Date August 28, 1992

Title of Project Fungal Pathogens for Biocontrol of Thrips in Greenhouses

Institution where work is being conducted University of Vermont

Amount of Endowment Grant $7,000
Covering Period 1/1/92 to 12/31/92

Anticipated Date of Project Completion/Final Report Project is on-going, but an interior report will be submitted 1/1/93

Individual(s) Conducting Project:

(List Project Leader First)

Bruce L. Parker - Title Research Director

Telephone Number 802-658-4453

Michael Brownbridge - Title Research Professor

Fungal Pathogens for Biocontrol of Thrips in Greenhouses

Bruce L. Parker and Michael Brownbridge

University of Vermont

Progress Report to the American Floral Endowment, 8/28/92

A. Objectives of Research:

1992

1. Select effective fungal strains

for control of western flower thrips

(WFT), from a range of isolates of

Verticillium lecanii, Beauveria bassiana,

Metarhizium anisopliae and

Paecilomyces farinosus.

1993

2. Conduct small-scale efficacy

trials on thrips-infested chrysanthemums

and soil using

promising fungal strains.

3. Monitor the survival and

maintenance of an effective level of

inoculum in soil treated with fungal

pathogens.

B. Summary of Work Conducted:

The goal of our research is the

development of entomopathogenic

fungi, native to the USA, for the

management of WFT. We have now

completed our program to screen 55

fungal isolates for activity to WFT.

From these we selected 16 isolates,

representing four fungal species, which

showed the best potential to control

WFT. These are now being bioassayed

against WFT to quantify their relative

pathogenicity and facilitate selection of

only the best strains for further

evaluation and development. This

stage of the project is nearing

completion. The assay system has

been further refined and has been

demonstrated to be a rapid and

effective means of testing the fungal

agents against WFT.

In a USDA-funded project, we

have isolated numerous additional

fungal pathogens from pear thrips.

These are presently being identified and

will increase the range of effective

isolates we have available for use

against WFT.

We have also made significant

progress in two additional research

projects, not funded through the AFE,

which are of particular relevance to the

WFT work. Firstly, artificial rearing

techniques for the mass production of

WFT have been successfully developed

to provide a constant supply of large

numbers of even-aged thrips for the

bioassay work. Secondly, ten of the

16 selected WFT-active strains have

been screened for pathogenicity to the

green peach aphid (GPA), which is

another serious floriculture pest.

C. Results to Date:

The 16 isolates selected for the

bioassay tests are as follows: 6 V.

lecanii strains, 5 M. anisopliae, 3 B.

bassiana and 2 P. farinosus. We have

therefore selected a broad range of

pathogen types which will enable us to

identify the most practical strains for

WFT-control according to the insect

stage targeted and the control strategy

adopted. Bioassays have been

conducted on all of these fungi and are

being repeated in cases where

exceptional thrips mortality was

achieved at the dose range originally

used. The dose-mortality response at

lower spore concentrations is now

being evaluated for these strains which

appear to be particularly potent against

WFT. Statistical analysis of the data

will show the relative efficacy of the

different isolates selected, and the best

strains can be tested in Obj. 2 and 3 of

the project.

The refined assay system is both

simple and efficient, maintaining WFT

in a healthy state in the control

treatments while facilitating a true

evaluation of the fungal isolates. A

manuscript is in preparation describing

these assay techniques and the results

of the assay tests done. Full recognition

of the support of the AFE will be given.

In the GPA trials, several of the

WFT-active fungi appear to be very

effective against this pest and some

have the ability to spread within a

developing aphid population. This

demonstrates our fungi potentially have

the ability to control a variety of floral

and greenhouse pests. This makes

them particularly attractive candidates

for incorporation into a greenhouse IPM

system.

D. Future Plans Covered by the Endowment Grant:

Upon completion of the bioassay

tests and analysis of the data, we will

select five strains for further testing in

on-plant and in-soil trials. With

continued AFE support of the project,

these experiments will provide

important information on the efficacy of

the selected isolates and the insect

stage and environment where they may

be most effectively utilized. This is an

essential step in the development of

practical and eff icient biocontrol

strategies for WFT management. This

work will also involve the development

of appropriate formulations to maximize

the efficacy of the fungal

entomopathogens.

E. Anticipated Benefits for Floral Industry:

The results produced so far

are extremely encouraging and

show that fungal pathogens have

great promise for control of WFT

and other important floral and

greenhouse pests. Their

development as effective,

sustainable, economically viable

and environmentally safe

components of an IPM system will

lead to a reduction in the large

amounts of chemicals currently

employed for plant protection in

the floriculture industry.

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