The Development of Integrated Pest Management in Floriculture Progress Report –September 1991
Date August 28, 1991
Title of Project The Development of Integrated Pest Management Strategies in Floriculture
Institution where work is being conducted Department of Entomology, University of California–Davis
Amount of Endowment Grant $ 41,880
Covering Period 1/1/91 to 12/31/91
Anticipated Date of Project Completion/Final Report –
Individual(s) Conducting Project:
(List Project Leader First)
Michael P. Parrella - Title Professor & Chairman
TelephoneNumber (916) 752-0492
The Development of Integrated Pest Management Strategies in Floriculture
Michael P. Parrella
University of California-Davis
- The four major areas of my research funded by the Endowment for1991 are:
- 1) biological control of major floriculture pests,
- 2) biological studies with major floriculture pests and their natural enemies,
- 3) pesticide efficacy and compatibility with natural enemies, and
- 4) continued search of the literature dealing with pests of floricultural crops.
- Each of these areas are briefly summarized below.
- 1. Biological Control:
- Biological control within the context of floriculture production differsfundamentally from biological control within general agriculture. Major
differences lie with the crops themselves because aesthetic value is the
ultimate measure of quality and there is a great need to keep pest
populations at low levels throughout the duration of the crop. This being
the case, the selection of the most suitable natural enemy to use in field or
greenhouse vegetables may prove to be an inadequate natural enemy
when used in floriculture production. Such was the case with the
commercially available natural enemy, Encarsia formosa, which has a
proven track record of successful whitefly control in greenhouse
vegetables but was less than satisfactory when used for control of
sweetpotato whitefly on commercially grown poinsettias (1). A search for
new, effective natural enemies must include criteria which evaluate the
following: 1) the ability of the natural enemy to locate low levels of
patchily distributed pests on plants in the greenhouse, and 2) once
discovered, the natural enemy must be able to eliminate (or nearly so) the
pest infestation.
- We are currently evaluating the following natural enemies forsweetpotato whitefly control utilizing the above criteria: five parasitoids -
Encarsia formosa, Encarsia tabacivora, Encarsia deserti, Encarsia transvena,
Eretmocerus californicus; one predator - Delphastus pusillus; and one
pathogen, Paecilomyces fumosoroseus. Each of these is currently being
reared in my laboratory (except the fungus) on sweetpotato whitefly
infested poinsettia; keeping the colonies separate and at suitable levels for
research is a major undertaking. Data is rapidly being assimilated but it is
still too early to make a definitive statement concerning which one(s)
might be the best to use for biological control of sweetpotato whitefly.
- The natural enemies are being evaluated in the following ways: 1) Dothey respond in an olfactometer to whitefly infested leaves? This test is
designed to measure long distance attraction and may reflect the ability of
the natural enemy to detect low levels of whiteflies in a poinsettia range.
2) Can the natural enemies distinguish between infested and non-infested
poinsettia leaves? This may relate to their searching efficiency in a
poinsettia greenhouse — those that can make the distinction may utilize
their time better in a greenhouse by avoiding leaves not infested with
whiteflies; and 3) what is the ability of the natural enemy to inflict
mortality on the whitefly population? This provides an overall indication
of innate ability to control the whitefly population.
- Currently E. tabacivora and D. pusillus have achieved high scoresfollowing the protocol outlined above. In addition, we have found that D.
pusillus will not feed on parasitized whiteflies so the predator may be
compatible with the best parasitoid. Furthermore, E. tabacivora has been
found to spontaneously invade poinsettia greenhouses in California and
provide appreciable mortality of sweetpotato whitefly. This suggests that
the parasitoid is able to survive and do well on poinsettia under
commercial greenhouse conditions. Putting all of this together, E.
tabacivora may be the best parasite. However, this opinion may change as
more data are collected. Ms. Judy Nelson (Ph.D candidate) has chosen to
examine various aspects of the biology/ecology, mass-rearing, and the
biological control potential of this parasite for her dissertation research.
- Identifying superior natural enemies is one phase in the biologicalcontrol effort; developing mass-rearing strategies and identifying
commercial insectaries willing to do the rearing are two other important
steps. Colony maintenance for research purposes provides valuable
information that can be used in a mass-rearing project so in that sense we
have applicable data. In addition, we plan to devote considerable time to
this effort utilizing host plants other than poinsettia; studies are planned
to make sure that rearing on this different host does not affect the natural
enemies ability to search and kill whiteflies on poinsettia. This work will
be done in conjunction with commercial insectaries to take advantage of
their expertise in mass-rearing. A number of commercial insectaries have
expressed an interest in working with us during this phase. For example
we have already supplied Bunting Biological Control, Inc. (a commercial
insectary in Ventura Calif.) with a number of D. pusillus which they could
use as a starter colony; they would be eager to receive a parasitoid.
- Data has been gathered which suggests that not all poinsettia cultivarsare the same in terms of a parasitoid’s ability to search leaves and to find
and kill whiteflies. It appears that those cultivars with a greater number
of hairs on the underside of leaves have a detrimental effect on the ability
of a parasitoid to find its host. This is a complicating aspect for successful
biological control but it is a fact that must be taken into consideration.
- Research with leafminer parasitoids continues and these are also rearedon a regular basis in my laboratory. For a time we produced both
Diglyphus begini and Diglyphus isaea (the latter is widely used for
leafminer control in Europe). Comparative studies suggested that there
was not much difference between the two, so we continued to focus on D.
begini. Considerable data has been collected on D. begini’s foraging ability
in the greenhouse: response in the olfactometer, response to infested and
non-infested plants, etc. Much of this work was used to develop the
bioassay for whitefly parasitoids outlined above. Two manuscripts have
been prepared on this work and are currently in internal review. Our D.
begini production is such that we are able to make substantial field
releases. These parasitoids have been used in further validation of the
predictive biological control model developed last year (this was done in
the greenhouses at UC Davis) and a manuscript is in preparation. In
addition, we plan to make greenhouses releases against the pea leafminer,
Liriomyza huidobrensis, attacking chrysanthemum (in Europe this species
is referred to as the South American leafminer). We are finding this
species attacking chrysanthemum in California with disturbing regularity.
- Research with biological control of aphids continues; the focus is on thecommercially available predator, Chrysoperla carnea. We have compared
commercial shipments of eggs glued to cards with eggs contained in lose
rice hulls and found less overall mortality with the eggs in rice hulls.
Studies are continuing with an evaluation this predator (and application
technique) for control of aphids on potted chrysanthemum.
- Biological control studies with the western flower thrips haveproceeded more slowly than originally planned because it has taken more
time to complete the biological/ecological studies. A thorough
understanding of the biology of western flower thrips is essential to the
effective use of any biological control agent.
- 2. Biological Studies:
- The biology/ecology of western flower thrips in carnation is beinginvestigated in detail. Initially, it appeared that oviposition was restricted
to the calyx and bracts around the opening flower bud. However, although
there is a marked preference for egg-laying in these areas, subsequent
studies have shown that oviposition can and does occur in the terminal
foliage. Studies are ongoing to further document this in choice studies. In
addition, the viability of eggs and survival of subsequent offspring will be
evaluated within different parts of the carnation plant. Studies are
ongoing to define the primary pupation site of the thrips in carnation.
Much of these data were presented at the Pacific Branch of the
Entomological Society of America meetings held in June, 1991. Additional
information on the general biology/ecology of the western flower thrips as
a general floricultural pest has been published (2).
- Research with the green peach and melon aphids on chrysanthemumhas been completed (7). In general, the chrysanthemum plant was found
to be a much better host for the melon aphid as compared to the green
peach aphid. While both species could be found all over the plant, the
melon aphid tended to be scattered on all leaves while the green peach
aphid was more concentrated in the terminal growth point.
- A considerable amount of data has been gathered on the distribution,abundance and phenology of sweetpotato and greenhouse whiteflies in a
commercial poinsettia range. Much of this data was presented at the
Pacific Branch of the Entomological Society of America meetings held in
June, 1991. These data can be used to develop a sampling plan but
additional data must be obtained from other production greenhouses
before a reliable sampling plan can be promulgated. The strong tendency
for whiteflies to oviposit on young foliage generated different age class
distributions within the poinsettia plant (top to bottom). Therefore, where
on the plant leaf samples are taken is critical if an accurate assessment of
the stage of whitefly in the crop is to be made. The overall study began
with mixed population of both whitefly species, but this was soon
dominated by the sweetpotato whitefly. This is further evidence that the
sweetpotato whitefly is a greater threat to the poinsettia crop and that
where mixed populations occur, the sweetpotato whitefly may soon be the
dominant species.
- A more efficient way to utilize yellow sticky cards to monitor a varietyof pests in the greenhouse (whiteflies, aphids, western flower thrips, and
leafminers) has been developed (6, 10). This technique requires that only
a portion of a card (a vertical one inch band) be counted. With this
technique, an accurate estimate of the total number of insects on the entire
card can be calculated quickly.
- 3. Pesticide Efficacy and Compatibility:
- Several new products continue to look good for control of a widevariety of floricultural pests. An example of this is Bay NTN 33893
(Mobay) which continues to amaze all with its total kill and longevity of
this action. Neem derived products (W. R. Grace and NPI) are being
evaluated in side by side comparisons. These studies are not completed
but to date Margosan 0 (W. R. Grace) has provided better control of aphids
and whiteflies than in last years trials. Evaluations of the fungi
Verticillium lecanii and Paecilomyces fumosoroseus, conducted with
cooperating growers, have proven to be disappointing. This is in marked
contrast to results reported from Florida. However, it should be stressed
that these studies must be repeated and data are still preliminary.
- The focus continues to be on ‘biorational’ type materials (e.g., insectgrowth regulators) and these studies are ongoing. Many of these products
are evaluated for their compatibility with leafminer and whitefly
parasitoids. Much of this work was outlined in a recent publication (9).
- Baseline data on the response of western flower thrips to abamectin(Avid, Merck & Co.) and the insect growth regulator fenoxycarb (Whitmire)
are being generated. For Avid, we are evaluating the response of first and
second instars and adults. The younger instars are more susceptible, but it
still requires as much as three days before mortality occurs. Baseline data
are being collected for our ’susceptible’ laboratory colony and this is being
compared to the response of thrips populations collected from cooperating
growers where abamectin has been used. We are finding evidence that
resistance may be developing. Such information is critical to extending the
effective field life of this important material. I am working with Merck
representatives to develop guidelines for managing resistance
development and these will be presented in a series of grower seminars in
California. In addition, as one of two agricultural advisors in the U. S. to
Merck, Sharp and Dohme., I will be presenting the baseline toxicological
data for thrips (discussed above) at an annual December meeting held in
New Jersey. At that time we will discus the prospects and possibilities for
adding western flower thrips to the Avid label.
- 4. Literature Search:
- Literature continues to be compiled across all crops and pests attackingornamentals. A book chapter, describing the greenhouse ecosystem, has
been completed and submitted (8). This is currently undergoing outside
external peer review.
- Scientific Articles (Published):
- 1. Parrella, M. P., T. D. Paine, J. A. Bethke, K. L. Robb, & J. Hall. 1991.Biological control of sweetpotato whitefly (Homoptera: Aleyrodidae) on
commercially grown poinsettia stock production. Environ. Entomol. 20:
713-719.
- 2. Robb, K. L., & M. P. Parrella. 1991. Western flower thrips: a serious pestof floricultural crops. pp. 343-357 In. B. L. Parker, M. Skinner, & T. Lewis
(eds.). Towards Understanding Thysanoptera. US Department of
Agriculture, Forest SeTVice, North East Forest Experiment Station,
Agriculture Experiment Station, University of Vermont: General Technical
Report NE-147.
- Scientific Articles (In Press):
- 3. Heinz, K. M., & M. P. Parrella. 1991. The effect of leaf-mining byLiriomyza trifolii (Burgess) on seed set in greenhouse marigolds. Ecological
Applications.
- 4. Lasalle, J., and M. P. Parrella. 1991. The Chalcidoid Parasites(Hymenoptera, Chalcidoidea) of Economically Important Liriomyza Species
(Diptera, Agromyzidae) in North America. Proceedings of the
Entomological Society of Washington.
- 5. Parrella, M. P., K. M. Heinz, & L. Nunney. 1991. Biological controlthrough augmentation of natural enemies: a strategy whose time has
come. American Entomologist.
- Scientific Articles/Book Chapters (Submitted):
- ^1 Some publications are listed only to provide a status report; they were discussedmore fully in the progress report from 1990. If a publications status has not changed
from last years progress report (e.g., if it is still ‘in press’) then it is not listed.
- 6. Heinz, K. M., & M. P. Parrella. 1991. Time efficient use of yellow stickytraps in monitoring insect populations. Journal of Economic Entomology.
- 7. Vehrs, S. L., G. P. Walker, & M. P. Parrella. 1991. Comparison ofpopulation growth rate and within plant distribution between Aphis
gossypii Glover and Myzus persicae (Sulzer) (Homoptera: Aphididae)
reared on potted chrysanthemum. Journal of Economic Entomology.
- 8. Parrella, M. P. 1991. Arthropod fauna. Chapter 10. Part C. TheGreenhouse Ecosystem. Part of the Elsevier Series — Ecosystems of the
World. 107 pp. submitted.
- Grower Articles/Monthly Column (Published):
- 9. Heinz, K. M., & M. P. Parrella. 1991. Pesticides compatible with naturalcontrol agents: putting integration into greenhouse IPM. Greenhouse
Grower 9(3): 67 - 68.
- 10. Heinz, K. M. & M. P. Parrella. 1991. A shortcut with sticky traps.GrowerTalks 55(4): 40 - 42, 45.
- 11. Parrella, M. P. 1991. IPM with Parrella: Putting IPM into Practice.GrowerTalks 54(10): 79.
- 12. Parrella, M. P. 1991. IPM with Parrella: New pests. GrowerTalks54(11): 75.
- 13. Parrella, M. P. 1991. IPM with Parrella: IPM cuts production costs.GrowerTalks 54(12): 105.
- 14. Parrella, M. P. 1991. IPM with Parrella: Timing sprays. GrowerTAlks55(1): 87.
- 15. Parrella, M. P. 1991. IPM with Parrella: At war with nature. 55(4):123.
