The Development of Integrated Pest Management in Floriculture 1996 proposal
Principal
Investigator: Michael P. Parrella Project
Title: Integrated Pest Management Strategies in Floriculture
for Thrips and Leafminers
Executive Summary of Proposal
Thrips (especially the western flower thrips [WFT] Frankliniella occidentalis
[Pergande]) are arguably among the most serious pests of floricultural
crops in the U.S. Direct feeding on opening flowers, feeding on pollen,
defecation and oviposition in developing buds, and feeding on foliage with
the concomitant transmission of tospoviruses causes serious damage to many
floriculture crops. The spread of F. occidentalis and Thrips palmi Karny
(melon thrips) has magnified the importance of quarantines as a regulatory
control measure. This puts tremendous pressure on regulatory agencies because
proper identification can be difficult and growers are placed in a position
where 100% control is required.
Obtaining complete control of thrips in a floricultural crop is difficult
to achieve. For most growers, management of western flower thrips involves
repeated application of insecticides. However, total reliance on this strategy
is unwise given the propensity of this thrips to develop resistance and
the increasing restrictions governing pesticide use. Screening greenhouses
is not an option for most growers, biological control and host plant resistance
have not evolved to the point where they can be incorporated into a thrips
management program for a floricultural crop, and managing crop production
cycles to mitigate thrips problems in a production range is often not possible
given the market demand for product and limitations in space. Taking these
limitations into account, we have begun a research program aimed at developing
sound thrips management strategies for floricultural producers. The full
scope of the program is presented.
Areas expanded in this proposal include development of a key to identify
common thrips attacking floriculture crops, development of a sampling program,
and development of efficacy data for new biorational pesticides. Leafminers
in the genus Liriomyza, most notably Liriomyza trifolii (Burgess), are
increasing dramatically as pests of floricultince crops in the greenhouse
and field. This pest will be revisitod with respect to insecticide resistance,
performance of new insecticides and biological control. 1, 2, & 3.
Introduction, Literature Review and Anticipated Benefits
Thrips Identification Few early entomologists have specialized in the
study of Thysanoptera (Thrips). The taxonomic and systematic classification
of this group have largely been documented since 1900, which is very recent
compared to most other economically important insect orders. However, many
revisions of the early descriptive work are necessary and new taxonomic
research is needed. The small size of thrips and the arduous but absolutely
necessary procedure of mounting them on microscopic slides for identification
is daunting to many entomologists.
In addition, despite the fact that systematics and proper classification
is an essential first step in the development of a pest management program,
there has been a general drift away from this research area as young professional
entomologists prepare their careers and develop areas of expertise. This
trend appears to be easing somewhat, but the lost ground may never be regained.
There are more than 6000 species of thrips that have been described, and
there are estimates that ultimately there will be 25,000 species described.
This brief discourse into the confusion regarding the proper identification
of thrips is important because: 1) it suggests that misidentifications
are probably rampant, and 2) the exclusion of ‘exotic’ thrips from the
U.S. is made more difficult by the very fact that we lack vital information
on how to effectively separate species. The asymmetry of the ventral surface
of the head, the vestigial right mandible (which possibly evolved as a
pollen feeding mechanism), the presence of a protrusble tarsal bladder
hae imposed stability and independent status to the Thysanoptera since
the Permian period (ca. 65 million years ago). The delicately fringed nature
of the wings gives the order its scientific name, Thysanoptera, derived
from the Greek words Thysano=fringe and ptera=wings.
However, this is not a characteristic of all thrips species and this
feature can also be found on some parasitic wasps (Order Hymenoptera) and
bark lice (Order Pscoptera). Specimens should be collected and placed into
a combination of 60% alcohol, glycerin and acetic acid in the proportions
10:1:1. This mixture is commonly referred to as AGA solution. To obtain
the best results, within 24 hours of collecting, each specimen should be
massaged with a bent needly to extend the body segments as well as the
legs and wings; the antennae should be laid out horizontally by pressing
on the basal segments. If not done, it may be difficult to see minute structures
on shriveled and distorted specimens. After this stint in AGA, the thrips
should be stored in clean 60% alcohol. If growers are planning to collect
thrips, obtaining some AGA solution from an extension specialist may be
advisable. If you only have 60% alcohol in which to put specimens. It is
important that these be delivered to a university/extension contact as
quickly as possible so the specimens can be prepared properly. Mounting
thrips on microscopic slides and examining them under a binocular microscope
is the only way to know what species is attacking your crop. Given the
range of thrips that do attack floricultural crops, it is almost ridiculous
for anyone to go into a greenhouse, examine a flower for the presence of
thrips and declare: Yes, this is the western flower thrips! This is impossible
to do even with a hand lens. Only adult thrips can be identified to the
species level; it is impossible to make a specific determination with only
immature stages.
Development of Sampling Monitoring/Sampling Programs
Effective IPM programs for floricultute crops have yet to be fully
implemented. In part because of the perception that high value floriculture
crops have such a low tolerance for feeding injury that IPM tactics are
not practical. Recent research into IPM strategies for floriculture crops
has begun to change this perception. Some cultural and physical control
recommendations such as soil sterilization, weed control and physical seclusion
have been shown to help to manage pests (Parrella & Iona 1987). Considerable
research and practical application has gone into the use of predators and
parasites (van Unteren 1992), and development of monitoring procedures
for pests of floriculture crops have also been advanced (Jones & Parrella
1986).
Because of increasing acceptance of the applicability of IPM a recent
Smith-Lever project was initiated to demonstrate the benefits of pest scouting
in ornamental greenhouse crops by the farm advisors in the major flower
growing areas of California (J. Newman in Santa Barbara and Ventura, S.
Tjosvold in Monterey, K. Robb in San Diego and A. King in Half Moon Bay).
This project demonstrated to growers the benefits of monitoring peat populations
and showed that pesticide usage could be induced at a cost savings equal
to, or in many cases greater than the cost of crop monitoring (a similar
program has been developing in New York State through the IPM Program at
Cornell University).
One major problem that has arisen in the California study was the lack
of knowledge about monitoring procedures and action thresholds for WFT.
This was perceived as the greatest single problem in implementing scouting
programs and IPM procedures in cut flowers and potted flowering plants.
If WFT monitoring procedures had been available, even larger pesticide
reductions and cost savings to growers would have been made. In the absence
of monitoring and control guidelines, management strategies for WFT have
relied on calendar based pesticide applications or casual observations
of WFT on foliage, flowers or sticky traps to time sprays. Consequently
pesticide sprays are often applied more frequently than necessary or not
until populations are too high to prevent damage.
Other workers in greenhouse crops suggest accurate predictions of WFT
numbers for pest control programs in greenhouse crops can be made using
traps, plant samples or a combination of both. Robb (1989) demonstrated
a significant correlation between WFT on traps and larval and adult populations
in carnation flowers. Shipp & Zariffa (1991) showed that by using biological
information on the spatial distribution of WFT that traps, flower, and
leaf samples could be used to estimate WFT abundance on greenhouse sweet
pepper. Steiner (1990) (also through an understanding of the spatial patterns
of WFT) developed a presence-absence leaf sampling procedure to estimate
WFT density in greenhouse cucumber and to relate density to leaf injury.
In response to the lack of WFT control guidelines we will develop monitoring
procedures and WFT control action guidelines on roses and chrysanthemums
to help fill the knowledge gap. These crops were selected because they
were the most often cited where this information would be of greatest benefit.
The objectives of this project examine the within and between-plant distribution
of WFT on both crops, evaluate the most efficient sampling method and develop
precision-level sampling procedures for commercial use.
Furthermore, our study will correlate WFT densities to feeding injury
on foliage and flowers to develop control action guidelines. If successful,
results of our study can then be used to improve the timing of pesticide
applications on roses and chrysanthemums, help reduce unnecessary pesticide
applications and provide a method to evaluate the efficacy of control tactics.
Results will be extended to growers through several avenues, including
an IPM floriculture manual under preparation in California, industry and
cooperative extension publications, grower demonstrations and trade magazine
articles. Availability of this information would aid growers in timing
pesticide applications, provide a method to monitor the effectiveness of
control measures, help reduce unnecessary pesticide application, and help
increase awareness of the benefits of IPM procedures, particularly biological
controls in ornamental crops. For roses and chrysanthemums, our approach
is to develop precision-level sampling procedures using traps, plant samples
or a combination of the two to improve monitoring procedures for WFT.
Leafminers Resistance Development and Biological Control The
serpentine leafminer, Liriomyza trofolii, was the major pest of chrysanthemums
from the mid 1970s to the mid 1980s. With considerable support from many
of the floricultme funding sources (lead by the American Floral Endowment)
as well as the large propagators, considerable information was developed
which represented the foundation of a good Integrated Pest Management (IPM)
program for the leafminer attacking chrysanthemums and other crops. When
implemented, these strategies were designed to reduce the leafminer problem
with an emphasis on non-chemical control strategies. There are many publications
regarding IPM of leafminers culminating in a general overview article on
the subject (Parrella & Jones 1987).
Pesticides are an important part of any IPM program (especially in floriculture)
and the major insecticide ‘discovered’ and registered as result of a national
combined effort was the product abamectin (Avid). The leafminer all but
disappeared as a major pest of chrysanthemums across the U.S.; unfortunately
it was replaced by other pests (such as western flower thrips, green peach
and melon aphids, etc.), but for the most part the leafminer itself was
relegated to minor pest status. It was very satisfying to think that components
of the IPM program, when linked together, provided control of the leafminer
on an industry wide basis. Whether one could separate and rank the impact
of the various IPM components and compare them to the use of abamectin
was always an interesting question but it was a good point because the
leafminer was under control. It is now time to refocus on that question
because the leafminer is definitely on the rise as a pest of chrysanthemum
and other floricultural crops. Recent visits to chrysanthemum growers in
the San Diego and San Jose areas where heavy populations of leafminers
were observed, together with reports of increasing leafminer problems in
celery in California, Arizona, and Florida suggest that the pest status
on this lefminer is on the rise.
In some situations the pest species has shifted (for example on celery
in California we are now experiencing a problem with L. Huidobrensis, the
pea leafminer), but in all other situations the pest we have found is the
‘old’ Liriomyza trifolii. (It is interesting that in Central and South
America and in Europe, the L. huidobrensis has is a major problem in greenhouse
vegetable and ornamental production.) What has contributed to the rise
in leafminers as pests in the United States? There are several possibilities:
1) growers have failed to implement existing management strategies or were
simply not aware of the full array of management options, 2) the leafminer
has developed resistance to one or more of the pesticides commonly used
for its control, and 3) there has been a loss of effective insecticides
or restrictions on potentially effective materials. It is likely that all
of the above reasons (and some that were not listed) are responsible. This
proposal will attempt to examine these possible scenarios more closely,
focusing primarily on the development of insecticide resistance. In addition,
we will examine biological control options for this pest.
Materials and Methods
Thrips Identification Most the literature available on thrips taxonomy,
biology and control has been assembled in my laboratory at UC Davis. In
addition, the Department of Entomology has one of the most complete collections
of slide mounted thrips in country. From these sources, together with our
own collections of thrips from around the county, we will develop a two
level key to the thrips attacking floriculture crops in the U.S. The first
level will be a traditional taxonomic approach designed for professionals
to use, and the second level will be a simple pictorial guide that will
be designed for growers and other interested in separating species of thrips
in their greenhouses.
Sampling/Monitoring Strategies Two greenhouses operated by different
growers will be selected from Santa Barbara county and two from Santa Cruz
/ Santa Clara counties. A number of potential cooperating growers have
been identified in each region. Most rose growers produce different cultivars
in the same house and observations suggest WFT distribution is influenced
by different cultivars.
For this study we will select at least three different cultivars per
house for study: a red, a yellow and a pink or lavender cultivar. These
color selections were made to reflect the largest differences in attraction
and sensitivity to feeding injury from WFT. Selections were made based
on personal observations by the PI’s, cooperators and growers. Cultivar
selections will be representative of the most common cultivars grown in
each region. For each greenhouse, at least two beds (usual dimensions,
100 by 4 ft. or 150 by 4 ft.) of the same cultivar will be monitored for
a total of four beds per cultivar per region. All greenhouses will be monitored
weekly for eight weeks during each of the spring, summer and fall growing
seasons prior to harvest.
The eight weeks prior to harvest was chosen because this is when roses
are most susceptible to damage and control measures are most often applied.
The purpose of these procedures is to determine the efficiency of visual
and trap sampling methods relative to absolute WFT densities determined
from whole plant samples. Rose beds will be sampled for WFT using the following
methods: blue sticky cards, leaf samples, terminal buds or flowers, and
whole plant samples.
Sticky cards. Four blue sticky cards (3″ by 5″) will be placed
in each rose bed to monitor adult WFT p; numbers on a weekly basis (24
sticky cards per house). Sticky cards will be hung from wires and positioned
near the top of the plant canopy and distributed along the row. Their position
will be at least 15 plants from row ends to reduce edge effects. Each week
cards will be removed and replaced with fresh cards. Cards will be returned
to the laboratory and the number of adult WFT captured will be recorded
with the bsp; aid of stereo microscopes. A simple key, developed in M.
Parrella’s lab, will be used to identify thrips on traps.
Leaf samples. Twenty rose shoots will be randomly selected for
sampling from each bed from at least three plants from either row end to
minimize edge effects. For each rose shoot, three leaves will be visually
examined for the presence of adult and larval WFT on a weekly basis. Leaves
will be taken as follows: one from the top third of the shoot, the middle
third and the basal third. Leaves will be examined with the aid of a 10x
hand lens and the leaf position and number of WFT recorded. Terminal bud
or flower samples. Because WFT sampling will occur over eight weeks either
terminal buds or rose flowers will be sampled. Twenty rose shoots will
be randomly selected for sampling from each bed. Flowers or buds will be
examined visually for the presence of adult or larval WFT with the aid
of a 10x hand lens and the number of adult and larval WFT found will be
recorded. Results from leaf and terminal bud or flower samples will be
used to estimate the within plant distribution of WFT as well as provide
data to compare the relative efficiency of visual sampling methods with
absolute estimates from the whole plant samples (below).
Whole plant samples. Whole plant samples are necessary to determine
the absolute WFT density and to compare the relative efficiency of the
different sampling methods. Because roses are grown as perennials over
many years it is not desirable to remove whole plants. Instead, whole rose
flower shoots (the harvestable portion of the upper half of rose plants)
will be sampled. Twenty whole rose shoots will be sampled from each bed
on a weekly basis. Samples will be taken at least three plants from the
row ends to minimize edge effects. Plastic bags will be placed over the
rose shoot tied off at the base and the entire shoot pruned from the plant
and returned to the laboratory. WFT will be extracted from the plants using
70% ethanol washes and filtered through a mesh screen and the number WFT
counted on the screens using stereo microscopes. Terminal buds or flowers
will be pruned from the shoot and dissected under stereo microscopes to
remove WFT within these structures and the number of WFT recorded.
Feeding injury. Leaves and flowers from the whole plant samples
(from above) will be examined for WFT feeding injury. The number of leaves
or petals that show feeding injury and their positions (leaf position on
shoots or petal position on flowers) will be recorded. In addition, the
area of petal or leaf tissue damaged will also be measured using clear
acetate film with a 1.0-mm2 grid superimposed. Leaf or petal area will
also be estimated by running them through a LICOR leaf area meter. This
data will provide estimates of the number of leaves or petals showing injury
as well as their position on that plant and the extent of tissue damage
and correlated to WFT density.
Chrysanthemums. The procedures used in the chrysanthemum study
will be identical to the rose study with the following exceptions. Differences
in attraction of WFT to chrysanthemum cultivars have also been noted. The
specific cultivar comparisons to be used will be selected on site in consultation
with the farm advisors and growers involved. Potted chrysanthemums will
be used for developing monitoring procedures.
Sticky cards. Cards will be attached to stakes instead of wires
at the level of the crop. Whole plant samples. Entire plants cut to the
base will be used to estimate absolute population densities of WFT.
Analysis.
Objective 1. Relationship between WFT density and distribution.
Within-plant WFT distribution. ANOVA and mean comparison tests will be
used to test and describe the within-plant distribution of WFT on rose
and chrysanthemums at different densities and at different times of the
season based on sample counts. Comparisons will be made among the three
leaf positions and the terminal bud or flower position. To determine the
most efficient sample unit, data from terminal bud or flower counts, leaf
positions and trap capture will be correlated to whole plant counts. The
sample method with the highest degree of correlation will be used as the
criteria for selecting the most robust sampling media for predicting WFT
densities in the field. Between-Plant WFT distribution.
The spatial distribution of WFT will be quantified two ways. The first
will determine the distribution characteristics within a rose or chrysanthemum
cultivar and the second will determine the distribution characteristics
among cultivars within a greenhouse. This second method will help determine
the relative attractiveness, and therefore the relative abundance of WFT
moving to one cultivar type relative to other cultivars present for a given
WFT density. This analysis will provide a measure of the relative preference
of WFT with respect to different cultivars.
For both methods we will estimate the degree of aggregation using the
variance to mean relationship using Taylor’s power law (Taylor 1961). Aggregation
coefficients within a cultivar will be used to estimate the sample size
needed for a given method at a known precision level to estimate WFT density
in the crop. Aggression coefficients between cultivars will be used to
assess the influence of different cultivar combinations on WFT spatial
distribution within the greenhouse.
Objective 2. WFT density to injury relationship Estimates of
WFT density to fedding injury relationship will be estimated using simple
regression analyses. WFT mean densities obtained from the whole plant samples
will be regressed against the number of leaves or flower petals showing
injury and the area of tissue damage to flowers and petals for each cultivar.
Mean densities obtained from leaf, bud or flower visual counts and trap
captures will also be regressed. The WFT density to injury relationships
for each cultivar will provide quantitative injury data to guide growers
in selecting the most appropriate action threshold for applying management
tactics within their particular management and marketing constraints.
5. Literature Cited
Jones, V. P. & M. P. Parrella. 1986. Development of sampling strategies
for larvae of Liriomyza trifolii (Diptera: Agromyzidae) in chrysanthemums.
Environ. Ent. 15: 268-273.
Parrella, M. P. & V. P. Jones 1987. Development of Integrated Pest
Management strategies in floricuiture. Bulletin of the Entomological Society
of America 33. 28-34.
Robb, K. L. 1989. Analysis of Frankliniella occidentalis (Pergande)
as a pest of floricultural crops in California greenhouses. Ph.D. Dissertation,
University of California, Riverside. 135 pp.
Shipp, J. L. & N. Zariffa. 1991. Spatial Patterns of and sampling
methods for western flower thrips (Thysanoptera: Thripidae) on greenhouse
sweet pepper. Can. Ent. 123. 939-1000.
Steiner, M. Y. 1990. Determining population characteristics and sampling
procedures for the western flower thrips (Thysanoptera: Thripidae) and
the predatory mite Amblyseius cucumeris (Acari: Phytoseiidae) on greenhouse
cucumber. Environ. Ent. 19: 1605-1613.
van Lenteren, J. C. 1992. Ed., IOBC/WPRS Bulletin Working Group “IPM
in Greenhouses, vol. 16. International Organization for biological and
Integrated Control of Noxious Animals and Plants, Western Paleartic Regional
Section, Pacific Grove, California.
6. Budget
1 full time laboratory Assistant II @ $4,880/month x 12 months (includes
benefits) $58,560.00
Note: This funding is requested for an individual already in this position
based on funding from previous years. This will maintain continuity of
the project.
7. Leader Qualifications
Dr. Parrella’s responsibilities at Davis are 80% research and
20% teaching in addition to being chairman of the Department. He teaches
Economic Entomology (Entomology 110) and contributes to other courses in
the Departments of Entomology and Environmental Horticulture and in the
Plant Sciences. His research program has concentrated in the area of ornamentals
with a focus on developing pest management systems with a firm reliance
on biological control.
Dr. Parrella has worked with many different ornamental crops and with
most of the major pests attacking these crops over the past 15 years. An
important part of Dr. Parrella’s research and teaching is directing graduate
students and postgraduate scientists - he currently has five (1 postdoctoral
scientist, 3 Ph.D.’s and 1 Master’s) working on different pest problems
affecting the floriculture/nursery industry. Dr. Parrella publishes regularly
in scientific and trade journals and is the author of more than 200 publications.
He is on the editorial board for the scientific magazines American Entomologist,
Entomophaga, and the Journal of Environmental Horticulture and he is a
contributing writer for the trade magazine GrowerTalks.
Dr. Parrella organized the ‘First Conference on Insect and Mite Management
on Ornamentals’ in 1985 sponsored by the Society of American Florists.
This has become an annual event. In 1986, Dr. Parrella received the Researcher
of the Year Award from the California Association of Nurserymen. In 1987,
Dr. Parrella received the Entomological Society of America (ESA) Recognition
Award in Entomology. This award, presented annually by the ESA, a professional
society with more than 9,200 members, is intended “to provide additional
recognition to entomologists who have made or are making significant contributions
to agriculture.” In 1991, Dr. Parrella received the Future Award from the
Professional Plant Growers Association in recognition of contributions
made to the floriculture industry by building for the future through teaching
and research.
