Invasive Species Compendium

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Abstract

Gruava rust control by means of spraying.

Abstract

The author describes the results of spraying experiments for the control of guava rust (Puccinia psidii) carried out from 1943 to 1950 on 250 ten-year-old trees in randomized blocks at Campinas, São Paulo, Brazil [R.A.M., 27, p. 122].
The sweet varieties, both white and red, were more susceptible to the disease than the sour. Although a direct correlation was observed between vigourous growth and a high incidence of infection, no influence on the course of the disease was exerted by soil amendments with nitrogen levels of 40 and 200 gm. per kg. of fertilizer mixture. Unless the winter was wet, resulting in an early outbreak of rust, treatment during the dormant period was not essential for control. Of the fungicides used throughout the investigation, 1 per cent. Bordeaux mixture conferred satisfactory protection on the fruits, while 1 per cent. home-made cuprous oxide, also effective in this respect, injured both foliage and fruits. Lime-sulphur, dusting sulphur, and wettable sulphur failed to control the pathogen. On the basis of these results it is recommended that 1 per cent. Bordeaux mixture be applied after the onset of the winter rains (end of July or beginning of August), again when the trees begin active growth, and then monthly until December or January, according to rainfall and the severity of the disease.