Calag Archive

Powdery mildew (Uncinula necator) has been a consistent disease problem in California vineyards for over a century. For nearly that long, elemental sulfur has been applied for its control. Agricultural bulletins dating to the 1890s describe the treatment schedule still in use today: regular applications of sulfur at 7- to 14-day intervals during the period of vine susceptibility. The interval may be adjusted for local conditions and grape variety, but no systematic method for determining the best timing has been previously presented. The past recommendations have led to under- or over-use of sulfur in years when environmental conditions are more or less favorable for epidemic spread.

California's 1975 Agricultural Labor Relations Act (ALRA) granted all farmworkers the right to form or join unions and to bargain collectively with farm employers, or to refrain from union activity, and to make these decisions without interference from employers. The law specified the rights of farmworkers, defined the unfair labor practices that employers and unions can commit, and established an Agricultural Labor Relations Board (ALRB) to supervise representation elections and to rule on unfair-labor-practice charges.

The salt tolerance of corn has not been well established, and published studies, none of which were done on organic soils, were thought to be site-specific. Published information indicates that corn production is not reduced until soil salinity, expressed as the average electrical conductivity of the soil water in the root zone, exceeds 3.4 dS/m (about 2,200 ppm salt). For each dS/m increase in salinity above this threshold, production decreases at a rate of 6 percent. Because corn is more sensitive to salinity than are other crops, such as wheat, barley, and asparagus, water quality standards and water management techniques acceptable for corn grown on organic soils should be suitable for more tolerant crops.

Significant concentrations of soluble salts are not normally found in organic soils. Organic soils, differentiated from mineral soils by an organic matter content greater than 20 percent, are formed from partially decayed plant remains that accumulated originally in shallow bodies of fresh water or in poorly drained areas where anaerobic conditions persisted. In contrast, saline soils usually occur in regions where water is lacking. The Sacramento-San Joaquin Delta is an important example of an agricultural area with organic soils that are threatened by salinity.

As a followup to the field test of salt tolerance of corn, we attempted to determine in greenhouse studies the salt sensitivity of corn at various growth stages. If corn is more sensitive during one stage than another, the salinity of the irrigation water could be regulated during the season to minimize salt injury during the more sensitive stage. Standards are needed, particularly during droughts and during the later part of the growing season when the water supply may be limited.

In the fall of 1979, a new mite pest was found damaging lemon fruit in a grove near the city of Ventura. This mite was identified as the broad mite, Polyphago-tarsonemus latus (Banks).

The tomato pinworm (TPW) is a major pest of tomatoes in southern California, Florida, southeastern Texas, and Mexico. In California, it is especially serious on fall-crop tomatoes, where it attacks both foliage and fruit and may cause extensive fruit damage if not controlled.