Kearney Agricultural Research and Extension Center
University of California
Kearney Agricultural Research and Extension Center

Tree Crops

757 - Management of Stone Fruit Diseases in California

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

The almond and stone fruit industries need to develop new disease management programs that include the use of newly registered fungicides that are more prone to the selection of resistance as older registered products are canceled or become more restricted in their usage. In general, these new fungicides are single-site mode of action materials and have a narrow spectrum of activity against pathogenic fungi as compared to older compounds. Many new fungicides have been registered in the United States in the last few years and a recent trend in fungicide registrations are pre-mixtures of usually two and sometimes three active ingredients with different modes of actions. In an ongoing effort of this project, protective or post-infection activities of new fungicides and pre-mixtures are being characterized and fungicides with different modes of action are being incorporated into management programs. With resistant populations of Monilinia spp. to AP (anilinopyrimidine) and Alternaria and Cladosporium spp. to QoI (strobilurin) and SDHI FRAC Groups now found on almond in many locations, new products such as the next generation FRAC Group 7/11 fungicides have to be developed, and resistance management strategies have gained increased importance. We are developing baseline sensitivities and are monitoring pathogen populations for fungicide sensitivity. Specifically for stone fruit, we are identifying proper handling and sanitation practices, as well as postharvest fungicide treatments to prevent crop losses in the future. For brown rot blossom blight and fruit rot, gray mold, as well as Rhizopus control, we are identifying the most effective materials for pre- and postharvest use. These treatments also include those that potentially can be used for organically grown fruit. In cooperation with the IR-4 program, our postharvest studies at KAC contributed to the registration of new reduced-risk fungicides such Penbotec, and Mentor in the last three years and Scholar and Judge, previously. Information will be made available to growers and packers for the most effective and long-term pre- and postharvest management of diseases. Thus, this research directly benefits growers by identifying and registering new materials and practices for control of pre- and postharvest stone fruit diseases.

2001 - Walnut Blight Management

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

This project is on the epidemiology and management walnut blight and walnut varietal susceptibility to the disease. A disease forecasting model (XanthoCast) with temperature and wetness period parameters for predicting walnut blight is available to growers, PCAs, and farm advisors to help in the appropriate timing of bactericide treatments. This model is being evaluated for use with dew point and precipitation instead of leaf wetness to conform to CIMIS data. Additionally, this project will continue to support the registration of the kasugamycin (Kasumin) in combination with copper or mancozeb for managing the disease and evaluate new treatments including new formulations of copper (e.g., Cueva, Previsto), and several natural products/biocontrols. New treatments will be compared to currently recommended compounds (e.g., copper, copper-mancozeb) for their protective action of walnut tissues as well as their post-infection activity. Timings of these treatments will also help to improve our understanding of the infection period of the pathogen in relation to environmental events such as rainfall. In epidemiological studies, bud populations vs. disease incidence (June drop) will be evaluated as predicts of disease risk the sebsequent sping season. We are also evaluating walnut varieties for their susceptibility against walnut blight to help breeding programs in their development of new cultivars with increased natural resistance against the disease. Overall, these goals could be directly beneficial to growers in developing new, environmentally safer materials with low human health risks, improved timings of bactericide applications, and possible new walnut cultivars for blight management.

0505 - Citrus Septoria Program for Korea

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

Septoria spot of citrus has been reported from many citrus-producing countries around the world, including the United States (California). Damage may occur to the fruit rind and thus, the disease decreases fruit appearance.  Septoria citri is the only species currently recognized in causing the disease in the United States. Although the disease is generally considered of minor importance, the Korean market was closed to California citrus in April 2004 because of detection of the disease on fruit upon arrival from California. In response to this situation, this facility project was initiated to provide early detection of Septoria spot on harvested fruit and forecasting of the disease, as well as a management project for developing new fungicides are part of an ongoing Navel and Valencia Exports to Korea (NAVEK) program. The potential risk of rejecting loads of citrus fruit in international markets requires that this project be maintained. Goals include screening of fruit lots planned for export to Korea using rapid detection methods for the pathogen for correct disease diagnoses, developing of a disease forecasting system based on regional climate, and developing of new pre- and post-harvest fungicides to manage the disease. This program will be conducted at the KARE Center under a USDA-APHIS and Korean trade agreement.

0506 - Kiwi Gray Mold Management

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

Gray mold is the most important postharvest disease of kiwifruit in California and is caused by the fungal pathogen Botrytis cinerea. With new fungicides registered for the management of gray mold, performance data is needed to submit for registration of these compounds to IR-4 for preharvest use on kiwifruit. Thus, we are continuing this project to evaluate the efficacy of new fungicides in the management of gray mold.

0814 - Management of Pomegranate Diseases in California

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

Gray mold is the most important postharvest disease of pomegranate in California and is caused by the fungal pathogen Botrytis cinerea. With the identification and pending registration of two new postharvest fungicides (e.g., pyrimethanil and cyprodinil) on pomegranate, we are continuing this project to evaluate the performance of new materials (e.g., polyoxin-D) that have different modes of action than the other compounds and can be registered with international MRLs. A monitoring program for Alternaria rot is planned with county agriculture commissioner offices and a cooperative effort is being made with USDA-APHIS for addressing disease problems that restrict international commodity trade.

1102 - Apple Disease Management in the San Joaquin Valley

Principle Investigator: Jim Adaskaveg

Affiliation: UC Riverside

Contact: jim.adaskaveg@ucr.edu

This research is on the development of new treatments for managing pome fruit diseases including fire blight and postharvest decays of fruit. Integration of existing registered materials, new antibiotics, and biologicals are essential practices for managing fire blight caused by the bacterial pathogen Erwinia amylovora. We are investigating timing of applications in relation to bloom and frequency of treatment applications on the performance of new materials. Statewide monitoring for resistance to antibiotics within the bacterial population and inconsistencies in the activity of biologicals are ongoing aspects of this research project. Additionally, we are evaluating new treatments and strategies to reduce postharvest decays for fruit. The development of fungicides with new modes of action that can be integrated into pre- and postharvest strategies is essential for preventing the selection of resistant populations of postharvest pathogens.

950 - Evaluation Response California Avocado

Principle Investigator: Mary Lu Arpaia

Affiliation: UC Riverside

Contact: mlarpaia@ucanr.edu

The overall objective of this project is to continue an applied research program aimed at improving the quality of avocado fruit at retail, and identifying the points in the handling and distribution chain where a loss of quality may occur.  This could encompass one or more aspects of harvest and post-harvest handling, including fruit picking and transfer, processing, packing, shipment and storage.  Improvements in temperature control, handling techniques, equipment type, and packaging with practical, commercial application are examples of research interest.   The results of this research is extended to the California avocado industry through presentations at grower and packer meetings and written reports to the industry.  We also upon request work with other fruit crops in response to requests from a particular industry.  In recent years we have also conducted sensory panels on unreleased varieties of table grapes at the request of the California Table Grape Commission.

812 - Pistachio Rootstock Trial

Principle Investigator: Bob Beede

Affiliation: UCCE

Contact: bbeede@ucanr.edu

This trial, in concert with two others located in key growing regions of the state, evaulated the four commercial rootstocks for  pistachio production. They are P. atlantica, P. integerrima, and two interspecific hybirds (P.atlantica x P. integerrima) of different parentage. Knowledge of these rootstocks' productivity prior to this trial was anecdotal. Experimentally determined information about cold susceptibility, vigor, productivity and alternate bearing index was needed due to the expansion of new plantings into climatic zones different than those found in the southern San Joaquin Valley.

1302 - Walnut Fumigation Alternatives

Principle Investigator: Bob Beede

Affiliation: UCCE

Contact: bbeede@ucanr.edu

Walnut growers, unlike other commodity producers, remain walnut growers for generations. Hence, re-establishment of this nut crop commonly occurs. Walnut re-establishment is a difficult and arduous task because of their extremely large tree size, and their sensitivity to nematodes (principally P. vulnus and M. incognita). Walnuts are also significantly affected by the “replant problem”, identified by some scientists as a disease, and others as a biological disorder associated with root exudates and substances from the previous and same plant species. Due to the cost and difficulty of fumigation, many growers have chosen not to fumigate. Some of the second generation orchards grow so poorly without fumigation that they threaten the economic survival of smaller farms. Others grow sufficiently well to tempt producers into thinking the benefits of fumigation do not justify the cost. The expanded buffer zones and pending loss of methyl bromide have also increased the need to evaluate the efficacy of alternative fumigants. To address these issues, a walnut pre-plant fumigation trial was established in northern Kings County, CA.  The field site is a uniformly deep, well drained Nord fine sandy loam formed from alluvial parent material. Permeability is moderate. Water holding capacity is high. Effective rooting depth is greater than 60”.  The 40 acre site was a 50 year-old walnut orchard consisting of Hartley and Franquette cultivars which were removed and chipped during the winter of 2006-2007.

1304 - Walnut Canker & Replant Diseases

Principle Investigator: Greg Browne

Affiliation: UC Davis

Contact: gtbrowne@ucdavis.edu

Lethal Paradox canker disease (LPC) is a crown and trunk rot of unknown cause that kills mature English walnut trees grafted on Paradox rootstock, the most-widely-used rootstock for walnuts in California.  LPC-affected trees can die within 2 years of symptom appearance.  Incidence of LPC has been less than 1 percent in most commercial orchards, but it has been found in major walnut districts throughout the San Joaquin and Sacramento Valleys, including at least one naturally affected tree at the Kearney Agricultural Research & Extension Center (KARE).  To date, organisms we have detected in LPC-affected tissue include the following: Brennaria nigrifluens (isolated very infrequently; cause of shallow bark canker, which has symptoms different from those of LPC); various bacteria, yeasts, and mycelial fungi (isolated infrequently), and a light, raised colony unknown (LRCU) (isolated frequently).  No known pathogens exhibit close association with LPC.  The project at KARE will involve testing pathogenicity of the LRCU and other isolates of microorganisms cultured from LPC cankers in California.  Each test isolate will be inoculated into wounds on the Paradox rootstock portion of English walnut trees.  Microorganisms that reproduce symptoms of LPC will be reisolated from the diseased tissues to confirm a constant association between the test isolate and the characteristic disease symptoms.  The work at KARE will be critical in completing Koch’s postulates-- key scientific criteria for determining the cause of a disease.  A permit for the test inoculations was given by the California Department of Food and Agriculture.

1305 - Almond Comparative Replant Study

Principle Investigator: Greg Browne

Affiliation: UC Davis

Contact: gtbrowne@ucdavis.edu

This project proposal focuses on integrated cultural management of “Prunus replant disease” (PRD), a poorly understood soilborne complex that suppresses growth and yields of replanted almond and stone fruit orchards.  PRD has widespread significance in California and occurs when almond or stone fruit orchards are replanted without precautions such as soil fumigation.  PRD is distinct from and occurs in the absence of plant parasitic nematode damage.  We have evidence that species of Cylindrocarpon and Pythium contribute to PRD, but their roles and contributions relative to those of other microorganisms likely vary among orchards.  This project is designed to address the need for reduced dependence on soil fumigation for management of PRD.  In the first experiment, hypotheses to be tested are: 1) thorough ripping and early orchard removal may effectively lessen severity of PRD and the need for soil fumigation; and 2) benefits of fumigation may be greater when it is applied by early Oct than when it is applied in or after late Nov.  In the second experiment, the main hypothesis is that anaerobic soil disinfestation (ASD), a method first developed in Japan and the Netherlands, and now being tested for California strawberries, can be used as an effective alternative to soil fumigation for management of PRD.  Results from the integrated cultural trials we propose at KARE will complement information we have gained from other research on genetic resistance of almond and peach rootstocks to PRD.  The ultimate intention of this and related projects is to foster sound, integrated, and economical approaches to almond and stone fruit orchard replacement.

312 - Study of Fruit & Nut Quality

Principle Investigator: Carlos Crisosto

Affiliation: UC Davis

Contact: chcrisosto@ucdavis.edu

Fruits, nuts, and vegetables are a very important part of the daily diet for consumers.  They provide the most variation in color, texture, taste, and aroma relative to other food groups.  Their contribution to human nutrition--especially in vitamins, minerals, and fiber--cannot be overemphasized.  Compositional changes in horticultural commodities continue after harvest at a rate that is influenced by genetic factors, preharvest environment and cultural practices, and postharvest handling procedures.  These compositional changes result in desirable or undesirable modification of nutritional quality and food value.  The goal of my research is to better understand how these preharvest and postharvest factors interact in order to develop strategies and technologies to deliver fresh, tasty and nutritious produce to the consumer.

0811 - California Fresh Fig Industry

Principle Investigator: Carlos Crisosto

Affiliation: UC Davis

Contact: chcrisosto@ucdavis.edu

A fresh fig program is being developed at the University of California and based at Kearney Agricultural Research & Extension Center.  It will have the goal of understanding the growth and development of new cultivars.  As a first step, we will consolidate domestic and overseas information and make it available to our growers.  We will also establish at the KARE a fig research plot that will include current fresh fig cultivars as well as promising varieties available through the USDA and commercial sources in Europe.  This planting will be used as a demonstration plot for growers and allow us to observe growing habits, requirements and respond to horticulture manipulations for promising cultivars under San Joaquin Valley conditions.  At the same time, this plot will be the basis for testing preharvest research techniques and physiological studies on new cultivars.

1004 - Testing Controls for Insect Pests in Olives

Principle Investigator: Kent Daane

Affiliation: UC Berkeley

Contact: kdaane@ucanr.edu

The olive fruit fly (OLF) is a new invasive pest to California that has become a serious threat to California’s olive industry.  Our work conducted at KAC produced fundamental information on OLF and natural enemy biologies, the impact of host plant and abiotic conditions on their population dynamics, and interactions of pest and natural enemies in order to optimize and balance chemical, biological and cultural controls.  Our research focus was on OLF biology and control.  First, we worked with a multi-agency team to import OLF natural enemies from Africa, the Middle East and Asia. Second, we conducted quarantine studies (UCB) to select appropriate species for release. Third, we conducted studies of natural enemy and OLF biologies to improve control strategies. The research resulted in better information on OLF field biology, the successful release and establishment of two natural enemy species, and the production of extension and research publications.

1403 - Ecology of Leafroll Disease

Principle Investigator: Kent Daane

Affiliation: UC Berkeley

Contact: kdaane@ucanr.edu

Grapevine leafroll disease (GLD) is an increasing problem in California and other wine grape regions, and mealybug vectors have been implicated as a key driving factor in disease spread. Mealybugs colonizing grapevines in California are vectors of various grapevine leafroll-associated virus (GLRaV) species. One virus species, GLRaV-3, is most commonly associated with disease and spread in Napa and other grape growing regions worldwide. No work has compared the amount of time after infection until symptom expression for grapevines infected by insects in the field versus development of symptoms from contaminated nursery material. Furthermore, nothing is known about the effects of irrigation on GLD severity.  Our research at KARE will compare the amount of time required for symptom development of plants infected by insect vectors in the field shortly after planting, versus graft-inoculated material. Two irrigation treatments will provide the further opportunity to observe the effects of water stress on GLD symptom development and severity.

0601 - Pedestrian Orchard Testing

Principle Investigator: Kevin Day

Affiliation: UCCE

Contact: krday@ucanr.edu

This project attempts to develop and demonstrate the feasibility of a pedestrian, or ladderless, orchard for peaches, nectarines, and plums.  We will use a systems approach combining rootstock, tree form, tree density, irrigation, nutrition, pruning, and other cultural techniques to maintain tree height.  Two blocks have already been established to this purpose: a plum block planted in March 2007, and a nectarine block planted in May 2008.

0902 - Peach NC-140 Rootstock Evaluation

Principle Investigator: Kevin Day

Affiliation: UCCE

Contact: krday@ucanr.edu

This project is just underway and has started off well. The trees have grown well in their first three years and are providing very useful information about the dwarfing potential of 15 different rootstocks. As the trees continue to grow and produce fruit, the project will be very useful to stone fruit growers.

502 - Prune Germplasm Evaluation and Development

Principle Investigator: Ted Dejong

Affiliation: UC Davis

Contact: tmdejong@ucdavis.edu

In 1985 the California Prune Board approached the Department of Pomology, UC Davis, indicating their interest in supporting a prune breeding program primarily directed at develooping cultivars with earlier and later harvest date that the current California standard cultivar, "Improved French".  In 1986 a new prune breeding and cultivar evaluation program was begun and after 22 years three new cultivars have been released and several more selections are in the latter stages of evaluation.  Intially the project was centered at the KREC but due to changes in personnel and project costs the seedling blocks have been moved to Davis and plots at KREC and Winters are used to do evaluations of advanced selections and hybridizations.

751 - Improve Peach Rootstock

Principle Investigator: Ted Dejong

Affiliation: UC Davis

Contact: tmdejong@ucdavis.edu

The objective of this project was to develop genetically improved rootstocks for peach and nectarine that combine tree size control and resistance to important diseases and pests including nematodes.  Data from this replicated trial showed that five rootstocks of the Harrow Blood x Okinawa cross (HBOK 32, 10, 50, 27 and 28) have significant commercial potential as size-controlling rootstocks. These rootstocks are resistant to root knot nematode.  The first of these three selections was re-replicated in spring of 2002 with O’Henry peach and May Fire nectarine in spring 2003.  The second selection was re-replicated, at KAC, with O’Henry peach and May Fire nectarine in spring 2003.  Both of these rootstocks were also grafted with Spring Crest peach and the Summer Fire nectarine and planted in a new replicated trial at KAC in February 2004.  The third selection was re-replicated at KAC with O’Henry peach in spring 2003. Evaluation of the three rootstocks, re-replicated in the 2003 trial showed that only the first and the second rootstocks (HBOK 32 and 10) offered significant tree size control; the third (HBOK 50) is modestly size-controlling but has other characteristics that may make it more satisfactory than the current standard (Nemaguard).  O'Henry peach trees on the two remaining rootstocks that are of significant interest (HBOK 27 and 28) were planted in 2004 and are of even more interest because of their strong size-controlling potential. Four of the rootstocks in this trial that appear to have the most commercial potential, HBOK 27, 32, 10 and 50, have been patented and are being sold as Controller 6, 7, 8, and 9.5. Additional rootstocks from our program, were grafted with O’Henry and planted  in  replicated trials since 2005. In 2007 a new planting with HBOK 10, 32 and 50 was made using three clingstone peaches (Lovell, Ross and Riegles) as the scions.  These plantings indicate these rootstocks should be also suitable for production of processing peaches. We anticipate that we will remove a major part of the project in 2014 and maintain only the portion of the project that was planted since 2005 until the 1016. This project has also been used to study the physiological basis of size-controlling in peach rootstocks and these studies have confirmed that the size controlling is a result of differences in xylem anatomy and hydraulic conductance of the rootstock genotypes.

1017 - Pomegranate Fertigation

Principle Investigator: Ted Dejong

Affiliation: UC Davis

Contact: tmdejong@ucdavis.edu

Research and demonstration have shown that well managed surface drip (DI) and subsurface drip irrigation (SDI) systems can eliminate runoff, deep drainage, minimize surface soil and plant evaporation thus, maximizing water use by crops. Reduction of runoff and deep drainage can also significantly reduce soluble fertilizer losses and improve groundwater quality. The total success of DI and SDI methods depends on the knowledge and management of fertigation, especially for deep SDI. Avoiding nutrient deficiency or excess is critical to maintaining high water and fertilizer use efficiencies (WUE & FUE).  Pomegranate acreage in California is now about 30,000 ac. and growing because of the rising demand for a source of potentially healthy bioactive compounds, mineral nutrients and high antioxidant contents.  Little research has been conducted on the fertility or water use of this crop.  The objective is to use high frequency drip irrigation to optimize water nitrogen interactions, to improve FUE of maturing pomegranate and to minimize leaching losses of nitrogen.  A 3.5 acre block was planted to pomegranate trees (var. Wonderful) in 2010 with rows spaced 16 ft apart and trees 12 ft in the row. The main irrigation treatments are DI and SDI (installation depth approximately 20 in.) systems.  The fertility sub treatments are 3 N treatments (50, 100 and 150% of adequate N, all applied by continuous injection). Tree and fruit responses will be determined by canopy measurements, pruned plant biomass and bimonthly plant tissue analyses.  When appropriate, flowers, fruit yields and quality will be measured and statistically analyzed.

1208 - Characterizing Solute Movement

Principle Investigator: Ted Dejong

Affiliation: UC Davis

Contact: tmdejong@ucdavis.edu

A field study will be conducted by the Kearney Agricultural Research and Extension Center and California Department of Pesticide Regulation to evaluate the use of zero tension column lysimeters to characterize pesticide movement in coarse-textured, leaching vulnerable soils. The lysimeters contain a sampling reservoir at their base to capture solute as it moves through the soil profile. The soil type and lysimeter design feature characteristics that minimize lysimeter casing or edge effects that could potentially lead to the development of preferential flow pathways and saturated boundary conditions at the base of the lysimeters. This study will ascertain the suitability of lysimeters for future research by determining if solute movement in the soil confined within a lysimeter is representative of solute movement in unconfined soil. Pesticides extracted from the lysimeter reservoirs also will provide a dataset upon which models simulating pesticide movement to ground water can be validated against. Degradates of various pesticides to be applied in this study and known to heavily impact California ground water have been difficult to detect in previous soil coring studies. It is anticipated that they will accumulate in the lysimeter reservoirs providing insight into their persistence and movement through the soil.

554 - Research & Demonstration Trees for Citrus IPM

Principle Investigator: Beth Grafton-Cardwell

Affiliation: UC Riverside

Contact: eegraftoncardwell@ucanr.edu

The goal of the citrus entomology research and extension program at is to develop integrated pest management (IPM) methods to reduce arthropod pest problems in citrus and to educate growers and pest control advisors how to use these methods.  At the Kearney Research and Extension Center we have a planting of 13 varieties of citrus that provide citrus leaves, twigs, and fruit for insect rearing and experiments.  In addition, the Citrus IPM program utilizes 4-6 greenhouse bays and the headhouse to rear insects and conduct experiments on insects such as citrus leafminer, European earwig and cottony cushion scale. We also utilize the KARE insectary for rearing California red scale and flat mites.  These resources and the experiments conducted in these facilites allow us to develop management tactics for endemic and invasive insect pests.

0813 - Carbon Sequestration and Stonefruit Replant Disease

Principle Investigator: Brent Holtz

Affiliation: UCCE

Contact: baholtz@ucdavis.edu

The chipping or grinding of prunings and whole trees during orchard removal could provide a sustainable method of brush and tree removal that enhances both air and soil quality.  Wood chipped prunings from any tree crop amended to agricultural soils would not only improve soil quality and reduce air pollution but enhance carbon sequestration and help to reduce the global emission of greenhouse gases.  The effect of this woody soil amendment on replant disease has yet to be determined.  We hypothesize that soils amended with woody debris will sequester carbon at a higher rate, have higher levels of soil organic matter, increased soil fertility, and increased water retention.  Current season shoot length determinations of second generation replanted trees showed no effect in tree growth between trees growing in plots where whole tree grinding and been performed when compared to trees in plots where the previous orchard had been burned.  We initially were concerned that the carbon-nitrogen ratio would be critically out of balance in the tree grinding treatments, but an associated growth response was not detected.

1109 - Almond Navel Orangeworm Insecticide

Principle Investigator: Brent Holtz

Affiliation: UCCE

Contact: baholtz@ucdavis.edu

Navel Orangeworm (Amyelois transitella) continues to be a major pest of harvestable almond nut meats throughout the San Joaquin and Sacramento Valleys of California.  In some cases multiple insecticide sprays are applied in addition to sanitation programs to remove overwintering inoculum sources. Several new insecticides that target worms have become registered for almonds in California, with several other products in developmental stages.   One group of products includes newer generation pyrethroids such as Brigade, Battalion, Baythroid, Danitol, Renounce and Warrior.  Additionally, there are a wide range of new reduced-risk insecticides that offer a wide range of existing and new modes of action such as Altacor, Belt, Delegate, Intrepid, Asana, Proclaim, Brigade, Athena, and Hero. Currently there is a gap in our understanding of the efficacy of these products.

851 - Speciality Small Fruit Variety Development

Principle Investigator: Manuel Jimenez

Affiliation: UCCE

Contact: mjjimrnrz@ucdavis.edu

Identifying new and specialty perennial niche crops that can be produced profitably is essential to the economic viability of small scale farmers in the San Joaquin Valley of California. Project 851 has focused on blueberries, blackberries and hoop house production of tropicals since 1997. The success of the project has resulted in the establishment of a commercial blueberry and blackberry industry, and a few small farmers are planting tropical crops. As these crops evolve, production issues are identified. Currently, the most critical blueberry issues revolve around plant health related to soil and water pH and irrigation. We have initiated an irrigation trial and a trial that will address soil water pH concerns.

1310 - Effect of ASD and Vermicompost on A. tumefaciens/crown gall

Principle Investigator: Daniel Kluepfel

Affiliation: UC Davis / USDA

Contact: daniel.kluepfel@ars.usda.gov

The primary walnut rootstock used in California is susceptible to Agrobacterium tumefaciens, which causes crown gall. Walnut nurseries currently fumigate the soil prior to planting to control weeds, nematodes, and other phytopathogenic agents. However, chemical fumigants are either being phased out or increasingly regulated, and in the case of crown gall, provide inconsistent disease control. To provide an economically viable alternative to fumigation, organic management strategies must suppress multiple pathogens, including nematodes, and provide weed control. We hypothesize that a combined strategy of anaerobic soil disinfestation (ASD) followed by vermicompost amendments will provide the disease and weed control equivalent to chemical fumigants.  ASD will provide the initial reduction of pathogen and weed seed populations followed by a more long-term control resulting from an elevated suppressive microbial populations resulting from vermicompost amendments. We will use a 3-treatment experiment in a random block design to determine the effect of ASD with or without vermicompost on A. tumefaciens populations, crown gall incidence, weed growth and nematode populations on the walnut hybrid rootstock Paradox. An additional separate block will be established in a fumigated plot to compare the organic and non-organic fumigant-based management strategies.

45 - Identify Procedures To Replace Soil Fumigation

Principle Investigator: Mike McKenry

Affiliation: UC Riverside

Contact: mvmckenry@ucanr.edu

In the next three years we plan to screen additional Juglans and Prunus seedlings for their resistance to endoparasitic nematodes.  These seedlings have been collected from China, Spain or elsewhere in the world and emanate from the National Germplasm Repository at UC Davis and various California nurserys  Many of these seedlings will involve the species J. cathayensis from which we have identified the first Juglans trees that are completely resistant to endoparasitic nematodes.  We will also be evaluating numerous commercially available Paradox walnut clones for there level of nematode resistance. Side by side comparisons will enable the first field evaluations of the best source of nematode protection currently available to walnut growers. We will also be conducting nematode evaluations of some of the more interesting Prunus spp having the potential to be a good rootstock to switch to after Nemaguard.  Included in these evaluations will be the HBOK (Harrow Blood x Okinawa) series which contains varying vigor levels and varying nematode resistance; several potential plum x peach or almond x peach cultivars from european breeding programs and Krymsk 1 or other P. tomentosa containing rootstocks. We will also be conducting tree site soil treatments followed by planting of trees having nematode resistance and tolerance to the rejection component of the replant problem.

425 - Alternatives to Pre-Plant Soil Fumigation

Principle Investigator: Mike McKenry

Affiliation: UC Riverside

Contact: mvmckenry@ucanr.edu

We need specialized sites to screen potential methyl bromide alternatives.  Site 425 is a series of micro and macroplots that enable large numbers of replicates using individual trees or vines as the bioassay.  In the coming three years these sites will be used for rootstock evaluations of walnut, grape, and Prunus: screening of nematicidal agents and screening of several biocontrol agents already endemic to KAC.

0803 - Field Validation of a New Replant Procedure

Principle Investigator: Mike McKenry

Affiliation: UC Riverside

Contact: mvmckenry@ucanr.edu

Two field sites, #92 is a plum the other #17 is a peach/nectarine, at Kearney Ag Center are now getting beyond 20 years of age making them ideal to validate our new strategy for replanting tree and vine crops.  These are not nematode infected sites but they are large enough to provide data for quantifying the value of our new strategy against the rejection component of the replant problem.  We will apply Roundup to the cut stumps of 1/2 of each block; leaving the remaining 1/2 for harvest in 2008.  In 2008 we will harvest and then push out the stumps.  Then the remaining 1/2 of the original field will either be fumigated or non -fumigated with the entire block in a randomized complete block design be replanted in spring 2009 to various rootstocks including a Nemaguard comparison.  We will assess for tree growth the first two years.  Eventually the block will be turned over to the two listed cooperators to continue studies.  Perhaps at that time they will only want the plum site which will be planted to dwarfing rootstocks but that decision has not yet been made.

054 - Control of Fig Endosepsis & Aspergillus Molds

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

In the last several years, fig growers in California have noticed some trees in a number of orchards loosing large limbs due to a severe dieback problem. The cause of this dieback was initially unknown. To identify this problem and offer solutions to California fig growers to manage this disease, we started a study in our KAC Calimyrna fig plot and also planted four rows of 8 trees each of various commercially grown fig cultivars. We plan to determine the pathogen(s) involved in causing this limb dieback of mature trees, the susceptibility of various cultivars to the pathogen(s), protection of fig from infection, and also understand the biology of the pathogen in the orchard.  How infections occur t to determine how and when infections occur by the newly-identified pathogen, Nattrassia mangiferae. This pathogen was found to cause major damage of older trees in commercial plantings.

203 - Fungul Diseases or Kerman Pistachios

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

We plan to continue our studies on fungicide efficacy against fungal (Botryosphaeria, Alternaria, and Botrytis blights) diseases of pistachio. In addition, we are developing practical methods to predict each of these diseases in pistachio. Results of these experiments provide efficacy data for registration of new fungicides that are needed to control these diseases and also combat resistance development by the pistachio fungal pathogens. In addition, we will study whether late harvests affect the staining of the nuts and whether fungicides alleviate these detrimental effects of shell staining. The atoxigenic strain of A. flavus (AF36) was registered and used for the first time in pistachios in 2012. About 73,000 acres were treated in the first year. The registration was for the AF36 wheat product, but now other researchers are investigating the possibility in using sorghum instead of wheat. Therefore, we will compare the persistence of the wheat and sorghum AF36 inocula and compare their ability in producing propagules of atoxigenic strain to displace the toxigenic A. flavus and A. parasiticus.  We are currently testing this strain in pistachio orchards in California under a granted EUP and treated 3,000 acres of commercial orchards each in 2008 and 2009. Results from our studies with atoxigenic strains from California suggest that atoxigenic strains might be able to reduce aflatoxin contamination in commercial pistachio orchards.

0401 - Almond Band Canker Control

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

During the 2007 - 2009 period our goals were do determine the spread of the band canker disease of almonds in the various counties, understand the sources of inoculum and variability among Botryosphaeria isolates from almond, pistachio, and other hosts, and develop control practices for this disease. During this period, we also studies a second disease, Lower Limb Dieback (LLDB) whose cause remains unknown. For the band canker we showed convincingly that disease moves from one crop to another (walnuts to almonds), and from riparian areas to almonds and the disease is more severe on trees in the proximity of the inoculum source. For the LLDB "disease", we showed that both Botryosphaeria and Phomopsis were isolated from symptomatic and asymptomatic tissues to about equal frequencies and in inoculation stuidies we were not able to reproduce the symptoms of the LLDB. Our emphasis now is on determining whether glyphosate drift predisposes these limbs to LLDB and eventually death of these limbs.

0511 - Walnut Variety Susceptibility to Aflatoxin Eval

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

Although we will continue with checking the effects of cultivar itself, levels of insect infestation, and special cultivar nut characteristics on mold contamination of walnuts, emphasis in the following 3 years will be given on Botryosphaeria and Phomopsis diseases of walnuts. In the last few years, farm advisors in Stanislaus, and Yuba and Yolo Counties have reported major branch killing in walnuts. We frequently isolated Botryosphaeria and Phomopsis from these branches with and without Nattrassia mangiferae (the branch wilt pathogen). We plan to survey walnut orchards in three geographic areas of California and isolate the pathogens from shoot and branch blights, cankers, and shoots with branch wilt symptoms. Then, complete pathogenicity studies with the major canker producing fungi and compare aggressiveness alone and synergistically (Botryosphaeria + Phomopsis, Botryosphaeria + Nattrassia, Phomopsis + Nattrassia, and all thee), and finally perform trials to protect pruning wounds from infection of walnut by Botryosphaeriaceae fungi.

0515 - Pomegranate Pathogens Evaluations

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

Pomegranate is a small specialty crop grown now on more than 20,000 acres in California. There is not much information known about diseases affecting pomegranates in California and worldwide. In the last several years, a disease that infects and decays the arils and known as "black heart" has caused major losses in this small industry. We showed that the major cause of black heart is Alternaria species. We have collected 120 isolates of Alternaria from fruit samples from various regions where pomegranates are grown. In this study, we plan to identify if more than one species of Alternaria are involved and whether there are differences in their virulence. We also want to determine the ways Alternaria spp. infect pomegranates, i.e., determine the infection courts of the pathogen. Several trials will be performed to protect the flowers of pomegranates with fungicides applied at the right developmental stage. Furthermore, an extract from the pomegranate rind and collected biological agents will be tested for any antifungal properties against pomegranate pathogens.

1409 - Management of Canker Diseases in Dried Plums

Principle Investigator: Themis Michailides

Affiliation: UC Davis

Contact: tjmichailides@ucanr.edu

We will survey systematically prune orchards in two major geographic areas (Sacramento and Central/Southern San Joaquin Valleys) to collect diseased samples of prune branches, make isolations and identify the species of putative canker fungi.  The collected species of canker causing fungi will be tested for pathogenicity on French prune trees at the Kearney Agric. Res. & Ext. Center. In addition, several fungi will be studied in detail and inoculated onto various ages of pruning cuts to determine how long wounds are susceptible and also to determine variations in host susceptiblity during different time periods of the growing season.  In addition, sunburned branches and pruning wounds will be inoculated with putative canker pathogens to determine the predisposition to infection by sunburn damage and duration of pruning wound susceptibility to canker fungi, respectively. The most aggressive fungi responsible for the most of the damage to the prune trees will be determined. Subsequently, management experiments will be designed.

1410 - Improving IPM of Spider Mites on Almond

Principle Investigator: Kris Tollerup

Affiliation: IPM

Contact: ketollerup@ucdavis.edu

The web-spinning mites, Tetranychus urticae Koch, and pacific mite, Tetranychus pacificus McGregor, are key arthropod pests on almond.  Integrated pest management strategies include using economic damage thresholds along with some population density at which preventative action is implemented.  On almond intervention is recommended at approximately two mites per leaf with economic damage occurring at approximately 5 mites per leaf for a period of 35 days.  Common practice, however, is that growers and pest control advisors manage spider mite populations to remain well below this density.  Almond trees likely can tolerate a greater level of mite damage than producers typically allow.  In this proposal, we aim to initiate long-term experiments to evaluate how mite damage i.e. defoliation affects yield.

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