California Agriculture

Light brown apple moth is an exotic pest that was confirmed in California in March 2007. It is a tortricid leaf-roller moth native to Australia, which has a broad range of plant hosts with the capacity to cause damage across a wide array of crops, natural areas and ornamental plants. California and federal agencies have issued quarantine orders affecting production and retail nurseries, and potentially fruit and vegetable exports. It is found thus far primarily in nurseries near urban areas. Eradication efforts are under way to prevent its spread into California crop areas and throughout the United States.

The recent phase-out of the soil fumigant methyl bromide (MB) due to its impact on stratospheric ozone pre-sents a huge challenge to strawberry nursery producers. We evaluated the effectiveness of alternative fumigants on soil pests and plant productivity, as well as production costs in California strawberry nurseries. Our trials followed nursery stock through low- and high-elevation phases of runner-plant propagation and a complete cycle of fruit production in coastal fields. Plant yields from the nurseries and fruit yields from Oxnard and Watsonville indicated that nursery plots treated with iodomethane plus chloropicrin, with 1,3-dichloropropene followed by dazomet, and with chloropicrin followed by dazomet produced runner-plant yields that were similar to methyl bromide plus chloropicrin. However, our economic analysis suggests that nursery profitability may nonetheless suffer from the loss of methyl bromide.

Growers of fresh produce on the Central Coast of California currently face conflicting demands regarding measures to protect food safety and those to protect environmental quality. To explore the extent of conflicting pressures and identify the range of possible impacts on the environment, we conducted a survey of Central Coast irrigated-row-crop growers during spring 2007. The results indicate that growers are experiencing a clear conflict, and some are incurring economic hardships because their practices to protect the environment have resulted in the rejection of crops by buyers. In addition, some growers are being encouraged to or are actively removing conservation practices for water quality, and most growers are taking action to discourage or eliminate wildlife from and adjacent to croplands. These actions could affect large areas of land on the Central Coast and, as indicated by growers, they are likely to increase over time.

We compared standard tillage (ST) and conservation tillage (CT) for tomato and cotton production systems, with winter cover crops (CC) and without (NO), in Five Points, Calif., from 1999 to 2003. Conservation tillage reduced tractor trips across the field by 50% for tomatoes and 40% for cotton compared to standard tillage. When averaged over the 2001 to 2003 period (when the conservation tillage systems were established), tomato yields in CTNO were 6 to 8 tons per acre higher than the other treatments. In cotton, the STNO cotton yields during this period were the highest of all treatments and were 276 pounds per acre higher than the CTNO system. In-field dust concentrations were also significantly reduced by conservation tillage. Our results suggest that conservation tillage may be a viable alternative for managing tomato and cotton crops in the San Joaquin Valley, but that fine-tuning of the systems is needed.