Möglichkeiten zur biologischen Bekämpfung des Zwiebelthrips Thrips tabaci LINDEMAN (Thys., Thripidae) durch verschiedene, entomopathogene Pilze aus Thailand

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.Thrips tabaci LINDEMAN (Thys., Thripidae) ist ein weltweit verbreiteter Schädling mit einem breiten Wirtspflanzenspektrum an verschiedenen Freiland und Gewächshauskulturen, dessen Bekämpfung durch die geringe Größe und ihre versteckte Lebensweise erschwert wird. Entomopathogene Pilze sind wichtige Krankheitserreger zahlreicher Insektenarten und infizieren Individuen verschiedenen Alters und verschiedener Entwicklungsstufen. In der vorliegenden Studie wurden 41 Isolate von 25 entomopathogenen Pilzarten aus 11 Gattungen (Akanthomyces, Aschersonia, Beauveria, Cordyceps, Hirsutella, Hymenostilbe, Hypocrella, Metarhizium, Paecilomyces, Torrubiella und Verticillium) auf ihre Pathogenität gegenüber T. tabaci-Larven untersucht. Bis auf Hymenostilbe sp., Torrubiella spp., Hypocrella discoidea und Cordyceps pseudomilitaris stellten sich alle Pilze als Pathogen für T. tabaci heraus. Zwischen den Isolaten wurden hoch signifikante Unterschiede festgestellt. Die Mortalität variierte je nach Pilzart, Pilzgattung und Isolat. Fünfzehn Isolate, 7 von Beauveria, 4 von Metarhizium, 3 von Paecilomyces und 1 von Cordyceps, wiesen die höchste Pathogenität gegenüber T. tabaci-Larven auf

Lebensdauer des räuberischen Marienkäfers Serangium parcesetosum Sicard (Col., Coccinellidae) mit natürlicher und künstlicher Nahrung

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.Der in der Literatur nur wenig bekannte Marienkäfer Serangium parcesetosum SICARD (Col., Coccinellidae) scheint, ein spezialisierter Prädator der Weißen Fliegen zu sein. Untersuchungen über die Lebensdauer eines Prädators sind eine der wichtigsten Parameter für seine erfolgreiche Verwendung in der biologischen Bekämpfung. Solche Informationen über S. parcesetosum sind bisher in der Literatur allerdings nur unzulänglich bekannt bzw. fehlen vollständig. Folglich war das Ziel dieser Arbeit, bei zwei unterschiedlichen Temperaturen im Labor zu untersuchen, wie lang S. parcesetosum mit Bemisia tabaci (GENN.) bzw. Trialeurodes vaporariorum WESTWOOD (Hom., Aleyrodidae) als Beute sowie mit bestimmten künstlichen Nahrungen überleben kann. Die Ergebnisse zeigten, dass beide Geschlechter von S. parcesetosum auf Baumwolle mit B. tabaci als Beute, mit Ausnahme der Männchen bei 30°C, signifikant länger mit allen anderen Nahrungen lebten. Bei beiden Temperaturen war die Lebensdauer der Weibchen, mit allen untersuchten Nahrungen, signifikant länger als die der Männchen. Sie schwankte bei beiden Geschlechtern von durchschnittlich 94,3 (♂♂) bis 175,4 (♀♀) Tagen bei 18°C bzw. 50,3 (♂♂) bis 92,4 (♀♀) Tage bei 30°C mit den getesteten Nahrungen. Die adulten Weibchen und Männchen von S. parcesetosum konnten für eine beträchtliche Zeit mit künstlichen Nahrungen überleben. Bei beiden Temperaturen war die durchschnittliche Überlebensdauer beider Geschlechter bei einem Angebot von 10%iger Honig-Emulsion als Nahrung signifikant länger als nur mit Baumwollblättern bzw. ohne ein Angebot an Nahrung

Randomness Efficient Testing of Sparse Black Box Identities of Unbounded Degree over the Reals

We construct a hitting set generator for sparse multivariate polynomials over the reals. The seed length of our generator is O(log^2 (mn/epsilon)) where m is the number of monomials, n is number of variables, and 1 - epsilon is the hitting probability. The generator can be evaluated in time polynomial in log m, n, and log 1/epsilon. This is the first hitting set generator whose seed length is independent of the degree of the polynomial. The seed length of the best generator so far by Klivans and Spielman [STOC 2001] depends logarithmically on the degree. From this, we get a randomized algorithm for testing sparse black box polynomial identities over the reals using O(log^2 (mn/epsilon)) random bits with running time polynomial in log m, n, and log(1/epsilon). We also design a deterministic test with running time ~O(m^3 n^3). Here, the ~O-notation suppresses polylogarithmic factors. The previously best deterministic test by Lipton and Vishnoi [SODA 2003] has a running time that depends polynomially on log delta, where $delta$ is the degree of the black box polynomial

Greedy Strikes Again: A Deterministic PTAS for Commutative Rank of Matrix Spaces

We consider the problem of commutative rank computation of a given matrix space. A matrix space is a (linear) subspace of the (linear) space of n x n matrices over a given field. The problem is fundamental, as it generalizes several computational problems from algebra and combinatorics. For instance, checking if the commutative rank of the space is n, subsumes problems such as testing perfect matching in graphs and identity testing of algebraic branching programs. An efficient deterministic computation of the commutative rank is a major open problem, although there is a simple and efficient randomized algorithm for it. Recently, there has been a series of results on computing the non-commutative rank of matrix spaces in deterministic polynomial time. Since the non-commutative rank of any matrix space is at most twice the commutative rank, one immediately gets a deterministic 1/2-approximation algorithm for the computation of the commutative rank. This leads to a natural question of whether this approximation ratio can be improved. In this paper, we answer this question affirmatively. We present a deterministic Polynomial-time approximation scheme (PTAS) for computing the commutative rank of a given matrix space B. More specifically, given a matrix space and a rational number e > 0, we give an algorithm, that runs in time O(n^(4 + 3/e)) and computes a matrix A in the given matrix space B such that the rank of A is at least (1-e) times the commutative rank of B. The algorithm is the natural greedy algorithm. It always takes the first set of k matrices that will increase the rank of the matrix constructed so far until it does not find any improvement, where the size of the set k depends on e

Comparative studies on the suitability of two aphelinids, Aphelinus asychis WALKER and Aphelinus varipes FÖRSTER (Hym., Aphelinidae), for the biological control of Aphis gossypii GLOVER (Hom., Aphididae)

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.The cotton aphid is a phytophagous cosmopolitan species and an important pest on cucumber in European greenhouses. Because of increased insecticide resistance and destruction of natural enemies through the use of pesticides current research is directed towards the development of management. systems that use biological control methods. The present laboratory study was designed to compare two aphelinids, Aphelinus asychis WALKER and Aphelinus varipes FÖRSTER, according to some life table characteristics parasitizing the cotton aphid, Aphis gossypii GLOVER. The traits studied were developmental time, adult emergence rate, host feeding and parasitation. The results showed that both species were able to complete their development with exclusively this host. Moreover, they can host feed and parasitize successfully on A. gossypii-nymphs. Developmental duration from egg to mummification and from mummification to emergence of adults were 7,1 days and 6,9 days for A. asychis and 9,1 days and 10,3 days for A. varipes, respectively. Adult emergence rates were higher for A. asychis (75%) than for A. varipes (53%). Comparison of the impact on A. gossypii of both parasitoids indicated that A. asychis was more effective than A. varipes. In total A. asychis killed an average of 17,1 and A. varipes an average of 4,8 A. gossypii-nymphs/day. Consequently, A. asychis seems to be a promising natural enemy which could contribute to a successful biological control program for A. gossypii. However, it´s biology, ecology and control efficiency need further information

Aged B lymphocytes retain their ability to express surface markers but are dysfunctional in their proliferative capability during early activation events

Abstract Background Ageing is associated with dysfunction in the humoral response leading to decreased protection against infectious diseases. Defects in T cell function due to age have been well characterized but it is unclear if dysfunctions in antibody responses are due to deficiencies in a helper environment or intrinsic B cell defects. Previous studies from our laboratory have shown that aged B lymphocytes are able to differentiate into high affinity antibody-secreting cells at a frequency similar to their young counterparts. However, expansion of B cells in vivo was reduced in aged animals when compared to young. Methods To further investigate the cause of this reduced expansion, we have now examined early activation events of aged B cells in response to anti-CD40 monoclonal antibody (mAb) and lipopolysaccharide (LPS) stimulation in vitro. To do this spleen cells were harvested from young, middle-aged and aged quasi-monoclonal (QM) mice and cultured in complete RPMI for 24 and 48 hours. Cultures contained either LPS or anti-CD40 mAb and murine IL-4. Cells were collected and analyzed using flow cytometry. To examine the proliferative capacity of aged B cells spleen cells were collected as before and cultured in 96 well microtiter plates with either LPS or anti-CD40 mAb and murine IL-4 for 24 hours. Tritiated thymidine ([3H]-Tdr) was added to each well and incubated for another 24 hours after which cells were collected and analyzed using a scintillation counter. Results Resting aged B cells exhibited similar levels of CD40 expression when compared to young cells and efficiently up-regulated CD86 and CD69 and also down-regulated CD38 upon stimulation. However, aged B cells proliferated less than young B cells and showed a consistent, but not statistically significant, reduction in their ability to form blast cells. Conclusion Aged B cells exhibited a reduced response in some early activation events but produced at least a partial response in all cases. Thus, therapeutic intervention may be possible, despite intrinsically different responses in aged B cells.</p