Three amides were isolated from Piper nigrum L. and identified from their spectral characteristics as (E,E)-N-(2-methylpropyl)-2,4-decadienamide (I), (E,E,E)-13-(1,3-benzodioxol-5-yl)-N-(2-methylpropyl)-2,4,12-tridecatrienamide (II), and (E,E,E)-11-(1,3-benzodioxol-5-yl)-N-(2-methylpropyl)-2,4,10-undecatrienamide (III). The topical LD50 values of compounds I, II, and III against Callosobruchus maculatus (F.) were 2.18, 0.25, and 0.84 µg/insect for males (weight 3.8-5.7 mg) and 6.70, 1.43, and 3.88 µg/insect for females (weight 5.4-7.9 mg), respectively. A rapid colorimetric method was developed to determine deposits of carbaryl insecticide on fruit tree foliage. Analyses take less than 3 min/sample when 50 or more samples are processed at a time. A 5-cm² disk punched from a leaf is used for the determination. Carbaryl is extracted and hydrolyzed by methanolic NaOH (0.03% w/v) and then coupled with p-nitrobenzenediazonium tetrafluoroborate which produces a spectrum of colors ranging from red to blue. Within a concentration range of 0.5-10 µg/cm² of leaf surface or 0.25-5 µg/mL of alkaline solution in a test tube, the absorbance of color obeyed Beer's law when measured at 580 nm. Little, if any, interference was observed from other commonly used pesticides, such as dicofol, tetradifon, azinphosmethyl, phosmet, captan, and folpet. If a spectrophotometer is not available or when a rapid field test is required, a semiquantitative determination is also possible.