

For each of 7 trials, 10 gypsy moth larvae were fed micro-sporidian spores in 1 ml of water from a metal loop and 10 additional larvae were fed 1 ml of water without spores. We then weighed each larva by picking it up with forceps and placing it on a sensitive scale. We recorded the weights on data sheets and used a calculator to average the weights of the control larvae and the infected larvae. We learned that there should always be a control group in an experiment to compare with the infected group.

After weighing, we placed the larvae in plastic cups with food in them, one larva per cup. These were kept in growth chambers. The larvae were weighed again 7 and 14 days later. Forty-five days after treatment, the developmental stage of each insect was recorded and they were dissected to make sure that larvae fed spores were infected and larvae fed water were uninfected.

The difference between the average weights of the infected and control groups of larvae was insignificant at the beginning of the experiment. For six of the seven groups, the average ending weight of the infected larvae was less than that of the controls. We also found that more individuals in the control group went to the stage of pupa than did the infected insects. This was true in all but two groups in which the larvae, both infected and controls, all made it to the pupal stage. Of the 140 larvae that started the experiment, 4 died. Each of the four were a part of the infected group. Three larvae were killed by the use of forceps.

From this experiment, we conclude that the micro-sporidium slightly decreased the growth rate of gypsy moth larvae that were fed spores. In order to find out more about the effects of microsporidia on the growth of gypsy moths, we should do other experiments. We might want to change the timing of infection by feeding younger larvae or the amount of microsporidian spores fed to each of the larvae.

This article was written by the following Leal School fourth graders:

M. Barnes
S. Bowdry
S. Brown
S. Bruce
S. Denny-deWitte
M. Farrell
S. Ferguson
W. Fisher
E. Gennis
R. Hargreaves
M. Hostetter
R. Jackson
C. Lindstrom
A. Marlow
L. Masar
M. McMillion
L. Powell
L. Rose
T. Sayles
S. Skadden
R. Solter
J. Steenbergen
E. Swann
S. Swords
A. Walling
J. Weissman
M. Wolynes

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