Abstract
In Latin America and the Caribbean, precious wood species like mahoganies (Swietenia spp.) and cedars (Cedrela spp.) are seriously injured by the mahogany shootborer, Hypsipyla grandella (Zeller) (Lepidoptera: Pyralidae) larva, which bores into the main shoot of trees. In previous experiments focused on searching for a preventive method for managing this pest, a wood extract of bitterwood, Quassia amara L. ex Blom (Simaroubaceae) had been shown to cause phagodeterrence to larvae. Therefore, three fractions (water, methanol and diethyl ether) of a wood extract were tested for their phagodeterrence to larvae, by means of laboratory and greenhouse trials. Phagodeterrence was assessed by determining their effect on foliage consumption, mortality and signs of damage (number of orifices, sawdust piles, fallen shoots, number of tunnels and tunnel length) caused by larvae on Spanish cedar (C. odorata). Both the methanol and diethyl ether fractions caused phagodeterrence, by strongly reducing foliage consumption and signs of damage, while not causing larval mortality. The lowest concentration at which phagodeterrence was detected for the methanol fraction corresponded to 0.0625%, which is equivalent to a 1.0% of the bitterwood crude extract. However, results with the diethyl ether fraction were unsatisfactory, as none of the treatments differed from the solvent, possibly because of an adverse effect of the solvent on foliar tissues. Phagodeterrent principles from Q. amara derivatives may play an important role in dealing with H. grandella if they are complemented with other integrated pest management preventative tactics.
Highlights
IntroductionSince a density as low as one larva per shoot is high enough to cause irreversible damage and high economic losses, this pest has precluded attempts to establish commercial plantations of mahoganies and cedars in Latin America and the Caribbean
Likewise, since a density as low as one larva per shoot is high enough to cause irreversible damage and high economic losses, this pest has precluded attempts to establish commercial plantations of mahoganies and cedars in Latin America and the Caribbean
The lowest consumption averages were attained with the methanol and diethyl ether fractions along with the crude extract (0.34-1.16%) and the highest (15-20%) with the water fraction and the water control treatment
Summary
Since a density as low as one larva per shoot is high enough to cause irreversible damage and high economic losses, this pest has precluded attempts to establish commercial plantations of mahoganies and cedars in Latin America and the Caribbean. In the search for a preventative approach to deal with this pest, it has been shown that some plant extracts can act as larval feeding deterrents (Hilje & Mora 2006), the main ones being methanol extracts of both the wood and. Considering preliminary results by Mancebo et al (2000), the objective of this research was to assess some fractions of Q. amara in regards of their phagodeterrent effect on H. grandella larvae, and to gain insight into more specific groups of substances causing such effect, under both laboratory and greenhouse conditions
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