Showing papers on "Toona published in 2009"

Flight and Host Selection Behaviour of the Mahogany Shoot Borer, Hypsipyla grandella Zeller (Lepid., Phycitidae)1

Abstract: Field and laboratory studies were established in Puerto Rico to investigate the flight and host selection behavior of Hypsipyla grandella. Barrier traps, placed in Cedrela odorata stands were used to elucidate patterns of host selection; laboratory feeding studies were used to determine the effects of native hosts and an introduced Meliaceae (Toona ciliata) on larval survival. The studies showed that moths fly between midnight and 0500 h, with a peak flight at 0300 h. Flight takes place at temperatures between 15–24° C. Infestations concentrate on C. odorata that evidence new growth, and the tallest trees are most subject to attack; open grown trees are more readily infested than shaded stems. The trapping studies also indicated the presence of a female sex pheromone. Acetone, methanol, and hexane extracts of new or mature foliage were ineffective in attracting moths. However, moths were attracted to acetone extracts of new leaves in association with Cedrela plants having only mature leaves. Feeding studies showed that T. ciliata acetone extracts were toxic to H. grandella larvae; hexane and methanol extracts were nontoxic. Results from the field and laboratory studies suggested a chemical affinity between primary Cedrela attractants and toxic Toona extracts; a hypothesis explaining these relationships is proposed. Zusammenfassung Flug und Wirtswahlverhalten von Hypsipyla grandella Zeller (Lepid., Phycitidae) Es wurden Freiland- und Laboruntersuchungen in Puerto Rico uber den Flug und das Wirtswahlverhalten der Falter von H. grandella durchgefuhrt. Zur Prufung der Wirtswahl dienten Barrierefallen in Pflanzungen der Spanischen Zeder (Toona ciliata). Laborexperimente sollten Aufschlus geben uber den Einflus des Blattalters sowie eingefuhrter Toona ciliata. Der Flug fand nachts zwischen 0 und 5 Uhr bei Temperaturen zwischen 15 und 24° C statt. Der Befall konzentrierte sich auf die Jungtriebe von T. ciliata, wobei schwachere Baume bevorzugt wurden. Freiwachsende wurden starker befallen als beschattete. Die ♀ Falter scheiden einen Sexuallockstoff aus. Aceton-, Methanol- und Hexa-Extrakte aus jungen Blattern zeigten keine Lockwirkung. Jedoch wurden die Falter durch einen Azetonextrakt aus neuen Blattern in Verbindung mit Zedern, die nur alte Blatter aufwiesen, angelockt. Futterungsversuche zeigten, das Acetonextrakte aus Toona-Blattern auf H. grandella-Raupen toxisch wirkten, nicht aber Hexa- und Methanol-Extrakte. Zwischen dem Cedrela-Lockstoff und dem toxischen Toona-Extrakt bestand chemische Affinitat. Dies gab Anlas zur Herstellung einer Hypothese uber die Beziehungen zwischen beiden Substanzen und Baumen.

Effects of aqueous leachates of multipurpose trees on test crops.

Abstract: The allelopathic potential of the agroforestry trees Ficus subincisa Buch.-Ham. ex J. E. Smith, Bauhinia purpurea L., and Toona hexandra Wallich ex Roxb. was investigated on Triticum aestivum L., Brassica campestris L., and Hordeum vulgare L. test crops. The leaf and bark leachates of trees were both toxic to the germination of the test crops. The inhibition of the germination of test crops was significant. The effects of leachates on test crops were concentration dependent. So, higher concentrations of leaf and bark leachates showed stimulatory effects on the radicle and plumule growth of all test crops. The acceptance of these multipurpose tree species as agroforestry trees in association with field crops decreased in the order Ficus subincisa, Bauhinia purpurea, and Toona hexandra.