University of California

Effect of zinc applications on the crop of grapefruit trees affected with mottle-leaf


E. R. Parker

Author Affiliations

E. R. Parker was Assistant Horticulturist in the Experiment Station.

Publication Information

Hilgardia 11(2):35-53. DOI:10.3733/hilg.v11n02p035. December 1937.

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The superficial effects of mottle-leaf are readily apparent in the character of the foliage and in the vigor of citrus trees (Fawcett, 1936).4 The reduced size of individual leaves and the retarding of growth causes an obvious decrease in leaf area. According to (Reed and Dufrénoy (1935)), the condition of partial chlorosis involves a reduction in the number of chloroplasts and in the photosynthetic capacity of the leaves.

Such abnormalities might be expected to alter the carbohydrate metabolism of plants and to affect their reproductive activities. In the case of citrus, such an effect might result in a decreased yield and possibly in an effect on the quality of the fruit. In extreme cases of mottle-leaf, these effects are clearly evident on casual inspection. Not only is the crop light, but fruits produced on severely affected branches are small and abnormal; the nature of the abnormalities varies with the species of citrus observed. Where trees are slightly to moderately affected with mottle-leaf, however, it is difficult to tell by casual observation what, if any, influence this disorder has on the amount and quality of the fruit produced.

Literature Cited

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Snedecor G. W. Calculation and interpretation of analysis of variance and covariance. 1934. Ames, Iowa: Collegiate Press, Inc. 96p. DOI: 10.1037/13308-000 [CrossRef]

Parker E. 1937. Effect of zinc applications on the crop of grapefruit trees affected with mottle-leaf. Hilgardia 11(2):35-53. DOI:10.3733/hilg.v11n02p035

Also in this issue:

Agricultural-business outlook: Farmers must understand and apply economic principles to the business of modern agricultural production by scientific means

Peach tree borer control tests: Fall treatments with soil fumigants and use of trunk sprays evaluated in experimental program during the 1955–56 seasons

Aphid resistance to parathion: Nonphosphate insecticides under study for control of spotted alfalfa aphid where pest develops resstance to parathion

Fungi on spotted alfalfa aphid: Spread of fungi by natural and artificial means is resulting in excellent biological control of aphid in many counties

Soil fumigation for nematodes: Nematocides tested for the control of root-knot nematodes affecting fresh market and canning tomato crops in California

Codling moth infestations up: Damage to harvested walnuts increased markedly in northern California during the 1956 season in comparison with 1955

California scaly bark disease of citrus: No known cure for infected trees but treatment in early stages of disease can retard its advance into successive stages with their increasing economic loss

Bartlett pears for canning: Ripeness of fruit at time of processing affects color, flavor, aroma, and over-all quality of finished product

Citrus weed control by monuron: Experiments with urea herbicides for weed control in citrus orchards encouraging but use of the chemicals is restricted

Weed control near grass areas: Soil fumigants and contact spray materials included in series of studies on control of weeds in relatively confined areas

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