The Development of Integrated Pest Management in Floriculture 1992 Proposal
This proposal continues research initiated over the last few years which
has emphasize the development of integrated pest management strategies
in floriculture with a focus on biological control. The project covers
a broad range of arthropod pests attacking the major floricultural crops
in the U.S. A major objective is to formulate practical alternatives to
pesticides in floriculture and still provide for the production of a high
quality product. Selected areas of my 1990 proposal include: Biological
Control Each year more and more is written about biological control in
professional and trade journals. Based on this one might think that it
is being widely adopted by our industry. However, while more growers are
thinking about biological control than ever before and some are actually
trying it, this is a far cry from wide scale adoption. There are essentially
two reasons for this: 1) lack of essential information on which natural
enemies to use and how to use them effectively, and 2) a lack of wide scale
implementation and grower education in situations where this information
is available.
Basic biological studies are planned on selected natural enemies where
each will be evaluated for their control potential. In addition this will
provide us with information on how to best use these in actual release
programs with cooperating growers. Implementation of IPM/biological control
studies with cooperating growers will be initiated for chrysanthemums and
poinsettias. Biological Studies Research will continue in this area with
primary focus on the western flower thrips. In addition, life histories
of selected natural enemies will be studied with the overall objective
of evaluating them for their effectiveness in biological control programs
in green- houses. Emphasis will be placed on parasites, predators and pathogens
of aphids and whiteflies.
Data on the distribution and abundance of selected pests in various
greenhouse crops will be collected. This will provide a means of accurately
assessing pest populations in greenhouses. Whiteflies will continue to
be the focus of this work. Pesticide Efficacy and Compatibility
New pesticide registrations for the floriculture industry in the area
of ‘biorational’ type materials are on the increase while the registration
of the more traditional pesticides are still declining. These new biorational
materials may be more compatible (in some cases) with natural enemies and
hence may fit into an overall integrated program where biological control
and pesticides and used together to control pests. There are some promising
new biorational materials forcontrol of western flower thrips, whiteflies,
aphids, and mites. Consequently, screening these insecticides for compatibility
with potential biological control agents in the greenhouse is an important
part of this project.
We will continue to monitor for insecticide resistance development in
the greenhouse for the major pests and work towards a system of coping
with this serious threat to the industry. The focus at the present time
is on the western flower thrips. Literature Review
Literature continues to be compiled in my laboratory on all the major
pests in floriculture.
OUTLINE OF PROPOSED RESEARCH 1. Biological Control a. Continue studies
on the development of a method of evaluating natural enemies, on a comparative
basis, for biological control of selected pests in greenhouses. This will
focus on selected parasites, predators and pathogens of greenhouse and
sweetpotato whiteflies. b. Continue studies on biological control of the
the melon and green peach aphid using the commerciaIly available predator,
Chrysoperla spp. and the naturally occurring parasite, Lysiphlebus spp.
c. Evaluate the potential of a commercially available fungus to control
the western flower thrips, the sweetpotato whitefly and aphids. d. Initiate
a statewide implementation of an IPM/Biological control program for potted
chrysanthemums. 2. Biological Studies a. Continue the basic biology of
thrips in an effort to understand feeding, oviposition, and pupation behavior
in selected floriculture crops. b. Continue studies on the distribution
and population development of pests in various greenhouse crops. The development
of statistically accurate sampling plans for whiteflies in poinsettia will
be an outcome of this work. The purpose here is to develop decision-making
sampling plans that growers can use in addition to population level sampling
which can be used where more detailed information is needed for research
purposes. 3. Pesticide Efficacy and Compatibility a. Continue the search
for new pesticides which have potential for use in floriculture. Maintain
continued contact with chemical manufacturers to assure that the ornamentals
industry is not overlooked for potential registrations. Assist in labeling
materials for ornamentals and help fill in data gaps for materials undergoing
registration. b. Evaluate new and old pesticides for compatibility with
selected natural enemies in culture at UC Davis. The main focus will be
on leafminer and Whitefly parasites. c. Continue monitoring for insecticide
resistance in the western flower thrips and develop alternative strategies
for controlling these arthropods and for managing the development of resistance.
4. Literature Data and references are continually compiled which deal with
arthropod pest problems and their control in greenhouses around the world.
EXPANSION OF OUTLINE 1. Biological Control a. Evaluation of natural enemies
for whitefly control Introduction and Background Information: The two most
widely used arthropods for biological control in greenhouses are E. formosa
for biological control of whiteflies and Phytoseiglo persimilis for biological
control of the twospotted spider mite. Neither of these were discovered
as a result of rigorous laboratory and greenhouse studies; rather they
were found by serendipity. In 1926, a tomato grower in England brought
some parasitized whitefly scales to the attention of a researcher in the
U. K. and the era of biological control in greenhouses was born. In 1960,
a German scientist found P. persimilis in Germany in a shipment of oranges
from Chile (see Hussey & Scopes [1985] for more information concerning
these discoveries). There is no doubt that detailed studies on the biology
and ecology of these natural enemies have contributed enormously to their
successful use in greenhouses. However, little has been learned about what
attributes constitute a successful natural enemy from the successes of
E. formosa and P. persimilis. As new pests invade greenhouses and as older
pests attain major pest status (e.g., through resistance development) there
is a greater emphasis on searching for other effective natural enernies.
Review of Significant Literature:
Considerable controversy exists over the appropriate selection criteria
to use when searching for and screening natural enemies. This is understandable
considering that the mechanisms leading to successful biological control
are also not fully understood.
van Lenteren (1980) suggested that the trial and error approach for
selecting and releasing natural enemies would probably lead to successful
selection of a good natural enemy rapidly and with minimum cost. In addition
this approach would probably be as accurate as oonducting more detailed
biological and ecological studies designed to compare natural enemies and
select the best one. van Lenteren (1980) proposed a three step approach
to evaluating natural enemies that eliminates the need for detailed laboratory
evaluations prior to making trial releases directly into the greenhouse:
1) can parasitoid species discover pest infested patches throughout the
greenhouse before the economic threshold is reached? 2) is it able to reduce
pest numbers sufficiently after locating a patch? and 3) is it able to
keep the pest density below the economic threshold throughout the growing
season? However, such studies are, clearly very time consuming and they
must be done in large commercial size greenhouses due to the discrepancy
reported for biological control research in small versus large greenhouses
(van Lenteren 1986). A more promising approach may be a combination of
laboratory studies designed to be as challenging as possible together with
actual greenhouse releases; these may provide the necessary data to evaluate
different natural enemies in an efficient manner. This is the approach
that we are taking in this proposal.
A thorough review of criteria for selecting parasitoids, based on the
type of natural enemy release, can be found in van Unteren (1986) and references
therein. Many of these criteria fall under the reductionist approach to
selection (Waage 1990) where agents are chosen on the basis of particular
biological attributes or life history traits. However, many of these characteristics
am not independent, so attempting to measure them in isolation is of questionable
value. It is are important to understand how these characteristics function
to reduce pest populations in the greenhouse. One example is the calculation
of intrinsic rate of increase for the natural enemy which may include fecundity,
longevity, handling time, rate of egg production, oviposition rate, host
stage preferences, larval survival, etc. All of these are, integrated to
provide an estimate of the potential of a natural enemy to reproduce on
and control a pest.
One of the most widely measured features of all biological control agents
is the functional response. Typical functional response experiments are
conducted by confining the natural enemy with a known number of pests and
by recording selected natural enemy characteristics (i.e. attack rate)
after a predetermined time period. Such studies are usually not that difficult
to conduct and may yield valuable data. For example, when a natural enemy
is unable to 10 most of the prey in the test arena when the density is
similar to what might be encountered in the greenhouse, then this natural
enemy may not be worth examining under more challenging circumstances.
Thus, as noted by Minkenberg (1990) one of the goals of a preselection
study is to identify those natural enemies likely to fail as biological
control agents. Predicting which biological control agent will be the best
to use is far more difficult More detailed studies of the functional response
where measurements are taken to determine how well a natural enemy is able
to find scarce high or low density patches of prey and whether it avoids
leaving these areas after an initial encounter could prove valuable as
evaluation criterion for effective natural enemies (Kareiva 1990). These
aspects are inherent in the three evaluation criteria discussed above (van
Lenteren 1986). However, Kareiva (1990) stresses that the issue is not
whether a natural enemy aggregates to pest outbreaks (i.e., generates spatially
density dependent mortality) but how rapidly it does so. Such a criterion
is of vital concern in an ornamental crop where the acceptable levels of
pests and their damage are very low. Noldus & van Lenteren (1990) tried
to explain observed levels of parasitism in the E. formosa - whitefly system
in tomato greenhouses taking into account the spatial distribution of the
prey and behavior of the parasite. They found that E. formosa was not attracted
to infested plants over long distances but did aggregate in areas of high
host density because honeydew associated with these whiteflies increased
parasitoid search and residence times. However, density dependent mortality
did not occur regardless of the scale used (greenhouse, plant, or leaf).
A mechanistic approach to understanding natural enemy foraging in a
greenhouse and how it responds to the pest population in time and space
can lead to important research that needs to be done for most of the natural
enemies used in greenhouse biological control programs. An understanding
of whether of not a natural enemy responds to chemical cues in the greenhouse
environment is an important aspect of its foraging behavior. This is currently
an active area of research because integration of chemical ecology with
population biology can be used as a powerful tool to evaluate the characteristics
of successful natural enemies. Roland (1990) proposed two approaches of
experimentation: 1) observe a pattern of search and host mortality over
several generations when a cue is present and absent, and 2) identify and
utilize chemical cues themselves in order to manipulate search behavior
and pattern of attack. The greenhouse environment has been used as a test
arena for some of this research, especially the latter experimentation
method (Roland 1990), but little work has been done with natural enemies
of economically important greenhouse pests. Objectives of Proposed Research:
The following parasites are being compared for their potential to control
the sweetpotato whitefly on poinsettia: Encarsia formosa, En. transvena,
En. deserti, En. tabacivora, Eretmocerus californicus, Delphastis pusillus,
and Paecilomyces fumosoroseus. All of these (with the exception of E. fumosorosem)
are being mared within my project at UC Davis. Materials and Methods: The
parasites and the predator will be examined for corrunon sense biological
attributes including: longevity, sex ratio, total mortality (includes oviposition,
host feeding and host rejection), and response to olfactory cues emitted
by whiteflies on poinsettia. (The fungus is potentially effective natural
enemy and this will be discussed later). The methodology is fairly standardized:
we utilize adults selected at random from our colony production and cage
them with a poinsettia plant with a precounted number of whitefly immature
stages. We do not control for the age of the adult parasite but account
for this by utilizing a large number of individuals in the trials. Each
day the parasite is transferred to a new caged poinsettia. The whitefly
stages are then examined to determine the number dead and this is compared
to a control plant similarly infested but without parasites. The plant
is then held in an isolated greenhouse to allow the parasitized whiteflies
to develop and emerge. Sex ratio of emergent adults is then recorded.
A four-arm olfactometer is utilized to assess the response of adult
natural enemies to semiochemicals given off by whiteflies on leaves. Adults
are selected from the colonies and then released into the center of the
olfactorneter with one of the arms containing air passed over whitefly
infested poinsettia leaves. The response of the parasite will be evaluated
by comparison to a previously run control without any odor source in any
of the arms. A response to the odor source may suggest that the parasite
can detect the whitefly infested leaves over distance, which could be a
decided advantage in locating hosts at low densities in the greenhouse.
However, this data must be combined with information from other biological
studies to fully assess the control capabilities of the natural enemies.
Field releases of the best natural enemies will be made at cooperating
grower nurseries; this will be the ultimate test of our natural enemy evaluation
method. b. Continue Studies on the Biological Control of Aphids Introduction
and Background Information: Aphids, especially the green peach and melon
aphids, continue to increase as pests of ornamentals in California and
other states (Vehrs and Parrella 1991). This could be due to the development
of insecticide resistance or perhaps due to the development of superior
biotypes on specific crops. In Europe where Pirimor was used for many years
as the primary aphid control material, there is evidence that resistance
is developing to this compound (Jacobsen 1990). There are many natural
enemies of aphids that have potential to provide control, and research
effort has concentrated on Aphidoletes aphidimyza (the aphid midge), Aphidius
matricariae, (and other aphid parasites), on Chrysoperla carnea (the green
lacewing) and on Verticillium lecanii (Parrella 1992), we chose to concentrate
on the C. carnea for several reasons 1) its general availability from many
insectaries which rear this insect in the U.S., (Bezark, 1990), 2) its
relative low cost, and 3) the general success that has been achieved sp;
previously on potted chrysanthemums (Scopes 169). Review of Significant
Literature: Chlysoperla camea does equally well feeding on green peach
and melon aphids. At 24 degrees C., the various developmental stages are
as follows: egg - 5.3 days, 1st instar 5.8 days, 2nd instar 3.5 days, 3rd
instar 5.2 days, and pupa - 13.4 days. The threshold temperature for development
is 9.3 degrees C. (Canard et p; al. 1985). Mating occurs within the first
few days of emergence and egg laying starts in 24 h. Adults live for 2
-3 months and can deposit 400-500 eggs. This adult information is not applicable
to a greenhouse situation where releases of larvae and/or eggs will be
made. Any immatures surviving to the adult stage will probably migrate
out of the greenhouse.
Larvae probably search at random with the area of perception being the
distance between the mandibles (0.04 inches). Different species are associated
with different habitats; C. carnea is cosmopolitan in distribution and
occurs in most habitats. The larvae feed on most soft bodied insects but
the order of preference is aphids > thrips > mites.
In field situations the green lacewing is always a conspicuous part
of the predator complex but it is not deemed as useful as the Coccinelidae
(ladybird beetles) because of its relatively high threshold temperature
of activity which causes it to be a late starter (in other words, they
migrate into fields when aphids are to the point where damage to the crop
has already occurred). The following statement, taken from Canard et al.
1984, is particularly true of the Chrysopidae: “Belief in, and sporadic
proof of, the ability of chrysopids, to control pests of field crops has
undoubtedly been a major impetus for their study”.
Field releases were first made against the grape meadybug in 194911950,
and since then releases have ban ma& an the following- cabbage, pepper,
tomato, chrysanthemum, eggplant, lettuce, celery, and cucumbers for aphid
control; potato, eggplant and peas for control of Colorado potato beetle;
pear for control of European red mite; mulberry and Catalpa for control
of mealybugs; and on cotton for control of Heliothis spp.
Only limited studies have been done in the greenhouse on floricultural
crops (Scopes 1969). From this study it was concluded that at least 4 applications
of lacewings were needed with a ratio of 1 predator to 50 aphids. In addition,
if there were 4 or fewer aphids per plant, these were not discovered by
the searching predator and no control was achieved. It was estimated that
Ist instars search an area ca. 15 cm from the release site and the best
control was achieved on dense bushy plants when the predators were distributed
evenly over the plant. Objectives of Proposed Research: Continuing studies
are evaluating the potential of the commercially available predator, Chrysoperla
carnea, to control aphids on chrysanthemums (other crops will be examined
after completion of this phase) At a later stage in the project, the aphid
parasite, Lysiphlebus sp. will. also be evaluated with the idea that this
parasite may be able to work in conjunction with the green lacewing when
low aphid densities occur on chrysanthemum. Materials and Methods: Following
procedures outlined in Vehrs (1989), chrysanthemum plants will be infested
with aphids. These will be placed inside cages to avoid mortality from
parasites in the greenhouse. Seven days will be allowed for populations
to develop and then all the aphids present will be counted; age distribution
will also be noted. Different numbers of Chrysoperla eggs and or larvae
(1, 10 and 100) per plant and the number of aphids will be counted per
plant after 7 and 14 days. With these rates we win be treating the predator
as an insecticide and thus will gain a further understanding of the rate
response. Based on results, rates can be adjusted in future studies. The
same dosages will be used with the aphid parasite in later studies. In
this situation newly emerged parasites will be released into cages with
a number of aphid-infested plants and their impact measured as with Chrysoperla.
Finally, both the predator and the parasite will be used together. This
will require the most effort because it will necessitate establishing treatments
with no natural enemies, with the predator alone, with the parasite alone,
and with the combination all at the same time. We will assume a synergism
ratio of 1 predator to 10 parasites and the reverse of 1 parasite to 10
predators. These rates are speculation and may be adjusted after we see
what the predator and parasite can do at various rates on their own. C.
Biological control of western flower thrips, aphids, and sweetpotato whitefly
with pathogens Introduction and Background Information: When total greenhouse
hectares on a worldwide basis are examined with respect to biological control,
more treatments are made with Bacillus thuringiensis var. kurstaki than
with any other biological control agent (van Lenteren, 1990). This reflects
the effectiveness of this bacteria/toxin and underscores the importance
of Lepidoptera as pests in the greenhouse on a worldwide scale. The application
of this pathogen is likely to increase with the discovery and registration
of new strains or isolates (e.g., B.. thuringiensis var. tenebrionis and
var. israelensis) which will expand the host range of this pathogen. In
addition, B. thuringiensi is currently one of the major focal points of
molecular biologists; the material itself is the target for alterations
and a great effort is being made to incorporate portions of the genetic
structure of B. thuringiensis (coding for the toxin) into plants. Other
than B. thuringiensia, fungi offer the greatest potential for biological
control in greenhouses. Review of Significant Literaturee The use of fungi
in the greenhouse has received considerable attention with much of the
focus on Verticillium lecanii (Hall, 1985a, 1985b). This fungus was very
appealing commercially because it could be easily mass-reared and several
biotypes existed which attacked important greenhouse pests (i.e., whiteflies,
aphids, and western flower thrips). In addition, against a pest such as
whiteflies, all stages of are infected except eggs. However, this material
has a rather narrow range of environmental conditions under which it functions
effectively (15 - 25 C’, 85 - 90% RH, with high humidity for at least 10-12
h per day). This material was met with skepticism by many European growers
when it was first introduced commercially in the early 1980s. However,
the mid-1980s saw this product widely used, but this use gradually declined
towards the end of the decade at which time the material was no longer
available commercially. A problem was that the material was the fact that
it was an inconsistent performer, probably due to the restrictive set of
environmental conditions under which epizootics developed. In addition,
it had to compete with the very effective aphidicide, pirimicarb. To counter
problems with environmental constraints, (Helyar & Wardlow, 1987) developed
a multiple low dose strategy which gives the fungus more of an opportunity
to encounter the right environmental conditions. Verticillium lecanii has
made a strong comeback in the 1990s and many commercial formulations are
available. One important reason for this is development of resistance to
pirimicarb in aphid populations throughout Europe (Jacobson, 1990).
Verticillium lecanii has the greatest chance of success where environmental
conditions necessary for infection are satisfied; such locations include
rooting areas with regular misting and production chrysanthemums after
black shade cloth is pulled to initiate flowering (Vehrs & Parrella,
1991) In more open greenhouses these conditions Will rarely be met and
the use of the product is probably not worthwhile. For example in Bogota,
Colombia, the endemic fungus Zoophthora erinacea appears to have much more
potential than V. lecanii for aphid control on chrysanthemums because it
is more locally adapted to growing conditions in the savannah (Hall, 1985b)
In this area shading of chrysanthemums with black cloth to induce flowering
is not necessary, this further reduces the possibility of correct environmental
conditions for V. lecanii. Fransen (1990) suggests that when searching
for and evaluating biotypes of fungi for biological control, studies should
be done on intact plants under fluctuating environmental conditions typical
of actual production areas.
Fungi in the genus Aschersonia are specific for whiteflies and do not
have the strict environmental conditions required for infection outlined
above. Successful whitefly control has been achieved at 50% RH and 20 C’.
However, the microenvironment of the plant may have allowed for a higher
RH near the boundary layer of the leaf where the fungus is active (Fransen,
1990). The conidia of Aschersonia may survive up to 28 days in the greenhouse
(as opposed to 5 days for V. lecanii) but a major drawback is that these
conidia must be dispersed by water in order to infect new whiteflies and
cause the desired epizootics. Hence good coverage of new foliage is essential
when making applications. Frequent low dose and low volume applications
of A. aleyrodis, as suggested for V. lecanii (Helyar & Wardlow, 1987)
may have great potential.
The fungus Paecilomyces fumosoroseus is being developed for commercial
use and may be available as early as 1992. The fungus was originally targeted
for whitefly control, but the broad spectrum of its activity has led to
a label that will probably also include aphids and western flower thrips
(Osbome et al., 1990). Materials and Methods: With material provided from
Grace/Sierra we plan to evaluate fumosoroseus for control of the sweetpotato
whitefly and western flower thrips with cooperating growers (Oki Nursery
in Sacramento will the site for this work). In normal production, three
pots infested with whiteflies from each bench in the trial will be flagged
and all stages counted from three leaves per plant. There will be five
benches per treatment set up in a randomized design in the greenhouse.
Applications of the fungus in dilute spray will be made and counts of whiteflies
will follow on days 7, 14, and 21 after the spray. Population development
and the age structure of whiteflies on leaves from flagged plants will
be determined. This will be compared to control plants on benches not treated
with pesticides and contrasted with plants from benches under the growers
normal spray program.
The same procedure will be followed with aphids and western flower thrips
except that chrysanthemums will be host plant. The impact of the the fungus
on WFT will be done in our greenhouses at Davis. Pots of chrysanthemum
will be artificially infected with WFT and then they will be sprayed with
the fungus. All thrips in the central terminal and leaves will be counted.
There will be 10 treated and untreated pots for comparison. To evaluate
the control potential of this fungus in the soil, second instar western
thrips will be added to the soil of 30 chrysanthemum pots; 10 will be treated
with water plus fungus, 10 with water alone, and 10 untreated. Plants will
be cut at the soil line and a plastic I liter container will be inverted
over the pot with a blue sticky card attached to the upper inside of the
container. After 7 days, the number of thrips on the cards will be counted.
d. Initiate the statewide implementation of an IPM/Biological control program
for potted chrysanthemums. Introduction and Background Information: The
focus of research funded by the Endowment in the area of pest management
is to develop pieces of a puzzle that when put together can lead to the
successful adoption of a pest management program by a grower. The best
way to characterize such a program is as follows: start with a clean crop
and greenhouse, screen where practical, implement cultural controls where
practical (weed control, etc.), monitor the pest populations so that pest
locations are pinpointed as to in the greenhouse and this is done early
in their development, and consider control strategies using the least toxic
chemical and/or biological control. The two crops considerable information
is available are poinsettias and chrysanthemums. However, there is a lack
of fully implemented programs that can be pointed to with pride as demonstrations
that the concepts can work in practice. It is these types of studies that
are needed for IPM/Biological control to be adapted on a wide scale (Parrella
1991). The lack of grower adoption of biological control/lPM is a major
criticism of the overall idea and much of this criticism is justified.
It is time that some of these programs be put together and put into practice.
The program ongoing on poinsettias in New York is an example of this implementation
effort (Miller 1990). In this proposal we plan to implement IPM/biological
control statewide in California for poinsettias and chrysanthemums. The
program for poinsettias must await the final evaluation of the ‘best’ sweet
potato whitefly natural enemy, but we are ready to implement a program
in chrysanthemums now.
