Lettucedrop is a persistent disease that causes economic loss in lettuce production around the world. In coastal California, the largest lettuce-producing region in the United States, the disease is caused predominantly by the soil dwelling
Lettucedrop is an economically important disease of lettuce. Complete control has not been achieved through cultural practices and fungicide applications, making resistant cultivars a potentially valuable tool in an integrated pest management
effects on Pythium spp. colonies and S. minor sclerotia (i.e., lettucedrop, in all five trials at the UC ANR Hartnell station) ( Table 1 ). Soil samples were assessed for propagules of Pythium spp. using a soil plating method. In addition, S. minor
, V.K. 1998 Progress toward integrated management of lettucedrop Plant Dis. 82 1068 1078 Turner, N.C. Long, M.J. 1980 Errors arising from rapid water loss in the measurement of leaf water potenti al by the pressure chamber technique Funct. Plant Biol
performance of four representative greenhouse crops (rose, gypsophila, cucumber, and lettuce) on four types of pumice differing in particle size (0 to 2, 0 to 5, 0 to 8, and 4 to 8 mm) placed either in bags or in pots. To assess the growth and yield
A low to moderate incidence of lettuce drop caused by Sclerotinia minor is commonly observed in commercial lettuce fields of all types of lettuce (e.g. crisphead, romaine, leaf, butter) and although partial resistance has been reported, no sources of immunity have been described. We sought to determine whether there was variability between different types of lettuce and among cultivars within types. Replicated experiments were conducted in an infested field using established inoculation procedures. Significant variation in susceptibility to S. minor was detected among cultivars within as well as between major lettuce types. Correlations between lettuce drop susceptibility and plant canopy size, seedling vigor, and additional morphological traits were determined. Variability between different field experiments was also evaluated for several traits and a subset of cultivars. Our results suggest that cultivated germplasm may provide genes that are as useful or more useful than those found in genotypes with more primitive growth habits in developing cultivars with tolerance to lettuce drop.
Production of commercial lettuce Lactuca sativa L. is plagued by a wide range of diseases and insects not yet controlled or only imperfectly controlled. These include the viral, virus-like, and mycoplasma diseases such as lettuce mosaic, cucumber mosaic, broad bean wilt, western yellows, big vein, and aster yellows; the fungal diseases—downy mildew and sclerotinia drop; and such insect pests as cabbage looper, beet army worm, white flies, and several species of aphids.
A simple, capillary, non-circulating hydroponic method is described. Lettuce seedlings are transplanted into 218-mm-long plastic tubes containing 160 ml of growing medium and the bottom 25 mm is submerged into a tank of nutrient solution. No additional fertilization, watering, or monitoring is required from transplanting until harvesting. Although the nutrient solution level may drop below the bottoms of the tubes, the roots continue to take up adequate water and nutrients to sustain growth. This method does not require pumps or electrical power. `Green Ice' leaf lettuce produced 24% more salable yield growing with this method than comparable plants growing in conventional soil culture.
Lettuce seedlings were grown in a modified Hoagland’s solution, with 9 treatments ranging from 0.06 to 16.0 mM/liter of H2PO4. In the low P solutions the deficiency symptoms shown by lettuce seedlings consisted of leaves showing a darker green and reduced growth. Tissue levels of soluble PO4–P in these deficient seedlings dropped to a low of 379 ppm PO4–P and a high of 13770 ppm PO4–P for plants well supplied with P. The critical level for the evaluation of the P nutrient status of seedling lettuce plants in the conductive, lamina, and root tissue were respectively: 780, 600, 580 ppm soluble PO4–P on a dry wt basis.