HORTICULTURAL ENTOMOLOGY Effects of UV-Absorbing Plastic Films on Greenhouse Whitefly (Homoptera: Aleyrodidae) URBANUS N. MUTWIWA, 1 CHRISTIAN BORGEMEISTER, 2 BURKHARD VON ELSNER, 1 AND HANS-JUERGEN TANTAU 1 Department of Horticulture, Herrenhauser Strasse 2, University of Hannover, D 30419, Hannover, Germany J. Econ. Entomol. 98(4): 1221Ð1228 (2005) ABSTRACT Studies were conducted to investigate the effects of ultraviolet (UV)-absorbing plastic Þlms on the orientation and distribution behavior of the greenhouse whiteßy, Trialeurodes vaporari- orum (Westwood). In Þeld experiments, small tunnels were constructed and covered with either an UV-transmitting (Thermilux) or UV-absorbing (K-Rose) plastic Þlm. Results show that signiÞcantly more whiteßies were recorded in the tunnels with high compared with those with low UV intensities. Moreover, whiteßy penetration and dispersion were less inside the UV-deÞcient tunnels. These results suggest that the type of plastic Þlm used for greenhouse covers may have a signiÞcant inßuence on both the initial immigration and distribution of T. vaporariorum into greenhouses. The possibilities of using UV-absorbing plastic Þlms for whiteßy integrated pest management in greenhouses are dis- cussed. KEY WORDS Trialeurodes vaporariorum, behavior, UV-absorbing, Þlms THE MAIN PURPOSE OF COVERED greenhouses is to create an internal climate that is conducive to plant growth regardless of the external environment and to opti- mally control plant production factors. The capability of the covering material to transmit light in wave- lengths useful to plants is therefore extremely impor- tant, because it has a tremendous inßuence on the production capability of the crop inside the green- house (Giacomelli and Roberts 1993). The availability of new types of covering materials and enhancements of previously existing materials, as well as the demand for technological improvements in greenhouse agri- culture, has led to an increase in the diversity of greenhouse covering materials over the past four de- cades (Moens 1990, Giacomelli and Roberts 1993, Ashekanzi 1996). The greenhouse whiteßy, Trialeurodes vaporari- orum (Westwood) (Homoptera: Aleyrodidae), is worldwide one of the most important greenhouse pests on vegetable and ornamental crops (Coombe 1982, van Lenteren and Noldus 1990). Whiteßies dam- age the plants directly through sap feeding (Russel 1997) and indirectly through the excretion of honey- dew and transmission of plant viruses such as Lettuce infectious yellow virus (Fasulo et al. 2003). Insecticide applications often fail to provide adequate control, and development of resistance to certain insecticides has been reported (Fasulo et al. 2003), whereas the use of screens as a physical control reduces the efÞ- ciency of natural ventilation (Michelle and Baker 2000, Ajwang et al. 2002). Additionally biological con- trol, primarily through inundative releases of the para- sitoid Encarsia formosa (Gahan) (Hymenoptera: Aph- elinidae) may not achieve the level of efÞcacy needed by growers, especially in the case of virus transmission. Recent quests for effective, environmentally safe, and sustainable pest management programs have been tar- geted primarily toward the development of new and less hazardous synthetic insecticides to replace con- ventional, often highly toxic ones (Lewis et al. 1997). This has led to an increased interest in complimentary control strategies, including the use of botanical in- secticides such as neem (von Elling et al. 2000). Previous studies by Coombe (1981, 1982) reported wavelength-speciÞc behavior in T. vaporariorum at 400 and 500 nm. In nature, ßying adults orient toward the sky but tend to land on a green plant because plants reßect maximally at 550 nm. Most greenhouse polyethylene plastic Þlms contain UV light (UV)-ab- sorbing components that block wavelengths of 200 Ð 400 nm. These components are added to prolong the life of the plastic Þlms, while maintaining high levels of photosynthetic active radiation (PAR) transmission at wavelengths of 400 Ð700 nm (Costa and Robb 1999). Crops grown in walk-in tunnels covered with UV- absorbing plastic Þlms were highly protected from infestation by sweetpotato whiteßy, Bemisia tabaci (Gennadius), and had reduced incidences of Tomato yellow leaf curl virus (TYLCV) (Antignus et al. 1996). 1 Department of Horticulture, Institute of Horticultural and Bio- systems Engineering, University of Hannover, D 30419, Hannover, Germany. 2 Department of Horticulture, Institute of Plant Diseases and Plant Protection, University of Hannover, D 30419, Hannover, Germany. 0022-0493/05/1221Ð1228$04.00/0  2005 Entomological Society of America Downloaded from https://academic.oup.com/jee/article/98/4/1221/883473 by guest on 30 December 2021