Insecticidal Controlled Atmosphere for Management of Sweetpotato Whitefly Progress Report –December 1994
Date Dec. 7, 1994
Title of Project Insecticidal Controlled Atmosphere for Management of Whitefly
Institution where work is being conducted University of Massachusetts-Amherst
Amount of Endowment Grant $ 6000
Covering Period 3/1/94 to 2/28/95
Anticipated Date of Project Completion/Final Report 2/28/96
Individual(s) Conducting Project:
(List Project Leader First)
Dr. Susan S. Han - Title Associate Professor
Telephone Number (413)545-5228
Ms. Jennifer Nobel - Title Laboratory assistant
Insecticidal Controlled Atmosphere for Management of Whitefly (Trialeurodes vaporarium and Bemisia argentifolii)
Susan S. Han
University of Massachusetts
- A. Project Objectives:
- The main objective of the study is to investigate the potential of use of controlled atmospheres for controlof greenhouse and silverleaf whitefly (Trialeurodes vaporarium and Bemisia argentifolii, respectively) on
poinsettias, a technology that has not been examined by the floricultural industry. Controlled atmospheres (CA)
for long-term storage of 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 use of elevated CO2 or reduced O2 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 the level of tolerance to reduced O2 and/or
elevated CO2 varies (Ke and Kader, 1992). Floricultural crops can tolerate higher levels of CO2 than most edible
crops, perhaps due to the higher surface to volume ratio (Joyce and Reid, 1985).
- B. Summary of Work Conducted:
- Results from my laboratory have demonstrated that either elevated CO2 or reduced O2 are effectiveagainst both greenhouse and silverleaf whitefly. Reduced O2 atmospheres proved to be more lethal to whitefly
than the elevated CO2. All adult greenhouse whitefly were killed with a treatment of low O2 (= 2 ppm O2) for
2 hours whereas 10 hr of elevated CO2 (25% CO2) were needed to achieve the some control. In addition, other
stages of whitefly were killed with <8h of low O2 treatment while even longer treatment times (up to 24 hr) of
elevated CO2 did not prove effective. The treatment time required for eradication of whitefly did not affect the
growth of poinsettias, suggesting that a reduced O2 atmosphere can be used in treatment of poinsettias for
quarantine purposes.
- C. Results to Date:
- We have focused our effort on the use of the more effective low-O2 CA, created by venting with factory-mixednitrogen. In general, the responses of both species of whitefly to the CA treatment are similar. The adult
stage was most sensitive to the CA treatment with 100% mortality occurring after an exposure time of < 2 hr at
20'C. The adult stage was most sensitive to the CA treatment with 100% mortality occurring after an exposure
time of < 2 hr at 20'C. In contrast, eggs were most resistant to the treatment. After a 4 or 8 hr treatment with
low-O2, 10% and 80%, respectively, of the eggs failed to hatch. The nymphal stage of greenhouse whitefly was
killed by a 4 hr treatment while sufficient control of silverleaf whitefly required 8 hrs. The pupal stage responded
somewhat to a 4 hr treatment but an 8 hr exposure was required to kill > 80% of the pupae. An 8 hr low-O2
treatment of nine cultivars of rooted poinsettia cuttings from Paul Eche Range demonstrated that the treatment
did not affect subsequent growth. In addition, there were no differences in root or vegetative growth between
unrooted cuttings treated with air or with low-O2, 4 weeks after the treatment. Results, therefore, indicated that
the low-O2 treatment can be used to disinfest whitefly on poinsettias without affecting the growth and development
of the plants.
- D. Future Plans:
- In a preliminary experiment where eggs of greenhouse whitefly were exposed to the low-O2 conditionsat 30′C, we observed that a 10′ increase in temperature significantly increased the insecticidal effects of the CA
treatment. A four-hr treatment at 30′C killed as many eggs mas an 8-hr treatment at 20′C. Since eggs are the
stage most resistant to the CA treatment, this result suggests that a 4- rather than 8-hr treatment, may be all that
is needed to disinfest plant materials. The shorter treatment time would also suggest that the technique could
be used on a wider range of crops. We are, therefore, planning to conduct studies at different temperatures and
to treat various plant species in order to assess the potential wide range use of this technique.
- E. Anticipated Benefits for Floral Industry:
- The proposed method of reduced-O2 insecticidal CA would provide the greenhouse industry with anenvironmentally-safe way of controlling the spread of whitefly through infested plant materials. In addition, we
casually observed that the efficacy of CA treatments increased when applied in conjunction with pesticides,
suggesting that insecticidal controlled atmospheres may be integrated into an 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.
