Residues of six pesticides in fresh peach—nectarine fruits after preharvest treatment

One of the key features of the new cultural systems is the control of harmful agents with environment-friendly methods. In this study, the residue levels of chlorothalonil, iprodione, bupirimate, pirimicarb, chlorpyrifos and fenoxycarb in different peach??nectarine cultivars were investigated. It was found that, with the exception of chlorpyrifos, the residue levels of all pesticides were lower than the Maximum Residues Limits (MRLs) in all peach??nectarine cultivars used. The detected levels of chlorpyrifos were higher than the MRLs in the cultivar ??Maria Bianca?? 7?days after application, but in cv. ??Legory Hkcb?? dropped to very low levels 27?days after application. The degradation over time of the above pesticides in fruits was investigated in the peach cv. ??Andross??. The detected residue levels of bupirimate, iprodione, fenoxycarb, chlorpyrifos and pirimicarb in this peach cultivar were much lower than those recommended by the European Union (MRLs) 33, 22, 22, 28, and 63?days, respectively, after application, whereas the residue levels of chlorothalonil were below the limit of detection by the analytical method used. All pesticides showed a reduction over time. When examining the levels of residues of pirimicarb and chlorpyrifos in peaches (cv. ??Andross??) sampled from different parts of the tree canopy, no significant difference was found between samples collected from the top and the middle parts of the canopy; however, residues of pirimicarb were significantly higher in samples collected at the bottom of the canopy. Overall, the pesticide regime gave residue levels much lower than those of MRLs, in all peach??nectarine cultivars. This use of chemicals is in accordance with features of the new cultural systems to produce fruits with no or minimal pesticide residues, in contrast to the conventional system in which pesticide residues are not considered. Attention should however be paid to chlorpyrifos which should be applied at least 27?days before harvest. Factors related to the cultivars and the position of fruits in the tree canopy should be considered when sampling fruits for pesticide residues analysis.     

Is tile drainage water representative of root zone leaching of pesticides?

Given the methods presently available, determination of flux-averaged concentrations of pesticides in structured soils is always a compromise. Most of the available methods entail major uncertainties and limitations. Tile drainage monitoring has several advantages, but the extent to which it is representative of overall leaching has been questioned because it comprises a mixture of water of different origins. This literature review evaluates whether drainage water pesticide concentrations are representative of root zone leaching of pesticides. As there are no reports quantifying the extent to which the flux-averaged concentration of pesticides in drainage water differs from that found between the drains, evidence-based conclusions cannot be drawn. Nevertheless, the existing literature does suggest that the concentration in drainage water does not always correspond to the concentration at drain depth between the drains; depending on the conditions pertaining, the concentrations may be higher or lower. As to whether the flux-averaged concentration of pesticides in drainage water is representative of the interdrain concentration at drain depth it is concluded that (1) the representativeness of drainage water concentrations can be questioned on very well-drained soils and on poorly drained soils with little capacity for lateral transport beneath the plough layer, (2) the conditions provided by relatively porous soils and moderate climatic conditions are conducive to the drainage water concentration being representative and (3) drainage water will be more representative in the case of weakly sorbed pesticides than for strongly sorbed pesticides. Used critically, it is thus believed that drainage water concentrations can serve to characterize the flux-averaged concentration of pesticides at drain depth. However, the use of drainage water for determining average concentrations necessitates thorough investigation and interpretation of precipitation, percolation, drain outflow and concentration dynamics.     

Strigolactones: how far is their commercial use for agricultural purposes?

Strigolactones are a class of natural and synthetic compounds that in the past decade have been exciting the scientific community not only for their intriguing biological properties but also for their potential applications in agriculture. These applications range from their use as hormones to modify and/or manage plant architecture, to their use as stimulants to induce seed germination of parasitic weeds and thus control their infestation by a reduced seed bank, to their use as ‘biostimulants’ of plant root colonisation by arbuscular mycorrhizal fungi, improving plant nutritional capabilities, to other still unknown effects on microbial soil communities. More recently, these compounds have also been attracting the interest of agrochemical companies. In spite of their biological attractiveness, practical applications are still greatly hampered by the low product yields obtainable by plant root exudates, by the costs of their synthesis, by the lack of knowledge of their off‐target effects and by the not yet specified or properly identified legislation that could regulate the use of these compounds, depending on the agricultural purposes. The aim of this article is to discuss, in the light of current knowledge, the different scenarios that might play out in the near future with regard to the practical application of strigolactones. © 2016 Society of Chemical Industry     

The β-tubulin Gene is a Useful Target for PCR-based Detection of an Albino Ophiostoma piliferum Used in Biological Control of Sapstain

The potential of Cartapip, an albino Ophiostoma piliferum, as a biocontrol agent against sapstain in logs has been tested in Germany. To detect the albino strain in field-tested wood, the usefulness of the -tubulin gene as a target region for developing PCR-based assays was evaluated with 102 strains of O. piliferum and 31 strains of other wood-inhabiting species. A partial -tubulin gene sequence of O. piliferum strains from different geographic origins was amplified by PCR and analyzed by restriction enzyme digestions and DNA sequencing. Variation in size and nucleotide sequences was found in intron regions indicating that intraspecific variation is present in the -tubulin gene. Consequently, -tubulin gene-derived PCR methods using PCR–RFLP patterns generated by HinfI and SpeI and sequence-specific primers Cat1 and Cat2, were developed and their specificity for Cartapip was accessed with field-tested logs and lumber. The -tubulin gene-based PCR methods were found to be valuable tools for rapid and reliable identification of Cartapip in field-tested logs and lumber in Germany. Specificity tests against other wood-inhabiting species and wild type O. piliferum strains from diverse nations showed that the Cat1 and Cat2 primers have potential to be used in other European countries, New Zealand, Alberta and British Columbia.     

How low can you go? Estimating impacts of reduced pesticide use

Recent research has suggested that a high proportion of farms can dramatically reduce pesticide applications without reducing crop yields or farm profits. Yet this research has made estimation choices that may systematically bias downwards estimates of the productivity and profitability of pesticides. Fifty years of agricultural economics research provides lessons about how to avoid pitfalls in estimating pesticide productivity. Carefully executed econometric studies have found evidence of overuse, underuse, and near‐optimal use of pesticides in different cropping systems. There are now standard methods to test and correct for sources of biases (either upward or downward) in estimates of pesticide productivity. Ignoring these lessons and methods can seriously bias estimates of the potential for reducing pesticide use at little or no economic cost. © 2018 Society of Chemical Industry     

Transgenic crops and beyond: how can biotechnology contribute to the sustainable control of plant diseases?

Disease resistance is without argument the best technological approach to control diseases in plants since no management input is required by the grower once the resistant variety has been planted. The biggest problems in using disease resistance lie in the facts that effective sources of resistance are not available for many important diseases, especially those caused by necrotrophic pathogens; and that pathogen populations adapt to the utilisation of novel sources of resistance, most notably for air-borne biotrophic pathogens. Several biotechnological approaches have been developed to produce disease resistant plants, the most recent known as NBT – New Breeding Technologies. This review focuses on recent advances in those technologies which adapt the knowledge obtained using molecular genetic approaches for the study of plant-microbe interactions to combat plant diseases.     

The spread of the fall armyworm Spodoptera frugiperda in Africa—What should be done next?

Journal of Plant Diseases and Protection - The following text summarizes the different perspectives of presenters participating in the section Plant Protection in the Tropics and Subtropics, 61st...     

Determinants of farmers’ decisions on pesticide use in oriental tobacco: a survey of common practices

Information about pesticide use and perceptions of their risks among farmers is important for identifying problems associated with pest-control decisions and developing appropriate management practices in given crops. In tobacco, a plant sensitive to many pests and diseases, such information is lacking. The patterns of pesticide use in oriental tobacco, as well as the most important factors for farmers’ decisions relating to chemical pest control were studied among randomly selected farmers in northern Greece on the basis of self-reported information acquired through a pre-tested questionnaire. High reliance of farmers on pesticides and field use of all well-known classes of chemical pesticides were reported. While all the active ingredients reported were registered for pest control in tobacco, they differed considerably in terms of toxicity. A normal cropping season received at least 14–16 pesticide applications for soil disinfection, pest control, and weed control. Most farmers stated that they usually spray chemicals on a calendar basis or on the first appearance of a pest. Efficacy on target pests and market price of the pesticide products to be used were the most important criteria for selection of pesticides, i.e. products that are considered to be highly effective and/or that are cheap are more likely to be selected. Better-educated and more experienced farmers were found to pay more attention to environmental safety and pesticide toxicity. Most farmers felt that pesticide use can reduce crop damage by more than 75%, assuring high yields. Main determinants of pesticide use were primarily the fear of severe yield and economic losses and the doubts about the effectiveness and the correct implementation of alternative pest-control methods. Pesticide use could be reduced by exposing farmers to improved pest-control practices such as site-specific integrated pest management.     

Regulation of semiochemicals — global aspects

A general awareness of environmental concerns, an increasing chemophobic populace and the reregistration of pesticides, both in the United States and in the European Community, with the concomitant loss of many pest control chemicals through cancellation of their registrations has provided an impetus for the research, development and commercialization of alternative, environmentally benign and safer plant protection products. Amongst such alternatives are pheromones, a class of semiochemicals whose commercial development is being championed by a neophyte industry made up, for the most part, of undercapitalized entrepreneurial companies for whom the major hurdle to the introduction of products into the marketplace is the time and cost required to complete the regulatory process. That pheromones and other semiochemicals are different from chemical insecticides has been recognized by several national regulatory agencies and the Food and Agricultural Organization of the United Nations [FAO]. Although these regulatory authorities have made significant contributions towards reducing the data requirements and hence the cost of pheromone product registration, it is widely felt that more can, and should be done to further expedite and harmonize pheromone regulation. The adoption of a structure/activity approach to the evaluation of health and environmental risks for types of lepidopteran pheromones together with a 90-day evaluation time-frame. This approach would satisfy the regulatory authorities' risk assessment for food and environmental safety while substantially reducing the cost to the registrants and expediting the registration. It is proposed that this approach be tested first in an actual product application to the US Environmental Protection Agency [EPA], with subsequent applications to other regulatory authorities. A database which could be modified already exists within the EPA and as other databases are incorporated, and shared with other regulatory authorities, harmonization of the regulation of pheromones may be possible. The application of this structure/activity approach should be expanded to other types of semiochemicals as the database is enlarged.     

Control of Farm Flies in Malta—III. The effect of residual insecticide sprays on Musca domestica and Stomoxys calcitrans in the Maltese Islands

Abstract

Field trials to control flies on animal farms in Malta were held during 1973 with tetrachlorvinphos, iodofenphos, fenitrothion, bioresmethrin and dimethoate applied as cover sprays to walls and ceilings. Results were assessed by fly population counts (using sticky fly-paper traps exposed for 24 h at weekly intervals), bioassay tests and visual assessments of flies on individual farms. Tetrachlorvinphos gave the best results and was applied as a cover spray on 12 large animal farms in the northwestern part of Gozo during 1974. Results, using the same criteria as in the 1973 trials, indicated that, although high fly mortality was observed and deposits on walls remained toxic throughout the season, effective control of houseflies and stableflies was not achieved.

It is suggested that residual spraying alone on the larger animal farms was not sufficient to overcome the breeding potential of the flies and that a residual spraying campaign could only be successful if more extensively applied and supplemented by a comprehensive programme of farm hygiene improvement.     

The more we do,the less we gain? Balancing effort and efficacy in managing the Solidago gigantea invasion

Developing invasive plant management strategies is an important task in modern ecology, conservation biology and land management. Solidago gigantea is considered a problematic invader in Europe and Asia, where it forms dominant stands that can decrease species diversity. There is, therefore, an urgent need for effective management to reduce S. gigantea infestations and their negative impacts. We examined the efficacy of multiple approaches to S. gigantea management in Hungary. In our study, we evaluated the effect of several long-term management techniques such as grazing, mowing and periodic flooding on the invader's density as well as native community diversity. In addition, we investigated the short- and long-term effects of mowing combined with other treatment options, to estimate the influence of increased management intensity. Our results indicate that all tested management techniques had negative impacts on S. gigantea density. Short-term mowing did not appear to improve species diversity in the resident community; however, all long-term options improved species diversity. Moreover, combining treatments with mowing varied in its effectiveness; mowing once increased the efficacy of flooding, but decreased the efficacy of grazing, while mowing twice decreased efficacy of flooding. We suspect this is due to the increased intensity of disturbance, which does not allow for the natural recovery of communities, and after management ceases, invasion is able to re-occur. Our results indicate that for effective management, we need to combine management options which act via different mechanisms, leading to cumulative positive effects on the resident community when applied at moderate levels.     

Phenological adaptation in weeds—an evolutionary response to the use of herbicides?

The possibility of phenological adaptation in weed species is discussed in terms of an evolved response to herbicide use. Weed populations often exhibit heritable variation in life history traits that may reflect phenological adaptations. Approaches to assessing ‘adaptedness’ are discussed. Selection for seed dormancy in a grass weed is considered through life history analysis. It is concluded that too little is known about both life histories and fitness of weed species in varying environments for conclusions to be drawn concerning phenological adaptation for use in herbicide resistance management. ©1997 SCI     

Pest Complex of Sunflower — A Bibliography

Abstract

Pests of sunflower are tabulated. The damaging stage of the insect, the part of the plant attacked and the importance of the pest indicated. The table of insect pests is cross-indexed to a comprehensive bibliography.     

Addition of Oil to Pesticide Sprays—Downwind Movement of Droplets

Abstract

An investigation of the downwind movement, distribution and distance covered from a spray source of insecticide to which oil is an additive. Vertical targets were placed at distances ranging from 0.25 to 64 m and at three heights, 35, 70 and 150 cm, downwind from the spray source. There was an increase in the number of droplets arriving at the targets when 20% oil was added to the aqueous solution. An even greater increase was seen when oil only was sprayed; these results are compared with sprays containing water and a 5% wetting agent. Droplet size and air turbulence effects are discussed, as is the faster evaporation of water-based sprays. The work was carried out on rhododendron leaves using Saturn yellow fluorescent dye as a tracer using a Micron Mini-ULVA and Ulvapron oil. A comparison is made with the use of Shell oil A and Risella 33 used by pest workers.     

Does agricultural use of azole fungicides contribute to resistance in the human pathogen Aspergillus fumigatus?

Azole resistance in human fungal pathogens has increased over the past twenty years, especially in immunocompromised patients. Similarities between medical and agricultural azoles, and extensive azole (14α‐demethylase inhibitor, DMI) use in crop protection, prompted speculation that resistance in patients with aspergillosis originated in the environment. Aspergillus species, and especially Aspergillus fumigatus, are the largest cause of patient deaths from fungi. Azole levels in soils following crop spraying, and differences in sensitivity between medical and agricultural azoles (DMIs), indicate weaker selection in cropping systems than in patients receiving azole therapy. Most fungi have just one CYP51 paralogue (isozyme CYP51B), but in Aspergillus sp. mutations conferring azole resistance are largely confined to a second paralogue, CYP51A. Binding within the active centre is similar for medical and agricultural azoles but differences elsewhere between the two paralogues may ensure selection depends on the DMI used on crops. Two imidazoles, imazalil and prochloraz, have been widely used since the early 1970s, yet unlike triazoles they have not been linked to resistance in patients. Evidence that DMIs are the origin, or increase the frequency, of azole resistance in human fungal pathogens is lacking. Limiting DMI use would have serious impacts on disease control in many crops, and remove key tools in anti‐resistance strategies. © 2017 Society of Chemical Industry     

What is the evidence for sexual reproduction of Phytophthora infestans in Europe?

The biology of late blight of potato and tomato, caused by Phytophthora infestans, changed when sexual reproduction by the pathogen became possible in many parts of the world, including Europe. In northern Europe, especially Scandinavia, there is increasing evidence that the pathogen is reproducing sexually on a regular basis, although in other regions further south or to the west it appears to reproduce primarily in a clonal manner. The presence of both mating types, the production of viable oospores, and observations of fields with soilborne sources of inoculum are consistent with sexual reproduction. Studies with different marker systems have revealed a population structure without any dominating clonal lineages in Scandinavia, and that is most easily explained by sexual reproduction. Phytophthora infestans recovered from the soil can also be linked to parental genotypes using likelihood‐based methods when codominant markers are used. A synthesis of all the available data points to a second centre of sexual reproduction in northern Europe.