- Alfalfa leafcutting bees, M. rotundata, are themost common pollinator of alfalfa inthe 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.
The Alfalfa leafcutting bee, M. rotundata, is a-solitary, but gregarious, cavity-nesting bee.- M. rotundata, was introduced to North Americafrom Eurasia in the 1930s.- 1950-1960s, growers weresuccessful at increasing alfalfaseed set by using permanentshelters with “bee nestingboards”, or premade cavities,near or in fields. Cross section of an alfalfa leafcutting bee nesting board.
M. rotundataEnvironmental factors Wind Rain TemperatureInsecticide use in alfalfa grown for seed
About the most economically damaging insect to alfalfa seed Lygus spp
Lygus sppMost economically damaging insectto alfalfa seed Several new chemistries have beenreleased for Lygus spp. suppression •Novaluron •Acetomiprod •Flonicamid
Novaluron- An insect growth regulator thatdisrupts cuticle formation andprevents molting.- Acts by contact or ingestion, andas with other insect growthregulators, targets immature lifestages
1st and 2nd : are lab and fieldexperiments designed toassess mortality by applyingnovaluron to nectar-pollenprovisions and adults. 3rd: measured novaluron concentrations in provisions.
= Provision Dosing =Four Novaluron treatments applied toM. 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 acreTwo controls used:• An untreated water control This is equal to• A blank treatment 3 µl of Rimon 0.83EC in 1 ml water
= Adult Dosing =Adults were divided into two feedingtreatments :• 10% sugar-water• 10% sugar-water + the full field ofnovaluron= Provision Testing =• A small M. rotundata bee shelter with aremovable nesting block was placed in the centerof each cage, approximately 1m off the groundwith a southeast orientation.
= Provision Dosing = Mortality was significantly higher for all novaluron treatments compared to the blank and water treatments.
Fig. 2 shows that the treatment with 10x of the field rate is significantly higher than all novaluron treatments.Fig. 3 shows that moreeggs and 1st-2nd instarsdied compared to olderlarvae for all treatments.