Two independent experiments were conducted during 1992 and 1993 using a Randomized Complete Block Design with four replications. The first experiment was designed to study the effect of mulch spectral properties on weed growth and development. The second was conducted to study the effect of polyethylene mulch on aphid population and on growth and yield of bell pepper. Initially, rye-grass germination under polyethylene mulches was significantly higher than that on bare soil, whereas mustard seed germination under mulches did not differ significantly from that on bare soil. However, at the end of 30 days, none of these weeds were observed in the mulched plots. Transmittance, reflectance, and absorbance were recorded in the Near Ultraviolet (390-399 nanometre), Photosynthetically Active Radiation (400-700 nanometre), and Near Infrared (701-1100 nanometre) bands for black, black microperforated, wavelength selective and silver mulches. Aging had little effect on the optical properties of the mulches. The wavelength selective (Infra red transmitting = IRT-76) green mulch had the warmest mean soil temperatures, followed by silver, black, microperforated black mulch, and bare soil. The soil moisture content was higher under plastic mulches than in bare soil. The use of mulches significantly increased both the early and total marketable yields of pepper. Plants grown with polyethylene mulch had significantly lower number of aphids on them than did their bare soil counterparts.

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