Evaluation of Controlled Atmosphere Anoxia Treatments as a Potential Disinfestation Technique for Thrips and Spider Mites in Greenhouses. 1996 proposal
Executive Summary
Controlled atmosphere (CA) Technology is a standard technique for the post
harvest
handling of fruits, vegetables and stored grains and is one of the main
reasons that high quality
produce is available throughout the year in the U.S. CA technology is a
simple and
environmentally safe way to manage post harvest insect and disease problems
in cold storage.
The use of low oxygen (anoxia) and high carbon dioxide and nitrogen environments
simply
smother insects. Anoxic environments could be a practical, cost-effective
and safe way to kill all
life stages of insects and mites that infest greenhouse flower crops. Unfortunately,
nearly all
information on effects of anoxic environments on insects concerns pests
of fruits, vegetables and
grains in storage.
This proposal evaluates the potential for using CA anoxia treatments to
control thrips and
two-spotted spider mites on garden impatiens and New Guinea impatiens,
common and
relatively fragile bedding plants. Combinations of N2, CO2 and O2 concentrations
and treatment
times will be evaluated for their impact on all life stages of thrips and
mites at cold, cool and
warm temperatures. This will be followed by an evaluation of the tolerance
of impatiens to
critical thresholds required for elimination of pests. Finally, impatiens
will be infested with
thrips and mites to evaluate the overall efficacy of CA anoxia treatments
under simulated
production conditions. If successful, it is feasible that truckloads of
bedding plants can be
disinfected with CA as they travel to their destinations or simply overnight
before shipment.
Introduction & Literature Review
The production of flowering plants, usually in protected cultivation, is
an economically
important part of agriculture and the fastest growing sector of agriculture
in grower cash receipts
(Johnson and Johnson 1993). Insects and mites account for significant economic
losses and
large scale pesticide usage in flowering plant production.
Thrips are among the most injurious and difficult to control of the greenhouse
pests.
Thrips not only cause damage by feeding but can also vector the important
pathogen, impatiens
necrotic spot virus, INSV (Lewis 1973, Moorman 1994). Similarly, spider
mites are an
important part of the greenhouse pest complex. Spider mites cause damage
by piercing plant
cells and feeding on the contents and by producing webbing on the host
plant. Consequences of
spider mite feeding for host plants include reduced vigor in flowering,
growth and yield
(Tomczyk and Kropczynska 1995). The webbing itself can reduce the marketability
of any
floricultural crop (Van De Vrie 1985).
Cultural, biological and chemical methods are used to control greenhouse
pests but all
have disadvantages. Cultural control practices for thrips and spider mites
include exclusion by
MA
screening, beginning the production cycle with pest-free propagules, and
maintaining a pest-free
facility (Baker 1994). Predaceous mites and thrips, as well as fungal pathogens,
are sometimes
effective for biological control of spider mites and thrips (Van Lenteren
and Woets 1988,
Lindquist 1995). Chemical controls are generally effective but have the
practical disadvantage
of the restrictions specified in the Worker Protection Standard (WPS).
In addition to these
restrictions, chemical controls can create resistance problems (Van Lenteren
and Woets 1999,
Immaraju et al 1992, Brodsgaard 1994).
Controlled atmosphere (CA) or modified atmosphere technology has been used
by the
gram, fruit, and vegetable industries for disinfection of their products
for at least 20 years.
Factors that can influence the effectiveness of the modified atmosphere
conditions include:
atmospheric composition (percent of carbon dioxide, oxygen, and nitrogen);
relative humidity
(water loss); time; pest species; and pest life stage (Ke and Kader 1992,
Fleurat-Lessard 1990).
The general effect of controlled atmosphere conditions is to remove or
limit the oxygen source of
arthropod pests. Typically, as the oxygen concentration decreases, the
rate of kill increases (Ke
and Kader 1992, Fleurat-Lessard 1990). Nitrogen gas alone induces hyperactivity
followed by
immobilization as a result of the anoxia or hypoxia. Carbon dioxide, like
nitrogen, causes
immobilization but it also induces opening of the spiracles. Thus, one
of the primary effects of
carbon dioxide is the loss of water by insects exposed to anoxic conditions
which ultimately
leads to mortality. Carbon dioxide alone at concentrations of 35-60% gives
almost 100% control
of all life stages of most stored grain pests (Fleurat-Lessard 1990).
Mites are generally harder to kill than insects. Age, condition (active
or quiescent) and
feeding status of arthropods can also influence their tolerance to elevated
levels of carbon
dioxide, or hypercarbic conditions. Hypercarbic conditions are also linked
to physiological
disorders such as decreased fecundity or longevity as well as disrupted
metamorphosis (Fleurat-
Lessard 1990).
In addition to the effect of CA on pests, the effect on the crop plant
is also important
Anoxic conditions have been used to disinfect cutflowers during storage
and/or transport to
market (Zheng et al 1993). Most of the insecticidal CA research has been
done at temperatures
in the range of 0-12C (Aharoni et al 1981, Bond and Herne 1983, Zheng et
al. 1993), while
other work (Akluting et al. 1991, 1995) has been at temperature ranges
of 20-40′C. Cutflowers
and chrysanthemum cuttings can be treated at temperatures of 0-10′C, but
potted plants and
Potter and Anderson - Anoxia Effects r,9 Greenhouse Insects
some other propagules cannot tolerate temperatures that low without suffering
quality loss
(Kooten and Peppelenbos 1993, Zheng et al. 1993).
Presently, most CA research for controlling Western flower thrips and spider
mites is
being done on fruit and vegetable crops. Aharoni et al (1981) demonstrated
that high levels of
carbon dioxide (50-90%) or low levels of oxygen (<1%) were successful
for killing thrips on
strawberries. For 100% control, hypercarbic conditions (90%) were required
for 48 h. Zheng et
al (1993) tested longer storage periods and found that low carbon dioxide
(10%) killed more
effectively in 6 days at lower temperatures than decreased oxygen for 2-3
weeks. Spider mite
eggs on apples in cold storage were killed in 4 days at 12C with both a
75% carbon dioxide and
1% oxygen treatment and a 9% carbon dioxide and 0.5% oxygen treatment (Bond
and Herne
1983). Whiting and van den Heuval (1995) killed mite eggs with 113 h exposure
to 0.4%
oxygen and 20% carbon dioxide.
Objectives and Anticipated Benefits
This project involves the development of a simple and safe technique fbr
bedding plant
growers to remove thrips and mites from their plants. It is primarily directed
at the relatively
large cutting and plug producers who inadvertantly distribute insect pests,
especially thrips, to
the hundreds of small and medium size greenhouses across the U.S. Although
the project is
primarily directed at large growers, the potential benefit to small growers
is immeasurable.
From our extension experience in Kentucky, most insect problem seen by
smaller growers come
from some of the plant stock they have purchased. Large growers make many
efforts to prevent
the shipment of insect pests, but it is difficult to completely disinfect
plant material with
conventional insecticides because of incomplete spray coverage, presence
of relatively
nonsusceptible life stages (e.g., eggs) or pest resistance. If successful,
the proposed research
might be applied in the following scenario:
A plug grower collects plants for tomorrow’s shipment. Plants are boxed
in the
afternoon and placed into a sealed fumigation chamber in the shipping area.
A
slight vacuum is created in the chamber and a mixture of nitrogen and carbon
dioxide gases is released, sufficient to replace 99.9% of the oxygen in
the
chamber. After overnight treatment, the N2 and CO2 are released into the
atmosphere and the low oxygen conditions have safely killed all the life
stages of
all the insect and mite pests on the plants.
Before CA technology can be adapted for greenhouse pest management, the
effects of
low oxygen (anoxia) enviromnents on thrips and mites must be determined.
The proposed
research differs from previous work on post harvest treatments of fruits
and vegetables because
it deals with pests and temperatures relevant to greenhouse production
systems, and because it
considers effects of CA on plant growth and quality as well as on pests.
The first objective will
be to evaluate the impact of anoxia and hypercarbic and hypernitrogen environments
on survival
and reproductive performance of thrips and mites. The purpose is to establish
critical thresholds
for mortality of the various pest life stages in a series of different
gaseous environments.
Second, seed impatiens and New Guinea impatiens will be treated with the
same environments to
determine their compatibility with production of high-quality bedding plants.
Finally, infested
impatiens will receive the best combination of treatments to determine
the overall efficiency of
the system for disinfecting whole plants under realistic production conditions.
Materials and Methods
Insect preparation and rearing. Stock colonies of thrips and mites will
be reared on bean plants
in the insectary. Leaf discs will be cut with a cork borer and placed on
a moistened cotton pad in
petri dishes. Adults will be placed on the leaf disc for 24 hours to allow
oviposition. After that
time they will be removed allowing the eggs to remain. Each life stage
(eggs, larvae, nymphs,
adults) will be tested independently. Active life stages will be obtained
by allowing the eggs to
develop under suitable conditions in the growth chamber. Leaf discs with
eggs or active stages
of thrips or mites will be placed into treatment chambers as described
below.
Plantproduction. Garden impatiens from seed and New Guinea impatiens
from cuttings will be
used in these experiments because both are very susceptible to thrips and
mites and both are
relatively fragile plants that may react negatively to CA environments.
Impatiens seed and
unrooted cuttings will be purchased from commercial sources. Seed germination
and cutting
development will occur in thrips-free double poly greenhouses equipped
with a Biotherm bench
heating system and a misting/watering boom (East Coast Designs, Inc.).
Plants used in
experiments will be moved to treatment chambers in the laboratory during
exposure or
disinfection treatments.
Treatment chambers. A constant flow system will be used for the
chambers. The gas mixture, at
controlled concentrations, will flow through the testing chambers for the
entire testing period at a
set flow rate in air exchanges per hour. This basic system has recently
given encouraging results
for control of whitefly on poinsettias (Han 1995). Our system was designed
with the assistance
of Dr. Richard Gates (Department of Agricultural and BioSystems Engineering)
and Dr. John
Loughrin (a volatiles expert in the Department of Entomology). The gases
will pass through a
series of filters, moisture traps, flow meters and regulators before flowing
into the chambers.
The gases move into a manifold, designed to ensure equal resistance and
distance from the gas
source, where they will mix and produce the desired test mixture needed.
The eighteen
individual chambers, Scienceware’ chemical-resistant vacuum desiccators
(10L volume), will
have a septum for sampling the atmosphere during each experiment. Samples
obtained through
the septa will be analyzed on a head space analyzer gas chromatograph.
CA environments. Temperature, time of exposure and the mixture of
gases are the important
variables for this research. Temperatures of 10, 20 and 30C will be used
while the treatment
chambers are maintained inside a Percival growth chamber. Exposure times
of 0, 12, 24 and 48
h will be used initially to determine overall effects of the CA treatments
and refined in later
experiments. The gases used in the experiments will be oxygen, nitrogen,
and carbon dioxide.
All gases will be obtained as bottled gas from a local source (Scott Gross,
Inc.; Lexington, KY.).
The nitrogen will be Ultra High Pure (UHP) grade similar to that used in
other studies (Whiting
et al. 1991, Whiting and Heuvel 1995). Carbon dioxide purity will be better
than food grade due
to extra container cleaning during processing. Medical grade oxygen will
be used to provide
Potter and Henderson - Anoxia Effects on Greenhouse Insects
precise control of oxygen levels. Gas mixtures with 0 or 5% O2, 0, 5, 10,
15 or 20% CO2 and 80,
85, 90, 95 or 100% N2 will be used in treatments with different exposure
times and different
exposure temperatures. Each CA environment will be replicated six times.
Initially, separate
experiments will conducted an insects or mites on leaf discs and on non-infested
impatiens
plants to determine the range of effects of the CA environments. Mortality
of pests will be
evaluated by direct inspection. Following exposure, impatiens plants will
be grown under
normal production conditions and evaluated for growth effects and days
to flowering. Later
experiments will utilize impatiens plants infested with thrips and mites
to determine specific gas
mixtures, treatment temperatures and exposure time for the optimum control
of the thrips and
mites.
Literature Cited
Aharoni, Y., J.K. Stewart and D.G. Guadagni. 1981. Modified atmospheres
to control Western
Flower Thrips on harvested strawberries. J. Econ. Entomol. 74: 338-340.
Baker, J.R. 1994. Insect and mites. pp.257-271. In E.J. Holcomb[ed.] Bedding
Plants IV. Ball,
Batavia, Illinois.
Bond, EJ. and D.H.C. Heme. 1983. The potential of carbon dioxide and low-oxygen
atmospheres
for control of winter eggs of the European Red Mite, Panonychus ulmi (Acari:
Tatranychidae), on harvested apples. Proc. Entomol. Soc. Ont. 114:11-14.
Brodsgaard, H.F. 1994. Insecticide resistance in European and African strains
of Western flower
thrips (Thysanoptera:Thripidae) tested in a new residue-on-glass test.
J. Econ. Entomol.
87:1141-1146.
Fleurat-Lessard, F. 1990. Effects of modified atmospheres on insects and
mites infesting stored
products, pp.21-38. In M. Calderon and R. Barakai-Golan[eds.], Food Preservation
by
modified atmospheres. CRC Press, Boca Raton, FL.
Han, S. 1995. Personal telephone interview.
Immaraju, J.A., T.D. Paine, J.A. Bethke, K.L. Robb and J.P. Newman. 1992.
Western flower
thrips (Thysanoptera:Thripidae) resistance to insecticides in coastal California
greenhouses. J.
Econ. Entomol. 85:9-14.
Johnson, D.C. and Johnson, T.M. Financial Performance of U.S. Floriculture
and Environmental
Horticulture Farm Businesses, 1987-1991. U.S. Dep. Agric. Statistical Bull.
N2.
Ke, D. and A.A. Kader. 1992. Potential of controlled atmospheres for the
postharvest insect
disinfection of fruits and vegetables. Postharv. News Info. 3:31N-37N.
Kooten, O.V. and H. Peppelenbos. 1993. Predicting the potential to form
roots on Chrysanthemum
cuttings during storage in controlled atmospheres. pp.610-619. In Proceedings,
6th
International Controlled Atmosphere Research Conference, 15-17 June 1993.
Ithaca, NY.
Lewis T. 1973. Thrips: their biology, ecology and economic importance.
Academic, New York,
NY.
Lindquist, R.K. 1995. Where we stand on western flower thrips. GMPro -
Greenhouse Management
Potter and Anderson - Anoxia Effects on Greenhouse Insects
and Production. March pp. 84-88.
Moorman, G.W. 1994. Bedding plant diseases. pp.245-255. In E.J. Holcomb
[ed.]. Bedding Plants
IV. Ball, Batavia, Illinois.
Tomczyk, A. and D. Kropczynska. 1985. Effects on the host plant. pp.317-329.
In W. Helle and
M.W. Sabelis[eds.], Spider mites their biology, natural enemies and control.
vol 1A.
Elsevier, New York, NY.
Van De Vrie, M. 1985. Control of Tetranychidae in crops: Greenhouse ornamentals.
pp. 2773-283.
In W. Helle and M.W. Sabelis[eds.], Spider mites their biology, natural
enemies and control.
vol 1B. Elsevier, New York, NY.
Van Lenteren, J.C. and J. Woets. 1988. Biological and integrated pest control
in greenhouses.
Annu. Rev. Entomol. 33: 239-269.
Whiting, D.C., S.P. Fester & J.H. Maindonald. 1991. Effect of oxygen,
carbon dioxide, and
temperature on the mortality responses of Epiphyas pottsvittanana (Lepidoptera:
Tortricidae). J.
Econ. Entomol. 84: 1544-1549.
Whiting, D.C. and J. van den Heuvel. 1995. Oxygen, carbon dioxide, and
temperature effects on
mortality responses of diapausing Terranychus urricae (Acari: Tetranychidae).
J. Econ-
Entomol. 88: 331-336.
Zheng, J., M.S. Reid, D. Ke, and M.I. Cantwell. 1993. Atmosphere modification
for postharvest
control on thrips and aphids on flowers and green leafy vegetables. pp.
394-401. In
Proceedings, 6th International Controlled Atmosphere Research Conference,
15-17 June 1993.
Ithaca, NY.
Budget requirements for controlled atmosphere anoxia research
Supplies
Pipe, fittings, regulators, flow meters, chambers for
3000.
control of 3 gases
N2, CO2 and O2 gases
500.
Use of greenhouse and growth chamber space
1500.
Plants, growing media, containers
2500.
Total
7500.
Personnel
Principal Investigator: Daniel A. Potter, Professor, Department
of Entomology, 17 yrs
research experience with urban landscape and greenhouse IPM, insect/plant
interactions,
more than 90 refereed articles. 14 book chapters. Education: B.S. degree,
Cornell
University, 1974; Ph.D, Ohio State University, 1978 (dissertation topic
dealt with biology of
the twospotted spider mite). Honors: Distinguished Achievement Award in
Urban
Entomology, Entomological Society of America, 1995; T.P. Cooper Award for
Outstanding
Research Program, Univ. KY College of Agriculture, 1989; about 30 invited
symposium
presentations worldwide.
Selected Publications Originating from Potter’s Laboratory:
Potter, D.A., D.L. Wrensch and D.G. Johnston. 1976. Aggression and mating
success in
male twospotted spider mites. Science 193: 160-161.
Potter, D.A. and R.G. Anderson. 1982. Resistance of ivy geraniums to the
twospotted
spider mite. J. Amer. Soc. Hort. Sci. 107-1089-1092.
Potter, D.A. and S.K. Braman. 1991. Ecology and management of turfgrass
insects.
Annual Review of Entomology 36: 383-406. (Invited)
Potter, D.A. and P.G. Spicer. 1993. Seasonal phenology, management and
host preferences
of the potato leafhopper on nursery-grown maples. J. Environ. Hort. II:
101-106.
Spicer, P.G., D. A. Potter & R.G. McNiel. 1995. Resistance of flowering
crabapple
cultivars to defoliation by the Japanese beetle. J. Econ. Entomol. 88:
979-985.
Loughrin, J.H., D.A. Potter & T.R. Hamilton-Kemp. 1995. Volatile compounds
induced by
herbivory act as aggregation kairomones for the Japanese beetle (Popillia
japonica Newman).
J. Chem. Ecol. 21: 1457-1467.
Principal Investigator: Robert G. Anderson, Professor of Extension Floriculture;
B.S. 1970,
Univ. of Minnesota; M.S. 1973, Univ. of Minnesota; PhD 1976, Univ. of Florida;
has
expertise in cut flower and bedding plant production and marketing.
Selected publications and presentations:
R.G. Anderson. Production of Field Grown Cutflowers. New Crops Symposium.
Indiana
Horticultural Congress, Indianapolis, Jan. 1996.
R.G. Anderson and J. Browne. Single stem cut flower production of corn
flower. Third
International New Crops Symposium, Indianapolis IN, Oct. 1995.
Chao, K., R.S. Gates, RG. Anderson. 1994. Neural-fuzzy inference system
for daily growth
of single stem roses. ASAE Paper No. 944015.
