Evaluation of Elevated CO2 for Control of Greenhouse Whiteflies on Poinsettias During Transit 1992 Proposal
whiteflies on poinsettias during transit
A. SUMMARY
For many years, poinsettias have been the leading flowering potted plant
in the United States. But even with the extensive research conducted on
this crop, elimination of whiteflies still remains a major challenge for
many growers. The problem arises frequently from purchased cuttings that
were infested with whiteflies in the propagation area. Growers face difficulties
with conventional spray because eggs and pupae are resistant to most insecticides.
In addition, the increasing pressure from many states restricting the amount
and type of pesticide used in greenhouses has forced the industry to examine
other non- chemical methods to control common greenhouse pests.
I propose to investigate the possible use of short-term elevated CO2
to eliminate whiteflies that may remain on poinsettia cuttings after shipment
from the propagators house. The short-term elevated CO2 treatment will
be applied during the transit period. The duration and concentration of
CO2 required to eradicate the pest will be investigated in this study.
If proven to be effective, the proposed method would provide the industry
a non- chemical way of controlling the spread of whiteflies through infested
cuttings, and consequently, reduce the application of pesticides. Exclusion
of insects from infested plant materials in conjunction with integrated
pest management may soon become a fundamental practice for growers to meet
the increasing expenses and restrictions associated with the use of pesticides.
B. DETAILED PROPOSAL
1. Introduction and background information
Poinsettias have been the leading flowering potted plant in the United
States for many years. But even with the extensive research conducted on
this crop, elimination of greenhouse whiteflies (Trialeurodes vaporariorum)
still remains a major challenge for many poinsettia growers. The problem
arises frequently from purchased cuttings that were infested with whiteflies
in the propagation area. Thus, one of the first “lines of defense” against
this pest should be the prevention of their entrance into the greenhouse.
Conventionally, whiteflies are controlled by spraying poinsettia plants
with insecticides. The main difficulty associated with chemical control
is the resistance of eggs and pupae to most insecticides available in the
market. The few eggs or pupae that arrive with the cuttings may go undetected
and later develop into a heavy infestation in the greenhouse. In addition
to the inadequate control of whiteflies with chemicals, the increasing
number of regulations and restrictions on chemical use in the greenhouse
have pressured the industry to seek alternative methods for insect controls.
Currently, many small greenhouse operations in the United States purchase
poinsettia cuttings from nearby operations that are licensed to propagate.
Cuttings delivered from these local establishments frequently carry some
whiteflies that will later develop into a heavy infestation in the grower’s
site. Finding a mean to completely eliminate those few whiteflies should
be a priority for the industry. I propose to test if short-term elevated
CO2 treatment can be used to eradicate whiteflies in poinsettia cuttings
prior to their arrival at the grower’s greenhouse. The treatment can be
applied prior to shipment or during transit. Commercially, elevated CO2
treatments are used for long-term storage of some edible commodities. In
recent years, the treatment was also evaluated for possible use as a quarantine
treatment on imported edible commodities. There are limitations when the
treatment is used on bulky tissue as anaerobic respiration occurs and afters
the flavor of the commodities. On the other hand, floricultural crops have
been shown to tolerate very high levels of CO2 with no adverse consequences.
The levels are much higher than those reported to eradicate many insects.
This has lead me to believe that short-term elevated CO2 treatment may
be used during the transit period (from propagator to grower) to eliminate
whiteflies on poinsettia cuttings. The effectiveness of the method should
greatly reduce the occurrence of whiteflies from purchasing infested cuttings.
2. Review of significant literature
Use of modified atmosphere (MA) for long-term storage and pathogenic
control on edible crops has been intensively investigated. The method refers
to changes in the composition of the air surrounding the commodity. Usually
this involves reduction of oxygen levels and/or elevation of carbon dioxide
levels. Differential responses of plant species to MA have been reported.
Responses include reduced respiration, inhibited initiation of ripening,
inhibited production and actions of ethylene, retarded chlorophyll degradation
and reduced chilling injury. Prolonged exposure of edible crops to the
modified atmosphere frequently causes anaerobic respiration, and consequently,
results in the accumulation of ethanol, acetaldehyde, and other volatile
compounds in the tissues (Davis, et al., 1973; Norman and Craft, 1971;
Pesis and Avissar, 1989). Commodities differ in their susceptibility to
modified atmosphere and the recommendations for the level of tolerance
to reduced O2 and/or elevated CO2 varies. The differences are suspected
to be due to the variations in structural (anatomical) rather than metabolic
differences among commodities.
MA studies showed more tolerance of floriculture crops than edible commodities
to elevated CO2 or reduced O2. Vase life of anthuriums (Akamine and Goo,
1981), carnations (Hanan, 1967), daffodils (Parson et al., 1967), gladiolus,
roses, and snapdragons (Thornton, 1930) were reportedly extended by MA
under various combinations of O2 and CO2 concentrations. More recently,
the possible use of MA to suppress pathogenic activities in floriculture
crops was investigated. The study was initiated to appraise the possible
use of MA to prolong the storage life of various species of cut flowers
(Joyce and Reid, 1985). Results from the study demonstrated that many floriculture
crops can tolerate very high concentrations of CO2. Exposure of cut lilies,
iris, carnation, gypsophila, daffodil and cyclamen to 60% CO2 for 7 days
had no deleterious effects on the flowers. This level of CO2 was significantly
higher than those normally considered harmless for edible crops. The authors
indicated that one major difference between flowers and many other horticultural
commodities is their high surface/volume ratio. This may reduce the CO2
injury caused by CO2 accumulation in bulky organs exposed to similar concentrations
of the gas.
The possible use of MA for insect control has been investigated in many
edible crops. Studies were conducted for two purposes: (a) insect control
in long-term storage areas or (b) short-term exposure of MA as a quarantine
treatment for postharvest insect control. In most cases, MA combinations
needed for long-term insect control could not be tolerated by the commodities
and resulted in faster deterioration. In contrast, short-term exposure
to MA has been reported to results in no detrimental effects on the appearance
or nutritional value of oranges (Ke and Kader, 1990) and other edible crops
and could possibly be used as a quarantine treatment on imported edible
crops.
The composition of atmosphere required for effective insect control
is dependent upon the species of insect. Both elevated CO2 and reduced
O2 were investigated. The former was more effective than the latter in
eliminating Caribbean fruit fly (Benschoter, 1987). Carbon dioxide level
>50% is required for effective control of codling moth (Soderstrom and
Brandl, 1987). A lower CO2 concentration was reported to be as effective
as higher concentrations for controlling the eggs and larvae of Caribbean
fruit fly (Benschoter, 1987). Exposure of eggs and larvae of Caribbean
fruit fly to CO2 concentrations of > 20% for 7 days resulted in complete
eradication of the insects.
As stated, many floriculture crops have been shown to tolerate up to
60% CO2 for 7 days without any signs of deleterious effects on their postharvest
life (Joyce and Reid, 1985). Correspondingly, 20% and 50% CO2 is sufficient
for effective control of Caribbean fruit fly and codling moth, respectively
(Benschoter, 1987; Soderstrom and Brandl, 1987). These data lead us to
believe that short-term exposure to elevated concentrations of CO2 prior
to or during shipping may be an effective way of eliminating whiteflies
on poinsettia cuttings. Elevated CO2 was chosen in this study over the
reduced O2 system for two reasons. First, elevated CO2 atmosphere has been
shown to be a more effective way of controlling Caribbean fruit fly than
the reduced O2 atmosphere (Benschoter, 1987). Second, an elevated CO2 atmosphere
system is a more feasible system for growers to install than the reduced
O2 system. Carbon dioxide cylinders or CO2 generators are available commercially
for CO2 enrichment in the greenhouse. A sealed room with proper air circulation
or a sealed container with an opening for CO2 injection is the only installation
needed for the application of this technique.
3. Objectives of proposed research project
I propose to study the efficacy of elevated CO2 for insect control of
whitefly on poinsettia cuttings. Presently, experimental data pertaining
to the tolerance level of different stages of whiteflies to elevated CO2
and the responses of poinsettia cuttings to short-term elevated CO2 treatment
are unknown. The objectives of this proposal are; 1) to determine the effects
of elevated CO2 on survival rate of different stages of whitefly; 2) to
determine the tolerance level of poinsettia cuttings to elevated CO2; 3)
to investigate the effects of elevated CO2 on rooting capability of unrooted
poinsettia cuttings; and 4) to examine the effects of elevated CO2 on establishment
of rooted cuttings.
4. Materials and Methods
The research to be conducted under each objective is outline independently.
Plant materials will initially be obtained from suppliers. Plants will
be grown in the Department of Plant and Soil Sciences glass-covered greenhouses
(18′C night temperature). The modified atmospheric chambers will be situated
in temperature controlled incubators in the laboratory. The elevated CO2
will be applied by venting atmospheric chambers with a constant flow of
factory-mixed gases.
(a) Optimum temperature and CO2 levels required for maximum control
of the insect Greenhouse whiteflies of different developmental stages will
be collected and placed in atmospheric chambers vented with a constant
flow of variable concentrations of CO2 at predetermined levels. Control
treatment will be vented with air (0.03% CO2). Chambers will be vented
with the modified air for 3, 5, 7, or 10 days and thereafter, vented with
air. The atmospheric chambers will be placed in temperature controlled
incubators. Two temperatures, 15′C and 20′C, will be tested for each of
the CO2 concentration chosen. Different temperatures are tested because
temperature will determine the lethal effects of atmospheric gases on insects
(Marzke et al., 1970). The optimum level of CO2 required for effective
insect control will be determined by the number of treatment days required
to achieve 100% elimination of the insects. For egg and larval stages,
the survival rate will be calculated after allowing sufficient time for
the development of the insects. Normally formed pupana will be counted
as survivors.
(b) Tolerance of poinsettia cuttings to elevated CO2 atmosphere Poinsettia
cuttings, both unrooted and rooted, will be placed in atmospheric chambers
vented with a constant flow of variable concentrations of CO2 at predetermined
levels. Control cuttings will be those treated with constant flow of atmospheric
air. The chambers will be placed in 2 temperature controlled incubators
as previously described in objective (a). Immediately after the 3-, 5-,
7-, or 10-day exposure, signs of physiological disorders such as discoloring
or wilting of the leaves and stems will be noted. Cuttings will then be
placed in a simulated shipping environment for 0 to 7 days. The extent
of chlorophyll degradation from the shipment will be recorded. Results
from this study should indicate to us the maximum level of CO2 poinsettia
cuttings can withstand without any subsequent deteriorating effects.
Effects of elevated CO2 on rooting of poinsettia cuttings The purpose
of this study is to evaluate if elevated CO2 treatment on unrooted cuttings
affects their subsequent ability to root. Unrooted poinsettia cuttings
will be placed in atmospheric chambers as previously described. After the
treatments, cuttings will be divided into 2 groups. Half of the cuttings
will be placed in a simulated shipping environment for 2 days before propagation,
the other half will be propagated immediately after the treatment. Cuttings
will be planted in pasteurized medium and placed in the propagation house
under mist for 21 days. Cuttings will be planted and grown at 18′C night
temperature greenhouse. Data will be collected on the number, length, and
dry weight of the roots at 2 and 3 weeks after propagation.
Effects of elevated CO2 on establishment of rooted cuttings The purpose
of this study is to investigate how elevated CO2 treatment on rooted cuttings
affects the establishment of the cuttings in growers’ site. Rooted cuttings
will be placed in atmospheric chambers as previously described. Cuttings
will be divided into 3 groups immediately after the treatments. Two groups
will be placed in a simulated shipping environment for 2 and 7 days before
planting. The third group will be planted immediately.
The cuttings will be planted in 10cm diameter pots and grown in a 17′C
night temperature greenhouse. Data will be collected on the height and
dry weight of the shoots at 4 and 6 weeks after planting.
5. Facilities and Equipment Available
All facilities and equipments needed for this project, including greenhouse
bench compartments, propagation benches, temperature-controlled incubators,
gassing chambers and gas chromatography are available at the University
of Massachusetts.
6. Literature Cited
Akamine, EX and T. Goo. 1981. Controlled atmosphere storage of anthurium
flowers. HortScience 16(2): 206-207.
Benschoter, C.A. 1987. Effects of modified atmospheres and refrigeration
temperatures on survival of eggs and larvae of the Caribbean fruit fly
in laboratory diet. J. Econ. Entomol. 80:1223-1225.
Davis, P.L. and W.G. Chace, Jr. 1969. Determination of alcohol in citrus
juice by gas chromatographic analysis of headspace. HortScience 4:117-119.
Hanan, J.J. 1967. Experiments with controlled atmosphere storage of
carnations. Proc. Amer. Soc. Hort. Sci. 30: 370-376.
Joyce, D.C. and M.S. Reid. 1985. Effect of pathogen-suppressing modified
atmospheres on stored cut flowers. In: Blankenship (ed.). Controlled atmospheres
for storage and transport of perishable agricultural commodities. Hort.
Report. No. 126. NC State Univ., Raleigh.
Ke, D. and A. A. Kader. 1990. Tolerance of ‘Valencia’ oranges to controlled
atmospheres as determined by physiological responses and quality attributes.
J. Amer. Soc. Hort. Sci. 115(5):779-783.
Marzke, F.O., A.F. Press, Jr., and G.C. Pearman, Jr. 1970. Mortality
of the rice weevil, the Indian-meal moth, and Trogoderma glabrum exposed
to mixtures of atmospheric gases at various temperatures. J. Econ. Entomol.
63:570-574.
Norman, S.M. and C.C. Craft. 1971. Production of ethanol, acetaldehyde
on postharvest quality of mechanically harvested strawberries for processing.
J. Amer. Soc. Hort. Sci. 104:242-264.
Parsons, C.S., Asen, S., and Stuart, N.W. 1967. Controlled atmosphere
storage of daffodil flowers. Proc. Amer. Soc. Hort. Sci: 90:506-514.
Pesis, E. and I. Avissar. 1989. The postharvest quality of orange fruits
as affected by pre- storage treatments with acetaldehyde vapor or anaerobic
conditions. J. Hort. Sci. 64: 107-113.
Soderstrom, E.L. and D.G. Brandl. 1987. Controlled atmospheres for postharvest
control of codling moth on fresh tree fruits. California Tree Fruit Agreement,
Sacramento. CTFA 1986 research report.
Thornton, N.C. 1930. The use of carbon dioxide for prolonging the life
of cut flowers, with special reference to roses. Amer. J. Bot. 17: 614-626.
7. Detailed Budget
The funds requested will fund a part-time technical support to work
on the project. The request for supplies is to support purchase of plant
materials, pots, growing media, gas cylinders and other materials which
will be required to conduct this research.
Salaries (part-time technical support)
$4,500
Supplies
$1,500
Publication
$ 350
Data Processing and Analysis
$ 150
Total
$6,500
C. PROJECT LEADER QUALIFICATIONS
The principal investgator has a Ph.D. degree in plant physiology from
the Univ. of California-Davis and a M.S. in floriculture from the Univ.
of Missouri-Columbia. This unique educational background has enabled me
to conduct both basic and applied research that are critical to the floricultural
industry. I have past experience in the installation of constant gas concentration
in a flow system. This experience will enable me to set up the proposed
elevated CO2 chambers. In addition, the proposed study will be conducted
with the assistance of an entomology professor and an extension floriculture
IPM specialist. Our combined specializations should well qualify us to
conduct the proposed research project.
