Fungal Pathogens for Biocontrol of Thrips in Greenhouses 1993 Proposal
EXECUTIVE SUMMARY
The greenhouse provides an ideal environment for the use of entomopathogens,
where humidity and temperature are generally high and can be easily controlled
to promote their efficacy. So why weren’t fungi developed for use in greenhouse
pest management years ago? There are many reasons. For example, different
strains of the same species of fungus often show considerable variation
in their virulence for a particular target pest. Screening is therefore
an essential first step to permit selection of the most promising isolates
from the thousands that occur naturally in the environment. In addition,
technological advances now permit the mass- production and formulation
of the types of fungi we have targeted so that stable and effective preparations
can be cost-effectively produced. Having already established that some
of the fungi are highly pathogenic to western flower thrips (WFT), one
of the major developmental steps now facing us is how to efficiently target
these agents against WFT in a form that would be available to a grower.
We will continue to evaluate additional fungal strains, but it is important
that we begin to identify appropriate means of formulating these fungi
for thrips suppression in an IPM program. With continued support from AFE
we therefore propose to evaluate in an experimental greenhouse, the efficacy
of selected strains in a variety of formulations against WFT infesting
chrysanthemums.
In addition we propose to initiate the establishment of a national network
of researchers and growers to work TOGETHER on the development of fungal
pathogens as integral components of greenhouse IPM. This team would develop
realistic research priorities and share research findings, techniques and
fungal materials. Each team member would possess particular expertise that
would benefit the group as a whole. Simply put, if two heads are better
than one, imagine what can be accomplished with even more. This network
would encourage communication among the scientists devoted to this aspect
of research, facilitate development of standard experimental methodology
and reduce the potential for redundancy in fungal pathology research.
INTRODUCTION
TODAY, for the Floriculture Industry, it is the best of times and the
worst of times. Consumer interest in plants remains high, despite a sagging
economy. Pest management technology continues to improve and use of hazardous
chemical pesticides is declining. Integrated pest management (IPM), utilizing
a broad range of strategies, prominent among them biological control, has
become a viable approach that many growers are implementing. BUT, more
than ever before, federal restrictions are limiting use of many chemicals
on which growers have relied for years. New pests and resistant populations
continue to surface requiring on-going research to develop controls. The
budgets of many federal and state agencies that traditionally supported
floriculture research and extension have been slashed. Demands on grower
associations have increased dramatically for support of the essential research,
development and ultimate implementation of innovative management strategies.
No longer can growers expect one or two applications of a chemical pesticide
to cure their diverse pest problems, and by necessity management is becoming
increasingly complex. Many factors, among them, biological and chemical
control, insect resistance, phytotoxicity, environmental contamination,
toxicity to non- target organisms and economics, must be considered when
developing an effective, comprehensive IPM plan. Researchers must develop
methods to maximize their resources and IPM demands teamwork. No single
control strategy can solve all pest problems plaguing the greenhouse, nor
can any single researcher be expected to. Instead, numerous strategies
must be used in concert, each contributing its part to overall reduction
of pest populations. This demands a coordinated, broad-based research effort
among several scientists, all with specific expertise, thereby allowing
the efficient, on-going development and refinement of greenhouse IPM.
In 1992 we received funding from AFE to screen native fungal isolates
for pathogenicity to western flower thrips, Frankliniella occidentalis
(WFT), a greenhouse pest of significant economic importance in the U.S.
(Robb & Parrella 1989). Results from this study led to the selection
of a few particularly promising strains for further lab testing. Funding
from AFE in 1993 is allowing us to evaluate these strains, in pure spore
form, on plants and in soil in the controlled lab environment. Contacts
have been made with companies in the U.S. and Europe to mass-produce and
formulate some of the strains for greenhouse testing. In 1994 we propose
testing of our fungi as formulated products (wettable powders or emulsifiable
concentrates) an plants and in soil in greenhouses, a crucial stop in the
development of an effective fungal-based product forgreenhouse use. Our
results will provide essential information on the efficacy of these fungal
strains in the real greenhouse world. In addition, we wish to look towards
the future of fungal pathogens as components of greenhouse IPM. We propose
to design a mechanism to promote cooperation among scientists involved
with fungal pathogen research nationwide. This will reduce redundancy,
increase productivity and efficiency, and encourage more rapid development
of fungi for IPM.
LITERATURE REVIEW
Biological control was once discounted as ineffectual for greenhouse
pest management, but today it has become a respected, integral part of
IPM. Several parasites and predators are commercially available but development
of fungi for greenhouse pests is progressing more slowly. “Mycotal,” a
product with Verticillium lecanii is available in Europe, but not in the
U.S. (Gillespie 1987, Van der Schaaf et al. 1991). Paecilomyces fumosoroseus
and Aschersonia aleyrodis are also under investigation, but are not yet
commercially available (Osborne & Landa 1992). Because insects have
the uncanny ability to develop resistance–even to biocontrol agents–a
broad array of management tools is needed (Abbott Labs 1993).
Parasites and predators are used in greenhouse IPM but alone, they are
often unable to reduce high pest populations to acceptable levels (M. Parrella,
pers. comm.). Rearing and maintaining large numbers of natural enemies
without the host is difficult. The price of such beneficials may also preclude
their use in certain cropping systems. For example, Orius, a commercially
available predacious bug, costs 10 cents each, and thus may not be cost-effective
for some growers (Parrella 1993). Insect-killing fungi can play an important
role in supplementing the natural enemy complex. Careful selection and
research will provide strains and management strategies compatible with
pesticides and natural enemies.
Past failures of fungi can be attributed to the use of inappropriate
mass-production, formulation and application methods (Andersch et al. 1990).
Recent technological advances now allow low cost production of many fungi
on artificial media and large amounts of viable and stable inocula can
be produced (Andersch et al. 1990, Pereira & Roberts 1990). New formulations
provide more efficient delivery systems capable of causing high infection
and mortality rates, even under conditions of low humidity (Pereira &
Roberts 1991, Kreuger et al. 1992, Bateman et al. 1993). Selection of suitable
strains, and optimizing dosage and application procedures must be done
to enhance success.
Several of our Vermont strains of V. lecanii, Metarhizium anisopliae,
Beauveria bassiana and P. tarinosus are highly pathogenic to WFT and readily
produce large numbers of spores–a trait important for mass-production
(Brownbridge et al. 1993, AFE progress rept. 1992). We are currently evaluating
several of these strains on flowers, plants and in soil against WFT (Table
1). Our studies show that some of these strains also kill sweetpotato whitefly
and green peach aphid, an added benefit.
OBJECTIVES
1. Determine if virulent strains of three Vermont fungi (V.
lecanii, M. anisopliae, B. bassiana) formulated as a wettable powder or
emulsifiable concentrate will control WFT on mums in a greenhouse.
2. Determine if a soil drench of the above fungal formulations will
reduce WFT pupal populations.
3. Design a plan to coordinate research activities on fungal pathogens
in the U.S. to maximize efficiency and speed the development of fungal
products for greenhouse IPM.
This plan would be submitted to the Soc. of Amer, Florists Research
& Development Committee, Poinsettia Growers Assoc., Bedding Plants
Foundation and the U.S.D.A. for consideration of future funding.
BENEFITS TO THE FLORICULTURE INDUSTRY
Our research is APPLIED with long-term direct implications to growers
and the IPM options they will have available. The process of developing
a biological agent for IPM is gradual–data must be generated carefully
and pooled to assess the organism’s overall suitability. Like building
a house, brick upon brick, each level of the process relies on the one
below it. Each step is an essential part of the final product, and if a
step is missed, the wall is weakened. Objectives 1 & 2 represent the
next logical steps in the development of fungi for use in greenhouse IPM.
We will learn which fungi are the most suitable in a greenhouse. We will
identify if soil or plant treatments are the most appropriate for controlling
WFT. This is critical for testing in a commercial greenhouse in the future.
We applaud the initiative taken by AFE to establish a focused approach
for distributing research support, targeting key priority topics. This
will foster team work and promote solving the critical management problems
facing the floriculture industry. With Objective 3 we propose that a network
of researchers be established to jointly tackle the complex aspects of
fungal development. This will benefit growers by maximizing research efforts,
and dollars, while speeding up the development process by reducing duplication
of research. Growers will participate in this network, providing the essential
reality base for research.
MATERIALS AND METHODS
Fungal isolates will be mass-produced and formulated by Mycotech Corp.,
MT; and Chr. Hansen’s BioSystems, Denmark. These companies were selected
for their specific expertise with the fungi we will test. Spores will be
formulated as emulsifiable concentrates (EC) (B. bassiana, M. anisopliae)
or wettable powders (WP) W. lecanii). Mums will be supplied by Yoder Brothers,
Inc.
OBJECTIVE 1
A. Strain Selection. Strains of V. lecanii, M. anisopliae and
B. bassiana are being evaluated now in lab trials against WFT in chrysanthemums.
Three of the most virulent ones will be chosen for these greenhouse trials.B. Plant Assays. Twenty mums, each with 3 flowers, will be placed in
thrips-proof cages, then 250 5-d old WFT adults will be introduced and
allowed to oviposit (Robb 1989). After 2 d, plants will be removed, adults
dislodged, and returned to the cages to allow the larvae to hatch. Temperature
and scientists around the country. Over the past few years we have amassed
a broad array of insect-killing fungi from diverse habitats and locations–from
New England to Europe and the Far East. We have begun the process of selecting
strains based on pathogenicity to specific greenhouse pests and are nearing
the stage when some of these materials can be tested in greenhouses. Once
efficacy has been confirmed, the compatibility of these materials with
other aspects of IPM must be assessed, i.e., toxicity to non- target organisms
and tolerance to chemical pesticides. We believe links must be established
NOW among scientists. In addition, input from grower associations should
be sought to ensure that the research directions meet their needs. We recognize
that the long-term benefits of the research we propose will serve growers
nationally, and AFE alone should not shoulder the responsibility for financing
it alone. Our fund raising efforts last year resulted in the construction
of two new greenhouses in which to conduct our research. We are also seeking
support from other grower groups (HRI, Ohio Floral Foundation), private
foundations (Kellogg Foundation) and federal agencies (USDA) for this and
other related research.OBJECTIVE 2 A. Soil Inoculation. Metro-Mixg potting soil will
be transferred to 3-in. plastic pots. It will be watered 24 h prior to
treatment, and then 1/wk throughout the experiment. Treatments will be
applied as drenches containing 0 (control), 10^6, 10^7 and 10^8 spores/ml
applied to the soil at 10 ml/pot. Each replicate will comprise four pots,
and four replicates/treatment will be done. B. Soil Assays. Flowers will
be infested as in Obj. 1. and cut from the plant 6 d after adult removal.
Flowers will be placed in vials over treated soils, one flower/pot, and
held in the greenhouse, allowing larvae to complete development and drop
to the soil to pupate. Flowers will be removed after 6 d and pots covered
with sticky lids. Adult emergence will be monitored for 10 d. C. Results.
These trials will enable us to determine if soil applications of the formulated
materials can be used to control thrips, and will help in designing strategies
for larger-scale greenhouse trials.OBJECTIVE 3 Our vision for the future is to establish a network of scientists
working together towards development of fungi for greenhouse IPM. As a
diverse range of insects plague the greenhouse environment and multiple
tools are needed to combat them, a holistic approach to their management
is essential. We propose to continue our evaluation of fungi for greenhouse
IPM within a coordinated framework with other
LITERATURE CITED
Abbott Labs. 1993. Global management of insecticide resistance in the
90’s. Abbott Labs, No. Chicago, IL.
Andersch, W., J. Hartwig, P. Reineche & K. Stenzel. 1990. Production
of mycelial granules of the entomopathogenic fungus Metarhizium anisopliae
for biological control of soil pests, pp. 320-325. In Proc. 5th Int. Colloq.
Invertebr. Pathol. & Microb. Ctri.
Adelaide, Aug. 1990. Bateman, R.P.. M. Carey, D. Moore & C. Prior.
1993. The enhanced infectivity of Metarhizium flavoviride in oil formulations
to desert locusts at low humidities. Ann. Appl. Biol. 122: 145-152.
Brownbridge, M., R. Humber, B.L. Parker & M. Skinner. 1993. Fungal
entomopathogens recovered from Vermont forest soils. Mycologia 85: 358-361.
Gillespie, A.T. 1987. Use of Verticillium lecanii to control thrips
(Thrips fact and red spider mite (Tetranychus urticae) on cucumber, pp.
95. In Proc., 20th Ann. Mtg. Soc. Invert. Pathol., Aug. 1987, FL.
Kreuger, S.R., M.G. Villani, A.S. Martins & D.W. Roberts. 1992.
Efficacy of soil applications of M. anisopliae conidia, and standard and
lyophilized mycelial particles against scarab grubs. J. Invertebr. Pathol.
59: 54-60.
Pereira, R.M. & D.W. Roberts. 1990. Dry mycelium preparations of
entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana.
J. Invertebr. Pathol. 56: 39-46.
Pereira, R.M. & D.W. Roberts. 1991. Alginate and corn starch mycelial
formulations of entomopathogenic fungi, Beauveria bassiana and Metarhizium
anisopliae. J. Invertebr. Pathol. 56: 39-46.
Robb, K.L. 1989. Analysis of Frankliniella occidentalis (Pergande) as
a pest of floricultural crops in California greenhouses. Ph.D. Dissertation,
Univ. of Calif., Riverside, CA.
Robb, K.L. & M. Parrella. 1991. An integrated approach to preventing
WFT and TSWV in the greenhouse. GrowerTalks: March: 26-32.
Parrella, M.P. 1993. Bugs to the rescue. GrowerTalks: May:67.
Van der Schaaf, D.A., W.J. Ravensberg & M. Malais. 1991. Verticillium
lecanii as a microbial insecticide against whitefly. In Proc. 3rd European
mtg. on microbial control of pests. IOBC working group on insect pathogens
and parasites nematodes, pp. 120-123.
QUALIFICATIONS OF THE UNIVERSITY OF VERMONT RESEARCH TEAM
The vision of the scientific team at the Univ. of VT Entomology Research
Laboratory is to enhance agricultural productivity throughout the U.S.
by addressing issues of insect pest management of national significance.
Through our work we attempt to develop management options that are environmentally
sound and economically viable, and encourage their implementation through
communication and education. Research on fungal pathogens for IPM of greenhouse
pests has been our major thrust for several years. Each member of our team
of six principal scientists possesses unique and complimentary expertise.
This team is rapidly assuming a leadership role in insect pest management
using fungi. Being located in Vermont, we are somewhat distant from the
national centers of floriculture, but we are committed to meeting the needs
of growers nationwide, and have shown that our local organisms offer new
and innovative benefits to pest management over a broad geographical range.
The wide participation in our 1993 International Conference on Thrips–scientists
from 25 countries and 30 states–attest to the fact that Vermont is not
so far away.
1994 BUDGET
Salary:
Bruce L. Parker $ 0
Michael Brownbridge $8,000
Margaret Skinner $7,500
Unassigned technician $10,000
Graduate student support $5,000
Fringe Benefits (36.3%) $9,257
Total Personnel $39,757
Operating Expenses: Supplies $3,295
Greenhouse utilities $3,000
Statistical services $2,000
Travel (to SAF meeting & grower outreach) $1,000
Total Operating $9,295
Direct Project Cost $49,052
Indirect University of VT costs (contributed) $4,580
TOTAL PROJECT COSTS $53,632
American Floral Endowment Contribution $20,000
UniversiTY of Vermont (Indirect costs) $ 4,580
Other external sources* $29,052
*Additional funds from private and federal sources are being sought
and have been obtained to further the goals of this project, including
$5,000 from the Bedding Plants Foundation and the USDA. The University
is also cost-sharing the unrecovered indirect costs associated with this
project.
WHY SHOULD AFE FUND THE RESEARCHERS IN VERMONT?
1. We have the EXPERTISE to do the research. -3 entomologists -4 technicians
-3 fungal pathologists -7 graduate students
2. We have the FACILITIES to conduct the research. -3 greenhouses,
facilities for insect rearing -growth chambers and temperature controlled
environments -continuous cultures of western flower thrips, sweetpotato
whitefly, and green peach aphid
3. We have the CONTACTS to enhance and expand the research. -companies
with experience with fungal mass-production and formulation technology
-researchers in greenhouse IPM and fungal pathogens
4. We have the ENTHUSIASM to communicate our research.
5. We have a PLAN to meet our ultimate research goals. Development
of Fungi for Greenhouse IPM - Five Year Plan -
