eFFECTS OF WHITEMARKED TUSSOCK MOTH (ORGYIA ...

COMPARISON OF THE EFFICACIES OF
OrleSNPV AND OpMNPV IN LARVAL ORGYIA
LEUCOSTIGMA IN THE LABORATORY AND THE
FIELD
Garrett Brodersen*, Renée Lapointe,
Graham Thurston, Chris Lucarotti and
Dan Quiring

Nucleopolyhedroviruses
• Nucleopolyhedrovirus (Fam. Baculoviridae)
• The viruses are ingested in “packages” (occlusion bodies), and are
released in the midgut when the envelope digests
• Viruses infect midgut cells and pass through into the body cavity where
they spread through the tissues, eventually killing the host.

Relevance?
• Contrary to many other forms of insect control, NPVs are
generally very host species-specific
• Successfully used in Brazil and China in agriculture
• Used in forestry to control Douglas fir tussock moth
(OpMNPV), Gypsy moth (LdMNPV) and Balsam fir sawfly
(NeabNPV) outbreaks in North America.

The Whitemarked Tussock Moth
• Polyphagous defoliator
• Range from eastern Canada to Manitoba
• Population explosions occur approx. every 7 years
• Susceptible to OrleSNPV and OpMNPV

General Objective
• Two viruses, one native to western North America
(OpMNPV) and the other to Maritime Canada (OrleSNPV),
are proposed for use in controlling the whitemarked tussock
moth
• OpMNPV has already been registered, but OrleSNPV has not
• The objective is to determine which virus is more efficacious
in larval WMTM

Laboratory Objectives
• Range-Finding Bioassays
– Find LC 50 (2 nd instar) and LD 50 (4 th instar) for each
virus
• Lethal Time Bioassays
– Find LT 50 (2 nd and 4 th instar) of each virus

2 nd instar WMTM larvae
were droplet-fed a range of
occlusion body (OB)
concentrations of each virus
for 15 min
LC 50/LD 50 Bioassays
4 th instar WMTM larvae
were left to feed on
artificial diet ‘plugs’ soaked
with a known concentration
of virus OBs for a day

• After feeding, larvae were placed individually
on artificial diet and checked daily for 10 days

Mortality at Day 10 Post-Infection
• In 2 nd instar WMTM larvae, OpMNPV’s LC 50 was 10x less than
OrleSNPV.
• No difference in 4 th instars

LT50 Bioassays
• 2nd and 4th instar WMTM larvae were fed LC/LD 85 of
each virus and checked every 12 hours for mortality rates

LT50
• POLO shows that LT 50 of OrleSNPV < LT 50 of OpMNPV (2 nd
instars); however, ANOVA showed no significant difference
• Both POLO and ANOVA showed no difference for 4th instars

Lab Summary
• The lab bioassays have shown that:
– OrleSNPV kills 2 nd instars half a day sooner
than OpMNPV
– OpMNPV’s LC50 is 10x less than OrleSNPV
– No difference in efficacy among 4 th instars

In Summary…
• When fed to lab-reared 2 nd instar WMTM
larvae, OpMNPV is 10x more efficacious than
OrleSNPV. OrleSNPV, however, kills 2 nd instar
larvae half a day sooner. No discernible
difference in 4 th instars.

Final Word
• Since both viruses have similar efficacies,
there seems to be little reason to pursue
OrleSNPV as a candidate for the biological
control of WMTM.
• However, from an environmental perspective,
it may be prudent to use OrleSNPV within its
native range to preserve the integrity of the
eastern North American ecosystem.

Acknowledgements
• David Thumbi, Sylvar Inc.
• Laura Forbes, Sylvar Inc.
• Kristy Robinson, Sylvar Inc.
• Lisa Friar, Sylvar Inc.
• Stephan Richard, Sylvar Inc.
• Drew Carleton, UNB
• Dillon Anthony, Berklee
• Caitlin Tarr, UNB
• Laura Buckingham, UNB
• Colin Baptiste
• Maxime Chautard
• The Atlantic Innovation Fund (AIF)
• Forest Protection Ltd. (FPL)
• Nova Scotia Dept. of Natural
Resources (NS-DNR)
• NSERC
• The University of New Brunswick
(UNB)
• Canadian Forest Service (CFS)