UC Riverside

In the first chapter we evaluate leaf pruning for management of cane Botrytis on fresh-market raspberries. In the study we determine the influence of removal of lower leaves from primocanes on: (i) incidence and severity of cane Botrytis caused by B. cinerea; and (ii) the air temperature and relative humidity within the raspberry canopy. The studies were conducted under two tunnel-row configurations: two studies under tunnels with three rows and one under tunnels with two rows. The leaf removal treatments consisted of a non-treated control and three methods twine, manual, and blade removal. We found that removal of leaves in the lower canopy of raspberry primocanes may affect cane Botrytis incidence or severity, but effect may be positive or negative depending on context.

The second chapter evaluates Southern blight, a disease of processing tomato caused by the soilborne fungus Athelia rolfsii. The objectives of this study were to: (i) evaluate susceptibility of commercial processing tomato cultivars to southern blight; and (ii) evaluate grafting and increased height of the graft union with the resistant rootstock Maxifort for southern blight management in processing tomato. Objective (i) greenhouse experiments evaluated 20 commercial processing tomato cultivars and six processing tomato breeding lines in pots inoculated with 10 A. rolfsii sclerotia per 100 cm3 soil. Cultivars exhibited a range of susceptibility, and several commercial cultivars performed similarly to the breeding lines. For objective (ii) we evaluated two cultivars (Heinz 5608 or Heinz 8504), three graft treatments (standard height graft to Maxifort, tall height graft to Maxifort, and non-grafted) in both greenhouse and field studies. Southern blight incidence was drastically reduced by grafting treatments regardless of height. Based on our studies, the approach of grafting for management of southern blight may not be the best application. The use of resistant cultivars is a better and accessible approach for California processing tomato growers.