There has been a lot of press related to pollinator health recently.
Some information suggests that certain fungicides when used during bloom can affect the health of honey bees.
This is a complicated problem and to understand this complex issue we need to appreciate the detailed relationships between chemicals, pollinators and pest management needs.
Research is on-going, and we do not know all of the details yet.
We do know that there are many species of solitary native bees, wasps and moths that also play an important role in pollinating many crops.
The susceptibility of these pollinators to fungicides and insecticides during flowering varies by pollinator species and pesticide.
For example, a recent trial at Penn State Ag Research Centre in the USA showed that the Japanese orchard bee was 26 times less susceptible to contact by imidacloprid than the honey bee, but 12 times more susceptible to acetamiprid. Both products are neonicotinoid insecticides and in the same pesticide class.
Fungicides thought to be safe
Fungicides had previously been thought to be quite safe for bees.
For decades we’ve known not to apply most insecticides during bloom. Now it’s thought that the combination of some fungicides tank mixed with some insecticides may synergize their toxicity.
The neonicotinoid insecticides (Group 4A) can be used pre-bloom in some crops. Because they are systemic and move through the plant tissues, residues have been found in apple pollen and nectar at low levels where they can be ingested along with fungicides even though these insecticides were not sprayed during bloom.
This systemic movement can also be found in some fungicides to varying degrees which helps their efficacy against disease (Apple Scab/Black Spot kick back products).
Spraying at night may help with many pesticides as they are less toxic when dried, but not with systemic pesticides that are ingested in the nectar and pollen.
Measuring movement of insecticides
Work at the Penn State Fruit Research and Extension Centre has measured the movement of most registered neonicotinoid insecticides into the pollen and nectar of apple from the pink (balloon) stage.
They found that some neonicotinoids are less toxic to bees than other compounds of the same class, as some are less systemic with little movement into the nectar and pollen.
They did find, however, higher levels of some fungicides in the nectar and pollen from the same pink application timing.
(continued next month)
See this article in Tree Fruit July 2016
