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The onion thrips, Thrips tabaci LINDEMAN (Thys., Thripidae) is an important pest of field and greenhouse crops around the world. It causes damage directly through feeding and indirectly through the transmission of lethal plant viruses. It is difficult to control this pest with insecticides because of its small size and cryptic habits (LEWIS 1997). Entomopathogenic fungi are currently being investigated for the control of many important insect pests on various crops around the world, and some are commercially available. There are many studies on the efficacy of several entomopathogenic fungi on thrips. CARL (1975) reported that Neozygites parvispora (MACLEOD, TYRRELL & CARL) REMAUDIERE and KELLER has been found frequently on T. tabaci but under field conditions the fungus was less successful than in the greenhouse. In addition, Entomophthora thripidum SAMSON, RAMAKERS & OSWALD was found infecting T. tabaci in Netherlands, but in field trials the fungus failed to suppress thrips populations below the economic acceptable level (SAMSON et al. 1979). In laboratory studies, T. tabaci was susceptible to Verticillium lecanii (ZIMMERMANN) VIÉGAS, Beauveria bassiana (BALSAMO) VUILLEMIN, Metarhizium anisopliae (METSCH.) SOROKIN and Paecilomyces fumosoroseus (WIZE) BROWN & SMITH (GILLESPIE 1986, FRANSEN 1990). VESTERGAARD et al. (1995) and BROWNBRIDGE (1995) showed that B. bassiana, M. anisopliae and V. lecanii were more active against the western flower thrips, Frankliniella occidentalis (PERGANDE) than P. fumosoroseus or Paecilomyces farinosus (HOLM ex S.F. GRAY) BROWN & SMITH. HALL et al. (1994) and SAITO (1991) suggested that Hirsutella sp., P. fumosoroseus and B. bassiana may be useful in the management of the melon thrips, Thrips palmi KARNY. EKESI et al. (1998) stated that B. bassiana and M. anisopliae are highly pathogenic to the legume flower thrips, Megalurothrips sjostedti (TRYBORN). In the glasshouse, V. lecanii has been used successfully to control T. tabaci on cucumber (GILLESPIE 1986).VACANTE et al. (1994) noted that N. parvispora caused up to 60 per cent mortality in motile developmental stages of F. occidentalis and reduced the insect populationdensity. Under greenhouse conditions, M. anisopliae was found to be effective in reducing the population growth of F. occidentalis on cucumber (AZAIZEH et al. 2002). Whereas, MANIANIA et al. (2001) observed that M. anisopliae had the potential to control F. occidentalis on chrysanthemum. The studies of MANIANIA et al. (2003) indicated that M. anisopliae had a potential to control T. tabaci in the field. Akanthomyces, Aschersonia, Cordyceps, Hypocrella, Hynennostilbe and Torrubiella were never observed to control thrips. Therefore, this study was conducted to investigate the pathogenicity of different entomopathogenic fungi from Thailand against T. tabaci larvae under controlled climatic conditions in the laboratory.
Die Gurkenblattlaus Aphis gossypii GLOVER (Hom., Aphididae) ist ein weltweit verbreiteter, polyphager Schädling, dessen Wirtspflanzenspektrum verschiedene Feld- und Gewächshauskulturen wie z. B. Malvaceen (Baumwolle, Hibiskus) und Curcurbitaceen (Gurken, Melonen, Zucchini) umfasst. In Europa stellt die Gurkenblattlaus einen wichtigen Schädling an Gurkenkulturen im Unterglasanbau dar (VAN SCHELT 1993) und sie tritt vermehrt auch an anderen Gewächshauskulturen auf (VAN STEENIS 1992). Aufgrund der Resistenzentwicklung von A. gossypii gegenüber zahlreichen chemischen Insektiziden gewinnt die biologische Bekämpfung unter Verwendung von Nützlingen zunehmend an Bedeutung. Bisher wurden der Parasitoid Aphelinus colemani VIERECK (Hym., Braconidae) und die räuberische Gallmückenlarve Aphidoletes aphidimyza RONDANI (Dipt., Cecidomyiidae) zur Bekämpfung dieser Blattlausart verwendet, jedoch mit nur mäßigen Erfolgen (VAN STEENIS 1994, VAN STEENIS & EL- KHAWASS 1995). TAKADA (2002) berichtet, dass die zwei Parasitoide Aphelinus asychis WALKER und Aphelinus varipes FÖRSTER (Hym., Aphelinidae) ein Potential zur biologischen Bekämpfung von A. gossypii an verschiedenen Gewächshauskulturen in Japan besitzen. Das Ziel der vorliegenden Studie war daher zu untersuchen, welcher dieser zwei Parasitoide zur biologischen Bekämpfung von A. gossypii an Gurken besser geeignet ist. Dazu wurden in Laborversuchen einige biologische Parameter wie Entwicklung, „host feeding“-Verhalten und Parasitierungsleistung beider Arten ermittelt und verglichen.
A new type of biocide GCSC-BtA, named from "Germany-China Scientific Cooperation-Bacillus thuringiensis-Abamectin", was successfully developed by conjugating delta-endotoxin of Bacillus thuringiensis (B.t.) with Abamectin from Streptomyces avermitilis through conjugator EDC for control of different agricultural arthropod pests. The laboratory results of efficiency of biocide GCSC-BtA to four different arthropod pests and its side-effect on two species of predators are presented in this paper. The results showed significant differences in the mortalities of Tetranychus cinnabarinus (BOISD.) (Acari, Tetranychidae), Frankliniella occidentalis PERGANDE (Thys., Thripidae), Aphis fabae SCOPOLI (Hom., Aphididae) and Cameraria ohridella DESCHKA ET DIMI´C (Lep., Gracillariidae) caused by treatment of 0.6250 mg/ml of formulated product of GCSC-BtA, B.t., Abamectin and Cypermethrin. GCSC-BtA treatment caused higher mortalities of 86.37%, 94.82%, 94.15% and 93.23% in T. cinnabarinus, F. occidentalis, A. fabae and C. ohridella, respectively. Mortalities caused by Abamectin treatment were 73.92%, 63.3%, 86.52% and 73.48%, and by Cypermethrin treatment were 44.29%, 57.28%, 97.68% and 51.26%, respectively. B.t. could only kill C. ohridella with 87.62% mortality. Pesticidal treatment gave variations in mortalities of Orius strigicollis POPPIUS (Het., Anthocoridae) and Stethorus cantonensis PANG (Col., Coccinellidae) predators at p < 0.01, where 0.6250 mg/ml GCSC-BtA caused 21.76% and 32.42% mortalities, while the same rate of products of Abamectin with 73.26% and 87.67% as well as Cypermethrin with 86.43% and 93.83% mortalities, respectively. It is concluded that the biocide GCSC-BtA has increased efficacies as well as host ranges of B.t. and Abamectin, but displayed safer to some predators.
The little known ladybird, Serangium parcesetosum SICARD (Col., Coccinellidae) seems to be an important predator of whiteflies. It has found attacking Bemisia tabaci (GENN.) (Hom., Aleyrodidae) (KAPADIA & PURI 1992), Aleurolobus barodensis MASK (PATEL et al. 1996), Aleurothrixus floccosus MASKELL (ABBOUD & AHMAD 1998), Bemisia argentifolii BELLOWS and PERRING (LEGASPI et al. 2001) as well as Dialeurodes citri (ASHMEAD) (YIGIT et al. 2003). However, in Germany the laboratory studies demonstrated that S. parcesetosum is a promising predator of B. tabaci (AL-ZYOUD & SENGONCA 2004; SENGONCA et al. 2004; AL-ZYOUD et al. 2005a, b; SENGONCA et al. 2005). One of the important features for a successful predator is to live for a long period on the prey species and also not feed on the plant in the prey absence. Long longevity accomplished by voraciously feeding of S. parcesetosum adults resulted in a successful control of B. argentifolii (ELLIS et al. 2001). To use this predator successfully in controlling the whiteflies, especially B. tabaci and Trialeurodes vaporariorum WESTWOOD (Hom., Aleyrodidae), it was important to investigate its natural and artificial nutritional sources. However, such knowledge of S. parcesetosum is still insufficient or completely lacking in the literature. Therefore, the present work was directed to study the longevity of S. parcesetosum on natural nutritional sources such as B. tabaci and T. vaporariorum as well as on certain artificial nutritional sources at two different temperatures in the laboratory.