California Almond Research Articles

Evaluating insecticide coverage in almond and pistachio for control of navel orangeworm (Amyelois transitella) (Lepidoptera: Pyralidae).

Insecticide application is essential to control navel orangeworm (Amyelois transitella) in California almond and pistachios. Coverage is difficult because of tree height and applicator practices. Studies were conducted to characterize insecticide deposition by both ground and air, and to develop alternatives to the use of water-sensitive cards to assess spray coverage. We used almond challenge bioassays to demonstrate that insecticide application failed first in the upper canopy (5.2-6.1 m) when application speed exceeded 2.9 kph. In pistachios, we used filter paper and insecticide extraction from hulls to demonstrate that deposition increased with application volume. Typically, in ground applications, coverage decreased with height, whereas for application by air, coverage was greatest at the top of the canopy (6 m) and decreased as the spray penetrated the canopy. In the best ground applications there was no loss over height. We were able to demonstrate a dose-response relationship for methoxyfenozide using contact toxicity bioassays. Coverage was best at or below the recommended speed of 3.2 kph and improved when water volume increased. There was a 50% loss in insecticide efficacy at the height of 4-4.8 m; we suggest that future monitoring concentrate on this portion of the canopy. The best ground application provided uniform deposition throughout the canopy, whereas the applications by air were most effective in the upper canopy. The use of filter paper can provide information for chemical deposition and enable contact toxicity bioassays, whereas water-sensitive paper cannot do this. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Capacity, pricing and production under supply and demand uncertainties with an application in agriculture

We consider capacitated joint lot-sizing and pricing problems when supply and a price-sensitive demand are uncertain. In cases where there is excess capacity, the decision maker has the option to rent her capacity. We model the case where price and production quantity are determined before the yield is realized (joint decisions) as well as the case where the price is determined after the yield is known (sequential decisions). In the joint decisions case, we introduce the concept of expected demand fill rate elasticity and characterize the conditions in which a one-sided production and pricing policy is optimal. We extend the results to the case when there is a fixed production cost and show that a two-sided production and pricing policy is optimal. We also investigate the conditions under which it is optimal for the decision maker to rent her capacity. In addition, we look at the case in which the decision maker is risk averse and analyze the effect of the risk attitude on the optimal price and production quantity. We extend our model to the multi-period case and the case where there is a lead time to acquire new capacity. We show that a one-sided production, pricing and capacity planning policy is optimal in this situation as well. We apply our model to the agricultural sector and present numerical examples using data from the California almond industry.

Molecular phylogeny of Cytospora species associated with canker diseases of fruit and nut crops in California, with the descriptions of ten new species and one new combination

Cytospora species are destructive canker and dieback pathogens of woody hosts in natural and agroecosystems around the world. In this genus, molecular identification has been limited due to the paucity of multi-locus sequence typing studies and the lack of sequence data from type specimens in public repositories, stalling robust phylogenetic reconstructions. In most cases a morphological species concept could not be applied due to the plasticity of characters and significant overlap of morphological features such as spore dimensions and fruiting body characters. In this study, we employed a molecular phylogenetic framework with the inclusion of four nuclear loci (ITS, translation elongation factor 1-alpha, actin, and beta-tubulin) to unveil the biodiversity and taxonomy of this understudied important genus of plant pathogens. Phylogenetic inferences based on 150 Californian isolates revealed 15 Cytospora species associated with branch and twig cankers and dieback of almond, apricot, cherry, cottonwood, olive, peach, pistachio, plum, pomegranate, and walnut trees in California. Of the 15 species recovered in this study, 10 are newly described and typified, in addition to one new combination. The pathogenic status of the newly described Cytospora species requires further investigation as most species were associated with severe dieback and decline of diverse and economically important fruit and nut crops in California.

New records of Psocoptera (Troctomorpha, Psocomorpha) in California (U.S.A.) almond and pistachio orchards

Historically, Psocoptera research has been lacking in agricultural field studies. This study is the first in California (U.S.A.) to survey almond and pistachio orchards for Psocoptera. The seven species we observed in orchards are the first host association records of psocids (Lachesilla pacifica Chapman, 1930, Lachesilla pedicularia (Linnaeus, 1758), Lachesilla rena Sommerman, 1946, Ectopsocus vachoni Badonnel, 1945, Ectopsocus californicus (Banks, 1903), Liposcelis bostrychophila Badonnel, 1931, and Liposcelis silvarum (Kolbe, 1888)) in two suborders (Psocomorpha and Troctomorpha) from California almond and pistachio orchards. The results of these observations also revealed a new California state record of L. silvarum. Implications of these findings are discussed.

Home sick: impacts of migratory beekeeping on honey bee (Apis mellifera) pests, pathogens, and colony size

Honey bees are important pollinators of agricultural crops and the dramatic losses of honey bee colonies have risen to a level of international concern. Potential contributors to such losses include pesticide exposure, lack of floral resources and parasites and pathogens. The damaging effects of all of these may be exacerbated by apicultural practices. To meet the pollination demand of US crops, bees are transported to areas of high pollination demand throughout the year. Compared to stationary colonies, risk of parasitism and infectious disease may be greater for migratory bees than those that remain in a single location, although this has not been experimentally established. Here, we conducted a manipulative experiment to test whether viral pathogen and parasite loads increase as a result of colonies being transported for pollination of a major US crop, California almonds. We also tested if they subsequently transmit those diseases to stationary colonies upon return to their home apiaries. Colonies started with equivalent numbers of bees, however migratory colonies returned with fewer bees compared to stationary colonies and this difference remained one month later. Migratory colonies returned with higher black queen cell virus loads than stationary colonies, but loads were similar between groups one month later. Colonies exposed to migratory bees experienced a greater increase of deformed wing virus prevalence and load compared to the isolated group. The three groups had similar infestations of Varroa mites upon return of the migratory colonies. However, one month later, mite loads in migratory colonies were significantly lower compared to the other groups, possibly because of lower number of host bees. Our study demonstrates that migratory pollination practices has varying health effects for honey bee colonies. Further research is necessary to clarify how migratory pollination practices influence the disease dynamics of honey bee diseases we describe here.

Etiology and management of trunk and scaffold canker diseases of almond in California

Etiology and management of trunk and scaffold canker diseases of almond in California

Changing insect pest management of pistachio and almond in California (2000 to 2014)

Changing insect pest management of pistachio and almond in California (2000 to 2014)

A re-examination of Ceratocystis canker in California almond orchards

A re-examination of Ceratocystis canker in California almond orchards

First Report of Collophora hispanica and C. paarla Causing Branch Cankers of Almond in California

First Report of <i>Collophora hispanica</i> and <i>C. paarla</i> Causing Branch Cankers of Almond in California

Conservation Incentives from an Ecosystem Service: How Much Farmland Might Be Devoted to Native Pollinators?

Some conservation advocates hope the ecosystem services that areas of natural habitat provide will generate sufficient incentives to offset the opportunity costs of habitat preservation. In this paper I consider a service that has received considerable attention: pollination. While many crops are pollinated by rented honeybees, wild organisms might also pollinate crops if habitats were maintained to sustain them. I develop conditions under which a farmer might choose to maintain such habitats rather than to pay to rent bees. For pollination, as with many other ecosystem services, there may be a “paradox of efficiency”. If areas of habitat provide services efficiently, they might prove to be quite valuable. Under the same circumstances, however, appeals to ecosystem services values might motivate only modest conservation. I illustrate these ideas using the example of California almond farming. Even if almond farmers could profitably rely on wild pollinators, they might devote only a small fraction of their holdings to habitat for such pollinators. It may be important in light of these findings to ask what the objectives of conservation really are, and whether they can be best achieved by instrumental arguments as opposed to appeals to the less tangible benefits of conservation.

Neoscytalidium dimidiatum Causing Canker, Shoot Blight and Fruit Rot of Almond in California.

Almond trees with trunk and branch cankers were observed in several orchards across almond-producing counties in California. Symptoms of cankers included bark lesions, discoloration of xylem tissues, longitudinal wood necrosis, and extensive gumming. Spur and shoot blight associated with rotted fruit were detected in two orchards in Kern County. The fungus Neoscytalidium dimidiatum was consistently recovered from the various cankers, infected fruit, and blighted shoots and its identity was confirmed based on phylogenetic and morphological studies. Phylogenetic analyses of the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin genes comparing 47 strains from California with reference specimens within the family Botryosphaeriaceae and coupled with detailed morphological observations validated the identity of the pathogenic fungus. Pathogenicity tests conducted in the field using 1- to 2-year-old branches inoculated with mycelium plugs or conidial suspensions and attached fruit inoculated with conidial suspensions fulfilled Koch's postulates. N. dimidiatum appeared highly virulent in almond-producing cankers of up to 22 cm in length within 4 weeks using mycelium plug inoculations as well as severe fruit rot combined with spur blight on the fruit-bearing spurs. This study reports, for the first time, the fungus N. dimidiatum as a pathogen of almond in California causing canker, shoot blight, and fruit rot. Disease symptoms are described and illustrated.

Fungal communities associated with almond throughout crop development: Implications for aflatoxin biocontrol management in California.

Interactions between pathogenic and nonpathogenic fungal species in the tree canopy are complex and can determine if disease will manifest in the plant and in other organisms such as honey bees. Seasonal dynamics of fungi were studied in an almond orchard in California where experimental release of the atoxigenic biopesticide Aspergillus flavus AF36 to displace toxigenic Aspergillus strains has been conducted for five years. The presence of the vegetative compatibility group (VCG) YV36, to which AF36 belongs, in the blossoms, and the honey bees that attend these blossoms, was assessed. In blossoms, A. flavus frequencies ranged from 0 to 4.5%, depending on the year of study. Frequencies of honey bees carrying A. flavus ranged from 6.5 to 10%. Only one A. flavus isolate recovered from a blossom in 2016 belonged to YV36, while members of the VCG were not detected contaminating honey bees. Exposure of pollinator honey bees to AF36 was detected to be very low. The density of several Aspergillus species was found to increase during almond hull split and throughout the final stages of maturation; this also occurred in pistachio orchards during the maturation period. Additionally, we found that AF36 effectively limited almond aflatoxin contamination in laboratory assays. This study provides knowledge and understanding of the seasonal dynamics of Aspergillus fungi and will help design aflatoxin management strategies for almond. The evidence of the low levels of VCG YV36 encountered on almond blossoms and bees during pollination and AF36’s effectiveness in limiting aflatoxin contamination in almond provided additional support for the registration of AF36 with USEPA to use in almond in California.

Water-indexed benefits and impacts of California almonds

California almonds have been the focus of recent media scrutiny because of the large amount of water required to grow individual nuts and, by extension, for the industry as a whole. With almond orchard acreage doubling in the last two decades and becoming California’s most extensive irrigated crop, the questions arise: what are the benefits and impacts derived from this use of scarce water? Can we use this information to make decisions about growing and consuming this particular crop? We first use a water footprint approach to estimate total impact on water per unit of almond production in California, including variation in the water footprint over time (2004–2015) and across the production area. We then compare almonds to a set of other foods and crops grown in California using water footprint values and three other dimensions: nutritional value, per-unit-weight economic value, and total economic value. The water footprint of California almonds averaged 10,240 liters per kilogram kernels (or, 12 liters per almond kernel), with substantial variation over the time period analyzed. Water footprint values also varied twofold across the production area, with the smallest water footprint being in the southern counties of California’s Central Valley. In relation to dietary benefits, almonds were among the top three foods analyzed providing the greatest nutritional benefit per unit weights, however they had the highest water footprint value per unit weight. The direct economic benefits of almond production based on market sales were also greater than for any other major crop in California, however almonds again had the largest water footprint on a per-unit and aggregate basis. We find that nutritionally and economically indexed water footprint indicators provide information to better-inform discussions on the benefits and impacts of growing almonds using California’s limited water resources, relative to other crops. Such composite indices can be used in combination with more local and contextual information on water availability/scarcity, existing impacts, and agricultural conditions to better optimize water use within single crops, such as the almond industry, and among crops within a region. We propose that this approach should be used to inform political- and value-weighted decisions about agricultural water allocation in California and beyond.

Flavor and Acceptance of Roasted California Almonds During Accelerated Storage

Monitoring oxidative flavor changes in almonds is possible only if the chemical and sensory profile during roasting and storage is first established. Herein, almonds roasted at two different temperatures (115 and 152 °C) were stored at 39 °C for 0 to 12 months and were analyzed by headspace solid-phase microextraction gas chromatography-mass spectrometry, descriptive analysis, and consumer hedonic analysis. Volatile profiles, descriptive sensory profiles, and consumer hedonic scores were analyzed for predictive relationships. Descriptive attributes involving Roasted and Nutty as well as consumer liking were highest in fresh almonds, while flavors typically associated with oxidative rancidity such as Cardboard, Painty/Solvent, Soapy, and Total Oxidized increased during storage. Compounds most important for predicting rancidity-related attributes were lipid oxidation products, including pentanal, hexanal, heptanal, and octanal. Consumer liking was best predicted by similar compounds to those predicting Clean Nutty flavor, including Maillard reaction products such as 2- and 3-methylbutanal, 2-methylpyrazine, and 2,5-dimethylpyrazine.

The Effects of the Insect Growth Regulators Methoxyfenozide and Pyriproxyfen and the Acaricide Bifenazate on Honey Bee (Hymenoptera: Apidae) Forager Survival.

The honey bee (Apis mellifera L. (Hymenoptera: Apidae)) contributes an essential role in the U.S. economy by pollinating major agricultural crops including almond, which depends entirely on honey bee pollination for successful nut set. Almond orchards are often treated with pesticides to control a variety of pests and pathogens, particularly during bloom. While the effects to honey bee health of some insecticides, particularly neonicotinoids, have received attention recently, the impact of other types of insecticides on honey bee health is less clear. In this study, we examined the effects to honey bee forager survival of three non-neonicotinoid pesticides widely used during the 2014 California almond bloom. We collected foragers from a local apiary and exposed them to three pesticides at the label dose, or at doses ranging from 0.5 to 3 times the label dose rate. The selected pesticides included the insect growth regulators methoxyfenozide and pyriproxyfen, and the acaricide bifenazate. We simulated field exposure of honey bees to these pesticides during aerial application in almond orchards by using a wind tunnel and atomizer set up with a wind speed of 2.9 m/s. Experimental groups consisting of 30-40 foragers each were exposed to either untreated controls or pesticide-laden treatments and were monitored every 24 hr over a 10-d period. Our results revealed a significant negative effect of all pesticides tested on forager survival. Therefore, we suggest increased caution in the application of these pesticides in almond orchards or any agricultural crop during bloom to avoid colony health problems.

A two-period sourcing model with demand and supply risks

In this paper, we study the problem of sourcing a product when the demand and supply may be uncertain. We consider a two-period model where the supplier’s production quantity in the second period is dependent on the amount produced in the first period. This is a common situation in industries where the production capacity cannot be changed in a short period of time such as in the almond industry. In this industry usually a two-year contract between the supplier (farmer) and buyer (handler) is preferred. The buyer can sign two sets of contracts: a production contract where she is responsible for the uncertainty of yield or a purchasing contract where the provided quantity is guaranteed by the supplier at a higher cost. The buyer has to decide about the quantities to buy through the production and purchasing contracts. The buyer has the option to carry excess inventory from the first period to the second. We establish some analytical properties of our proposed model and perform comparative static analysis to study the buyers decisions. In particular, we show under which conditions the buyer may benefit from purchasing contracts. In addition, we shed some light the debate of the merits of inventory carry-over in mitigating the yield risk in the almond industry. To gain some practical insights, we also apply our model to some real data from the California almond industry. Finally, we extend the model to investigate two cases: when the prices in the primary and the secondary markets are functions of yield and when the amount of carry-over is a decision variable.

Almond (Prunus dulcis) is susceptible to Fusarium euwallaceae, a fungal pathogen vectored by the Polyphagous Shot Hole Borer in California

Fusarium euwallaceae is a vascular fungal pathogen vectored by the ambrosia beetle Polyphagous shot hole borer (PSHB) (Euwallacea sp. nr. fornicatus) which was recently introduced in California and together cause Fusarium Dieback on multiple hardwood tree species. During previous surveys done by Eskalen et al. 2013, several Prunus spp. were identified as reproductive hosts for this pest-disease complex. Nonetheless, the suitability of almond as a reproductive host for this pest-disease complex remains unknown despite the significant production of almond in California, which accounts for 82% of the world’s total production (The Almond Board of California 2015). Moreover, the northern advancement of invasive shot hole borers into the coastal counties of Santa Barbara and recently in San Luis Obispo has raised concerns about the potential progression of the beetle into the San Joaquin Valley, where the majority of almonds are grown. The beetles cause the most damage on reproductive hosts due to mass accumula...

First Report of Phytophthora cinnamomi Causing Trunk Canker of Almond in California

Almond (Prunus dulcis) is the most economically important nut crop in California, accounting for $5.9 billion value in 2016. During fall of 2015, declining 2-year-old almond trees on clonal Hansen 536 (peach × almond) rootstock were observed in a commercial orchard in Kern County, California. Affected trees expressed early defoliation with amber-colored gummosis on the trunk. Cankers developed at the bud union and extended into the scion in trees planted with their bud union placed at or below the soil surface. To isolate the causal agent, necrotic pieces of bark and subtending vascular tissue were cut from the canker margin, surface sterilized in 0.5% sodium hypochlorite solution for 3 min, rinsed twice in sterile water, and plated on corn meal agar amended with selective antibiotics (PARP) (Jeffers and Martin 1986). After several days of incubation at 25°C, Phytophthora-like colonies grew from the diseased tissues and were transferred onto acidified potato dextrose agar medium (APDA). The isolates were tentatively identified as Phytophthora cinnamomi Rands based on morphological characteristics. Sporangia were nonpapillate and ovoid to obpyriform or ellipsoidal to elongate-ellipsoid with an apical thickening, avg. 57.2 × 36.6 µm with a length-width ratio of 1.56; mycelium with abundant coralloid hyphal swellings. Globose chlamydospores formed abundantly in culture on the parent hyphae or on new hyphal branches (18 to 42 [avg. 27.65] μm in diameter) (Erwin and Ribeiro 1996). For all isolates, the internal transcribed spacer (ITS) regions of the rRNA gene and a portion of the β-tubulin (TUB) gene were amplified and sequenced with primers ITS1/ITS4 and TUBUF2/TUBUR1 (Lan et al. 2016), respectively. Two representative sequences for each locus were deposited in GenBank (ITS; KY924650 and KY924651, TUB; KY924648 and KY924649). BLASTn analysis against Phytophthora Database (www.phytophthoradb.org) showed that the ITS sequences had 99% identity and the β-tubulin sequences had 97 to 98% identity to reference sequences of P. cinnamomi (ITS: GU259227; TUB: EU079894). Two of the almond isolates of P. cinnamomi were tested for pathogenicity by wound inoculating 2-year-old potted almond trees of cv. Nonpareil on rootstocks of Hansen 536 and Nemaguard (Prunus persica × Prunus davidiana). Five-millimeter-diameter mycelial disks from PDA cultures of each isolate (and sterile PDA as a control) were used for inoculating wounds of the same size (5 mm) made in stems of: i) the almond scion on Hansen 536 rootstock, ii) the almond scion on Nemaguard rootstock, iii) Hansen 536 rootstock below the scion, and iv) Nemaguard rootstock below the scion. Five replicate trees were inoculated per combination of the three inoculants (two of P. cinnamomi, one control) and the four inoculation treatments in a randomized complete block design. After inoculation, the wounds were covered with petroleum jelly and wrapped with Parafilm. Two months after inoculation, all plants inoculated with the control remained healthy, whereas all scions and rootstocks inoculated with either isolate developed stem cankers. None of the trees inoculated on the rootstocks died during the experiment, but 40% of the trees inoculated on the scion were killed. P. cinnamomi was reisolated only from the infected plants. More than 10 other species of Phytophthora were reported to cause root and crown rots as well as aerial cankers on almond (Browne and Viveros 1999; Browne et al. 2015). To our knowledge, this is the first report of P. cinnamomi causing trunk canker disease of almond in California.

Honey bee (Apis mellifera) colony health and pathogen composition in migratory beekeeping operations involved in California almond pollination.

Honey bees are important pollinators of agricultural crops. Pathogens and other factors have been implicated in high annual losses of honey bee colonies in North America and some European countries. To further investigate the relationship between multiple factors, including pathogen prevalence and abundance and colony health, we monitored commercially managed migratory honey bee colonies involved in California almond pollination in 2014. At each sampling event, honey bee colony health was assessed, using colony population size as a proxy for health, and the prevalence and abundance of seven honey bee pathogens was evaluated using PCR and quantitative PCR, respectively. In this sample cohort, pathogen prevalence and abundance did not correlate with colony health, but did correlate with the date of sampling. In general, pathogen prevalence (i.e., the number of specific pathogens harbored within a colony) was lower early in the year (January—March) and was greater in the summer, with peak prevalence occurring in June. Pathogen abundance in individual honey bee colonies varied throughout the year and was strongly associated with the sampling date, and was influenced by beekeeping operation, colony health, and mite infestation level. Together, data from this and other observational cohort studies that monitor individual honey bee colonies and precisely account for sampling date (i.e., day of year) will lead to a better understanding of the influence of pathogens on colony mortality and the effects of other factors on these associations.

A History of Almond Pollination in California

Almost all commercial beekeepers in the United States could not survive without income from renting bees to California almond growers. This dependence on almond pollination has occurred gradually o...