Driving factors of the communities of phytophagous and predatory mites in a physic nut plantation and spontaneous plants associated

Seasonal changes in climate and plant diversity are known to affect the population dynamics of both pests and natural enemies within agroecosystems. In Brazil, spontaneous plants are usually tolerated in small-scale physic nut plantations over the year, which in turn may mediate interactions between pests and natural enemies within this agroecosystem. Here, we aimed to access the influence of seasonal variation of abiotic (temperature, relative humidity and rainfall) and biotic (diversity of spontaneous plants, overall richness and density of mites) factors on the communities of phytophagous and predatory mites found in a physic nut plantation and its associated spontaneous plants. Mite sampling was monthly conducted in dicotyledonous and monocotyledonous leaves of spontaneous plants as well as in physic nut shrubs over an entire year. In the dry season there was a higher abundance of phytophagous mites (Tenuipalpidae, Tarsonemidae and Tetranychidae) on spontaneous plants than on physic nut shrubs, while predatory mites (Phytoseiidae) showed the opposite pattern. The overall density of mites on spontaneous plants increased with relative humidity and diversity of spontaneous plants. Rainfall was the variable that most influenced the density of mites inhabiting physic nut shrubs. Agroecosystems comprising spontaneous plants associated with crops harbour a rich mite community including species of different trophic levels which potentially benefit natural pest control due to increased diversity and abundance of natural enemies.     

Co-composting of physic nut (Jatropha curcas) deoiled cake with rice straw and different animal dung

To address the dispensing of this growing volume, a study on utilization of jatropha (Jatropha curcas) deoiled cake through compost production was carried out. The deoiled cake was composted with rice straw, four different animal dung (cow dung, buffalo dung, horse dung and goat dung) and hen droppings in different proportions followed by assessment, and comparison of biochemical characteristics among finished composts. Nutrient content in finished compost was within the desired level whereas metals such as copper, lead and nickel were much below the maximum allowable concentrations. Although a few finished material contained phorbol ester (0.12 mg/g), but it was far below the original level found in the deoiled cake. Such a study indicates that a huge volume of jatropha deoiled cake can be eliminated through composting.     

Potential of the predatory mite Amblydromalus zannoui to control pest mites on Jatropha curcas

Amblydromalus zannoui Sourassou, Sarmento and Moraes is a phytoseiid mite of the limonicus group described from central Brazil from leaves of physic nut, Jatropha curcas L. (Malpighiales: Euphorbiaceae), a plant potentially useful as a source of biofuel. This plant is often attacked by the mites Polyphagotarsonemus latus (Banks) (Prostigmata: Tarsonemidae) and Tetranychus bastosi Tuttle, Baker and Sales (Prostigmata: Tetranychidae). The objectives of this work were to evaluate the predation rate of A. zannoui on those phytophagous mites, to assess its life cycle on these prey and on pollen of Ricinus communis L. (Euphorbiaceae), and to determine its attraction to physic nut leaves infested by P. latus or T. bastosi. Amblydromalus zannoui attacked more nymphs and adults than eggs of P. latus, and more eggs and larvae than adults of T. bastosi. The life table parameters suggest that A. zannoui performs better on P. latus (r_m: 0.20, R_o: 18.77; λ: 1.23) and pollen (r_m: 0.18, R_o: 23.32, λ: 1.18). The predator seems to be attracted to plants with P. latus, but attraction was not clear cut for plants with T. bastosi. The results suggested that A. zannoui is a potential control agent to be used against P. latus on physic nut plants, and that R. communis pollen can be used as supplementary food to maintain the predator population in the absence of prey.

     

Joint analysis of phenotypic and molecular diversity provides new insights on the genetic variability of the Brazilian physic nut germplasm bank

The genetic variability of the Brazilian physic nut (Jatropha curcas) germplasm bank (117 accessions) was assessed using a combination of phenotypic and molecular data. The joint dissimilarity matrix showed moderate correlation with the original matrices of phenotypic and molecular data. However, the correlation between the phenotypic dissimilarity matrix and the genotypic dissimilarity matrix was low. This finding indicated that molecular markers (RAPD and SSR) did not adequately sample the genomic regions that were relevant for phenotypic differentiation of the accessions. The dissimilarity values of the joint dissimilarity matrix were used to measure phenotypic + molecular diversity. This diversity varied from 0 to 1.29 among the 117 accessions, with an average dissimilarity among genotypes of 0.51. Joint analysis of phenotypic and molecular diversity indicated that the genetic diversity of the physic nut germplasm was 156% and 64% higher than the diversity estimated from phenotypic and molecular data, respectively. These results show that Jatropha genetic variability in Brazil is not as limited as previously thought.     

Natural enemies of mass-reared predatory mites (family Phytoseiidae) used for biological pest control

Predatory mites of the family Phytoseiidae are valued natural enemies that provide effective pest control in greenhouses and on agricultural crops. Mass-reared phytoseiids are occasionally associated with microorganisms and although their effects are not always apparent, some are pathogenic and reduce host fitness. Invertebrate pathogens are encountered more frequently in mass production systems than in nature because rearing environments often cause overcrowding and other stresses that favour pathogen transmission and increase an individual's susceptibility to disease. Although unidentified microorganisms have been reported in phytoseiids, bacteria and microsporidia have been detected with considerable frequency. The bacterium Acaricomes phytoseiuli is associated with an accumulation of birefringent crystals in the legs of Phytoseiulus persimilis and infection reduces the fitness of this spider mite predator. Wolbachia, detected in Metaseiulus occidentalis and other phytoseiids, may cause cytoplasmic incompatibilities that affect fecundity. However, the effects of Rickettsiella phytoseiuli on P. persimilis are unknown. Microsporidia are spore-forming pathogens that infect Neoseiulus cucumeris, N. barkeri, M. occidentalis and P. persimilis. Microsporidia cause chronic, debilitating disease and these pathogens often remain undetected in mass-rearings until a decrease in productivity is noticed. Routine screening of individuals is important to prevent diseased mites from being introduced into existing mass-rearings and to ensure that mite populations remain free from pathogens. The means by which bacteria and microsporidia are detected and strategies for their management in phytoseiid mass-rearings are discussed.     

Species composition and arthropod pest feeding of phytoseiid mites in a Japanese pear greenhouse

A population survey of spider mites and phytoseiid mites was conducted on Japanese pear leaves in a greenhouse. For the survey, the method to estimate phytoseiid mite species composition using quantitative sequencing was modified to be applicable for phytoseiid mite species inhabiting in the greenhouse. Results show the dominant appearance of Neoseiulus californicus (McGregor), Neoseiulus womersleyi (Schicha), and Neoseiulus makuwa (Ehara) from the end of June to late September and their contribution in spider mite control. PCR-based method to detect the ribosomal internal transcribed spacer (ITS) sequences of spider mites from phytoseiid mites was developed. The method shows sensitivity to detect the ITS sequences of Tetranychus urticae Koch from single N. californicus adult at 168 h after ingestion of the spider mite. PCR-based method to detect the cytochrome c oxidase subunit I sequences of several arthropod pests belonging to Hemiptera, Thysanoptera, and Acari from phytoseiid mites was also developed. Results show that phytoseiid mites prey on Eriophyes chibaensis (Kadono) and Aphis gossypii (Glover), in addition to spider mites.     

Competitive interactions among four pest species of earth mites (Acari: Penthaleidae)

Earth mites are major winter pests of a variety of crops and pastures in southern Australia. Competition between four earth mite species was investigated using field and shadehouse experiments. The influence of different plant hosts on the frequency and intensity of competitive interactions also were examined. This information is important, because control attempts that eradicate one species of mite could be directly followed by an increase in abundance of another earth mite species. There were strong effects of intraspecific competition on the reproductive rate of species, while interspecific interactions between Halotydeus destructor (Tucker) and Penthaleus species and between the three Penthaleus species also were detected. Competitive abilities were altered on the different plant types. On pasture, the competitive advantage swayed between Penthaleus major (Dugés), H. destructor, and Penthaleus falcatus (Qin & Halliday). Penthaleus sp. x was the strongest competitor in a mixture of wheat, Triticum aestivum (L.), and oats, Avena sativa (L.), whereas on canola, Brassica napus (L.), and bristly ox-tongue, Picris echioides (L.), P. falcatus, and H. destructor were superior competitors. These results suggest that competition is a strong force influencing the abundance of earth mites in the field and that host plant factors are important in shaping the type of interactions. This highlights the importance of identifying mite species when considering control options and suggests that effective control recommendations need to be developed for each individual species.     

Suitability of physic nut (Jatropha curcas L.) as single host plant for the leaf-footed bug Leptoglossus zonatus Dallas (Het., Coreidae)

The leaf-footed bug Leptoglossus zonatus (Dallas) (Het., Coreidae) was reared in Nicaragua on a diet consisting of unripe physic nut ( Jatropha curcas L., Euphorbiaceae) fruit only. The suitability of this host plant is described by the mortalities in the developmental stages from egg to adult, which are presented in a life table, and the durations of the different stages. Pre-oviposition time, number of ovipositions and total number of eggs per female are given. Biometric measurements of all instars were made. Protein, oil and water content of fresh physic nut fruit were measured throughout a whole year. The results show that physic nut is a highly suitable host plant, which can maintain populations of this insect pest throughout the whole year as fruit are constantly present with only little fluctuation in their nutritional quality.     

Dispersal patterns of pest earth mites (Acari: Penthaleidae) in pastures and crops

Control methods in pest earth mites and other mites often depend on low dispersal rates, yet there are no experimental estimates of these rates. To rectify this, adult movement rates were estimated in the earth mite Halotydeus destructor Tucker and the winter grain mite, Penthaleus major (Duges), using mark-release-recapture techniques. Mean square dispersal distances were used to estimate diffusion coefficients. In pasture, coefficients were in the range 0.3-1.3 for these species. This suggests that 90% of the population moves < 5-11 m in a 10-d period, or 7-16 m within their adult lifetime. Releases of mites in adjacent pea/wheat crops indicated directional movement toward the more favored pea host. However, there was no directional movement when adjacent plots of peas and lupins were compared, even though lupins are poor hosts. These results indicate that broad border sprays or border culturing will be needed to prevent mite movement from adjacent paddocks.     

Predatory mites of the Phytoseiidae family in integrated and ecological pest management systems in orchards in Slovakia

During 2005–2007, 1,332 individuals of predatory mites were found in integrated and ecological orchards in Slovakia. Seven predatory mite species of the family Phytoseiidae, namely Phytoseius echinus, Phytoseiulus macropilis, Euseius finlandicus, Typhlodromus pyri, Paraseiulus triporus, Amblyseius andersoni and Neoseiulella tiliarum, were identified. Out of 1,332 individuals, 519 (39.0%) were found in the apple orchards and 813 (61.0%) in the pear orchards. Out of all predatory mite individuals, 460 (34.5%) were found in the integrated pest management system (IPM) and 872 (65.5%) in the ecological pest management system (EPM). In apple orchards, P. echinus was dominant and constituted 49.3% of the detected mites. In pear orchards, E. finlandicus was dominant and constituted 48.7% of the detected mites. Typhlodromus pyri was also abundant, especially in pear orchards. The other species were less abundant.     

作物重要叶螨综合防控技术研究与示范推广

叶螨是一类重要的农业有害生物,近年来,在我国各地危害呈上升趋势,严重制约了粮棉果蔬等产业的可持续健康发展。在公益性行业(农业)科研专项叶螨项目资助下,课题组明确了东北果园、华北果园和北方蔬菜田叶螨种群消长规律,开展了朱砂叶螨Tetranychus cinnabarinus(Boisduval)、二斑叶螨Tetranychus urticae Koch和柑橘全爪螨Panonychus citri(McGregor)的种群遗传结构研究,在共生菌对叶螨生殖影响方面取得了重要进展,在生物防治和药剂防治方面已取得可喜的成绩,组建了3个叶螨的综合防治技术体系,示范面积共达3万多亩。     

Competitive interactions between two pest species of earth mites, Halotydeus destructor and Penthaleus major (Acarina: Penthaleidae)

Competition was investigated between two pest earth mite species, Penthaleus major Dugés and Halotydeus destructor Tucker, which occur sympatrically and are major pests of southern Australian pastures and crops. Three geographically separate pasture sites within Victoria were sampled monthly. Abundance patterns were similar across sites in that there was a marked increase in number of H. destructor in spring. Field competition plots were set up on pasture. In the first season, H. destructor had a negative effect on P. major but not vice versa. During the summer, diapause and ensuing generation, density-dependent (intraspecific) competition was evident in P. major but not in H. destructor. The interspecific asymmetry was switched in the following season, with P. major dominating most plots and having a negative effect on the reproductive output of H. destructor. These findings indicate that suppression or eradication of one species of earth mite from pastures may result in another species increasing in relative abundance.     

Negative interactions between Willamette mites and Pacific mites: possible management strategies for grapes

Willamette mites and Pacific mites are often negatively associated on grape vines. In particular, vineyards with early season infestations of the less damaging Willamette mite rarely develop high populations of the economically important Pacific mite. We report that Willamette mites had a negative effect on Pacific mite populations in both the greenhouse and field. In some experiments, the negative effect was more pronounced when vines had been damaged by previous feeding of Willamette mites and in other experiments concurrent feeding by both mite species was necessary to demonstrate a negative effect. Therefore, we cannot conclude if the mechanism of the response involves induced resistance against Pacific mites, more conventional interspecific competition, or both. Since predators were uncommon in our experiments, predator build up on Willamette mites did not cause the low Pacific mite population that we observed, although this mechanism may be important in many vineyards. Further, larger scale experiments are necesary to determine if growers can introduce Willamette mites to help control Pacific mites.

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Résumé E. willametti et T. pacificus sont souvent antagonistes dans les vignobles. En particulier, dans les vignobles contaminés tôt dans la saison par E. willametti,-dont les dégâts sont moins conséquents-, on observe rarement des populations élevées de T. pacificus, dont les dégâts sont économiquement importants. Nous avons constaté que E. Willametti a réduit les populations de T. pacificus, tant en serres qu'à l'extérieur. Dans quelques cas, l'effet antagoniste était plus marqué quand les vignes avaient été préalablement endommagées par l'alimentation de E. willametti. Dans d'autres expériences, la compétition alimentaire entre les deux espèces d'acariens était nécessaire pour produire un effet antagoniste. Cependant, nous ne pouvons pas en conclure que la réponse implique une résistance induite contre T. pacificus, ou une compétition interspécifique plus classique, ou les deux à la fois. Puisque les prédateurs étaient rares dans nos expériences, une explosion des prédateurs sur E. willametti n'a pu provoquer le faible niveau de population observé avec T. pacificus, bien qu'un tel méchanisme puisse être important dans certains vignobles. Quoi qu'il en soit, des expériences à plus grande échelle sont nécessaires pour déterminer si les vignerons peuvent introduire Eotetranychus willametti afin de limiter les populations de Tetranychus pacificus.

     

Genetic analysis for physical nut traits in almond

Almond breeding is increasingly taking into account kernel quality as a breeding objective. Although information on nut and kernel physical parameters involved in almond quality has already been compiled, the genetic control of these traits has not been studied. This genetic information would improve the efficacy of almond breeding programs. A linkage map with 56 simple-sequence repeat markers was constructed for the “Vivot” × “Blanquerna” almond population showing a wide range of variability for the physical parameters of nut and kernel. A total of 14 putative quantitative trait loci (QTLs) controlling these physical traits were detected in the current study, corresponding to six genomic regions of the eight almond linkage groups (LG). Some QTLs are colocated in the same region or shared the same molecular markers, in a manner that reflects the correlations between the physical traits, as well as with the chemical components of the almond kernel. The limit of detection values for any given trait ranged from 2.06 to 5.17, explaining between 13.0 and 44.0 % of the phenotypic variance of the trait. This new genetic information needs to be taken into account when breeding for physical traits in almond. Increases in the positive quality traits, both physical and chemical, need to be considered simultaneously whenever they are genetically independent, even if they are negatively correlated. This is the first complete genetic framework map for physical components of almond nut and kernel, with 14 putative QTLs associated with a large number of parameters controlling physical traits in almond.