Thirty-six insecticides, used both as emulsifiable concentrates and wettable powders—when both were available—and 19 types of inert dust diluents were included in laboratory studies on their immediate and residual effectiveness in the control of vinegar flies—Drosophila melanogaster Meigen.

It is probable that effective control of Rhizopus rot—Rhizopus nigricans Ehr.—on peaches can be obtained—without fruit injury—by two 6-hour fumigations of an average ammonia concentration of about 250 ppm—parts per million.

Variable conditions in the fruit growing areas of California make it difficult to project the results from evaluation tests in one area to another. As a consequence, field plots were established for the 1957 season in Bartlett pear orchards—in Sacramento, Solano, El Dorado, Lake, and Mendocino counties—for University personnel to evaluate spray materials under local conditions. As a correlative evaluation, spray chemicals used in codling moth and aphid control plots were checked for their effects on spider mites.

Pp. 25.

Thesis (DScAgric)--University of Stellenbosch, 1958. | OBJECTIVE. High economic production has ever been the aim and aspiration of the agriculturist and no less that of the fruit farmer. In striving towards this aim the latter has for a long time been at a disadvantage with regard to control of his nutritional programme. Even on naturally fertile soil, the question continually arises as to what the correct fertilizer treatment should be to maintain high productivity and how such a decision can be arrived at. A satisfactory answer to these questions could have been obtained from fertilizer trials if it was not such a difficult matter, in view of the extensive and long-term nature of such trials with fruit trees, to establish a sufficient number for each fruit species on different soil types and under different climatic conditions. Efforts to find a new approach to the problem have turned attention to the plant itself and its chemical make-up as affording the best index of its nutritional requirements. Intensive work in this direction has resulted in the evolution of a new tool in agriculture, the technique of diagnostic leaf analysis or 1Toliar diagnosis" as originally proposed by Lagatu and Maume in France and Thomas in u.s.A. A review of the literature is presented indicating the prodigous amount of research which has been applied to studies of the relationship between plant response and nutrient supply in terms of plant composition. Agriculturists have been quick to recognize the potentialities of leaf analysis as a practical guide in nutritional problems and advisory services based on foliar analysis have already been established for certain crops overseas. The experimental basis for formulating such a scheme for deciduous fruit in the Western Cape Province is provided by the factual evidence presented in this thesis.THE TECHNIQUE. The technique of diagnostic leaf analysis comprises sampling of leaves, preparation of sample for analysis and the analysis itself followed by interpretation of the analytical results by comparison with previously determined nutritional standards. Numerous factors were found to influence the final composition of the leaf sample as determined by analysis, such that strict adherence to a standardized procedure through all phases of sampling and preparation of leaf samples for analysis is required to eliminate or reduce errors likely to cause misleading interpretations. Experimental data are presented suggesting how the leaf sample should be selected on a tree and how it should be handled, cleaned, dried, ground and stored to reduce sampling and other errors. The final procedure as adopted eliminates most of the potential sources of experimental error but two unavoidable sources of e~ror remain to be accounted for, that due to tree variation and seasonal effect. The variation in leaf composition from tree to tree was found to be very considerable, so that aampling from a large enough group of trees (6 to 10) to reduce the error involved is essential in order to obtain leaf data which correctly reflects the nutrient status of the portion of the orchard concerned. Secondly, on the grounds of marked consistency found in different fruit species as to seasonal and year to year variation in mineral nutrient concentration, correction factors have been formulated and are suggested as a means of overcoming these sources of error. THEORETICAL BASIS. A diagnosis of the nutrient status in terms of the analytical results as finally determined is obtained by comparison of the data with previously established leaf composition standards of reference and by correct interpretation of the deviations from these standards. The theoretical basis for setting up these index values is discussed. The criterion used is based on the concept of Optimum Values which aaequately integrates the known relationships between plant response and nutrient supply in terms of internal nutrient concentration. A modification of this concept is proposed to the effect that for maximum growth and yield there exists an optimum range of nutrient concentrations with upper and lower limits for each of the functional elements, and that within this range the interrelationship between the individual nutrient elements is also optimal. Since no local fertilize~ trials with deciduous fruit trees are available and only one for grapes, data from highly productive plants in commercial orchards and vineyards were used to determine the upper and lower limits of the "optimum range", on the following premise. If leaf analysis data are available from a sufficient number of high performance orchards in different localities representing a wide range of nutrient supply and environment, the highest and lowest values obtained may be considered to represent a close approximation of the limits of the range required for optimum performance. It is contended that index values obtained in this way must be of practical value in assessing the nutrient status of fruit trees. It is further postulated that the lower limits for the micro-nutrients and even for magnesium may be justifiably adjusted according to the concentration levels associated with symptom expression. INDEX VALUES. The necessary data for determining standards of leaf composition were obtained from leaf analysis surveys of orchards and vineyards and from a grape fertilizer experiment in the Western Cape Province. Visual symptoms of prevailing nutritional disorders are described (supplemented by photographic illustrations) and their relation to leaf composition indicated. Tentative index values have been determined on the basis indicated for each fruit species, apple, pear, peach, apricot, plum, prune and grapes. These nutritional levels comprise upper and lower limits for the nutrients N, P, K, Ca, Mg 1 Mn 1 Fe and Cu, as well as the upper limits for B and Na. DIAGNOSTIC INTERPRETATIONS. Assessment of the nutrient status in terms of these index values suggests that many orchards and vineyards in the Western Cape Province, particularly prune, apricot and grapes, are suffering from malnutrition in some form and are likely to show a marked response to nutritional treatment as suggested by foliar diagnosis. The use of diagnostic leaf analysis constitutes an important advance in dealing with orohard problems in that an immediate decision is possible regarding nutrient status and related aspects such as selection of suitable sites for fertilizer trials and adjustment of the fertilizer programme. | AFRIKAANSE OPSOMMING: geen opsomming | Doctoral

No presente trabalho são apresentados os dados de produção de cafeeiros plantados a quatro mudas por cova, variando, contudo, a maneira de sua distribuição dentro da cova. Um dos tratamentos corresponde ao sistema comum de plantio, no qual as mudas são dispostas em quadrado, na cova. O outro refere-se à disposição das quatro mudas em linha na cova. Visava-se, plantando as mudas desta última forma, facilitar o combate à broca do café pela retirada dos grãos que normalmente caem e ficam presos no centro dos quatro troncos formados pelo sistema comum. Os resultados obtidos, correspondentes ao período de 1951 a 1956, não indicaram diferenças significativas entre as produções dos dois tratamentos. Desta forma, embora o problema do combate à broca do café esteja resolvido com o emprêgo de inseticidas modernos, os resultados dêste ensaio mostram que qualquer um dos sistemas de plantio pode ser adotado no estabelecimento de cafèzais. | Individual trees in coffee plantations established in the state of São Paulo usually result from four seedlings that were placed in a square within the planting hole. When the plants begin to bear, this planting system favors the coffee berry-borer infestation because many fruits fall in between the stems of the four plants and are hard to be collected, thus remaining as a food source for the insect between two successive crops. Placing the seedlings in a straight line within the planting hole was thought as a method that would facilitate the harvest and permit the collection of fruits left behind on the trees or near their trunks. An experiment designed to compare this planting method with the usual one was undertaken at the Central Experiment Station, instituto Agronômico, Campinas. The red Bourbon variety of Coffea arabica was used. the seedlings in line were placed 15 cm apart, and at about 30 cm when in a square. A randomized block design with 20 replications for the two treatments was used, each plot comprising a single hole with four seedlings. Yield records were taken for the years 1951 through 1956 (Table 1). The size of the beans was also studied (Table 2). The total yield in dried fruit for this period was 135.2 kg for the plots with the seedlings in line and 131.6 kg for those with seedlings planted in a square. The difference between the two treatments was not significant. Large differences were observed between years for the same treatment, but the interaction treatments x years was not significant. Today the control of the coffee berry-borer is efficiently carried out by dusting or spraying BHC on the trees; the method of placing the seedlings in a line within the planting hole does not present advantages anymore. The results here discussed indicate, however, that both methods of seedling placement in the planting hole can be used by the farmers without affecting the yield.