Pistachio Orchards Research Articles

Resistance to Thiophanate-Methyl in Botrytis cinerea Isolates From Californian Vineyards and Pistachio and Pomegranate Orchards.

In this study, a mycelial growth assay was used to evaluate the sensitivity to thiophanate-methyl of 144 Botrytis cinerea isolates (collection A) from Californian vineyards and pistachio and pomegranate orchards. Based on the effective concentration that inhibits 50% of growth (EC50) values for mycelial growth inhibition on fungicide-amended media, 3, 28, 10, and 58% of the isolates showed sensitivity (SS; EC50 < 1 µg/ml), low resistance (LR; 1 < EC50 < 10 µg/ml), weak resistance (WR; 10 < EC50 < 50 µg/ml), and high resistance (HR; EC50 > 100 µg/ml) toward thiophanate-methyl, respectively. The LR and HR phenotypes were observed in pistachio and pomegranate orchards, even though pomegranate was not sprayed with thiophanate-methyl. Sensitivity to thiophanate-methyl of a historical collection of 257 B. cinerea isolates (collection B) isolated from pistachio orchards in 1992, 2005, and 2006 was assessed on potato dextrose agar amended with thiophanate-methyl at the discriminatory concentration of 10 µg/ml. Average percentages of thiophanate-methyl-resistant isolates were 50, 72, and 64% in the orchards in 1992, 2005, and 2006, respectively. A study of fitness components of selected thiophanate-methyl-resistant (LR, WR, and HR) and -sensitive (SS) isolates from collection A did not reveal any significant difference between them with respect to mycelial growth on fungicide-free media and pathogenicity on cultivar Crimson Seedless berries. Comparison of β-tubulin sequences from resistant and sensitive phenotypes revealed that a glutamic acid at position 198 was changed to alanine in all HR isolates and three LR isolates. The occurrence of thiophanate-methyl resistance in B. cinerea populations should be considered when designing spray programs against blossom and shoot blight of pistachio and gray mold of grape.

Age-Stage, Two-Sex Life Tables of Anthocoris minki pistaciae (Hemiptera: Anthocoridae) Reared on Agonoscena pistaciae (Hemiptera: Aphalaridae) at Three Constant Temperatures

Agonoscena pistaciae Burckhardt & Lauterer (Hemiptera: Aphalaridae) is the most important pest of pistachio trees in Iran and the world. Anthocoris minki pistaciae Wagner (Hemiptera: Anthocoridae) is a predator of A. pistaciae. Biological characteristics of this predatory bug were determined at three constant temperatures (17, 26 and 30 ± 2°C), 55 ± 5% R.H., and a photoperiod of 16:8 h (L:D). Data were analyzed by age-stage, two-sex life table to assess the variable developmental rates. Pre-adult developmental time of this predator at 17, 26 and 30°C were 24.5, 15.2 and 14.2 d, respectively. Adult longevities were 61.8, 51.9 and 43.7 d for males, and 60.3, 49.2 and 43 d for females at 17, 26 and 30°C, respectively. Fecundity at 17, 26 and 30°C were 50.3, 51.9 and 41.6 eggs/female, respectively. Intrinsic rates of increase (r) were 0.0707, 0.1042 and 0.1102 d–1 at 17, 26 and 30°C, respectively. The mean generation time (T) was 27.3 d (the shortest time) at 30°C and 42 d (the longest time) at 17°C. The net reproductive rate (R0), the age-stage-specific fecundity (fxj), age-specific fecundity (mx) and age-specific maternity (lxmx) at 26°C were higher than those at 17 and 30°C. This research suggests that this predator can retain higher population densities at 26°C than at the other temperatures tested. Results of this study provide the biological basis for using A. minki pistaciae in a biological control program against A. pistaciae in pistachio orchards.

Macrophomina Crown and Root Rot of Pistachio in California.

In this study, declining pistachio rootstocks were detected in newly planted commercial pistachio orchards in Kern County, California. Symptoms were characterized by wilted foliage combined with crown rot in the rootstock. From diseased trees, 42 isolates were obtained, and all had similar cultural and morphological characteristics of Macrophomina phaseolina. Analyses of nucleotide sequences of three gene fragments, the internal transcribed spacer region (ITS1–5.8S–ITS2), partial sequences of β-tubulin, and translation elongation factor 1-α (TEF1) confirmed this identification, and 20 representative isolates are presented in the phylogenetic study. Testing of Koch’s postulates showed that M. phaseolina, when inoculated to stems and roots of the pistachio rootstocks using mycelial plugs or a microsclerotial suspension, is indeed pathogenic to this host. The widely used clonal University of California Berkeley I (UCBI) rootstock appeared highly susceptible to M. phaseolina, suggesting that this pathogen is an emerging threat to the production of pistachio in California. This study confirmed the association of M. phaseolina with the decline of pistachio trees and represents the first description of this fungus as a crown rot-causing agent of pistachio in California.

Lethal and sublethal effects of spirotetramat and abamectin on predatory beetles (Menochilus sexmaculatus) via prey (Agonoscena pistaciae) exposure, important for integrated pest management in pistachio orchards

Menochilus sexmaculatus Fabricius (Coleoptera: Coccinellidae) is an important biological control agent in pistachio orchards, especially against Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Psyllidae), which is the most damaging pest of pistachio. In this project we exposed M. sexmaculatus adults to two important commonly-used insecticides through feeding on treated prey (A. pistaciae) to evaluate the side-effects on this predator. We tested spirotetramat, which belongs to the keto-enol group inhibiting lipid biosynthesis in insects, at 2/1, 1/1 and 1/2 of the maximum field recommended concentration (MFRC), and abamectin, which is a mixture of avermectins and a natural fermentation product of the bacterium Streptomyces avermitilis, at 1/1, 1/2, 1/4, 1/8 and 1/16 of its MFRC. Spirotetramat did not affect adult survival of M. sexmaculatus at all three concentrations when ingested via treated prey, while in marked contrast abamectin caused 100% adult mortality of M. sexmaculatus when ingested via treated prey at 1/1, 1/2, 1/4 and 1/8 of the MFRC. At sublethal levels, spirotetramat reduced total and daily fecundity of M. sexmaculatus at all three concentrations tested, but did not affect egg hatching at 1/1 and 1/2 of the MFRC. Moreover, prey consumption was decreased when beetles were exposed to the prey treated with spirotetramat at 1/1 and 2/1 of the MFRC concentrations. With abamectin, even at 1/16 of the MFRC, total fecundity, daily fecundity and prey consumption of M. sexmaculatus adults were significantly affected. In conclusion, no acute toxicity was observed on M. sexmaculatus by ingestion of prey treated with spirotetramat, although reproduction parameters and prey consumption were affected at MFRC and lower concentrations. In marked contrast, abamectin was notably very harmful at its MFRC and also at lower concentrations. This research highlighted the importance of toxicity risk assessments, including lethal and sublethal effects, to obtain a more accurate estimation of the compatibility of insecticides in current integrated pest management (IPM) programs.

Selecting high performance rootstocks for pistachio cultivars under salinity stress based on their morpho-physiological characteristics

ABSTRACT In Iran, the most pistachio orchards are located in semi-arid regions and irrigated with saline water which influences their growth and yield. The present investigation was conducted to evaluate the effects of salinity on growth, and morpho-physiological parameters of six pistachio genotypes as rootstock (ʽAkbariʼ, ʽAhmad-Aghaiʼ, ʽUCB-1ʼ, ʽItalyayiʼ, ʽGhazviniʼ and ʽBadamiʼ). Treatments were different salinity concentrations using NaCl at 0.5, 12 and 18 dSm-1 on six genotypes of pistachio. According to the results, by increasing salinity, the FW, DW, number of growing leaves, SPAD index of leaves, chlorophyll content and stomatal conductance were reduced, but electrolyte leakage of leaf and root tissues, soluble sugars and antioxidant capacity were increased. ʽUCB-1ʼ, ʽAkbariʼ and ʽAhmad-Aghaiʼ had the highest leaf area compared to other genotypes under salinity conditions. The lowest leaf abscission was belonged to ʽUCB-1ʼ and its difference was significant with other genotypes. The WUE of ʽUCB-1ʼ reduced and it was higher than ʽAkbariʼ. The growth of ʽUCB-1ʼ significantly declined up to 79.6% under salinity stress. Salinity stress had the lowest adverse effect on the growth of ʽAkbariʼ and ʽAhmad-Aghaiʼ genotypes. There was no significant difference among genotypes in regard to RWC under salinity stress. It can be concluded that ʽUCB-1ʼ, ʽAkbariʼ and to some extent ʽAhmad-Aghaiʼ were tolerant to salinity stress and can be recommended to use as rootstock under moderate salinity conditions.

Assessing water security of Rafsanjan Plain, Iran – Adopting the SEEA framework of water accounting

Abstract Rafsanjan Plain, located in the central Iran, is a dry area relying solely on its local aquifer for Pistachio production as its dominant economy. During the past few decades, unsustainable growth of Pistachio orchards and correspondingly overexploitation of the local aquifer have resulted in about 18 m fall of the groundwater table with terrible consequences such as reduction in the groundwater yield and about 1.2 m of land subsidence. The aim of the present paper is to analyze water security of the water resources system in the Rafsanjan plain in terms of the system vulnerability to water scarcity. Adopting an analytical framework for assessing the system vulnerability to water scarcity, the paper derives vulnerability indicators based on the data organized in terms of the System of Environmental and Economic Accounting for Water (SEEA-Water) for different water accounts associated to 2001 and 2006. The paper suggests policy options to reduce the system vulnerability using a system dynamics simulation model. The results showed that the water resources system of the study area is highly vulnerable to water scarcity due to large amount of water stress (more than 2), high dependency to groundwater (more than 95%), and high share of water consumption in agricultural sector (more than 90%). To alleviate the system vulnerability, the policy options are suggested to shift partly from agricultural activities to industrial and mining activities. It was shown that the policies could be effective to save water resources volume (more than 40%), improve water productivity (more than 25%), employment productivity (more than 17%), and labor productivity (more than 5%), and enhance per capita income (more than 3%) in comparison to the current state in the Rafsanjan plain.

Occurrence and Extent of Boscalid Resistance in Populations of Alternaria alternata from California Pistachio Orchards.

Alternaria late blight (ALB) caused by Alternaria spp. is an annual disease problem in California pistachio and requires repeated applications of fungicides to prevent significant losses of pistachio foliage and nut quality. From 2003 onward, the succinate dehydrogenase inhibiting fungicide boscalid has played a key role in ALB management. The development of boscalid resistance in A. alternata populations was monitored from 2005 to 2012 in pistachio producing areas in California. A total of 1,765 single-spore isolates, collected from commercial and experimental pistachio orchards with or without a history of boscalid exposure, were tested in a radial growth assay in agar media amended with the discriminatory dose of 10 µg/ml of boscalid. The frequency of boscalid-resistant isolates in 2005 was 12% but increased significantly and remained stable toward the end of the survey period. Most of the resistant isolates exhibited a high level of resistance (R) to boscalid with percent of mycelial growth inhibition (PGI) values between 0 and 50%, whereas significantly fewer isolates had an intermediate level (IR) of resistance (50 < PGI < 75%). The frequency of sensitive (S) isolates (75 < PGI < 100%) was generally the highest in orchards with no history of boscalid usage, whereas mean incidences of boscalid-resistant populations of Alternaria were 81, 92.4, 80.2, and 98%, in 2006, 2007, 2011, and 2012, respectively, in orchards that received a high number (at least three per season) of boscalid spray applications. In comparison, none to relatively low frequencies (0 to 12%) of resistance were observed in populations with no or limited exposure to Pristine, suggesting an air-movement of resistant spores through wind from treated to nontreated areas. In 2012, boscalid-resistant isolates were found practically in every sampled location in all counties, with the orchards in Fresno, Madera, Tulare, and King Counties being the locations with the highest frequencies of resistance (100%). Monitoring of A. alternata AaSDHB, AaSDHC, and AaSDHD mutations in 286 boscalid-resistant phenotypes identified 11 mutations, leading to amino acid substitutions in AaSDHB (seven mutations: H277Y/R/L, P230A/R, N235D/T), AaSDHC (one mutation: H134R), and AaSDHD (three mutations: D123E, H133R/P), with AaSDHB mutations being the most prevalent (80%) ones throughout the survey period. The majority of isolates carrying these mutations exhibited the R phenotype toward boscalid. The increased prevalence of boscalid resistance in populations of A. alternata is a likely contributing factor to the inability of pistachio farmers to successfully control ALB with Pristine. Other factors implicated in the rapid and widespread occurrence of A. alternata boscalid-resistant populations in California pistachios are further discussed.

Dust Interferes with Pollen–Stigma Interaction and Fruit Set in Pistachio Pistacia vera cv. Kerman

Springtime flail mowing of row middles for weed control in California pistachio (Pistacia vera L.) orchards blows dust into the leafless canopy if it occurs during bloom. The effect of dust on pistachio pollination and fruit set is unknown. Rachises were bagged prebloom and hand pollinated with pollen and dust mixtures at 1:0, 1:1, 1:4, 1:16, and 0:1 volume/volume ratios on five successive days. The 2016 and 2017 trials demonstrated that the inflorescences treated with a high pollen:dust ratio (0:1, 1:4, and 1:16) had significantly lower split nut rates (commercially less profitable) compared with low dust ratio tests (1:0 and 1:1). Our results also showed that dust damaged both pollen viability and stigma quality, particularly if contaminated with herbicide residues (GlyStar® Plus and Treevix®). Decreased yield was a function of decreased fruit set; increased embryo abortion, parthenocarpy, or both; and a lower split nut percentage. The GA3 content in flowers of both the pollen and dust treatments was significantly higher than that in nonpollinated flowers, suggesting dust stimulated parthenocarpy, resulting in empty nutshells, “blanks” at harvest.

Variations in nutrient uptake, yield and nut quality of different pistachio cultivars grafted on Pistacia khinjuk rootstock

Nutrient accumulation in plant leaves provides empirical information about the uptake, translocation and utilization of available resources, which is ultimately reflected in yield. Several studies have reported that rootstock significantly affect nutrient uptake and yield in pistachio; however, little is known about the differences among cultivars of different origin grafted on the same rootstock. This study was conducted to assess the differences in nutrient uptake, yield and nut quality of different pistachio cultivars grafted on Pistacia khinjuk rootstock in Sanliurfa province, Turkey. An orchard with 14 different cultivars grafted on same rootstock was established in 1994 with 7 m × 5 m spacing. Leaf samples were collected at the beginning of fruit maturation and analyzed for N, P, K, Ca, Mg, Fe, Zn, Mn, and Cu contents. Yield and nut quality were evaluated at maturity. Significant differences were observed among cultivars for nutrient uptake, yield and nut quality. The highest N, P and K were accumulated by ‘Haciserifi’ cultivar, whereas the highest uptake of Ca, Mg and Cu was noted for ‘Mumtaz’ cultivar. Similarly, ‘Vahidi’ cultivar accumulated the highest amounts of Fe and Zn, whereas the highest accumulation of Mn was recorded for ‘Sel-15′ cultivar. The highest 100-fruit weight and yield were recorded for ‘Mumtaz’ cultivar. Similarly, the highest percentage of split nuts was recorded for ‘Sel-2′, ‘Sel-5′ and ‘Siirt’ cultivars, whereas the highest kernel ratio was noted for ‘Ohadi’ cultivar. Principal component analysis divided the cultivars in 3 groups. The cultivars in the first group had similar Cu, Mg, Ca, K accumulation, 100-fruit weight and yield, while the second group cultivars had similar accumulation of N, P, Zn and Fe. The third group had the cultivars with heterogenous accumulation of plant nutrients. It is concluded that nutrient accumulation, yield and quality of pistachio is not only influenced by rootstock; rather, grafted cultivars also significantly differ for nutrient uptake. Therefore, both rootstock and cultivars should be considered while establishing pistachio orchards for efficient utilization of available resources and better economic returns.

Population fluctuations of the pistachio twig borer, Kermania pistaciella Amsel, 1964 (Lep.: Oinophylidae) using delta pheromone trap

Population fluctuations of adult insects of pistachio twig borer, Kermania pistaciella Amsel were studied using delta pheromone traps and sampling from 2016-2017 in Kashan pistachio orchards. Delta type traps baited with sex pheromones were hung in pistachio orchards (‘Akbari’) at 20 lures per one hectare and the numbers of captured male insects were counted every three days. Kermania pistaciella males have begun to attract the traps from 18th March and 8th April in the first and second year, respectively and this trend continued to 31st April and 4th May and flight period of about 42 days in the first year and the second year that lasted 27 days. First, peak and end of each catch insects occurred on 18 March, 8-21 April and 31 April in the first year and on 8 March, 23-26 April and 4 May in the second year, respectively. There was no association in the first year and a weak positive association in the second year of study between the average daily temperature and the number of K. pistaciella moths captured in pheromone traps. It seems that moths capture was different because of the weather conditions of these orchards was different in two consecutive years.

Leaching of Saline Calcareous Soil under Laboratory Conditions

Soil salinity is a major problem in Kerman pistachio (Pistacia vera) orchards which caused low pistachio’s productivity in recent years. Farmers excessively use gypsum and sulfuric acid amendments to remediate saline soils in their pistachio orchards overcoming this problem. The aim of this study was to investigate type of amendments and the pore volumes of water (PVs) required to efficiently leach excessive salts from saline-calcareous soil. Laboratory experiments were conducted using soil columns that were collected from a pistachio orchard near Kerman city. Four treatments, including irrigation water (control), sulfuric acid, gypsum, and dissolved gypsum were applied to remove salt from these soil columns with using different PVs of water. The concentrations of removed cations and salt from the soil columns were measured by analysis of effluent continuously. The results demonstrated that the effect of chemical amendments in removing soluble salts, sodium, magnesium and calcium was similar to irrigation water and did not differ significantly. Thus, irrigation water removed 62% of the total sodium, 73% of magnesium, and 70% of soluble salts from the soil column up to 1.5 PVs of effluent. Application of chemical amendments was not beneficial to infiltration rate in comparison with irrigation water. Thus, the efficiency of only 1.5 PVs of irrigation water without any amendments can be recommended as the appropriate strategy for practical reclamation of the studied soil.

Modeling the relationship between cadmium and some soil physical and chemical properties in Pistachio orchards using regression and artificial neural network

سابقه و هدف: افزایش روز افزون غلظت فلز­های سنگین در محیط زیست، سبب ایجاد نگرانی‌های جدی ‌محیط زیستی شده است. کادمیم یکی از سمی‌ترین عنصر­های سنگین برای موجود­های زنده است که نقش زیستی ندارد. تاکنون در مورد وضعیت عنصر­های سنگین در خاک باغ‌های پسته و شناسایی عامل­های خاکی مؤثر بر آن‌ها، پژوهش‌های چندانی انجام نشده است. بنابراین، هدف از انجام این پژوهش، تعیین رابطه کادمیم عصاره‌گیری شده با دی تی پی ا در خاک با دیگر ویژگی­ های فیزیکی و شیمیایی خاک، در خاک‌های کشاورزی شهرستان رفسنجان به کمک مدل‌سازی مبتنی بر روش رگرسیون گام‌به‌گام و شبکه عصبی مصنوعی بود. مواد و روش‌ها: در این تحقیق 140 نمونه خاک از دو عمق صفر تا 40 و 40 تا 80 سانتی‌متری از باغ‌های پسته‌ی شش منطقه از حومه‌ی رفسنجان تهیه شد. ویژگی‌های خاک شامل غلظت کادمیم و روی قابل‌جذب در خاک با استفاده از روشدی تی پی ا، غلظت فسفر به روش اولسن، درصد شن، رس و سیلت خاک به روش هیدرومتر، pH و رسانایی الکتریکی عصاره اشباع خاک بترتیب توسط دستگاه‌های pH متر و EC متر اندازه‌گیری شدند. بمنظور بررسی رابطه‌ی بین کادمیم قابل جذب و ویژگی­ های فیزیکی و شیمیایی خاک، از روش رگرسیون گام‌به‌گام و شبکه‌ی عصبی مصنوعی (پیش‌خور چندلایه) استفاده شد. نتایج و بحث: نتایج نشان داد که بین فسفر و درصد رس با کادمیم خاک، همبستگی مثبت و معنی‌دار، بین Cd-DTPA با pH و درصد رس خاک، همبستگی منفی و معنی‌دار و بین کادمیم قابل جذب با روی قابل جذب، روی کل و کادمیم کل خاک همبستگی مثبت معنی‌داری وجود دارد. همچنین نتایج نشان داد که هر دو روش مدل‌سازی از دقت مناسبی برای تخمین غلظت کادمیم در خاک برخوردارند اگرچه مدل شبکه عصبی دقت خیلی بیشتری داشت. ضریب تبیین و ریشه میانگین خطا برای مدل شبکه عصبی برای داده‌های آزمون بترتیب 84.3 درصد و 0.01 و برای مدل رگرسیون گام به گام 27.2 درصد و درصد1.43 بود. همچنین غلظت کادمیم، بیشترین حساسیت را به غلظت روی در خاک نشان داد و دیگر پارامترهای رس، pH، فسفر، EC و شن ‌بترتیب، در درجه بعدی از اهمیت قرار داشتند. این نتایج تایید می‌کند که در باغ های پسته بدلیل مصرف کودهای حاوی روی و افزایش مصرف کود‌های فسفاته که دارای ناخالصی زیادی از نظر مقدار کادمیم هستند، افزایش غلظت کادمیم در خاک باغ های پسته مشاهده می‌شود. نتیجه­ گیری: کودهای شیمیایی روی و فسفر مورد استفاده در باغ‌های پسته دارای ناخالصی قابل‌توجهی از کادمیم هستند که در اثر استفاده بی‌رویه و درازمدت می‌توانند سبب آلودگی خاک نسبت به کادمیم و جذب این عنصر سمی در گیاه و میوه پسته شوند. بنابراین باید ضمن رعایت استانداردهای ملی و بین ­المللی در تولید و واردات کودها، استفاده از این کودها نیز براساس نیاز و با تحلیل و تفسیر نتایج تجزیه خاک و برگ، بهینه باشد تا خطر آلودگی میوه پسته به کادمیم کاهش یابد.

Identification and Pathogenicity of Fungal Species Associated with Canker Diseases of Pistachio in California.

A survey was conducted during 2015 and 2016 in pistachio orchards throughout the San Joaquin Valley of California to investigate the occurrence of canker diseases and identify the pathogens involved. Cankers and dieback symptoms were observed mainly in orchards aged >15 years. Symptoms of canker diseases included brown to dark brown discoloration of vascular tissues, wood necrosis, and branch dieback. In total, 58 fungal isolates were obtained from cankers and identified based on multilocus phylogenetic analyses (internal transcribed spacer, glyceraldehyde 3-phosphate dehydrogenase, β-tubulin, calmodulin, actin 1, and translation elongation factor 1α) representing 11 fungal species: Colletotrichum karstii, Cytospora californica, Cytospora joaquinensis, Cytospora parapistaciae, Cytospora pistaciae, Diaporthe ambigua, Didymella glomerata, Diplodia mutila, Neofusicoccum mediterraneum, Phaeoacremonium canadense, and Schizophyllum commune. Pathogenicity tests conducted in the main pistachio cultivars Kerman, Golden Hills, and Lost Hills using the mycelium-plug method indicated that all fungal species were pathogenic to Pistacia vera. All species tested caused cankers in pistachio branches, although virulence among species varied from high to moderate. Overall, N. mediterraneum and Cytospora spp. were the most widespread and virulent species associated with canker diseases of pistachio in California.

The role of iron (Fe) in the population dynamics of pistachio psyllid, Agonoscena pistaciae (Hemiptera: Aphalaridae) in Pistacia orchards

The common pistachio psyllid (CPP) is thought to respond to nutrient availability in pistachio trees. We determined the effect of a deficiency of leaf iron (Fe) has on the abundance of the pistachio psyllid at a regional scale. First, we monitored the abundance pistachio psyllid in four pistachio orchards (24 trees as 24 repetitions) located in Maybod County, Yazd province in the centre of Iran and then measured leaf nutrient levels. Orchards were located up to 2.6 km apart. Multivariate regressions were used to determine the relationship between leaf nutrients and CPP population growth. The results indicate that the number of psyllid eggs and population growth rate of the nymphs was negatively correlated with Fe levels in the leaves, while peak numbers of psyllid eggs were positively correlated with the levels of Cu in the leaves. In a manipulative field experiment, we conducted two experiments: (1) pistachio trees treated with iron compared with control trees, and (2) pistachio trees previously treated with iron were treated with ammonium sulphate and compared with trees treated with ammonium sulphate. In the first experiment, psyllids in leaf disc-cages had a significantly greater intrinsic rate of population increase and net reproductive rate on Fe-treated trees than the control trees (Stage 1). In the second experiment, psyllids in leaf disc-cages had similar intrinsic rates of population increase and net reproduction both on the ammonium sulphate treated trees (control) and those previously treated with iron. This indicates that iron may have reacted negatively with nitrogen content of the leaves. In general, these findings indicate that when there is a deficiency of iron in the leaves, the application of nitrogen fertilizer had little effect on the performance of CPP and may have played a minor role in the population dynamics of CPP, but the application of a Fe fertilizer without considering the nitrogen content of the leaves may lead to a population outbreak.

Inferring Biological Control Potential of Adult Predatory Coccinellids Using Life History Traits and Putative Habitat Preference.

Aspects of the nutritional ecology and life histories of five predatory coccinellids (Coleoptera: Coccinellidae)-two arboreal predator species, Oenopia conglobata contaminata (Menetries) and Adalia bipunctata (Linnaeus), and three herbaceous dwelling predator species, Coccinella undecimpunctata aegyptica (Reiche), Exochomus nigripennis (Erichson), and Hippodamia variegata (Goeze) (Coleoptera: Coccinellidae)-were compared when fed either Agonoscena pistaciae Burckhardt and Lauterer (Hemiptera: Aphalaridae), the key psylla pest of pistachio trees, or Aphis gossypii Glover (Hemiptera: Aphididae), a common aphid on herbaceous plants in pistachio orchards. The putative habitat preferences of four of the five coccinellids studied were consistent with their performance on the major herbivore present in those two habitats in terms of net reproductive rate. Oenopia conglobata contaminata and Ad. bipunctata showed higher net reproductive rates when fed on pistachio psylla prey, whereas C. undecimpunctata aegyptiaca and E. nigripennis had better reproductive output on aphid prey. Moreover, E. nigripennis was the most specialized of these generalist predators, eating more and reproducing better when fed aphids. Hippodamia variegata was relatively unaffected by the diet offered, suggesting greater ability to switch among herbivore prey and perhaps better potential as a biocontrol agent with abilities to exploit Ag. pistaciae without large life history tradeoffs.

Phenotypic and molecular characterization of resistance to the SDHI fungicide fluopyram in populations of Alternaria alternata from pistachio orchards in California

In this study, the sensitivity of 902 isolates of A. alternata collected before and after the commercial use of fluopyram were assessed using mycelial growth tests. Distribution of 50% effective concentration (EC50) values for 116 A. alternata isolates (population A), collected in 2011 from an experimental orchard that had been treated with fluopyram products or boscalid showed that 86% of the isolates displayed different levels of resistance to boscalid while 87 (76%) and 28 (24%) showed sensitivity and different levels of resistance to fluopyram, respectively. Among the last group of isolates, only 5 and 23 showed moderate (MR) and low (LR) resistance to fluopyram, respectively. The sensitivity to fluopyram was further evaluated in agar medium at the discriminatory dose of 5 μg/ml fluopyram for a total of 786 A. alternata isolates collected in 2012 from commercial pistachio orchards with (173 isolates, population B; 373 isolates, population C) or without a history of use of fluopyram products (240 isolates, population D). Among the 240 isolates from 31 boscalid-treated orchards, 93 and 7% showed sensitivity (S) and low resistance (LR) to fluopyram, respectively, while 65 and 33 were resistant (R) and LR to boscalid, respectively. Analyses of the sensitivities to boscalid and fluopyram of the 546 isolates from populations B and C collected from orchards exposed to fluopyram or other SDHIs showed fluopyram-resistant isolates did not occur at the same frequency as boscalid resistance. In both populations, the frequencies of boscalid resistance isolates in all plots, exposed or not to fluopyram products, were significantly higher than those observed for fluopyram. Sequence analyses of the A. alternata SDHB, C, and D proteins showed the presence of several amino acid substitutions (SDHB: H277Y/R/L, P230 A/R/I/F,D, N235D/T/E/G; SDHC: H134R, S135R; SDHD: D123E, H133P) in boscalid- and fluopyram-resistant phenotypes. Current data provided further evidences of the good performance of fluopyram and the various and interactive impacts of SDH mutations on the levels of resistance to SDHIs. Although their frequency is still very low, fluopyram-resistant phenotypes could quickly build up in Alternaria populations under continual selection pressure by SDHI-containing products and ultimately affect fluopyram efficacy. As fluopyram products become extensively used in pistachio orchards, continual monitoring of Alternaria sensitivities to fluopyram and other active ingredients in these mixtures (tebuconazole in particular) will be required to detect any shifts in sensitivity that could result in disease control failures.

Effect of Exogenous Application of L-arginine and Sodium Nitroprusside on Fruit Abscission and Physiological Disorders of Pistachio (Pistacia Vera L.) Scions

Pistachio yield are often negatively affected by some physiological problems such as abscission of inflorescence buds and fruits, deformed or blank nuts, and non-split shells. In the present study the effect of exogenous application of arginine (Arg) (a substrate for nitric oxide (NO) synthase) and sodium nitroproside (SNP), as a NO-donor was investigated on yield production, fruit and inflorescence buds abscission, and physiological parameters of Pistacia vera. The experiment was conducted in randomized complete block design with factorial structure in a commercial pistachio orchard. Factors were included two levels of Arg (0.5 and 1 mM), two levels of SNP (50 and 100 μM) and their combination applied at two distinct time; one week before full bloom (first stage) and five weeks after full bloom (second stage). Comparing to SNP-treated trees, Arg was more effective on growth and physiological parameters of shoots and on fruit and inflorescence buds abscission, and on fruit parameters such as split and non-split shells, blank nuts, number of nuts per ounce. Effects of these treatments were considerably depending on the time of application and the concentrations of applied compounds. It is proposed that the effects of Arg and SNP may be related to the NO signaling and polyamines production.

Actual Evapotranspiration and Tree Performance of Mature Micro-Irrigated Pistachio Orchards Grown on Saline-Sodic Soils in the San Joaquin Valley of California

In California, a significant percentage of the pistachio acreage is in the San Joaquin Valley on saline and saline-sodic soils. However, irrigation management practices in commercial pistachio production are based on water-use information developed nearly two decades ago from experiments conducted in non-saline orchards sprinkler-irrigated with good quality water. No information is currently available that quantify the effect of salinity or combined salinity and sodicity on water use of micro-irrigated pistachio orchards, even though such information would help growers schedule irrigations and control soil salinity through leaching. To fill this gap, a field research study was conducted in 2016 and 2017 to measure the actual evapotranspiration (ETa) from commercial pistachio orchards grown on non-saline and saline-sodic soils in the southern portion of the San Joaquin Valley of California. The study aimed at investigating the functional relations between soil salinity/sodicity and tree performance, and understanding the mechanisms regulating water-use reduction under saline and saline-sodic conditions. Pistachio ETa was measured with the residual of energy balance method using a combination of surface renewal and eddy covariance equipment. Saline and saline-sodic conditions in the soil adversely affected tree performance with different intensity. The analysis of field data showed that ETa, light interception by the tree canopy, and nut yield were highly and linearly related (r2 &gt; 0.9). Moving from non-saline to saline and saline-sodic conditions, the canopy light interception decreased from 75% (non-saline) to around 50% (saline) and 30% (saline-sodic), and ETa decreased by 32% to 46% relative to the non-saline orchard. In saline-sodic soils, the nut yield resulted around 50% lower than that of non-saline orchard. A statistical analysis performed on the correlations between soil physical-chemical parameters and selected tree performance indicators (ETa, light interception, and nut yield) revealed that the sodium adsorption ratio (SAR) adversely affected tree performance more than the soil electrical conductivity (ECe). Results suggest that secondary effects of sodicity (i.e., degradation of soil structure, possibly leading to poor soil aeration and root hypoxia) might have had a stronger impact on pistachio performance than did salinity in the long term. The information presented in this paper can help pistachio growers and farm managers better tailor irrigation water allocation and management to site-specific orchard conditions (e.g., canopy features and soil-water salinity/sodicity), and potentially lead to water and energy savings through improved irrigation management practices.

Assessment of Resilience of Pistachio Agroecosystems in Rafsanjan Plain in Iran

This study assessed the resilience of pistachio production systems in the Rafsanjan plain in Iran using an index of behavior-based indicators. One-hundred fifty pistachio orchards located in five major production areas were studied in 2016. The data was subjected to three-step multi-criteria analysis, including (i) normalization and aggregation; (ii) determination of the weights representing the priorities for each criterion and evaluation of the performance of each indicator; and (iii) comparison. The results showed that the study areas had problematic statuses regarding the indicators of membership in grassroots organizations, innate abilities, water sources, production stability, and insurance. They had critical or moderate statuses concerning the indicators of use of organic fertilizers, use of pesticides, soil fertility index, water-use efficiency (kg/m3), trust in government, access to advisor services (extension), on-the-job training, and diversity of marketing. They had positive levels for the indicators of productivity, diversity of cultivars, diversity of on-farm practices, and exchange of information. We recommend the enhancement of the transformability capacity in PPSs by changing the focus from optimal states and the determinants of maximum sustainable yield (MSY paradigm) to adaptive resource management that includes developing participatory platforms for collaboration of usage of water resources.

Biochemical Characterization of the Induced Immune System of Pistachio (Pistacia vera) by Salicylic Acid

ABSTRACTDespite the economic importance of pistachio very little studies have been performed on its defense physiology. Due to lack of effective method among pest management programs, pesticides, despite their known some adverse features, is the only and last option for control of pests in pistachio orchards in most cases. The present study has been conducted to determine total phenolic, total protein content, antioxidant defense response and phenylalanine ammonia-lyase activity in the leaves of pistachio seedling induced by salicylic acid (SA). Results showed that the concentrations 1 and 4 mM of SA increased the phenolic content and PAL activity. The enhanced PAL activity led to the improvement of the quantity of phenolic compounds. In addition, the SA application showed an enhancing impact on total protein content and oxidative enzymes (catalase, guaiacol peroxidase, ascorbate peroxidase, and polyphenol oxidase) activity. In all experiments the SA elicitation effect was concentration- and time-dependent. Repeated measurement statistical analysis revealed that the maximum elicitation effect of SA occurred in 3 to 9 days after the treatment. SA effects on plant defensive systems are highly complicated, and further investigations are needed to clarify the underlying mechanisms. These results can be used in designing of integrated pest management programs of pistachio pests focusing on applying safe and environment-friendly controlling methods.