Quarantine Application of Bio-Generated
Atmospheres for Control of the Large Narcissus Fly

Simcha Finkelman
Department of Food Science Agricultural Research Organization
The Volcani Center, P.O. Box 6
Bet-Dagan 50250, Israel
e-mail: simchaf@volcani.agri.gov.il

The large narcissus fly Merodon eques F. attacks narcissus bulbs and also bulbs of other geophytes. This species has not been recorded in the USA; and is therefore included within quarantine requirements that demand total mortality prior to export to the USA (Donahaye et al. 1997). Fumigation with methyl bromide (MB) has been used to eliminate narcissus fly infestation in flower bulbs due to its rapid killing time (4 hours). However, MB is also known to cause damage to the bulbs. Therefore, our initial trials were aimed at reducing the MB dosage so as to minimize phytotoxicity and to stabilize concentrations. These trials were carried out in flexible plastic chambers that replaced the rigid fumigation chambers (rooms) previously used.

In experimental procedures, Navarro et al. (1997) found that there was an extremely rapid increase in CO₂ due to the respiration of the newly harvested bulbs. This procedure also revealed the significant toxic effect of CO₂ during treatment and the possibility of using it alone as a control measure. By this time the limitations on MB fumigations were already being defined in meetings of the Montreal Protocol (United Nations Environment Programme 1998) and required the growers to find a permanent non-chemical solution that would also be economical and easy to implement in the field. Consequently, in our laboratory, we studied three treatments of modified atmospheres: high CO₂ concentration (95 percent), vacuum (low pressure of about 50 mm Hg), and storage under hermetic conditions alone. The results showed that the time needed to achieve a 99 percent mortality of fly maggots was about 24 h for the first two treatments and 34 h under hermetic conditions alone. More work is needed to determine the exposure time of Probit 9 for the acceptability of the method to control quarantine pests. Although high CO₂ and vacuum treatments provided a shorter treatment time than storage under hermetic conditions alone, the possibility of obtaining a bio-generated modified atmosphere utilizing the bulb respiration was too tempting to ignore and we adopted this approach.

For the pilot commercial trials conducted in Israel, we applied the vacuum-hermetic fumigation (V-HF) process used in a newly developed transportable PITS Tunnel (patent-applied Pesticide-free Integrated Transportation and Storage) that is specially designed for rapid machine loading and unloading (Villers 2001). It has two main components: a sealed chamber and a supporting light metal frame. This system consists of an 18.75 m³ sleeve-shaped chamber made of flexible liner sheeting that can hold vacuum or modified atmospheric gas compositions, with a front opening that is sealed by an air-tight zipper. The supporting portable light metal-frame can be assembled in the designated location and used to hold the chamber in shape for easy loading and unloading of the commodity.

The bulbs were placed in the PITS Tunnel on their original shipping pallets using a forklift. Each pallet was loaded 8 rows high, 5 crates in each row (40 crates totaling approximately 400 kg). In each trial three pallets were arranged inside the PITS Tunnel to evaluate the effectiveness of each treatment. In addition to the three pallets of sorted bulbs, three crates of bulbs infested with fly maggots at sorting were placed at the bottom center and top rows of the crates. In each of these locations a data logger recorded the temperature and humidity. The system was then sealed for 48 h. To minimize space, a slight vacuum of 10 Pa (0.007 mm Hg below ambient) was applied using a hand-held household vacuum cleaner to adhere the PITS Tunnel liner to the crates.

Under these hermetically sealed conditions, there was a rapid depletion of O₂ to 0.1 percent within 18 h, while the CO^₂ concentration increased to 21 percent. The temperatures in the chamber ranged from 28 °C to 30 °C, although under the top liner it reached 34 °C at midday. Ambient temperatures outside the chamber ranged from 22 °C at night up to 34 °C at midday. The humidity in the chamber rose steadily from 60 percent to 84 percent relative humidity, while under the top liner it reached 100 percent within 18 h. The ambient humidity changed from 54 percent at midday to 92 percent relative humidity at night.

After treatment in the PITS Tunnel, the three crates of infested bulbs, as well as three samples of non-infested bulbs from crates at the bottom, center and top rows of the pallets, and control, non-treated bulbs were collected. All treated bulbs were examined for live maggots by the researchers, as well as by the Israeli Plant Protection Service inspectors. The results of examining each bulb in the 3 crates of treated infested bulbs revealed 100 percent mortality in all 3 treatments. The treated non-infested bulbs were evaluated at the end of each treatment and bulbs from all pallets passed the requirement needed for export approval. Samples of non-infested treated bulbs and control bulbs were planted in a greenhouse to ensure that there were no phytotoxic effects and to evaluate the quality of the narcissus bulbs. In all cases, no phytotoxic effects were observed and the quality of the treated bulbs was as good as the control bulbs.

In addition to the specific benefits of the V-HF process as an MB alternative for quarantine fumigation of narcissus bulbs, the benefits are several: absence of pesticide residues, reduced safety risk when compared to fumigation, and environmental safety. The PITS Tunnel is transportable and can be assembled by a three-man team. The main drawback to this treatment is the longer exposure time needed compared to MB fumigation. This environmentally friendly method to control quarantine insect pests is applicable to other commodities and is also safe for the operator and the environment.

Acknowledgment: I wish to express my thanks to Dr. Shlomo Navarro, Dr. Jonathan Donahaye, Miriam Rindner, Rafael Dias, and Avi Azrieli. This research was partially funded by a grant from the United States-Israel Science and Technology Foundation (USISTF), ARO Project No. 417-0384-01.

References

Donahaye, E.J., S. Navarro, R. Diaz, and M. Rindner. 1997. Sensitivity of narcissus flies (genera: Eumerus and Merodon) to Methyl Bromide. In E.J. Donahaye, S. Navarro, and A. Varnava, eds., Proceedings of the International Conference on Controlled Atmosphere and Fumigation in Stored Products, April 21-26, 1996, pp. 25-30. Printco Ltd., Nicosia, Cyprus.

Navarro, S., E. Donahaye, R. Diaz, M. Rindner, and A. Azrieli. 1997. Commercial quarantine fumigation of bulbs to control Narcissus flies. In E.J. Donahaye, S. Navarro, and A. Varnava, eds., Proceedings of the International Conference on Controlled Atmosphere and Fumigation in Stored Products, April 21-26, 1996, pp. 589-599. Printco Ltd., Nicosia, Cyprus.

United Nations Environment Programme. 1998. Montreal protocol on substances that deplete the ozone layer, 1998 assessment of alternatives of Methyl Bromide. Methyl Bromide Alternatives Committee. Nairobi, Kenya.

Villers, P. 2001. Advanced vacuum fumigation and its applications. Proceedings of the Annual International Research Conference on Methyl Bromide Alternatives and Emission Reductions, Abstract 65-1, November 5-9, 2001, San Diego, CA.

Table 1. Effect of soil fumigation on plant heights of two snapdragon cultivars planted on October 23, 2002.

Last Updated: July 2, 2003