Effects of the insect growth regulator,

novaluron on immature leafcutting

bees, Megachile rotundata

Megachile rotundata

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tMegachile rotundata

ABSTRACT-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.

INTRODUCTION-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 alfalfaseed set by using permanentshelters with “bee nestingboards”, or premade cavities, near or in fields.

Cross section of an alfalfa leafcutting bee nesting board.

Reasons why M. rotundata are difficult to sustain in the U.S.:

Environmental factors Wind Rain Temperature

Insecticide use in alfalfa grown for seed

Lygus spp

About

the

most economically damaging insect

to alfalfa seed

Lygus spp

Most economically damaging insect to alfalfa seed

Several new chemistries have been released for Lygus spp. suppression•Novaluron•Acetomiprod•Flonicamid

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

THREE EXPERIMENTS:

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.

METHODS:= Provision Dosing = Four Novaluron treatments applied to M. rotundata provisions:• 10 times the field rate• 2 times the field rate• the field rate• ½ the field rateTwo controls used:• An untreated water control• A blank treatment

Field rate for Lygus spp.:12 fl/oz per acre using 30 gal/water per acre

This is equal to3 µl of Rimon 0.83EC in 1 ml water

= 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.

RESULTS= 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 more eggs and 1st-2nd instars died compared to older larvae for all treatments.

= Adult Dosing =

= Provision Testing =