Summary Various methods were tested to control the annual grass Rottboellia exaltata L.f. in maize (Zea mays L.) under small‐farm conditions in Bukidnon Province, Mindanao, Philippines during 1977 and 1978. No single method was satisfactory. Despite adequate early season control, late‐germinating Rottboellia tillered profusely. By harvest, plots had heavy infestations and were carpeted with seed. At harvest, untreated controls averaged 8·6 t Rottboellia dry matter ha−1 and only half the maize yield of handweeded plots. The ‘karase’ spike‐tooth harrow, or 0·2 kg paraquat ha−1, effectively removed Rottboellia flushes before maize emergence, but these techniques delayed planting, which can intensify downy mildew disease (Sclerospora sp.). Even though handweeding increased maize yields and decreased Rottboellia dry weights, it is impractical on typical 3‐ to 5‐ha maize farms. Mungbean (Vigna radiata (L.) Wilczek var. aureus), intercropped with maize, suppressed Rottboellia initially. Openings caused by mungbean harvest, however, allowed explosive late‐season weed growth in maize. Three herbicide treatments were as effective as handweeding: pendimethalin plus atrazine, either banded over the maize row (followed by cultivation), or broadcast; and pendimethalin followed by 2, 4‐D, both broadcast. In one experiment, low‐cost practices, including weed flush removal, cultivation, or handweeding, provided high net returns, whereas expensive herbicide treatments produced low net returns. Fertilizer, applied without weed control, increased maize yield 62%. Without fertilizer, weed control increased yield 107%. Combining the two raised yield 167%.

Polyacrylamide electrophoresis and spectroscopic methods were used to characterize biotypes A and B itchgrass [Rottboellia exaltataL.f. # ROOEX] and their F2progeny. Electrophoretic analyses of F2progeny showed that differences between these two biotypes are multiallelic. Spectrophotometric data indicated differences between the photosynthetic apparatus of the two biotypes. These differences may reflect different abilities to adapt to varying light conditions and infer that these biotypes promote survival of the species by increasing the number of environmental nitches thatR. exaltatacan occupy.

Herbicides can increase agricultural productivity and rural welfare where agronomic considerations or labor shortages favor their utilization, but ecological, social, and economic conditions in developing countries often favor alternative weed control methods. Traditional hoeing by peasant farmers in a Northeast Brazil upland region was found to be both effective and economical in comparison with other methods. In another Northeast Brazil region, government herbicide subsidies and payroll taxes were projected to encourage excessive use of herbicides at the expense of displaced workers with few alternative employment opportunities.

The purpose of this publication is to provide a brief description o-the cacao clones being held at the U.S. Plant Introduction Station, Mia.-ni, Fla. This information should be of value to cacao workers who are in need of disease-free, documented clonal stock. The material is available in small quantities for research purposes. Requests sent to the Miami station will be honored on an availability basis. It is not intended to duplicate in any way the more complete catalog being published by the

This publication reports on surveys of the deciduous fruit and nut clones being maintained at the Federal and State experiment stations in the United States. It will bs published in three parts: I. Apples, II. Stone Fruits, III. Pears, Nuts, and Other Fruits. This survey was conducted at the request of the National Coordinating Committee on New Crops. Its purpose is to obtain an indication of the volume of material that would be involved in establishing clonal germ plasm repositories for the use of fruit breeders throughout the country.