Evaluation of Elevated CO2 for Control of Greenhouse Whiteflies on Poinsettias During Transit Progress Report — September 1992
Date August 27, 1992
Title of Project Evaluation of Elevated CO2 for Control of Greenhouse Whiteflies on Poinsettias During Transit
Institution where work is being conducted University of Massachusetts at Amherst
Amount of Endowment Grant $ 5,000
Covering Period 1/1/92 to 12/31/92
Anticipated Date of Project Completion/Final Report June 1993
Individual(s) Conducting Project:
(List Project Leader First)
Dr. Susan S. Han - Title Assistant Professor
Telephone Number 413-545-5228
Evaluation of Elevated CO2 for Control of Greenhouse Whiteflies on Poinsettias During Transit
Susan S. Han
University of Massachusetts-Amherst
- A. Project Objectives:
- Control of whiteflies on poinsettias still remains a challenge for many commercial growers. Theproblem is less severe when growers start the season with clean, non-infested cuttings.
Unfortunately, cuttings are frequently shipped with some degree of infestation. These infested
cuttings when left unnoticed can develop into major problems later into the growing season. The
objectives of the project are 1) to evaluate the effectiveness of elevated CO2 in excluding all stages
of whitefly from the cuttings prior to arrival at the production area. The treatment can be applied prior
to shipment, during shipment, or at destination. 2) To investigate the tolerance level of poinsettias
to elevated level of CO2.
- B. Results to Date:
- To date, our experiments demonstrated that whiteflies are highly susceptible to an elevatedlevel of CO2. To conduct the experiments, aspirators were constructed to collect adult whiteflies.
The aspirators were constructed with two venting holes allowing us to introduce a constant flow of
a known concentration of CO2. Aspirators for the control treatment were vented with atmospheric
air (0.03% CO2). Each treatment consisted of 3 replicate aspirators with approximately 80 - 100
whiteflies per aspirator. Our first experiment revealed that adult whiteflies are very sensitive to high
levels of CO2. All whiteflies appeared dead after exposure to 25% and 50% CO2 for 80 and 20
minutes, respectively. Subsequently, we found that these short-exposure times only caused
temporary unconsciousness of the insects and the majority of them revived after they were
transferred back to the atmospheric air. Further studies revealed that exposure of adult greenhouse
whiteflies (Triale urodes vaporarium) to 25% or 50% CO2 resulted in 100% death in less than 12
hours. To investigate the sensitivity of different stages of whitefly to elevated CO2, plant materials
infested with uniform stages of whiteflies are needed. One obstacle which still requires investigation
is obtaining a large number of eggs laid on the same day. Overcoming this difficulty will allow us to
Ccoordinate further development of all stages with scheduling Of CO2 treatment. We had attempted
twice to inoculate a tomato cultivar with whiteflies but had limited success. We are currently growing
poinsettias from cuttings and will inoculate these plants once they are established in the greenhouse.
We had studied the tolerance level of poinsettia cuttings to elevated level of CO2. Rooted
cuttings of ‘Supjibi’ and ‘Lilo’ were exposed to 50% CO2 or air (control) for 24 hours and were then
potted up and grown in a glasshouse for evaluation. Results revealed significant differences in the
tolerance level of the 2 cultivars studied. Eighty-five percent of the cuttings of ‘Supjibi’ developed
severe toxic symptom on the mature and expanding leaves from the CO2 treatment whereas only 5%
of the ‘Lilo’ cuttings developed minor toxic symptoms. The initial toxic symptom appeared as upward
curling of the leaves which later abscised. All expanding and mature leaves in ‘Supjibi’ cuttings were
affected whereas only a few mature leaves were affected in ‘Lilo’. This result indicated vast
differences in the sensitivity of different cultivars of poinsettias to an elevated level of CO2 and
suggested that more cultivars should be evaluated. Additionally, a lower level of CO2 (25%) should
be tested on poinsettia cuttings since this level of CO2 has been shown to effectively control the
adult whitefly.
- C. Anticipated Benefits for Floral Industry:
- The proposed study will benefit the industry by providing growers a means to prevent the spread ofwhiteflies through contaminated plant materials. The relatively simple set up will enable all growers
to establish their own mini-quarantine treatment, if desired. This practice in conjunction with
integrated pest management should drastically reduce the hazards and expenses associated with
application of pesticides.
