HORT 5009, Pesticides in horticulture: their use and abuse,

Dr. Vera Krischik's Insecticide Section (Weeks 6-8, Feb. 21 to Mar. 7)

Lecture Syllabus 2007, Syllabus posted at http://www.entomology.umn.edu/cues/

 

Readings:

1. Honey Council Gaucho/Admire http://www.honeycouncil.ca/users/folder.asp?FolderID=49731a. Landmark, A. G.

2. Rortais, A., G. Arnold, M. P. Halm, and F. Touffet-Briens. 2005. Modes of honeybees exposure to systemic insecticides: estimated amounts of contaminated pollen and nectar consumed by different categories of bees. Apidologie. 36:71-83

http://www.edpsciences.org/articles/apido/abs/2005/01/M4053/M4053.html

 

Week 7 essay question:

Most of your answer to the question will come from the Honey Council, which is paper #1.

This paper by Rortais et al. 2005 is #2 and is difficult to follow, but it represents synthesis of years of research on whether imidacloprid can affect honey bee behavior and survivorship. Summary for use in your essay:

1. Rortais et al. 2005 is describing a new way to link toxicology work on oral LD50 to actual honey bee behavior and how much the different stages of honey bees eat. That is to try and determine cumulative amount of food eaten and then multiple that by the know amount of imidacloprid in those food items (nectar and pollen).

2. The authors describe in section 2 how much nectar and pollen is returned to the hive.

3. The authors describe in section 3 how much nectar and pollen is consumed based on the needs of the different stages of the honey bee: worker larvae, drone larvae, nurse bees, wax-producing bees, brood-attending bees, winter bees, pollen and nectar foraging bees.

4. The authors provide the data in section 4 on how much imidacloprid is found in the field in:

pollen (residual analysis): 3.4 microg/kg pollen

pollen returned to the hive in pollen traps outside the entrance of the hive: depends on amounts of contaminated pollen in the field

fresh nectar: 1.9microg/kg or 4.7 pg/mg sugar

honey: data not determined

The authors go on to calculate the amount of exposure per life stage.

worker larvae: in  5 days=0.28ng in nectar and 0.02ng in pollen

drone larvae in 6.5 days=0.5ng in nectar

nurse bees in 10 days=2.5ng in polllen

wax-producing bees in 6 days=0.5ng in nectar

brood-attending bees in 8days=1.3-1.9ng in nectar

winter bees in 3 months=3.8ng in nectar

pollen-and nectar-foraging bees in 7 days: 1-4.3ng nectar and 0.3-0.5ng pollen

5. In section 5 the authors weave this information together. The conclusion is on pg. 78 second column.

Nurse bees consume the most pollen and in 10 days can consume 2.5ng in pollen 

from Gaucho-treated sunflower and maize pollen which contains 3.4microg/kg imidacloprid.

 

Nectar-foraging bees consume the most nectar and can consume 0.15-0.61ng /day or 1.1- 4.3ng/ 7 days from Gaucho-treated sunflower nectar which contains 1.9microg/kg imidacloprid.

 

The acute toxicity of imidacloprid is a few picograms/8 days to 3.7ng/2 days. A picogram is one thousandth of a nanogram.

 

So the answer is yes, at published levels of imidacloprid in nectar and pollen it is possible for honey bees based on the needs of the different life stages to consume a lethal dose of imidacloprid. Also, sublethal effects on learning and orientation are published at 0.1ng/bee (Guez et al. 2001) and 1.25ng/bee (Lambin et al. 2001).

 

            Table on units of grams

1 kilogram (kg)

1000 grams  or 103

1 gram (g)

1000 milligrams or103

1 milligram (mg)    

0.001 gram  or 10-3

1 microgram (µg)

0.000001 gram  or 10-6

1 nanogram

10-9

1 picogram

10-12

 
 
1 mg/kg=1 ppm 
1 mg/g = 1000 ppm
1 mg/kg or mg/L = 1 ppm
1 ug/g = 1 ppm

1 ug/kg or 1 ug/L = 1 ppb

1 nanogram/g = 1 ppb

1 picogram/g = 1 ppt