Abstracts The effects of overstory trees and birds on coffee pests are poorly understood. This study documents (a) the effect of bird exclusion on foliagedwelling arthropod abundance and insect-caused leaf damage, and (b) the relationships between vegetation complexity and insect abundance, leaf damage, and prevalence of fungal leaf symptoms on coffee farms in the Blue Mountains of Jamaica, West Indies. Overall arthropod abundance was reduced inside bird-proof exclosures, and this corresponded to reduced insect-caused leaf damage. The reduction in leaf damage increased with greater shade, but fungal leaf symptoms increased with greater shade and proximity to non-coffee habitat patches. There appears to be a trade-off for coffee farmers in our study region: vegetation complexity may attract beneficial insect-eating birds that can reduce insect damage, but it is also associated with the prevalence of fungal leaf symptoms.

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The 2-week no observed effect (NOEC) and lowest observed effect (LOEC) concentrations of dieldrin were determined for Macrobrachium faustinum de Sassure in fresh and brackish waters. LOEC1,10,50,95 values in fresh water were 0.001, 0.003, 0.011 and 0.058 microg l(-1), respectively, and in brackish water, 0.00006, 0.00027, 0.00165, and 0.0172 microg l(-1), respectively. The 96-hr LC10, LC50 and LC95 values were 0.029, 0.123 and 0.771 microg l(-1), respectively. It is proposed that NOEC and LOEC be redefined to take into account the percentage of individuals affected, the severity of symptoms and the recovery of poisoned individuals. Two new terms are proposed--Median Observable Effect Concentration (MOEC) for pronounced toxic symptoms in most individuals but mortality in <50%, and Pronounced Observed Effect Concentration (POEC), which inflicts mortality in >50% individuals. Bioaccumulation of dieldrin by M. faustinum from surrounding fresh and brackish waters were rapid and fairly uniform for the first 48 h when the bioconcentration equilibrium (14.4 +/- 0.42 ng g(-1) at 0.001 microg l(-1) and 42.5 +/- 1.72 ng g(-1) at 0.01 phi g l(-1)) was achieved. Relative partitioning of residues (ng g(-1) wet wt.), after 24h exposure to 0.001 microg l(-1) of dieldrin in fresh water, in the different tissues was hepatopancreas > gonads > gills > large claws > muscle and exoskeleton. Shrimp which had accumulated 10.5 +/- 0.52 ng g(-1) dieldrin in fresh and brackish water, eliminated only about 52% of the residues after eight days in uncontaminated water.

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