The hostÐpathogen interactions of Musa spp[ and Myco! sphaerella _jiensis were investigated in order to determine the function of secondary metabolites within the patho! system of the Black Sigatoka disease[ The pentaketide metabolites~aviolin\ 1!hydroxyjuglone\ juglone and 1\3\7!trihydroxytetralone "1\3\7!THT# of the pathogen were identi_ed[ The concentration of 1\3\7!THT was sig! ni_cantly increased by application of the synthetic com! pound tricyclazole and by natural activators extracted from the intercellular space of leaf tissue of resistant Musa cultivars[ When inoculated host plants were treated with tricyclazole\ extensive necrosis of both susceptible and resistant Musa cultivar leaves were observed[ Plant defence mechanisms of resistant Musa cultivars were _rst detected as an activation of phenylalanineÐammonia lyase and the subsequent accumulation of post!infec! tional substances which blocked fungal growth[ These results indicated the bivalent importance of 1\3\7!THT for host!speci_c reactions\ depending on its con! centration at di}erent stages of pathogenesis[ Early acti! vation of fungal 1\3\7!THT metabolism by resistant Musa cultivars caused necrotic micro!lesions and elicitation of post!infectional defence reactions leading to incom! patibility between pathogen and host plant^growth of the fungus on susceptible cultivars caused necrotizing doses of 1\3\7!THT only after the establishment of a compatible interaction and development of typical symp! toms at late stages of pathogenesis[

The predator Teretriosoma nigrescens Lewis was released in southern Togo for the first time in 1991. Followup storage trials were carried out after this first release of the predator in order to investigate effects on its prey, the storage pest Prostephanus truncatus (Horn), in maize stores. Two trials were installed in the same villages (Tsagba as release village and Dafo as control), one in the storage season 1990/91 and the other in 1992/93. A third trial was set up in Moretan (release village) and Akaba (control) in 1993 together with the second release of T. nigrescens. The storage period lasted 8 months with sampling every 2 months. The number of P. truncatus was reduced by 56.4% in stores with presence of T. nigrescens as compared to the control after 8 months of storage in 1990/91. Damage and losses of stored maize cobs were 40.7% and 47.4% smaller than without the predator. One year after the release, larger numbers of the predator were observed in stores. Again, P. truncatus was reduced by T. nigrescens, but this was not as visible as before.In the third trial in Moretan, 1993, shortly after the second release of T. nigrescens, again a decrease of numbers of the Larger Grain Borer was observed in stores after 8 months of storage, together with a reduction of damage and losses.

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In the course of three storage periods "0877Ð89# the predacious insects that occur in traditional maize stores in southern Togo were observed and their relationship to the introduced pest Prostephanus truncatus was investigated[ The bug Xylocoris~avipes\ a predator on a wide range of post!harvest pests\ was the only one observed regularly and in higher numbers[ Laboratory trials with P[ truncatus showed that the larvae were preyed on\ and no preference for any one of the three instars was detected[ On average\ 6[2 pest larvae were killed by larvae or adults of the predator[ In glass jar trials on loose maize X[~avipes reduced the numbers of P[ truncatus by 46[5) after 7 weeks[ The losses and damage were reduced by 49 and 06[5)\ respectively[ Observations in traditional maize stores indicated a tendency to decreasing populations of X[~avipes when populations of P[ truncatus increased\ presumably due to the unfavourable environmental conditions created by the pest[ Therefore\ it is concluded that X[~avipes does not play an important role in the control of this pest[

No abstract