Insecticidal Controlled Atmosphere for Management of Sweetpotato Whitefly 1993 Proposal
whiteflies
1) EXECUTIVE SUMMARY
I propose to continue my investigation on the use of controlled atmospheres
to manage whitefly on poinsettias. Results to date show that 8h of anoxic
conditions kill most of the greenhouse whitefly, regardless of the developmental
stage, whereas the some treatment does not affect the growth of most cultivars
of poinsettias. The system is simple to set up and the short-term treatment
can be applied to cuttings prior to shipment, during transit, or at the
final destination. Studies suggest that the use of anoxia is a promising
method for disinfesting greenhouse whitefly on poinsettias and I propose
to examine if the some technique can be used to kill sweetpotato whitefly.
2) INTRODUCTION AND LITERATURE REVIIEW
The extensive crop losses causes by sweetpotato or silver leaf whitefly
(Bemisia tabaci), since the outbreak in California in 1991, have raised
considerable attention in the agricultural community. The wide range of
hosts has allowed this new strain or species of whitefly to survive year
round and to spread rapidly through many regions. Increased application
of currently available pesticides and the practices of integrated pest
management have failed to control this whitefly, and the estimated economic
losses in 1991 alone were over half a billion dollars (Perring et al.,
1993). Growers in parts of California were forced to produce alternative
crops due to the massive destruction of some crops by this tiny insect
(Parrella, personal communication). Researchers around the country are
teaming up to search for an effective method of control, with many projects
emphasizing the search for natural enemies of this whitefly. “The overall
goal is to find which method or combination of methods best controls the
whitefly infestation in a given area” stated Robert Faust, one of the two
coordinators of the Agriculture Research Service anti-whitefly effort at
USDA (USDA, 1992).
Use of controlled atmosphere (CA) for long-term storage and pathogenic
control on edible crops has been extensively investigated. The method refers
to changes in the composition of the air surrounding the commodity and
generally involves reduction of oxygen and/or elevation of carbon dioxide.
In recent years, the treatment has been reported to effectively control
Caribbean fruit fly (Benschoter, 1987), codling moth (Soderstrom and Brandl,
1987), and San Jose Scale (Chu, 1992) on various commodities and has been
suggested as a possible quarantine treatment on imported edible crops (Ke
and Kader, 1992). Commodities differ in their susceptibility to controlled
atmosphere and the recommendations for the level of tolerance to reduced
O2 and/or elevated CO2 varies (Ke and Kader, 1991). 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. In
general, floricultural crops hove been shown to tolerate very high levels
of CO2 (Joyce and Reid, 1985), above those reported to eradicate insects
(Benschoter, 1987, Soderstrom and Brandl, 1987). The differences are suspected
to be due to the anatomic vs. metabolic variation among commodities.
With funding from AFE, my laboratory has been studying the effects of
elevated CO2 and reduced O2 on greenhouse whitefly (Trialeurodes vaporarium).
We envision that this technique could be used to prevent spread of whitefly
from one location to the other via shipment of infested plant material.
By disinfesting plant material prior to planting in the field, the growing
season would begin with a low or no whitefly population. Furthermore, the
method can be used in conjunction with IPM practices of biocontrol as there
is no residual on plants materials, and can be used in greenhouses that
cannot be sprayed with insecticides.
Results showed that adult greenhouse whitefly are highly susceptible
to elevated levels of CO2 (25% or 50%). All adults were killed in <
10 h. Eggs and pupae, however, are more resistant than adults to the elevated
CO2 and the some treatment had little effect on these stages (data not
shown). Further investigation revealed that low oxygen treatment has a
greater effect on whitefly and we are currently focusing our effort on
the use of no or low-O2 CA. Anoxic conditions, created by venting with
100% nitrogen, resulted in mortality of all stages of greenhouse whitefly.
All adults were killed with 2 hr of anoxic treatment (Fig. 1 a). Sixty
percent and 30% of the adult whitefly exposed to 1/2 hr and 1 hr of anoxia
revived after being transferred to the atmospheric conditions. Those reviving,
however, were dead in less than 24 hr (data not shown). Other stages of
greenhouse whitefly require a longer treatment time where 4 hr of anoxia
killed 90% of the nymphs (Fig. 1 b) and 8 h killed > 80% of the eggs and
pupae (Fig. 1 c and 1 d).
These studies indicated that 8h of anoxia killed the majority of the
whitefly, thus, a minimum treatment time of Fig. 1 . Effects of anoxia
(100% N2) on the percent (a) mortality of adults, (b) mortality of nymphs,
(c) hatch of eggs, and (d) emergence of pupae of greenhouse whitefly (Trialeurodes
vaporarium). Data are means +/- SE. 8h of air or N2 was tested on nine
cultivars of rooted poinsettia cuttings from Paul Eche Range. Following
the treatment, cuttings were potted in 10-cm diameter plastic pots and
placed in the glasshouse under interrupted night (8h natural light plus
night interruption with 3.6 umol*s-1*m-2 incandescent lamp between 10PM
and 2AM). The height and weight of six replicate plants measured four weeks
after the treatment demonstrated that, with the exception of ‘Supjibi Red’
and ‘V-17 Angelico’, there were no differences in growth between those
treated with air or N2 (Table 1). We are currently evaluating the responses
of unrooted cuttings which, based on the development of phytotoxicity (necrotic
lesions), appear to be more sensitive to the anoxia treatment. These results
suggest that the use of no O2 is thus a promising method for disinfestation
of whitefly on poinsettias.
3) OBJECTIVES AND ANTICIPATED BENEFITS
The main objective of this proposal is to evaluate the effects of anoxia
on eggs, nymphs and pupae of sweetpotato whitefly. In addition, the effect
of repeated treatments of anoxia will be tested on poinsettia plants to
examine the possibility of eradicating the remaining 10 to 20% of eggs
and pupae that were not killed with the first treatment. The proposed study
will benefit the industry by providing growers an environmentally safe
method of controlling whiteflies. The relatively simple set up will enable
all growers to establish their own mini-quarantine treatment, if desired.
Growers can then start their poinsettia season with clean, non-infested
cuttings, and thus, reduce the hazards and expenses associated with application
of pesticides.
4) MATERIALS AND METHODS
Plant material will be obtained from Paul Eche Range, Encinitas, CA.
The controlled atmosphere chambers are constructed of covered containers
with two venting holes for continuous flow of the factory-mixed gas. The
chambers will be placed in 20′C temperature-controlled incubators with
12h of photoperiod illuminated with 25umol*s-1*m-2 fluorescent lamp.
a) Effectiveness of Anoxia on Eggs, Nymphs, and Pupae of Sweetpotato
Whitefly
Non-infested plant materials will be inoculated with adult
sweetpotato whitefly in order to obtain uniform stages of whitefly on the
leaves. Treatment will be applied when the whitefly reach egg, nymphal
and pupal stages, respectively. Leaves containing each stage of whitefly
will be placed in atmospheric chambers vented continuously with air or
N2 for a predetermined length of time. The survival rate of the various
stages will be assessed following the passage of sufficient time for the
development of insects into the next developmental stage.
b) Effects of Anoxia on Growth of Unrooted Poinsettia Cuttings
The purpose of this study is to determine if the anoxia treatment
affects the rooting potential of unrooted poinsettia cuttings. Unrooted
poinsettia cuttings will be collected at the day of the treatment from
stock plants grown in the glasshouse. Following the treatments, cuttings
will be placed either in a simulated shipping environment for 2 days prior
to propagation or will be propagated immediately. Percent roofing and length
and weight of the roots will be determined 4 weeks after propagation.
c) Repeated Applications of Anoxia on Poinsettia Plants
The goal of this study is to determine if repeated N2 applications
can kill remaining whitefly without causing phytotaxicity to the poinsettias.
The second application can be given when the surviving eggs and pupae from
the first treatment hove developed into the more susceptible stages, nymphs
and adults, respectively. To test this hypothesis, poinsettias will be
repeatedly treated with N2 at 3 days intervals for up to 4 treatments sufficient
time for all eggs and pupae to develop into the next stage). Height and
dry weight of the plants will be measured four weeks after the treatments.
5) LITERATURE CITED
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.
Chu, C.L. 1992. Postharvest control of Son Jose scale on apples by controlled
atmosphere storage. Postharvest Biol. and Technol. 1: 361-369.
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. 1991. Potential of controlled atmospheres for
postharvest insect disinfestation of fruits and vegetables. Postharvest
News and Information. 3: 31-37.
Perring, T.M., A.D. Cooper, R.J. Rodriguez, C.A. Farrar, T.S. Bellows,
Jr. 1993. Identification of a whitefly species by genomic and behavioral
studies. Science 259: 74-77.
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. U.S. Department of Agriculture. Agriculture
Research, Nov. 1992, p. 4-13.
6) 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 gas cylinders, pots, growing media, and other materials which will be
required to conduct this research. Salaries (part-time technical support)
$6,000
FICA (1.45%) $ 87
Supplies $1,500
Publication $ 500
Total $8,087
7) PROJECT LEADER QUALIFICATIONS
The principal investigator 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 educational background has enabled me to conduct
both basic and applied research that are critical to the floricultural
industry. My laboratory is well equipped with the atmospheric chambers,
growth incubators, glasshouses needed for the proposed study.
