Plant Resistance as a Part of Integrated Pest Management for Whiteflies on Floral Crops Progress Report — September 1992
Date 23 August 1992
Title of Project Plant Resistance as Part of IPM for Whiteflies on Floral Crops
Institution where work is being conducted Cornell University
Amount of Endowment Grant $27,000
Covering Period 1/92 to 12/92
Anticipated Date of Project Completion/Final Report one year hence
Individual(s) Conducting Project:
(List Project Leader First)
Dr. John P. Sanderson - Title Asst. Professor of Entomology
Telephone Number (607) 255-5419
Plant Resistance as part of IPM for Whiteflies on Floral Crops
John P. Sanderson
Cornell University
- A. Project Objectives:
- 1. Screen cultivars of several important floral crops for resistance to whiteflies.
- 2. Investigate the degree to which crop fertilizing practices affect whitefly biology (and
perhaps that of other pests), and determine if pest problems can be reduced by modifying
crop fertilizer programs without sacrificing crop quality.
cultivars.
Disease Mgt. (Feb., 1992, in Orlando, FL) presents an overview of much of our
progress.]
numbers. We are currently testing our suspicion that trichome (leaf hair) characteristics are
important. Trichome numbers per sq. mm vary significantly among the 26 poinsettia
cultivars tested. When whiteflies are provided a choice among cultivars, whitefly numbers
seem to be somewhat positively correlated with those cultivars that have higher trichome
densities. To test whether trichomes influence egg production, we tried several ways to
remove leaf trichomes without damaging the leaf, but were not successful. We are now
testing our hunch by looking at sweetpotato whitefly egg production in choice and no-
choice tests within and between groups of cultivars that have similar trichome densities.
We predict that egg production will be greatest on the cultivars with the most trichomes.
examining the influence of nitrogen fertilizer on whitefly biology for her M.S. thesis. She
has completed her last set of experiments and is currently analyzing her results. Generally
speaking, within the range of nitrogen fertilizer rates that are commercially typical, she has
seen relatively minor affects on sweetpotato whitefly egg production and developmental
time. We will provide a full report when her results are fully analyzed.
on chemical effectiveness is whether a cultivar’s plant architecture allows for effective
coverage and canopy penetration. Besides our on-going insecticide studies for sweetpotato
whitefly control, we recently evaluated the performance of two aerosol insecticide
formulations among several poinsettia cultivars. We Were interested in how cultivar
characteristics such as leaf shape, size, and canopy density would affect the effectiveness
of these aerosols against immature whiteflies (nymphs). One insecticide was a typical
nerve poison (PT 1200 Orthene plus PT 1800 Attain); the other was an insect growth
regulator (Preclude). No difference in mortality due to cultivar was noticed, but this was
largely because none of the insecticides were very effective in killing the nymphs. We
suspect that the aerosol formulations were not contacting the numphs where they occur on
the leaf undersurfaces, thus we saw no difference in nymph mortality among cultivars.
The mixture of PT 1200 Othene plus PT 1800 Attain was effective in killing adult
whiteflies, however, although more than 10 applications at 4 day intervals were necessary
to achieve adequate control of the serious whitefly infestation that was present at the start of
the trial. This information is important in order to properly know how to use these aerosol
insecticides and what to expect of them, We have additional studies planned or underway
with seven new insecticides or new insecticide formulations.
performance as well as whitefly numbers. The pattern of percent parasitism by Encarsia
formosa differed significantly among seven poinsettia cultivars in a previous study,
indicating a potential cultivar effect on the effectiveness of the wasps. We are examining
the impact of trichomes on parasitoid performance in conjunction with the work mentioned
in Objective 1. We are also beginning some evaluations of a new parasitoid species for
sweetpotato whitefly in these studies.
resistance to whiteflies. We will evaluate the importance of leaf trichome density (”leaf
hairiness”) on SPWF numbers on poinsettia in the short term, and other plant
characterisitics (e.g., sap content) in the future.
interpreted.
control, including an analysis of cultivar effect on insecticide performance.
efficiency and effectiveness. We plan to examine this experimentally in conjunction with
Objective 1, as well as with small scale field tests.
growers with more “least toxic” pest control strategies, and avoid problems associated with
the overuse of insecticides. Knowledge of plant resistance factors to whiteflies in
floricultural crops can be a valuable tool in breeding programs. For example, if trichomes
are important in plant resistance to whiteflies, this trait could be modified via breeding
programs. Screening popular cultivars for plant resistance can give growers information
on which cultivars should be carefully inspected and monitored for pest populations, or
those cultivars on which chemical or biological control will be more effective.
our New York State Greenhouse IPM effort, thereby testing it in the hands of growers and
eventually implementing it. From a scientific standpoint, these studies may be useful to
other scientists involved in plant breeding, chemical control, biological control, and IPM.
For example, our work with the influence of cultivar on whitefly parasites will complement
biological control studies underway by other entomologists. Our results may also be
directly applicable to plant resistance studies of other greenhouse pests.
