Biological Control of Trialeurodes Vaporariorum by Encarsia Formosa on Tomato in Unheated Greenhouses in the High Altitude Tropics
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Bulletin of Insectology 61 (1): 43-57, 2008 ISSN 1721-8861 Biological control of Trialeurodes vaporariorum by Encarsia formosa on tomato in unheated greenhouses in the high altitude tropics 1,2 3 Raf M. J. DE VIS , Joop C. VAN LENTEREN 1Centro de Investigaciones y Asesorías Agroindustriales, Universidad de Bogotá Jorge Tadeo Lozano, Cundinamarca, Colombia 2Current address: Research Station for Vegetable Production, Sint-Katelijne-Waver, Belgium 3Laboratory of Entomology, Wageningen University, The Netherlands Abstract Biological control of Trialeurodes vaporariorum (Westwood) by Encarsia formosa Gahan was tested during three consecutive production cycles (16-28 weeks) on a beef tomato (Solanum lycopersicum L.) crop in a glasshouse and a plastic greenhouse on the Bogota Plateau in Colombia. During the course of this study over the period 1997-1999, the mean temperature was around 16 °C in the plastic greenhouse and around 17 °C in the glasshouse. E. formosa was introduced at a rate of 3 adults per m2 per week in the 1997 production cycle, and at a rate of 3 and 5 pupae per m2 per week in 1998 and 1999, respectively. In 1997, the adult whitefly population increased exponentially to a peak of 76 adults per plant in the plastic greenhouse, while the whitefly population in the glasshouse reached a peak of only 12 adults per plant. The percentage parasitism fluctuated between 42 and 82% in the glasshouse and between 28 and 47% in the plastic greenhouse. In 1998, the T. vaporariorum population could not be brought under control in both greenhouses and reached a peak of 80 and 53 T. vaporariorum adults per plant in the plastic green- house and the glasshouse, respectively. Parasitism fluctuated between 55 and 97% in the glasshouse and between 32 and 84% in the plastic greenhouse. In 1999, biological control was successful in both greenhouses. Most of the time, populations of T. vapo- rariorum were lower than 1.2 adults per plant and parasitism by E. formosa was 80% or higher. We suggest that the higher tem- perature is the main reason for better parasitism in the glasshouse when compared to the plastic greenhouse. The successful results of 1999 show that biological control is possible under the short day and low temperature conditions of greenhouses situated in the high altitude tropics such as the Bogota Plateau. Recommendations are given for the application of E. formosa based on the results of these experiments. Key words: greenhouse, tomatoes, biological control, Trialeurodes vaporariorum, Encarsia formosa, high altitude tropics. Introduction the predator Macrolophus caliginosus Wagner and the parasitoids Eretmocerus eremicus Rose et Zolnerowich The protected cultivation of tomatoes is a recent devel- and Eretmocerus mundus Mercet for control of white- opment in Colombia, generally replacing field-grown to- flies (van Lenteren, 2000; Ardeh et al., 2005). A model matoes. The high risk due to pests and diseases, in some of the tritrophic tomato-T. vaporariorum-E. formosa cases causing total loss of the crop in the field, is one of system in greenhouses showed that biological control the reasons that induced the change to greenhouse pro- does not work under certain conditions; for example, duction. The use of greenhouses reduces pest and disease control is not achieved when the quality of the host risks, and increases production and profits. Greenhouses plants for T. vaporariorum is high, and when tempera- are currently used for tomato production in the intermedi- ture conditions are unsuitable (van Lenteren et al., ate climate zone (altitude 1800-2000 m) where tradition- 1996). These are exactly the conditions found in crops ally field-grown tomatoes are cultivated, but also in cold of beef tomatoes in unheated greenhouses in the high climate zones such as the Bogota Plateau (altitude 2665 altitude tropics such as the Bogota Plateau: high host m). One of the particular advantages of tomato produc- plant quality and unsuitable temperature conditions. tion on the Bogota Plateau is the generally reduced pest Only few studies have been done on tomatoes under spectrum. From 1995 on, greenhouse tomatoes have been these conditions: Christochowitz et al. (1981), Hulspas- produced at the Horticultural Research Centre of the Uni- Jordaan et al. (1987), van Es (1982), van der Laan et al. versity of Bogota Jorge Tadeo Lozano, where the most (1982) and van Lenteren and Hulspas-Jordaan (1985). important pest has been the greenhouse whitefly Trialeu- Studies by van Es (1982) have shown that the green- rodes vaporariorum (Westwood). Leafminers and aphids house whitefly population develops better on beef to- were generally kept at low densities by naturally occur- mato than on round tomato varieties. Whitefly fecundity ring parasitoids (De Vis and van Lenteren, 1999). increased by a factor of 2 or more and adult longevity Biological control of pests on greenhouse grown to- by a factor of 1.5-1.9 on beef tomato varieties when matoes has become a common practice in a number of compared to a round tomato cultivar (van Es, 1982). In countries (van Lenteren and Woets, 1988; van Lenteren, addition, the temperature in greenhouses on the Bogota 1992; 1995; 2000). The parasitoid Encarsia formosa Plateau is lower than the temperature in the climatised Gahan is traditionally used for biological control of greenhouses in Western Europe (in Colombia, mean greenhouse whitefly (van Lenteren, 1992; 1995). In temperatures are 15-16 °C, day temperatures are 18-22 Europe, E. formosa has also been complemented with ºC and night temperatures are 5-12 °C). Pre-1979 data (see van Lenteren and Hulspas-Jordaan, controlled by a climate computer (Midi-Clima, Van 1985) suggested that the intrinsic rate of increase (rm) of Vliet, The Netherlands). This computer also recorded E. formosa was lower than that of T. vaporariorum at temperature in both greenhouses using NTC tempera- temperatures lower than 20 °C. However, more recent ture sensors installed in a ventilated box. Relative hu- studies showed that the rm was higher than that of T. va- midity was calculated using the temperature data of a porariorum for temperatures above 12 °C (van Lenteren dry and a wet sensor installed in the same box. The and Hulspas-Jordaan, 1985). This was later confirmed boxes were installed in the centre of each greenhouse at by the modelling work of van Roermund et al. (1997). plant height and every ten minutes the mean value of the Therefore, biological control should be possible under temperature sensors of the previous 10 minutes were the climatic conditions prevailing in greenhouses in the stored. Tomato plants of the variety Boris (Bruinsma high altitude tropics of Colombia. But other factors such Seeds, ’s Gravenzande, The Netherlands) were trans- as the parasitoid’s searching behaviour might be limited planted in both greenhouses during three consecutive at these low temperatures. Madueke (1979) showed that production cycles: 1) 6-week old plants were trans- E. formosa did not fly and showed hardly any activity at planted on May 23, 1997 and the crop was finished on temperatures lower than 21 °C. However, Christochow- January 15, 1998; 2) 7-week old plants were trans- itz et al. (1981) showed that E. formosa could still fly at planted on May 22, 1998 and the crop was finished on temperatures around 17 ºC and van der Laan et al. January 8, 1999; and 3) 10-week old plants were trans- (1982) showed that E. formosa could migrate at tem- planted on January 25, 1999 and the crop was finished peratures as low as 13 °C. But later, van Roermund and on August 12, 1999. Each production cycle, a total of van Lenteren (1995) showed that the Dutch E. formosa 1152 plants (12 beds of two rows of 48 plants each) on did no longer fly at 18 °C or lower temperatures in the an area of 510 m2 (25 m by 20.4 m) were planted in the 1990s. This fact could seriously lower the parasitoid's plastic greenhouse. In the glasshouse, 1008 and 672 dispersal over the greenhouse and prevent whitefly pa- plants (9 and 6 beds of two rows of 56 plants each) were tches from being found and parasitized. planted on an area of 364 and 273m2 (28 by 13 and Greenhouse experiments in The Netherlands in the 9.6 m) during the first and the two last experiments, re- 1980s showed that E. formosa is able to control whitefly spectively. At the beginning of the experiments, when population in greenhouses with a relatively low tem- the first E. formosa were introduced, the plants were 10 perature regime (18 °C day and 7 °C night) during win- weeks old (4 weeks after transplant) in 1997, 14 weeks ter in Holland (Hulspas-Jordaan et al., 1987), when day old (7 weeks after transplant) in 1998 and 11 weeks old length is shorter and solar radiation lower than in Co- (1 week after transplant) in 1999. At that moment, a lombian greenhouses. But these conditions last only a natural infestation of T. vaporariorum adults was al- few months at the beginning of the year in The Nether- ready present in all experimental greenhouses. These lands, while unheated greenhouses on the Bogota Pla- adults may have survived from previous crops. No im- teau have a constant low mean temperature during the portant immigration of T. vaporariorum adults could whole year. Therefore, the success of E. formosa as bio- have taken place at that time as the outside climate con- logical control agent of T. vaporariorum could not eas- ditions on the Bogota plateau are too cold for T. vapo- ily be predicted when growing beef tomatoes in green- rariorum population build-up. In adjacent greenhouses, houses situated on the Bogota Plateau.