The Effect of Trichoderma harzianum on Honey Bee Survival

return to The Effect of Trichoderma harzianum on Honey Bee Survival, CONTENTS

DISCUSSION

All experimental hives in both treatments lost weight during this test. One reason for this weight loss was that a few hives in the test were so strong in the final days of the experiment that they swarmed, reducing total number of bees in the hive and causing a reduction in overall hive weight. The second and more important reason for hive weight reduction was that during the third week of the experiment some hives in both treatments, and surrounding hives not involved in the experiment, experienced substantial bee death typical of pesticide poisoning. Since the hive weakening was not confined to just the test hives we tried to determine the cause of this death. Bees were collected from the weak or dying hives and sent to the New York State Department of Agriculture and Market in Albany, NY for pesticide residue analysis. Methyl parathion (Penncap-M) residues were found in these samples. It was later learned that an apple grower having an orchard within a quarter to half mile of our test hives had applied methyl parathion for leafroller control in his apple orchard. At the time of this pesticide application, clover was blooming in the orchard ground cover. As the bees visited the clover they pick up the microencapsulated methyl parathion along with the clover nectar and pollen and brought it back to their respective hives resulting in the weakening of the hives. Although it was unfortunate that this occurred during our test, bees from hives in both treatments were equally as likely to have visited the contaminated clover. Since the number of marked bees were already in natural decline at the time of the pesticide application and the majority of the brood was already established, we feel that this methyl parathion poisoning did not significantly affected the between treatment results collected on these two parameters. However the methyl parathion poisoning does explain why there was a reduction in hive weight at the end of this experiment.

In conclusion, the results from this experiment showed that there were no significance differences in the bee hive health parameters measured (bee longevity, brood size, and hive weight) between untreated hives and hives exposed to over 150 g of Trichoderma harzianum strain T.39 (Trichodex) over a 30 day period. Given the several years of observational data and the results of this experiment, we believe that T. harzianum does not significantly impact honey bee health and that the risk associated with bees visiting crops sprayed with T. harzianum formulations or exposed to the concentrated product of this biocontrol agent are minimal.

About This Site

These pages are maintained by the New York State IPM Program, part of Cornell Cooperative Extension. All material is protected by Section 107 of the 1976 copyright law. Copyright is held by Cornell University and the New York State IPM Program.