Temperate Orchards Research Articles

Evaluating pheromone dispenser density and longevity for San Jose scale mating disruption in apple orchards

San Jose scale (Comstockaspis perniciosus Comstock) (Hemiptera: Diaspididae) is a cryptic sap-sucking pest in temperate orchards. In recent years, San Jose scale has become more challenging to manage, in part due to the loss of registered insecticides and difficulty in timing insecticide applications with the appropriate life stage. For insects like San Jose scale whose sex pheromones are known, mating disruption presents a biorational alternative to insecticide use in orchards. In 2020 and 2021, we evaluated this approach for San Jose scale in on-farm trials in Michigan apple orchards. ISOMATE® twin-tube reservoir dispensers primed with San Jose scale mating pheromone were placed into small orchard plots with densities ranging from 62 to 926 per ha to determine optimum density for control. In both years, male capture using baited traps was significantly reduced in plots under mating disruption, suggesting competitive population suppression. Optimum density of dispensers was determined to be 247 per hectare. A separate comparison study of the ISOMATE® twin-tube and CIDETRAK® MESO pheromone dispensers showed comparable efficacy despite differing release rates between the two types of dispensers. However, higher rates did provide greater suppression during the lower population densities in the first generation. We suggest there is some flexibility with rate and dispenser types for efficacious control. We also provide updated information on the phenology of the male San Jose scale flight activity. These results provide evidence for the potential utility of pheromone mating disruption for managing San Jose scale in apple orchards and highlight focus for further optimization.

Developing perennial wildflower strips for use in Mediterranean orchard systems.

To support sustainable food production and the delivery of ecosystem services through ecological intensification, wildflower strips have become a popular strategy. Despite their success in temperate orchard systems, they remain understudied in Mediterranean ecosystems, which poses a significant barrier to uptake. In order to further promote their adoption, seed mixes must be optimised for commercial orchard systems and for the Mediterranean climate. Plant species should be selected for their consistent performance, whilst the availability of resources for ecosystem service providers determines the quality of the wildflower strip. In this study, the suitability of 12 native perennial forbs and two tussock-forming grass species for wildflower strips in commercial Citrus orchards was assessed over a 3-year period. Distinct resources for natural enemies according to the different plant growth stages were used an indicator of wildflower strip quality. The wildflower strips were managed under two different cutting strategies: (i) standard management, in which wildflower strips were cut once annually in February, and (ii) active management, in which wildflower strips were cut two additional times each year. The establishment and success of the sown species were compared. The influence of wildflower strips and their management on plant species richness, community structure, and the provision of resources was compared with a control treatment, in which alleyways were managed conventionally by cutting any naturally occurring vegetation to a height of ≤5 cm, four to five times annual. For the first time, the performance of native perennial plant species has been assessed in Mediterranean orchard systems and a seed mix developed for targeting pest regulation services. The wildflower strips were successful in increasing plant species richness and the available resources expected to support natural enemies. However, only wildflower strips managed with cutting once annually enhanced vegetation cover relative to the control, whilst extending the flowering period. This study therefore provides crucial tools for the further development of sustainable approaches to food production in Mediterranean orchard systems.

Climate change impacts on winter chill in Mediterranean temperate fruit orchards

Temperate trees require low temperatures during winter and subsequent warm conditions in early spring to flower and eventually bear fruit. Many parts of the Mediterranean region feature winters with low and sometimes marginal chill accumulation. To assess historic and future agroclimatic conditions for cultivating temperate trees (including almonds, pistachios, apricots, sweet cherries and apples), we mapped winter chill throughout this important growing region. We used on-site weather records (1974–2020) to calibrate a weather generator and produced data for historic and future scenarios. To broaden our analysis, we spatially interpolated chill for the whole Mediterranean basin. We supplemented our simulation outcomes by collecting expert knowledge (from farmers and researchers) regarding observed climate change impacts on temperate orchards as well as future risks and concerns generated by climate change. Results showed that northern African growing regions have experienced major chill losses, a likely cause of the irregular and delayed bloom highlighted by experts. The same regions, together with southern Europe, may lose up to 30 Chill Portions by 2050 under a moderate warming scenario. For the future, experts foresee increasing risk of spring frost in early-blooming cultivars, exacerbated bloom-related problems and increasing occurrence of heat waves. Our results provide evidence of likely climate change impacts on temperate orchards. Expert knowledge proved instrumental in interpreting the simulation results as well as in orienting climate change adaptation strategies. The results we present are useful for farmers and orchard managers planning new plantings, as well as for researchers and policy makers developing strategies to adapt fruit orchards to the impacts of climate change.

Genetic fingerprinting identifies apple (Malus domestica Borkh.) fruit cultivars in historic orchards on public lands

The National Historic Preservation Act of 1966 mandates that historic resources, including orchards, on federal lands be evaluated for potential significance. Evaluations include assessments and documentation of an orchard’s layout and location, as well as the architecture, ages, conditions, and cultivars of trees. These factors may reveal an orchard’s history and uniqueness and determine an orchard’s historic importance. Fruit tree cultivar identities are a key piece of this puzzle. They reveal information about an orchard’s use, origin, and uniqueness. In the past, historic preservationists relied on pomologists to identify cultivars based primarily on the phenotypic traits of the tree. DNA fingerprinting technologies, in combination with high-quality reference cultivar collections, have dramatically improved the accuracy of heritage cultivar identification. We demonstrate the utility of using DNA technologies for cultivar identifications on federal lands using examples from trees in orchards of Redwood National and State Parks and the Eldorado National Forest. A total of 87 historic apple trees from these locations were genotyped and cultivar names were determined for 35 trees, using a reference set of 1319 apple cultivars from the USDA National Plant Germplasm System, Washington State University, Seed Savers Exchange, and Temperate Orchard Conservancy. Some of the trees that were not identified may be cultivars that are not included in the reference sets and others may be unique trees derived from seeds. The information derived from genetic fingerprinting analyses will aid in the determination of the historic significance of orchards on public lands.

The importance of chill model selection — a multi-site analysis

Abstract Winter chill, which temperate trees require in order to overcome dormancy, is expected to decrease substantially in the future in most deciduous fruit tree growing areas. Several mathematical models have been developed in different regions to quantify chill requirements of tree species and cultivars. The Dynamic model has emerged as the most plausible and reliable model, yet all chill models have been found inadequate in at least some growing regions. Accurate models are crucial for the development of quantitatively appropriate climate change adaptation strategies for temperate orchards. To demonstrate the importance of model choice we compared the outputs from 13 agricultural and forest chill models using past and projected future weather data for nine sites in Chile, Tunisia and Germany. To evaluate chill risk, we used a weather generator calibrated with 45 years of temperature data to generate 100 years of synthetic temperature records per scenario for multiple climate scenarios. Chill was computed for 10 past scenarios and projected for 60 future scenarios (for 2050 and 2085 according to greenhouse gas concentration scenarios RCP4.5 and RCP8.5, using projections from 15 climate models). Results show that estimations differ substantially across chill models, even for the same sites and scenarios. The “Chilling Hours” model and the “Chilling Rate” function showed high sensitivity across regions in future scenarios. The “North Carolina”, “Utah”, “Modified Utah” and “Low Chill” models all suggest negative chill levels for past and future scenarios in Tunisia (despite the thriving fruit tree industry there). Only two models projected chill decreases in all sites. In Mediterranean climate areas (central Chile and Tunisia) the “Dynamic” and “Positive Utah” models forecasted similar chill reductions for future scenarios, whereas in temperate locations (Germany) the “Dynamic” model forecasted lower chill increase compared with the “Utah” and “Positive Utah” models. Despite the “Dynamic” and the “Positive Utah” models showing similar performance among climates, the “Dynamic” model appears to be the best current option, due its more physiologically credible structure. However, further research is needed to develop or identify models that are valid across wide climatic gradients. Our results show that a major source of variation and inaccuracy in chilling assessments is the choice of the chill model used to make the assessment.

Anatomical structure associated with vegetative growth variation in macadamia

Low-vigour scion cultivars and dwarfing rootstocks are a significant contributing factor to the success of modern temperate orchard systems. Planting density and canopy efficiency are currently limited in macadamia by a lack of low-vigour cultivars and rootstocks. The relationships between xylem vessel diameter, hydraulic conductivity and vigour are implicated in dwarf cultivars and low-vigour rootstocks of peach and apple. This study aims to determine relationships between vessel anatomy and tree-scale vigour in subtropical macadamia, to stimulate the development of low vigour cultivars and dwarfing rootstocks. Stem sections from the most recent mature flush were collected from five replicates of three macadamia cultivars: ‘D4’ (high vigour), ‘B25’ (intermediate vigour) and ‘B63’ (low vigour). Sections were imaged under a fluorescence microscope in order to measure the number and size of all xylem vessels in the stem. The three cultivars showed distinct differences in height over 5 years of measurement (P < 0.001). Change in tree height related to the xylem vessel characteristics of mean vessel area of the ten largest vessels per section (R2 = 0.57, P < 0.001), pith size (R2 = 0.70, P < 0.001) and total additive vessel area (R2 = 0.41, P < 0.01). This study indicates that relationships between anatomical structure and vigour in macadamia are likely to be similar to those of well-studied temperate tree crops and that anatomical traits may be useful in the selection of low-vigour cultivars. Future work should investigate hydraulic relationships with vigour and rootstock-scion interactions in macadamia.

Effectiveness of vole control by owls in apple orchards

Abstract Biological pest control is gaining greater acceptance as an important part of integrated pest management for sustainable agriculture. However, knowledge regarding biological control of rodent pests is limited, and its effectiveness in temperate areas has not been quantified. In traditional Japanese apple orchards, the Ural owl Strix uralensis breeds in tree hollows and preys on the Japanese field vole Microtus montebelli, a native pest species that can harm fruit production. In this study, we hypothesised that the Ural owl, a generalist predator, can act as a biological control agent by reducing vole densities in temperate orchards. To quantify the pest control effects of breeding Ural owls, we first analysed the diet of individual owls nesting in apple tree hollows. Second, we installed nest boxes in orchards to attract breeding owl pairs and collected data on vole population changes around owl nests to compare with control areas. The population changes were analysed using a generalised linear mixed model to assess the effect of breeding owls within their breeding territory. The model considered seasonal fluctuations in vole population size as well as surrounding land‐use. We also examined vole populations around the owl nests in April, and the distance between nests and forested areas, to determine if these variables influenced nest site selection. Voles were the primary prey of Ural owls breeding in orchards and the owls reduced vole populations within their estimated breeding territories by 63% (±SE: 53%–70%) compared with the predicted density without owls. Owls preferred to nest in orchards with higher vole population densities in April. Our findings also indicate that higher occupancy rates are possible by distributing nest boxes based on Ural owl breeding territory size (306 m radius circle in our study). Synthesis and applications. As breeding Ural owls provide significant pest control effects within their breeding territories, the reintroduction of breeding Ural owl pairs within orchards would contribute to rodent pest control. Promoting the reproduction of native raptors in agricultural areas can be an option for developing integrated pest management while simultaneously maintaining regional biodiversity.

Organically acceptable practices to improve replant success of temperate tree-fruit crops

For most temperate perennial fruit crops, replanting into soil that was used previously to grow the same or a related crop species usually results in poor early growth, preventing new plantings from reaching potential levels of productivity and economic returns to growers. Increases in population densities of root pathogens along with deleterious changes in soil quality under the preceding crops are largely responsible for these replant disease complexes. Driven by the rise in organic fruit production and new restrictions on fumigants and fumigation practices in the conventional sector, considerable research has been aimed, over the past two decades, to the development of non-chemical and organically-acceptable means of managing replant disease complexes. As apple is the most widely grown temperate perennial fruit crop, the majority of this research has been directed at the apple replant disease complex. This review summarizes knowledge of the causes of replant disease complexes of temperate orchard crops, and recent applied research on organically-acceptable practices to reduce the impacts of these disease complexes. Brassica seed meal amendments and composts show considerable promise as pre-plant soil amendments to improve replanted tree establishment. Composts have the added benefit of contributing to improvements in overall soil health that may enhance productivity in the long-term. Additional research to understand better the mechanisms by which compost amendments enhance replanted tree establishment would lead to improvements in the effectiveness and reliability of their utilization to alleviate replant disease.

Seasonal variation in life history traits in two Drosophila species.

Seasonal environmental heterogeneity is cyclic, persistent and geographically widespread. In species that reproduce multiple times annually, environmental changes across seasonal time may create different selection regimes that may shape the population ecology and life history adaptation in these species. Here, we investigate how two closely related species of Drosophila in a temperate orchard respond to environmental changes across seasonal time. Natural populations of Drosophila melanogaster and Drosophila simulans were sampled at four timepoints from June through November to assess seasonal change in fundamental aspects of population dynamics as well as life history traits. D.melanogaster exhibit pronounced change across seasonal time: early in the season, the population is inferred to be uniformly young and potentially represents the early generation following overwintering survivorship. D.melanogaster isofemale lines derived from the early population and reared in a common garden are characterized by high tolerance to a variety of stressors as well as a fast rate of development in the laboratory environment that declines across seasonal time. In contrast, wild D.simulans populations were inferred to be consistently heterogeneous in age distribution across seasonal collections; only starvation tolerance changed predictably over seasonal time in a parallel manner as in D.melanogaster. These results suggest fundamental differences in population and evolutionary dynamics between these two taxa associated with seasonal heterogeneity in environmental parameters and associated selection pressures.

Spider Fauna (Arachnida: Araneae) in Temperate Fruit Orchards of Kashmir

The spider fauna associated with temperate orchards of three fruit crops (apple, pear and cherry) of Kashmir comprising 14 families, 35 genera and 51 species during was recorded 2008-2009. Among the recorded species, 19 belong to web-building, 20 to visual hunter and 12 to tactile hunter group. The proportion of visual hunters was highest (44.97%), followed by web-builders (31.91%) and tactile hunter (23.12%). In web-spinning spider guild, Araneus sp. followed by Neoscona mukerjei Tikader of Araneidae; Tetragnatha sp. followed by Leucauge celebesiana (Walckenaer) of Tetragnathidae; Theridula sp. of Theridiidae and Linyphia sp. of Linyphiidae were found abundant. Among visual hunters, Pardosa altitudus Tikader and Malhotra of Lycosidae; Ctenus himalayensis Gravely of Ctenidae; Myrmarachne. sp. of Salticidae; Oxyopes sp. of Oxyopidae; Setaphis sp. of Gnaphosidae and Pisaurat sp. of Pisauridae and among tactile hunters, Thomisus sp. followed by Xysticus sp. of Thomisidae; Clubiona sp. of Clubionidae and Cheiracanthium sp. of Miturgidae were found abundant in the fruit orchards of Kashmir. The maximum population was recorded under family Lycosidae (12.22%), followed by Theridiidae (12.17%) and Thomisidae (9.51%). Margalef's richness index, Shannon-Wiener diversity index and Pielou's evenness index of visual hunters were greater followed by web-builders. The species richness was greater in pear orchard followed by cherry orchard while the species diversity was greater in apple orchard followed by cherry orchard and the variation in communities between species was recorded highest in pear orchard followed by apple orchard.

Microbial Control of Insect Pests in Temperate Orchard Systems: Potential for Incorporation into IPM

Because of their selectivity and safety, microbial control agents (MCAs) appear to be ready-made components of integrated pest management (IPM) systems that do not pose a threat to applicators or the environment and allow other natural enemies to function. Control of several orchard pest insects using MCAs, including viruses, Bacillus thuringiensis, fungi, and entomopathogenic nematodes (EPNs), have been demonstrated in apple, pear, stone fruits, citrus, and several nut crops. B. thuringiensis is the most used MCA for control of lepidopteran orchard pests. Significant use of EPNs in citrus for control of root weevils is also reported. The granulovirus of codling moth is used increasingly in apple and pear by organic growers, with interest also shown by conventional growers. Although some success has been achieved, in most orchard systems MCAs account for a relatively small proportion of the pest control tactics employed, and in some systems they are not used at all. Research toward improving MCA efficacy and economic competitiveness is required to enhance the role of MCAs in IPM.

Tetrathiobacter kashmirensis gen. nov., sp. nov., a novel mesophilic, neutrophilic, tetrathionate-oxidizing, facultatively chemolithotrophic betaproteobacterium isolated from soil from a temperate orchard in Jammu and Kashmir, India

Twelve chemolithotrophic strains were isolated from temperate orchard soil on reduced sulfur compounds as energy and electron sources and characterized on the basis of their physiological properties and ability to oxidize various reduced sulfur compounds. The new isolates could oxidize tetrathionate as well as thiosulfate, and oxidation of the latter involved conversion of thiosulfate to tetrathionate followed by its accumulation and eventual oxidation to sulfate, manifested in the production of acid. The mesophilic, neutrophilic, Gram-negative and coccoid bacteria had a respiratory metabolism. Physiologically and biochemically, all the strains were more or less similar, differing only in their growth rates and ability to utilize a few carbon compounds as single heterotrophic substrates. 16S rRNA gene sequence analysis was performed with five representative strains, which revealed a high degree of similarity (> or =99%) among them and placed the cluster in the 'Betaproteobacteria'. The strains showed low levels (93.5-95.3 %) of 16S rRNA gene sequence similarity to Pigmentiphaga kullae, Achromobacter xylosoxidans, Pelistega europaea and species belonging to the genera Alcaligenes, Taylorella and Bordetella. The taxonomic coherence of the new isolates was confirmed by DNA-DNA hybridization. On the basis of their uniformly low 16S rRNA gene sequence similarities to species of all the closest genera, unique fatty acid profile, distinct G+C content (54-55.2 mol%) and phenotypic characteristics that include efficient chemolithotrophic utilization of tetrathionate, the organisms were classified in a new genus, Tetrathiobacter gen. nov. In the absence of any significant discriminatory phenotypic or genotypic characteristics, all the new isolates are considered to constitute a single species, for which the name Tetrathiobacter kashmirensis sp. nov. (type strain WT001(T)=LMG 22695(T)=MTCC 7002(T)) is proposed.

A nuclear polyhedrosis virus of the light brown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae)

Temperate orchards systems have several environmental features that make them conducive to microbial control strategies including adequate soil moisture, shading (protection from harmful UV) and stability. This chapter reviews and analyzes microbial control efforts in temperate orchards, including pome fruit, stone fruit, and nut crops. Emphasis is placed on pest complexes that have received most attention as targets for microbial control in North America. Examples where microbial control has been successful include the use of granulovirus and entomopathogenic nematodes against codling moth, the use of entomopathogenic nematodes against plum curculio, peachtree borer or lesser peachtree borer, and the combined or single applications of entomopathogenic nematodes, fungi (Beauveria bassiana or Metarhizium spp.) and bacteria (Chromobacterium subtsugae) against pecan weevil. Improvements in efficacy have been made through careful selection of pathogen strains or species as well as recent advances in formulation or application techniques. Currently, commercially produced microbial control agents and their derivatives are applied to an increasing number of insect pests in temperate orchard systems; based on current and future research directions outlined in this chapter, there is great potential for expansion.