Central Coast Agriculture Highlights

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1 University of California Cooperative Extension Agriculture and Natural Resources Central Coast Agriculture Highlights September, 2012 SANTA BARBARA COUNTY UC COOPERATIVE EXTENSION 2156 Sierra Way Suite C San Luis Obispo, CA Phone: Fax: cesantabarbara@ucdavis.edu cesanluisobispo@ucdavis.edu EXECUTIVE EDITOR Surendra Dara, PhD, DAIT Strawberry and Vegetable Crops Advisor and Affiliated IPM Advisor ASSISTANT EDITOR Ingrid Schumann AA III Exotic Bagrada bug in Santa Barbara and San Luis Obispo Counties Surendra Dara, UC Cooperative Extension, San Luis Obispo and Santa Barbara Counties Bagrada bug, Bagrada hilaris (family Pentatomidae, order Hemiptera) is an exotic stink bug that has been a concern in parts of Arizona and southern California was recently found in Santa Barbara County. A few unofficial reports suggested the arrival of this pest in the county earlier, but the specimens that Ag Commissioner s office received early this month were the first official record of this insect in Santa Barbara County. Within a couple of weeks, Bagrada bugs were also reported in San Luis Obispo County by the Ag Commissioner s office in Arroyo Grande. AUTHORS Graeme Baird Surendra Dara Oleg Daugovish Steven Fennimore Mark Gaskell Steven Koike Mark Mazzola George Lazarovits Carol Shennan Krishna Subbarao CONTENTS Exotic Bagrada bug in Santa Barbara and San Luis Obispo Counties CIMIS Information Website Offers Help with Irrigation Scheduling Lettuce Drop Caused by Sclerotinia Species Anaerobic Soil Disinfestation Bagrada bugs on peppers (Photo by Brendan Kreute, PCA in Ventura Co) Bagrada bug feeds mainly on cruciferous hosts and their presence on wild crucifers and migration to field crops, home gardens, landscapes, and urban areas causes a major concern. In some recent incidents, Bagrada bugs were found on Monterey pine, peppers, and strawberries along with their normal hosts like broccoli, kale, mustard, and rad-

2 ish. Some chemical insecticides can provide effective control, but management appears to be a challenge for organic farms and home gardens. Some literature refers to Bagrada bug as painted bug. Adults can be confused with the harlequin bug, Murgantia histrionic because of some similarities in the orange, white, and black patterns on the body. Nymphs resemble ladybugs due to their dark head and thorax and reddish or orange abdomen with white or black markings. Origin and distribution: It is native to Africa and is reported to infest and/or cause crop damage in parts of Asia and Europe. It is an exotic pest in the US. It was first reported in Los Angeles in June, 2008 and started causing damage to broccoli, cabbage, cauliflower, kale, radish, rutabaga, collards and other crops by the next year. It is now seen in Orange, Imeperial and Riverside Counties of California and all over Yuma Co in Arizona. Host range: Feeds mainly on crucifers like cole crops, but can infest a variety of other hosts including solanaceous plants like potato, malvaceous plants like okra and cotton, leguminoseous plants like legumes, cucurbits like cantaloupes and watermelons, and graminaceous plants like wheat, corn and millets. Biology: Adults are 5-7 mm long and 3-4 mm wide. They are black with orange and white markings. Females are larger than males and lay an average of 95 barrel shaped whitish eggs in clusters on foliage or in the soil. Eggs turn orange as they mature in 3-6 days. They go through five instars before adults emerge in 5-8 weeks depending on the temperature. They have multiple generations in a year. from stippling with necrotic spots, stunted growth, loss of apical dominance and formation of multiple heads to death. Multiple heads in broccoli (Courtesy: John Palumbo, Univ. of Arizona) Management: Reports indicate that Bagrada bug can be controlled with pyrethroids, organophosphates like chlorpyrifos and malathion and neonicotinoids like imidacloprid in conventional fields using different treatment methods. Someone reported effective control with mechanical exclusion and azadirachtin. Biological and microbial control options are being evaluated by some researchers. Cultural control through pest monitoring and early detection, removal of weed hosts, mechanical removal through handpicking or vacuuming, cultivation to destroy eggs in the soil, and overhead irrigation to dislodge nymphs and adults from the plants are some of the options suggested in the literature. CIMIS Information Website Offers Help with Irrigation Scheduling. Mark Gaskell, UC Cooperative Extension, San Luis Obispo and Santa Barbara Counties Life stages of Bagrada bug Damage: Bagrada bugs have piercing and sucking mouthparts and feed on the plant juices. Depending on the crop and plant part they infest, damage can vary The California Irrigation Management Information System has been in place since the early 1980s providing growers with data on estimates of crop evapotranspiration from a network of sites throughout the state. There are over 150 active sites that provide valuable water management information to growers including landscape professionals, engineers, and researchers. These sites allow reporting of historical summaries of crop water use and real-time micro-climate information from which crop water use can be calculated. An irriga-

3 tion scheduling program can then be designed around a water budget that incorporates the inputs and outputs of water to and from the crop rooting zone. Based on the characteristics of the irrigation system, amounts and timing of irrigations can be scheduled for a specific crop and situation. Evapotranspiration or ET is a term used to generally describe the total amount of water moving through a crop surface. There are several different formulas used to calculate a reference ET value to estimate crop water use and irrigation requirements. The CIMIS stations use data loggers to continuously measure such parameters as air and soil temperature, wind speed, solar radiation, wind direction, and precipitation. These measurements are then used in complex equations that have been tested under different circumstances and found to be reliable reference indices for crop ET. The data for different sites is regularly recorded and maintained and is publicly available on the CIMIS website at welcome.jsp. There is a wealth of additional information on the site that further explains the ET calculations in greater detail and how these and other data can be effectively incorporated into irrigation management programs. It is possible to set up an service on the site that allows users to receive periodic water use values for a specific site or sites that best approximates conditions in a specific area. An overall map of specific sites in California is maintained on the website and each specific site is described in more detail on the sites list. sites to plan irrigation scheduling, is that the site allows establishment of free daily s that summarize ET related information for the prior 7 days for different stations that best match the conditions of specific field sites. Or alternatively, Spatial CIMIS data can also be setup to match a specific location(s) and daily s will be sent to the user summarizing the prior 7 days of data for those sites. The CIMIS webpage has detailed basic instructions and examples of how best to incorporate CIMIS information into specific irrigation management regimes. Lettuce Drop Caused by Sclerotinia Species Krishna V. Subbarao, UC Cooperative Extension, Salinas Lettuce drop has long been one of the most threatening diseases for lettuce production in California. As the name of the disease suggests, infected plants collapse when the crop is at or near harvest maturity. Usually, lettuce drop occurs in two phases. The first phase occurs at the rosette stage or immediately after thinning but very few plants are infected at this stage. The more damaging phase occurs at or near harvest maturity. Average seasonal losses of up to 15% are common, and individual fields with losses of up to 60% are not uncommon. All types of lettuce are affected by this disease but Despite its long existence, many growers are unfamiliar with CIMIS; therefore, they don t know how they might use it in their own irrigation management programs. The reference ET values must be adjusted based on the requirements of the specific crop and soil conditions to arrive at estimates of crop water use. This involves estimates of crop development how much of the surface area is covered with crop- as well as a reliable estimate of rooting depth and soil texture. Another limitation to efficient use of the CIMIS is that many farm fields and orchards are too far from a station to make the data useful and there has not been a site that reliably represents the specific conditions. The CIMIS site has Spatial CIMIS available that allows growers to target specific fields on a map and the CIMIS will generate estimates of crop ET based on remotely sensed data that are then incorporated into a formula that predicts ET values based on those conditions. One of the easiest aspects of using data from the CIMIS Large sclerotia of Sclerotinia sclerotiorum compared with smaller sclerotia produced by S. minor. Sclerotia of both species can germinate carpogenically to produce apothecia. much of the information was derived from research on crisphead lettuce since this was the dominant type grown in California until recently. The information, however, is equally applicable to all types of lettuce. The disease is caused by two species of Sclerotinia, S. minor and S. sclerotiorum. Both species survive in the

4 soil for many years as sclerotia. Generally, sclerotia from S. minor are small and mustard-like and those from S. sclerotiorum are large and irregularly shaped. Under optimal soil moisture conditions, sclerotia from S. minor germinate eruptively, producing masses of hyphae that come in contact with senescing roots, stems and leaves to cause lettuce drop. In contrast, infections from mycelial infection by S. sclerotiorum are rare in California. Sclerotia of S. sclerotiorum germinate to produce small, tan, cup-shaped bodies called apothecia that release millions of ascospores into the air. These ascospores land on senescing outer leaves of lettuce plants to cause infection. Thus, losses from this mode of infection by S. sclerotiorum can be very high and unpredictable. California is unique with respect to the distribution of the two species in the different lettuce production areas. In the Salinas Valley and adjoining coastal valleys, the predominant cause of lettuce drop is S. minor, while in the San Joaquin Valley, the majority of lettuce drop infections are caused by S. sclerotiorum. In the Santa Maria and Lompoc areas, infections are caused by either species, although the dominant species is S. minor. Rare infections by S. sclerotiorum occur in the Salinas Valley Aerial infection caused by ascospores and production of apothecia by Sclerotinia sclerotiorum but are caused by directly germinated sclerotia, whereas in the San Joaquin Valley, the majority of infections are caused by airborne ascospores, which is also common in the Santa Maria and Lompoc areas. The reasons behind this unique distribution of the two species in California had remained a mystery for a long time but research in the past 10 years has uncovered factors that determine this distribution. Survival of sclerotia from the two species in different valleys partially explains their distribution. Only a small fraction of sclerotia of S. minor survive in the San Joaquin Valley for six months or more while more than 90% survive in the Salinas Valley. In contrast, sclerotia of S. sclerotiorum survive well in both valleys after prolonged burial. While this study explained why S. minor infections in the San Joaquin Valley lettuce fields are rare, the lack of S. sclerotiorum airborne infections in the Salinas Valley lettuce fields remained unanswered. S. sclerotiorum has been considered an insignificant threat to lettuce production in the Salinas Valley because the pathogen is believed unable to produce adequate apothecia and airborne ascospores to infect lettuce during the irrigated crop production each year. S. sclerotiorum requires about 35 days of continuous soil moisture at field capacity in the upper cm soil profile to produce apothecia. These conditions are routinely met during winter lettuce production periods in the San Joaquin Valley (because it coincides with the onset of rain in California), but are rarely met during the irrigated lettuce production in the Salinas Valley. These conditions are also met in the Salinas Valley during the rainy season from December to February, but there is either little lettuce in commercial fields (because of the mandated lettuce-free period) or when present, is at growth stages unsuitable for infection. Thus, even though ascospores are abundant during December February, lack of lettuce crops at stages conducive to infection prevents infection by ascospores. Furthermore, any prolonged (>10 days) dry period resets the clock for apothecial production and thus, ascospore infections in lettuce in coastal California rarely occur during the irrigated spring and summer lettuce production. Since Santa Maria and Lompoc do not have the mandated lettuce-free period, ascospore infections by S. sclerotiorum on lettuce can also occur. Application of fungicides immediately after thinning and cultivation (at the four to six true-leaf stage) significantly reduces the incidence of lettuce drop caused by S. minor. Among the currently registered fungicides that have proven to be effective is boscalid (Endura). The involvement of airborne ascospores in S. sclerotiorum makes it more difficult to manage lettuce drop caused by this species using fungicides. However, application of Coniothyrium minitans-based biocontrol product (Contans) to soil prior to planting has been shown to be highly effective. Currently, commercial lettuce cultivars with resistance to either Sclerotinia spp. are unavailable. Crop rotation with nonhost broccoli significantly reduces both sclerotium density of S. minor and lettuce drop incidence. How-

5 ever, rotation with broccoli or fallowing land for even brief periods in coastal California is often not economically feasible. Reducing surface moisture close to harvest by surface or subsurface drip irrigation can also reduce disease incidence significantly. Anaerobic Soil Disinfestation (ASD) Carol Shennan, Joji Muramoto, Graeme Baird (UC Santa Cruz), Mark Mazzola (USDA ARS, Wenatchee), Oleg Daugovish (UCCE, Ventura), Steve Fennimore (UCCE, Salinas), Surendra Dara (UCCE, San Luis Obispo), Steve Koike (UCCE, Salinas), and George Lazarovits (A&L Biologicals, Canada) History of ASD ASD was developed as an alternative to soil fumigation in the Netherlands and Japan, and is currently used extensively in greenhouse production in Japan. It has been found to be effective at suppressing many soil borne diseases, as well as nematodes for a range of crops. When combined with solarization, where temperatures are high enough, it may also control weeds. With ASD we consistently get an % reduction of Verticillium dahliae microsclerotia in soils using 9 ton/ac of rice bran as a carbon source. 3. Form beds and lay drip tape. 4. Cover with plastic tarp. 5. Irrigate and keep at field capacity (~3 in). 6. Leave for 3 weeks. 7. Punch holes in plastic. 8. Transplant strawberries a few days later. Field preparation for administering ASD Strawberry Plants April 19, 2011, Ventura County in untreated plot Strawberry Plants April 19, 2011, Ventura County with ASD 3 weeks Yields under ASD generally equivalent or better than fumigant controls. Initial data suggest it is an economically viable option. Currently testing its effectiveness against other key pathogens. Also now testing at a larger field scale. STAY CONNECTED How to Perform ASD 1. Spread carbon source such as rice bran. 2. Incorporate into soil-mixing well throughout bed.

6 Marketable fruit yield lbs/acre Soil pathogen levels Santa Maria Trial 2011/2012 Treatments: 1. Untreated control 2. ASD = 9 tons/ac Rice Bran 3. ASD + MSM = Mustard Seed Meal 1.5 t/ac + rice bran 7.5t/ac 4. Fish Emulsion = 2 pre plant applications of 117 gal/ac, then every other irrigation in Feb - July added gal/ac 5. ASD + Fish Emulsion = ASD followed by in- season fish emulsion applied as above 6. Pic-Clor 60 = fumigant control Note: 3 acre-inches of water added for all ASD treat- Strawberry yields Main plots (P=0.0013**): Black Clear Ventura 2010/ Sub plots (P<0.0001***): UTC UTC ASD ASD +Water 3 6 Main x Sub (P=0.22): n.s UTC UTC + water ASD 3 ASD 6 UTC UTC + water ASD 3 ASD 6 Black Black Black Black Clear Clear Clear Clear Cumulative marketable yields as of 8/8/2012 Ventura Trial 2011 Treatments: 1. Untreated control (UTC) 2. Untreated control + water where 3 in of irrigation water added after tarping beds, but no rice bran added 3. ASD treatment with 9 ton/ac rice bran added - tarped for 3 weeks before cutting planting holes (ASD 3 ) 4. ASD with 9 ton/ac rice bran - tarped for 6 weeks before cutting planting holes (ASD 6 ) 5. All the abovementioned treatments under black and clear plastic tarp Note: 3 in total of water added after tarping beds for all ASD treatments. Talks presented at our extension meetings can be found at: Meeting_Presentations/ Previous issues of the newsletter could be found at: Central_Coast_Agriculture_Highlights_962/ Please note the change in our websites from to The University of California prohibits discrimination or harassment of any person in any of its programs or activities. (Complete nondiscrimination policy statement can be found at Direct inquiries regarding the University=s nondiscrimination policies to the Affirmative Action Director, University of California, ANR, 1111 Franklin St., 6th Floor, Oakland, CA 94607, (510)