The study evaluated the effects of the insect growth regulator novaluron on immature alfalfa leafcutting bees, Megachile rotundata. In laboratory experiments, various concentrations of novaluron were applied to nectar-pollen provisions and directly to adult bees. Mortality was significantly higher for bee larvae developing in provisions treated with novaluron compared to the untreated controls. The highest mortality occurred at the highest novaluron concentration tested, 10 times the field rate used for Lygus bugs. Younger bee life stages, eggs and early instar larvae, experienced greater mortality than older larvae from novaluron exposure. Novaluron residues were detected in provisions for up to 15 days.

1. Effects of the insect
growth
regulator, novaluron on
immature leafcutting
bees, Megachile
rotundata

2. Megachile rotundata

3. Megachile rotundata
Background about

4. - Alfalfa leafcutting bees, M. rotundata, are the
most common pollinator of alfalfa in
the Pacific Northwest.
- GOALS:
- To evaluate novaluron toxicity to immature M.
rotundata using 2 different possible
mechanisms of exposure
-To assess immature mortality via treating
nectar-pollen provisions and adults with
novalurons.

5. The Alfalfa leafcutting bee, M. rotundata, is a
-
solitary, but gregarious, cavity-nesting bee.
- M. rotundata, was introduced to North America
from Eurasia in the 1930s.
- 1950-1960s, growers were
successful at increasing alfalfa
seed set by using permanent
shelters with “bee nesting
boards”, or premade cavities,
near or in fields.
Cross section of an alfalfa leafcutting
bee nesting board.

6. M. rotundata
Environmental factors
 Wind
 Rain
 Temperature
Insecticide use in alfalfa grown
for seed

7. About the
most economically
damaging insect
to alfalfa
seed
Lygus spp

8. Lygus spp
Most economically damaging insect
to alfalfa seed
 Several new chemistries have been
released for Lygus spp. suppression
•Novaluron
•Acetomiprod
•Flonicamid

9. Novaluron
- An insect growth regulator that
disrupts cuticle formation and
prevents molting.
- Acts by contact or ingestion, and
as with other insect growth
regulators, targets immature life
stages

10. 1st and 2nd : are lab and field
experiments designed to
assess mortality by applying
novaluron to nectar-pollen
provisions and adults.
3rd: measured
novaluron
concentrations in
provisions.

11. = Provision Dosing =
Four Novaluron treatments applied to
M. rotundata provisions:
• 10 times the field rate Field rate for Lygus
• 2 times the field rate spp.:
• the field rate
12 fl/oz per acre
• ½ the field rate
using 30 gal/water
per acre
Two controls used:
• An untreated water control
This is equal to
• A blank treatment 3 µl of Rimon 0.83EC
in 1 ml water

12. = Adult Dosing =
Adults were divided into two feeding
treatments :
• 10% sugar-water
• 10% sugar-water + the full field of
novaluron
= Provision Testing =
• A small M. rotundata bee shelter with a
removable nesting block was placed in the center
of each cage, approximately 1m off the ground
with a southeast orientation.

13. = Provision Dosing =
Mortality was
significantly
higher for all
novaluron
treatments
compared to
the blank and
water
treatments.

14. Fig. 2 shows that the
treatment with 10x of the
field rate is significantly
higher than all novaluron
treatments.
Fig. 3 shows that more
eggs and 1st-2nd instars
died compared to older
larvae for all treatments.

15. = Adult Dosing =

17. = Provision Testing =