Insecticidal Controlled Atmosphere for Management of Sweetpotato Whitefly Progress Report — December 1995
Date
12/22/95
Title of Project Insecticidal Controlled Atmosphere for Management
of Silverleaf Whitefly
Institution where work is being conducted University of Massachusetts
Amount of Endowment Grant $14,174
Covering Period 2/95 to 1/96
Anticipated Date of Project Completion/Final Report 1/96
Individual(s) Conducting Project:
(List Project Leader First)
Dr. Susan S. Han - Title Assistant Professor
Telephone Number 413-545-5228
Insecticidal Controlled Atmosphere for Management of Silverleaf Whitefly
Susan S. Han
University of Massachusetts
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A. Project Objectives:
-
The main objective of the study is to investigate the potential use of
low-oxygen
atmospheres for control of silverleaf whitefly (Bemisia argentifolii)
on floricultural crops. The method
refers to reducing the levels of oxygen surrounding the plants. In
recent years, the use of elevated
CO2 or reduced 02 atmospheres to induce sublethal and lethal effects
on insects has provided an
excellent alternative to chemical fumigation for quarantine treatment
of imported edible crops. The
time required for 100% mortality of an insect depends on the species,
its developmental stage, and
the temperature and atmospheric composition during the treatment. Commodities
differ in their
susceptibility to CA and the recommendations for tile level of tolerance
to reduced 02 and/or
elevated CO2, varies (Ke and Kader, 1992). Floricultural crops can
tolerate higher levels of CO,
than most edible crops, perhaps due to the higher surface to volume
ratio (Joyce and Reid, 1985).
B. Results to date
Results from my laboratory have demonstrated that reduced 02 treatments
(<2 ppm
O2) are effective against both greenhouse and silverleaf whitefly.
Treatment time required for high
mortality rates depends on the developmental stage of the whitefly.
Adults and nymphs are sensitive
to the treatment where a 2 and 4 hr treatment at 20′C, respectively,
killed most of the insect. In
contrast, the egg and pupal stages are more resistant and required
an 8-hr treatment at 20′C to a
achieve high rate of mortality. The efficacy of the treatment increased
with an increased in
temperature from 20′C to 30′C. At 30′C, a treatment time of one-half
that of 20′C can be used to
achieve the same mortality rate.
We have evaluated the tolerance level of two cultivars
of geraniums
(’Red Orbit’and ‘Red Elite’) and two cultivars of coleus (Jazz Ruby’
and ‘Wizard Velvet) to tile
low-oxygen treatment. During the spring, seeds were sown and plants
were grown in the glasshouse
at the University of Massachusetts at Amherst. Plants were then treated
with a constant flow of air
(control) or with factory-mixed nitrogen gas (containing < 2 ppm
O2) at 200C for 0, 4, and 8 hr at
the 72-plug, 606 cell-pak, or 4″-pot stage. Following the gas treatment,
plants were transferred to a
larger container and were grown in the glasshouse for 4 weeks before
harvest. Data such as the
height, width, fresh weight and dry weight of the plants were collected
and analyzed statistically.
Results showed that of the two cultivars of geraniums tested, 8 hr
of low-oxygen treatment did not
affect the growth and develpment of the plants treated at the 6-pak
and 4″-pot stage. Geraniums
treated for 8 hr with low oxygen at the 72-plug stage were smaller
than those treated with air or 4-hr
low oxygen. The same studies repeated on two cultivars of coleus in
the summer showed that
treatments with low oxygen, up to 8 hr at 20′C, did not affect the
subsequent growth of the plants,
regardless of the stage of development. Results thus suggested that
the susceptibility of plants to the
low oxygen treatment depends on the developmental stages of the plants.
Casual observation
indicated that plants grown in the summer were less susceptible to
the low-oxygen treatment than
those grown in the spring perhaps owing to the higher light levels
in the summer. Further studies will
be conducted to confirm the observation.
C. Future plans
We are currently evaluating the insecticidal effects
of low-oxygen atmospheres on silverleaf whitefly when treated at 25′C.
In addition, we will
continue our investigations on the tolerance levels of various species
of annuals to the reduced-02
environment. D. Benefits for floral industry With the anticipated ban
of methyl bromide, a fumigant
widely used by the floricultural industry, finding a alternative means
to disinfest plant materials will
become a priority in the industry. The proposed method of reduced-02
insecticidal controlled
atmosphere would provide the greenhouse industry wit an environmentally-safe
way of controlling the
spread of whitefly through infested plant materials. The use of this
technique can be incorporated into
an Integrated Pest Management (IPM) program. Practice of such an approach
would drastically
reduce the amount of hazardous pesticides used, and would increase
profitability to the greenhouse
industry by reducing pesticide costs and increasing the quality of
the product.
