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Bakersfield, CA, United States

Molinar R.H.,University of California Cooperative Extension

Sinqua and moqua, better known as Luffa actuangula and Benincasa hispida var. chiehgua, are but a few of the 70 or so Asian vegetables being grown in Fresno, CA. These little-known vegetables are very common to the 1300 Hmong, Mien, Lao, and Chinese farmers growing them for the specialty and wholesale markets in Fresno. This article discusses 24 Asian vegetables commonly grown on farms and sold to more than a dozen specialty crop packing houses in Fresno and at farmers markets in California. Cultural information, pest problems, and culinary uses are also briefly discussed. Source

Field experiments were conducted during 2009 and 2010 on commercial rice fields in the Sacramento Valley of California to validate observations regarding the prevalence of immature populations of the rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), near field borders, and to assess their impact on yield. In 5 commercial fields, insecticide-treated and untreated plots were established 4.5, 30 and 60 m from one edge of the field. Soil core samples were collected on 2 dates and inspected for L. oryzophilus immatures. Rice yields were determined by harvesting 15 m2 plots in 2009 or 1 m2 per plot in 2010. Analysis of variance (ANOVA) showed that in most locations, immature populations were higher in plots 4.5 or 30 m from the field's edge than in plots 60 m from the field's edge. Yields from treated and untreated plots did not differ significantly. Linear regression of immature populations and rice grain yield per plot per location did not yield a significant, inverse density-yield relationship. Results indicate that border applications of insecticides for L. oryzophilus management are appropriate; however, growers are advised to inspect their fields to confirm border populations and effects on yield. Research needs regarding sampling and economic thresholds are discussed. Source

Cloyd R.A.,Kansas State University | Bethke J.A.,University of California Cooperative Extension
Pest Management Science

The neonicotinoid insecticides imidacloprid, acetamiprid, dinotefuran, thiamethoxam and clothianidin are commonly used in greenhouses and/or interiorscapes (plant interiorscapes and conservatories) to manage a wide range of plant-feeding insects such as aphids, mealybugs and whiteflies. However, these systemic insecticides may also be harmful to natural enemies, including predators and parasitoids. Predatory insects and mites may be adversely affected by neonicotinoid systemic insecticides when they: (1) feed on pollen, nectar or plant tissue contaminated with the active ingredient; (2) consume the active ingredient of neonicotinoid insecticides while ingesting plant fluids; (3) feed on hosts (prey) that have consumed leaves contaminated with the active ingredient. Parasitoids may be affected negatively by neonicotinoid insecticides because foliar, drench or granular applications may decrease host population levels so that there are not enough hosts to attack and thus sustain parasitoid populations. Furthermore, host quality may be unacceptable for egg laying by parasitoid females. In addition, female parasitoids that host feed may inadvertently ingest a lethal concentration of the active ingredient or a sublethal dose that inhibits foraging or egg laying. There are, however, issues that require further consideration, such as: the types of plant and flower that accumulate active ingredients, and the concentrations in which they are accumulated; the influence of flower age on the level of exposure of natural enemies to the active ingredient; the effect of neonicotinoid metabolites produced within the plant. As such, the application of neonicotinoid insecticides in conjunction with natural enemies in protected culture and interiorscape environments needs further investigation. © 2010 Society of Chemical Industry. Source

Koike S.T.,University of California Cooperative Extension
Plant Disease

Mexican sunflower (Tithonia rotundifolia) is a plant in the Asteraceae that is grown commercially as a cutflower commodity and also as a beneficial insectary plant. In June 2012 in coastal California (Santa Cruz County), several fields of organic lettuce (Lactuca sativa) were interplanted with direct-seeded rows of Mexican sunflower (cv. Torch) in order to attract beneficial insects. When approximately 2 to 3 weeks from harvest, lettuce plants began to wilt and collapse. Lettuce crowns were decayed and covered with white mycelium and small (0.5 to 3 mm diameter), irregularly shaped, black sclerotia. These plants were confirmed to have lettuce drop disease caused by Sclerotinia minor (2). In addition, Mexican sunflower plants began to wilt and eventually died. Initial symptoms on crowns and bases of the main stems in contact with soil consisted of a light tan discoloration. These discolored areas turned darker brown, became necrotic, and later were covered with white mycelium and sclerotia that were identical to those found on lettuce. Symptomatic sunflower stems were surface disinfested and small pieces from the margins of necrotic areas were placed into petri plates containing acidified potato dextrose agar. Resulting fungal colonies were white, produced profuse numbers (approx. 39 sclerotia/cm2) of small black sclerotia, and were identified as S. minor. Six-week-old Mexican sunflower plants grown in a peat moss-based rooting medium in 5-cm square pots were used to test the pathogenicity of four isolates. Isolates were grown on cubed and autoclaved potato pieces and resulting sclerotia were recovered and dried (1). For each isolate, 12 plants for each of three cultivars (cvs. Fiesta del Sol, Torch, and Yellow Torch) were inoculated by placing 3 to 5 sclerotia 1 cm below the soil level and adjacent to the plant crowns/stem bases. Sterile sand was placed next to crowns of the control plants. Plants were maintained in a greenhouse at 22 to 24°C. Symptom development was rapid and after 6 to 7 days, inoculated Tithonia plants exhibited brown necrosis at inoculated areas. After 10 days, Tithonia crowns were decayed and plants wilted. S. minor was reisolated from selected necrotic crown and stem tissues. Diseased plants that were not used for reisolations later supported the growth of the characteristic white mycelium and black sclerotia. There were no significant differences between the Tithonia cultivars, and overall disease incidence ranged from 74 to 100%. Non-inoculated plants were asymptomatic. The experiment was repeated and results were similar. In addition, the sclerotia of the four Tithonia isolates were similarly inoculated onto sets of 12 romaine lettuce plants (cv. Green Towers). After 5 to 6 days, all plants developed lettuce drop disease and the pathogen was reisolated. To my knowledge, this is the first report of Mexican sunflower as a host of S. minor. These findings indicate that Mexican sunflower and lettuce are susceptible to the same lettuce drop pathogen, and that this beneficial insectary plant could increase soilborne inoculum of S. minor. Growers should therefore be aware of the host status of beneficial insectary and other plants interplanted with crops. © The American Phytopathological Society. Source

Alexander J.,University of California Cooperative Extension
Environmental Management

Sudden Oak Death has been impacting California's coastal forests for more than a decade. In that time, and in the absence of a centrally organized and coordinated set of mandatory management actions for this disease in California's wildlands and open spaces, many local communities have initiated their own management programs. We present five case studies to explore how local-level management has attempted to control this disease. From these case studies, we glean three lessons: connections count, scale matters, and building capacity is crucial. These lessons may help management, research, and education planning for future pest and disease outbreaks. © 2010 The Author(s). Source

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