Orchards In China Research Articles

Characteristics of neonicotinoid imidacloprid in urine following exposure of humans to orchards in China

Imidacloprid (IMI) is a typical neonicotinoid with the largest usage in agricultural orchards in China. The long-term repeated use and the lack of proper protective measures may result in rural farmers and people living near orchards to be inevitably exposed to IMI. Excessive exposure may cause potential adverse effects on human health. To explore the characteristics of human exposure to IMI in urine, different groups of people, including pesticide applicators and their family members, and kindergarten children near IMI-applied orchards were investigated. The IMI and metabolite, 6-chloronicotinic acid (6-CNA), concentrations in urine were creatinine-adjusted to compensate for a possible dilution effect. Target analytes were detected in 100% of 1926 urine samples. The results showed that the IMI concentration in the 1-d urine from the rural residents significantly increased after a spraying event (p < 0.05) and reached the highest concentration (Geomean: 16.42 μg/g creatinine for IMI; 7.33 μg/g creatinine for 6-CNA) in the 2-d urine samples. The pesticide applicators of different genders had almost the same exposure environment (IMI Geomean of 13.25 μg/g creatinine for males and 14.71 μg/g creatinine for females) (p > 0.05). Females had higher exposure concentrations than that of males. People from different villages demonstrated diverse exposure levels with Geomean differences of 1.13–3.28 fold. For 3–6 years-old children, urinary concentrations from the rural group (Geomean: 3.73 μg/g creatinine for IMI; 3.95 μg/g creatinine for 6-CNA) were significantly higher than that of the urban group (Geomean: 1.13 μg/g creatinine for IMI; 0.88 μg/g creatinine for 6-CNA) (p = 0.00001), and the younger children tended to have higher exposure risk. Our findings showed that people in the Henan orchard areas were likely exposed to IMI to varying degrees. Further research on the health risk evaluation of IMI and controlling the exposure risks is needed.

Effect of bag-controlled release fertilizer on nitrogen loss, greenhouse gas emissions, and nitrogen applied amount in peach production

In common nutrient management in peach orchards in China, a large amount of nitrogen fertilizer is used. However, low nitrogen absorption and utilization rate results in nitrogen loss and greenhouse gas emissions, which is not favorable for cleaner production in peach orchards. In this experiment, nitrogen leaching, ammonia volatilization, greenhouse gas emissions under bag-controlled release fertilizer (BCRF) were evaluated. In addition, the impact of BCRF on soil nutrient status in peach orchards, peach root system growth, nitrogen absorption and utilization rate, fruit quality, and the potential for using BCRF in major peach-producing areas in China to reduce the amount of nitrogen fertilizer application were also investigated. Results showed that BCRF maintained a stable supply of nutrients to soil, decreased nitrogen leaching, ammonia volatilization and greenhouse gas emissions while nitrogen loss was significantly reduced from peach orchard soil. Also, BCRF reduced the combined global warming potential at 20-, 100-, and 500-years. A 5-year study revealed that application of BCRF promoted the formation of a dense root system in peach trees by the development of fine roots and a more concentrated root distribution. This extended the lifespan of the root system and improved fruit quality. 15N tracer experiments showed that BCRF significantly increased the absorption and utilization rate of nitrogen by peach trees. BCRF reduced the amount of nitrogen fertilizers applied by 65–82% compared to common fertilizer application methods without decreasing peach yield, so it has huge potential for reducing the amount of nitrogen fertilizer used as well as fertilizer input costs in peach production. The results showed that BCRF has huge application potential as a new, environmentally friendly, low-cost, and efficient fertilizer for cleaner production in peach orchards.

Survival and lifespan of Diaphorina citri on non-host plants at various temperatures

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is the insect vector of Candidatus Liberibacter asiaticus (Las), the causal bacteria of the devastating citrus disease Huanglongbing (HLB). Many citrus orchards in China have been destroyed by HLB infection.The survival time of ACPs without food was related to the temperature they experienced. The longest survival time of adult ACPs was 5.93 ± 0.12 days when the mean temperature was approximately 12 °C. The shortest lifespan of ACP adults was 2.33 ± 0.12 days when the mean temperature on the test day was approximately 26 °C. Surprisingly, ACP could feed on herbaceous plants in the absence of preferred hosts. The most suitable weed species for the ACP was Solanum nigrum, with the longest survival time of 41 days for all individuals tested. The survival time of ACPs feeding on herbaceous plants was also related to temperature. The surviving 20% and 10% of ACP adults in the Solanum nigrum treatment showed no decline but slight improvement as compared with control in the fecundity.In conclusion, some ACPs may be able to live for a month or even longer in an orchard if suitable plants and temperatures are available. The Las-infected ACPs that can survive by feeding on herbaceous plants may be sources of Las infection in replanted orchards. The suggested time to replant citrus in groves that were previously infected with Las is summer to autumn, or it is recommended to leave the land idle for more than three months.

Identification of a Novel Hypovirulence-Inducing Hypovirus From Alternaria alternata.

Mycoviruses are wide spread throughout almost all groups of fungi but only a small number of mycoviruses can attenuate the growth and virulence of their fungal hosts. Alternaria alternata is an ascomycete fungus that causes leaf spot diseases on various crop plants. In this study, we identified a novel ssRNA mycovirus infecting an A. alternata f. sp. mali strain isolated from an apple orchard in China. Sequence analyses revealed that this virus is related to hypoviruses, in particular to Wuhan insect virus 14, an unclassified hypovirus identified from insect meta-transcriptomics, as well as other hypoviruses belonging to the genus Hypovirus, and therefore this virus is designed as Alternaria alternata hypovirus 1 (AaHV1). The genome of AaHV1 contains a single large open-reading frame encoding a putative polyprotein (∼479 kDa) with a cysteine proteinase-like and replication-associated domains. Curing AaHV1 from the fungal host strain indicated that the virus is responsible for the slow growth and reduced virulence of the host. AaHV1 defective RNA (D-RNA) with internal deletions emerging during fungal subcultures but the presence of D-RNA does not affect AaHV1 accumulation and pathogenicities. Moreover, AaHV1 could replicate and confer hypovirulence in Botryosphaeria dothidea, a fungal pathogen of apple white rot disease. This finding could facilitate better understanding of A. alternata pathogenicity and is relevant for development of biocontrol methods of fungal diseases.

Laboratory Screening of 26 Essential Oils Against Cacopsylla chinensis (Hemiptera: Psyllidae) and Field Confirmation of the Top Performer, Perilla frutescens (Lamiales: Lamiaceae).

Similar to other pear psylla species in Europe and America, Cacopsylla chinensis (Yang and Li) is one of the most important pests that causes yield loss in commercial pear orchards in China. To investigate effective essential oils as alternatives to conventional pesticides against C. chinensis, 26 essential oils derived from commonly used Chinese spices and medicinal herbs were screened for insecticidal activity. Among these, the essential oil from Perilla frutescens (L.) Britton leaves was the top performer; it exhibited strong and acute toxicity against pear psylla, with an LD50 value of 0.63 μg per adult. Then, we tested the constituents of the essential oil and its toxicity in the field. Field trials showed a 72% corrected reduction in the first-second-instar population 7 d after spraying P. frutescens leaf oil solution at a concentration of 1 mg/ml and a 47% corrected reduction at days 3 and 14. This report is the first to document the application of essential oil from P. frutescens leaves to control C. chinensis under field conditions. Our results suggest that P. frutescens oil can be considered a novel potential pesticide for C. chinensis control in pear orchards.

Identification and Phylogenetic Analysis of Pear Psyllids (Hemiptera: Psyllidae) in Chinese Pear Orchards

Pear psyllids are among the most damaging pests in pear orchards, but little knowledge exists of psyllid species in cultivated pear orchards in China. In this study, DNA sequence analyses of the 16S rDNA and cytochrome oxidase I (COI) DNA regions were performed to identify pear psyllids from 28 regions of 20 provinces in China and to classify their genetic relationships to understand the origin of the species. The results showed that Cacopsylla chinensis Yang et Li (Hemiptera: Psyllidae) was found in most pear orchards in China, but Cacopsylla qianli (Hemiptera: Psyllidae) was found in only the cities of Guiyang (Guizhou province) and Xiangyang (Hubei province). The results for the 16S rDNA and COI regions were similar. Based on the nucleotide sequences and phylogenetic analyses of 16S rDNA and COI, C. chinensis could be divided into three groups: lineages I, II, and III. Based on 16S rDNA and COI, lineage II showed approximately 4% and 3% difference from lineage I, and lineage III showed approximately 12% and 9% difference from lineage I, respectively. C. chinensis lineage I was found in most provinces of China, while C. chinensis lineage II samples were mainly found in the Bohai rim region of China, and lineage III samples were found in Northeast China. The results of this study will provide information to pear producers regarding effective control measures to prevent further damage from pear psyllids.

Mating patterns and pollen dispersal in a Japanese larch (Larix kaempferi) clonal seed orchard: a case study.

Pollination dynamics highly determines the genetic quality of seed orchard crops. However, there is less research about the effect of mating patterns on seed productivity of orchard crops. So far, clonal seed orchards have been producing genetically improved seedlings used for most Japanese larch (Larix kaempferi (Lamb.) Carr.) plantations in China. In the present study, a total of 17 highly variable simple sequence repeat (SSR) markers were used for genotyping a progeny trial population consisting of 647 open-pollinated progenies germinated from seeds which were collected from 63 maternal clones with 140 potential paternal clones in a Japanese larch clonal seed orchard in China. Paternity analysis was used in the present case study in order to evaluate the level of paternal gametic contribution, estimate pollen contamination and selfing rates, and investigate pollination patterns, pollen dispersal patterns and the impact of mating patterns on seed productivity of orchard crops. We observed 93.7% of the success rate of the parental assignment, unequal paternal gametic contribution (0-12.4%) with 6.3% of the progenies derived from pollen contamination or unsampled pollen donors, and absence of evidence for selfing. We also found that pollination rate highly depended on the distance between pollen donors and maternal parents, the majority of the identified crossing (65.7%) occurred between clones within a 150-m radius, and large variations in growth performance existed among the paternal half-siblings. Progeny growth performance (diameter at breast (DBH) and height (HGT)) was measured at Age-20 in order to investigate the impact of mating patterns on timber production of orchard crops. As either the paternal or maternal, two clones (i. e., clones Z38 and Z62) were identified to have produced progenies with higher average stem volume breeding values than that of all of the progenies. Specifically, the genetic gains for volume were 3.53% for the two clones as paternal parents, and 8.26% as the maternal parents at Age-20. Thus, both elite clones were ideal candidates for the construction of next-generation clonal seed orchards due to their synchronous reproductive phenology with greater crossing rate and higher genetic gain. These results improved the pedigree information to provide solid evidence of mating patterns for future design and effective management of seed orchards and for the development of viable long-term breeding strategies for other coniferous species.

Penicillium and patulin distribution in pears contaminated with Penicillium expansum. Determination of patulin in pears by UHPLC-MS/MS

The danger of mycotoxin contamination entering the food supply through post-harvest infection is of perennial concern to food safety experts. To explore the distribution of Penicillium expansum and diffusion of its mycotoxin, patulin, in blue mold-damaged pears, Pyrus bretschneideri Rehd. cv. Yali obtained from markets and orchards in China were artificially inoculated with P. expansum and assayed for patulin accumulation and degree of fungal colonization. The inoculated pears were incubated until the lesions were 5, 10, 20, or 30 mm in diameter. We sampled tissue at a range of distances from the lesion, measured the spread of Penicillium by plate colony-counting methods, and used UHPLC-MS/MS to detect and quantify the patulin concentration. More P. expansum colony-forming units were isolated from pears with a higher degree of decay. Farther from the lesion, the fewer P. expansum colonies were observed, and the lower the patulin content detected. We found a significant difference in the patulin content between samples due to lesion size, and also in tissue sampled 10 mm away from the lesion. In consideration of this finding, to ensure food safety, we recommend that when a blue mold rot lesion on pear is 5, 10, or 20 mm in diameter, 20, 30, and 40 mm beyond the lesion should be removed, respectively. If a lesion surpasses 30 mm in diameter, the whole pear should be thrown away.

Molecular cloning, mRNA expression and alternative splicing of a ryanodine receptor gene from the citrus whitefly, Dialeurodes citri (Ashmead)

Insect ryanodine receptors are the main targets of diamide insecticides that have highly selective insecticidal activity but are less toxic to mammals. Therefore, these insecticides are ideal for pest control. Ryanodine receptors (RyRs) play a critical role in Ca2+ signaling in muscle and non-muscle cells. In this study, we cloned the complete cDNA (DcRyR) of the RyR from the citrus whitefly, Dialeurodes citri, a serious pest of citrus orchards in China. The open reading frame of RyR is 15,378bp long and encodes a protein with 5126 amino acids with a computed molecular weight of 579.523kDa. DcRyR shows a high amino acid sequence identity to RyRs from other insects (76%–95%) and low identity to those from nematodes and mammals (44%–52%). DcRyR shares many features of insect and vertebrate RyRs, including a MIR domain, two RIH domains, three SPRY domains, four copies of RyR repeat domain, RIH-associated domain at the N-terminus, two consensus calcium-binding EF-hands and six transmembrane domains at the C-terminus. The expression of DcRyR mRNA was the highest in the nymphs and lowest in eggs; DcRyR mRNA was 1.85-fold higher in the nymphs than in the eggs. Among the tissues, DcRyR mRNA expression was 4.18- and 4.02-fold higher in the adult head and thorax than in the abdomen. DcRyR had three alternative splice sites and the splice variants showed body part-specific expression and were developmentally regulated. These results may help investigate target-based resistance to diamide insecticides in D. citri.

Leaf Potential Productivity at Different Canopy Levels in Densely-planted and Intermediately-thinned Apple Orchards

Most apple orchards in the apple production districts in China were densely planted with vigorous rootstocks during the 1980s. These orchards have suffered micro-environmental deterioration and loss of fruit quality because of the closed canopy. Modification of the densely-planted orchards is a priority in current apple production. Intermediate thinning is a basic technique used to transform densely-planted apple orchards in China. Our goal was to provide theoretical basis for studying the effect of thinning on the efficiency of photosynthetically active radiation (PAR), fruit quality, and yield. We measured leaf area, solar radiation, and leaf air exchange at different tree canopy levels and by fitting relevant photosynthetic models, vertical distribution characteristics of leaf photosynthetic potentials and PAR were analyzed in various levels within canopies in densely-planted and intermediately-thinned orchards. Intermediate thinning significantly improved the radiant environment inside the canopies. PAR distribution within the canopies in the intermediately-thinned orchard was better distributed than in the densely-planted orchards. The invalid space under 30.0% of relative photosynthetically active radiation (PARr) was nearly zero in the intermediately-thinned orchard; but minimum PARr was 17.0% and the space under 0.30 of the relative height of the canopy was invalid for photosynthesis in the densely-planted orchard. The leaf photosynthetic efficiency in the intermediately-thinned orchard was improved. Photosynthetic rates (Pn) at the middle and bottom levels of the canopy, respectively, were increased by 7.80% and 10.20% in the intermediately-thinned orchard. Leaf development, which influences photosynthetic potential, was closely related to the surrounding micro-environment, especially light. Leaf photosynthetic potentials were correlated with leaf nitrogen content (Nl) and specific leaf weight (Ml) at various levels of canopies. Compared with the densely-planted orchard, the photosynthetic capacity parameters, such as maximum carboxylation rate (CEmax) and maximum electron transfer rate (Jmax), significantly increased in the intermediately-thinned orchard. Leaf photosynthetic potentials mainly depended on Nl and Nl was closely related to PARr. Leaf photosynthetic potentials and PARr can be assessed using spatial distribution patterns of relative leaf nitrogen content (Nlr).

Long-Term Boron-Excess-Induced Alterations of Gene Profiles in Roots of Two Citrus Species Differing in Boron-Tolerance Revealed by cDNA-AFLP.

Boron (B) toxicity is observed in some citrus orchards in China. However, limited data are available on the molecular mechanisms of citrus B-toxicity and B-tolerance. Using cDNA-AFLP, we identified 20 up- and 52 down-regulated genes, and 44 up- and 66 down-regulated genes from excess B-treated Citrus sinensis and Citrus grandis roots, respectively, thereby demonstrating that gene expression profiles were more affected in the latter. In addition, phosphorus and total soluble protein concentrations were lowered only in excess B-treated C. grandis roots. Apparently, C. sinensis had higher B-tolerance than C. grandis. Our results suggested that the following several aspects were responsible for the difference in the B-tolerance between the two citrus species including: (a) B-excess induced Root Hair Defective 3 expression in C. sinensis roots, and repressed villin4 expression in C. grandis roots; accordingly, root growth was less inhibited by B-excess in the former; (b) antioxidant systems were impaired in excess B-treated C. grandis roots, hence accelerating root senescence; (c) genes related to Ca2+ signals were inhibited (induced) by B-excess in C. grandis (C. sinensis) roots. B-excess-responsive genes related to energy (i.e., alternative oxidase and cytochrome P450), lipid (i.e., Glycerol-3-phosphate acyltransferase 9 and citrus dioxygenase), and nucleic acid (i.e., HDA19, histone 4, and ribonucleotide reductase RNR1 like protein) metabolisms also possibly accounted for the difference in the B-tolerance between the two citrus species. These data increased our understanding of the mechanisms on citrus B-toxicity and B-tolerance at transcriptional level.

Optimized algorithm of sensor node deployment for intelligent agricultural monitoring

This paper searches for a deployment method with minimum sensor nodes to achieve agricultural intelligent monitoring. Because of the various features, topographies and complicated weather conditions, the selection of the location for deploying sensor nodes is difficult, especially in hilly areas. This paper puts forward a sensor node deployment algorithm for agricultural intelligent monitoring based on an optimized theory. It first develops a mathematical model for the node location selection. During the solution process, the features of the locations are of primary concern, as a location with more features is easier to choose than other locations. Next, a theoretical analysis and experimental simulation are carried out. Finally, OASNDFA is used in 3000 mu orange orchards in China. The result demonstrates that OASNDFA could perform relevant monitoring tasks with fewer monitoring nodes.

Loop-Mediated Isothermal Amplification for the Detection of Tylenchulus semipenetrans in Soil.

Tylenchulus semipenetrans is an economically important plant-parasitic nematode occurring in all citrus-producing regions of the world and causing a disease called "slow decline". For the rapid detection of this nematode, a loop-mediated isothermal amplification (LAMP) assay was developed, based on the ribosomal DNA internal transcribed spacer sequence. The optimal condition for the LAMP assay was 65°C for 50 min. The LAMP products were confirmed using conventional polymerase chain reaction (PCR) and restriction analysis with the BamHI enzyme, and by adding SYBR Green I to the LAMP products for visual inspection. The LAMP assay was highly specific for the detection of T. semipenetrans populations from different geographical origins. It was also sensitive, detecting a tenth of the DNA from an individual specimen of T. semipenetrans, which was 10 times more sensitive than conventional PCR. The LAMP protocol was applied to natural citrus rhizosphere soil samples from several orchards in China and the results were fast, sensitive, robust, and accurate. This study is the first to provide a diagnostic tool for T. semipenetrans using DNA extracted directly from citrus rhizosphere soils. This LAMP assay could be used as a practical molecular tool to identify T. semipenetrans and diagnose slow decline disease, even in remote locations.

Effect of Application Ratio of Potassium over Nitrogen on Litchi Fruit Yield, Quality, and Storability

Soils of litchi orchards in China are commonly deficient in nitrogen and potassium. The cultivar Feizixiao litchis planted in a typical acidic upland orchard, which is low in nitrogen and potassium, were used as a subject in field experiments with different ratios of potassium to nitrogen (K2O:N = 0.6, 0.8, 1.0, 1.2, and 1.4). Field experiments were conducted from 2009 to 2012. The effects of K2O:N ratio on the yield, quality, and storability of litchi were investigated and discussed. Results indicated that with the increase of K2O:N ratio, fruit yield initially increased and then decreased, and litchi had the highest yield when K2O:N was 1.2. When K and N fertilizers were applied at the ratio of 1.2, litchi had a better fruit quality with higher vitamin C content, soluble sugar, and soluble solid. With the increase of K2O:N ratio, healthy fruit rate initially increased and then decreased. This rate reached the maximum value when K2O:N was 1.2. Meanwhile, fruit-rotting rate, peel-browning index, cell membrane permeability, and peroxidase (POD) activity decreased at first and then increased and reached the minimum value when the K2O:N ratio was 1.2. Therefore, litchi fruit had the highest yield, better quality, and best storage property when K2O:N was 1.2. Thus, this ratio is recommended for the main litchi production areas in China.

Key minerals influencing apple quality in Chinese orchard identified by nutritional diagnosis of leaf and soil analysis

We investigated the correlation between leaf/soil minerals and fruit quality in apple trees grown in orchards, with the ultimate goal of improving the latter. Leaf mineral nutrients; soil nutrients in the 0–20, 20–40, and 40–60 cm layers; and fruit quality traits in 32 apple orchards in China were monitored for 2 years. Significant factors associated with fruit quality were identified via correlation analysis. An analysis of leaf data revealed that leaf nitrogen (N) and leaf magnesium (Mg) levels were extremely high in 75 and 89% of the orchards, respectively. In the Bohai Gulf region, 94% of the orchards showed significantly higher values than the standard. The soil pH values of the orchards in eastern China like eastern Shandong or Liaoning were lower than 7.0, while the pH values in the Loess Plateau of northwestern China like Shaanxi were much higher than 7. Soil alkali-hydrolyzable N levels in 47% of the orchards were lower than the optimal level of 70 mg kg−1. Generally, the soil alkali-hydrolyzable N levels of orchards in the Bohai Gulf region were significantly higher than those in the Loess Plateau region. The available P levels in the orchards of the Bohai Gulf region were up to three times higher than those of the Loess Plateau region. However, although the available potassium (K) in most orchards was sufficient (51.39–309.94 mg kg−1), leaf K content in 73% of the orchards was low, possibly due to fruit bagging or fruit overload. Approximately 63% of the orchards in Shandong and 29% of the orchards in Shannxi showed leaf Fe deficiencies. In the Loess Plateau, most orchards showed high leaf Ca levels, a strong correlation was observed between leaf and soil phosphorus/potassium (P/K) content and fruit organic acid content. The amounts of fruit soluble sugar or fructose were positively correlated with soil calcium/potassium (Ca/K) levels and leaf calcium/boron (Ca/B) levels in most orchards. The excessive leaf N levels caused by the extensive application of N fertilizers had a negative effect on fruit quality in most apple orchards in China. P, K, Ca, and B were key minerals associated with fruit quality.

Genetic variation in Eucalyptus camaldulensis and E. tereticornis for early growth and susceptibility to the gall wasp Leptocybe invasa in China

The gall wasp Leptocybe invasa is a major insect pest on plantation Eucalyptus in many countries. Since appearing in China in 2007 it has had major impacts on commercial plantations—some commonly planted Eucalyptus varieties have proven particularly susceptible, including hybrids involving Eucalyptus camaldulensis and E. tereticornis parent species. Intra-specific variation within each species for L. invasa susceptibility was examined in two seed source and family trials in southwest of Guangdong. The E. camaldulensis trial included 101 seedlots representing five natural stand and six seed orchard sources which also represented three sub-specific taxa. The E. tereticornis trial included 143 seedlots representing 11 natural stand and four seed orchard sources, including breeding seed orchards in China. Both trials were assessed for susceptibility to L. invasa along with height at age 9 months. Sub-specific taxa within E. camaldulensis differed significantly (P < 0.01) in L. invasa susceptibility but not height or survival; subsp. acuta had the lowest average susceptibility and subsp. simulata and obtusa were of intermediate susceptibility whilst material of uncertain sub-specific taxa from India had the highest average susceptibility. In E. tereticornis regions of origin and seed sources within regions differed significantly (P < 0.01) for both L. invasa susceptibility and height; the region China (all somewhat improved sources) had both the best average height growth and lowest susceptibility whilst the region Australia (all natural stand sources) proved inferior to China for both average susceptibility and height. A strong significant correlation was found between seed source average L. invasa susceptibility and annual rainfall at seed source geographic origin in E. tereticornis (r = −0.873; P < 0.01), implying that seedlots from higher rainfall environments are markedly less susceptible to L. invasa. The equivalent parameter in E. camaldulensis was also strong (r = −0.730) though not significant, perhaps due to having only five data points available. Differences between families within seed sources for both L. invasa susceptibility and height growth were also highly significant (P < 0.01) with the former trait proving moderately to strongly heritable (h i 2 = 0.54 ± 0.40 in E. camaldulensis; 0.52 ± 0.50 in E. tereticornis). Height had low to moderate heritability in both species (h i 2 = 0.11 ± 0.15 and 0.26 ± 0.08 respectively). Tree height and L. invasa susceptibility showed a moderate negative (favourable) genetic correlation in E. camaldulensis (−0.33 ± 0.64) and a moderate to strong negative (favourable) genetic correlation in E. tereticornis (−0.47 ± 0.31). Corresponding phenotypic correlations, though significant, were somewhat weaker (−0.16 and −0.29 respectively), indicating a trend for taller trees to have lower levels of L. invasa susceptibility.

Biological control of insect pests in apple orchards in China

Apple is one of the most important fruits in China, and both yield and quality are greatly affected by insect pests. According to surveys, there are more than 200 species of natural enemies in apple orchards. Few, however, have been closely studied. Major natural enemies including parasitoids, predators and pathogens are briefly described in this review, especially focusing on two parasitoids of Trichogramma dendrolimi Matsumura and Aphelinus mali Haldeman, predatory mites and a pathogenic fungus of Beauveria bassiana (Balsamo) Vuillemin as case studies. Augmentation, one important strategy of biological control, supplements the natural control provided by the existing natural enemy community in apple orchards, and greatly increases their efficiency in controlling pests. Conservation biological control is also widely applied in four major apple-producing areas. Based on habitat manipulation, the ground cover planting system helps regulate the microclimate and enhance the biodiversity of apple orchards, effectively conserving the richness and diversity of beneficial insect species. Certain achievements have been made in the main biological control strategies including successful introduction of some exotic natural enemies such as A. mali and Typhlodromus occidentalis Nesbitt, augmentative production and application of biological control agents such as T. dendrolimi, B. bassiana and Bacillus thuringiensis, and further research in conservation of establishing adaptive ground cover planting patterns to local environment. Challenges, however, still exist. Biological control of insect pests in apple orchards is an important part of integrated pest management programs, requiring more research and application in China.

Biological control of insect pests in litchi orchards in China

This paper describes the current state of the biological control of insect pests in litchi orchards in China. Litchi is growing in importance as a fruit in China and the control of litchi stink bug, Tessaratoma papillosa (Drury) (Hemiptera: Pentatomidae) by the solitary egg endoparasitoid Anastatus japonicus (Ashmead) (Hymenoptera: Eulophidae) is an example of successful classical biological control. This review will cover the current economic status of litchi production in China, the challenges faced in litchi pest management, and possible solutions. The review will also focus on research activities and experiences drawn from many years of experimentation and field work by researchers in an attempt to promote biological control and reduce insecticide use to produce healthier food and a safer environment. Studies on the biology and ecology of T. papillosa and its egg parasitoid A. japonicas will be summarized. The adult longevity and long oviposition period, in combination with the short life cycle, high fecundity, and resistance to harsh environmental conditions make this parasitoid ideal for biological control. The straightforwardness of mass-rearing and easy access to high quality factitious host eggs have made it possible to control T. papillosa with this parasitoid in litchi orchards over large areas in China. Both pest and parasitoid have been thoroughly studied, and A. japonicus has been used in the field for control since late 1960s. The introduction of techniques for mass-rearing of A. japonicus and the parasitoid’s efficacy in controlling T. papillosa once released will be discussed. Finally, we will address the problems currently facing litchi pest management and the importance of conservation biological control in the development and implementation of integrated pest management (IPM).

Biological control of arthropod pests in citrus orchards in China

China has a very long history of biological control in citrus. Hundreds years ago, predatory ants (Oecophylla smaragdina Fabricius) were used to manage pests by Chinese citrus growers. Considerable effort has been placed on the use of biological control in citrus plant landscapes during last three decades. Many scientific studies have now been published, and some additional implementations have already working. In this paper, we review the research, development and application of biological control of citrus insect pests in China. In addition, the importance of biological control for the future control of citrus insect pests is also discussed.

The effects of conservation tillage practices on the soil water-holding capacity of a non-irrigated apple orchard in the Loess Plateau, China

Six tillage practices were studied in an apple orchard located in the Loess Plateau from 2007 to 2009. The objective was to investigate the effects of tillage practices on the soil water-holding capacity in a non-irrigated orchard in China. The results showed that different tillage practices had varied effects on the water-holding properties. Subsoil tillage with straw mulching, plow tillage with straw mulching and no tillage with straw mulching showed a decrease in the soil bulk density and an increase in the soil porosity, soil saturated water content and soil moisture relative to plow tillage in bare soil (i.e., conventional tillage). Among these three tillage practices, the subsoil tillage with straw mulching and no tillage with straw mulching treatments had a significant effect on the soil porosity, soil saturated water content and soil moisture compared to the plow tillage with straw mulching treatment. These results indicate that the subsoil tillage with straw mulching, plow tillage with mulching and no tillage with mulching treatments improved the soil structure and water-holding capacity of the apple orchard. However, the no tillage with bare soil and no tillage with grass treatments increased the soil bulk density and decreased the soil porosity and soil moisture content compared to conventional tillage. This finding demonstrates that no tillage with bare soil and no tillage with grass had adverse effects on the soil structure and water-holding capacity. From the results of this study, we concluded that the subsoil tillage with straw mulching treatment is the optimum practice of the six studied treatments for improving the soil water-holding capacity in this non-irrigated apple orchard in the Loess Plateau of China.