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(originally published March/April 2018)

Weeds can be defined as plants growing out of place and can rapidly populate in ecosystems that do not support their natural enemies.  Many methods are being used to keep weeds under control. These include burning them, pulling them out or chopping them down, and treating them with herbicides.

Vegetable growers ranked weeds as number one obstacle to organic crop production. In early stages of crop growth, weeds compete at a faster rate than crop seeds for water, space, and nutrients especially in the first 20-30 days of crop growth. Organic growers have been using mechanical cultivation and hand weeding to control weeds. However, frequent soil cultivation decreases soil health and disrupts the ecological system; increases fuel and labor costs, and brings buried weed seeds to the soil surface. Biological control holds much promise for long-term, economical, and environmentally sensitive weed management.

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(originally published January/February 2017)

Navel orangeworm (NOW) populations exploded in 2017, costing growers tens of millions of dollars in reduced quality and lost yields. In a year where double-digit damage estimates from nut processors were not uncommon, the question heading into the coming growing season (and future seasons beyond 2018)—how do we limit damage from this pest? Is our current arsenal of integrated pest management (IPM) tactics enough to keep damage in the desired 1 to 2 percent range given the two million (plus) acres of commercial nut crop habitat in California (not to mention the myriad other crop and non-crop plants that play host to NOW)? This article covers the “tried-and-true” strategies, as well as where we need to head in the future of NOW management to ensure clean, safe, and profitable nut crops for years to come.

A four-pronged approach to NOW management in nut crops has been suggested for years based on University research and field success stories. These include: sanitation, minimizing damage by other sources, timely (early) harvest to avoid late generation flights, and insecticide treatments as deemed necessary by monitoring pest activity and crop phenology.

anthr Red Aleppo 8 Aug 24

(originally published November/December 2017)

 

Anthracnose of pistachio: In July 2016, putative diseased samples were collected from two pistachio (Pistacia vera) orchards in northern California (Glenn County) with black and sunken lesions on leaves and rachises. Samples were of the Red Aleppo, Joley, and Kerman cultivars. Eventually, individual fruit were totally blighted.  . These fruit blight symptoms looked different from the Botryosphaeria (Bot) panicle and shoot blight and did not bear any characteristic pycnidia of Botryosphaeriaceae fungi. Instead some of the fruit lesions developed slimy, pink ooze by harvest time. Lesions on the leaves were black and angular and also some developed the same slimy, pink ooze on the surface

Figure 6 Actual SWP Measurement

(originally published September/October 2017)

Among the most basic observations that can be used to manage irrigation in orchard crops are visual cues of crop water stress. However, these cues can be somewhat subjective and are often expressed after plant stress is higher than desired. Measuring midday stem water potential (SWP) using a pressure chamber is a quantitative method for evaluating plant water status, and relationships have been established between pressure chamber measurements and tree growth and productivity. From these relationships, guidelines have been developed to assist growers in making irrigation scheduling decisions.