Analysis of the relationship between parameters of resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight and <Emphasis Type="Italic">in vitro</Emphasis> tolerance to deoxynivalenol of the winter wheat cultivar WEK0609 <Superscript>®</Superscript>

Fusarium head blight (FHB) symptom development, relative spikelet weight (RSW), fungal DNA (FDNA) and deoxynivalenol (DON) content of grain was assessed in the FHB resistant winter wheat cv. WEK0609 and the FHB susceptible cv. Hobbit sib, and among doubled haploid progeny lines (DHLs) developed from a cross between these cultivars. In addition, the relationship between FHB resistance traits and germination on DON-containing medium (in vitro DON tolerance (IVDT)) was also investigated to assess the possibility of using this test as in vitro method of screening for FHB resistance in this cultivar. Analysis indicated that WEK0609 resistance significantly reduced symptom development, yield loss and the FDNA and DON content of grain relative to Hobbit sib. Although both the DON and FDNA content were greater in susceptible than in resistant progeny lines, the ratio of DON to FDNA decreased with increasing susceptibility. The resistance derived from WEK0609 appears to have a greater effect on colonisation of the grain by the fungus than on the accumulation of DON within the grain. In vitro tolerance to DON does not appear to relate to FHB resistance in WEK0609 and thus does not provide a means of selecting for FHB resistance derived from this cultivar.     

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     

Effect of polyploidisation on the response of apple (<Emphasis Type="Italic">Malus</Emphasis> × <Emphasis Type="Italic">domestica</Emphasis> Borkh.) to <Emphasis Type="Italic">Venturia inaequalis</Emphasis> infection

Spinach is one of the most nutritious green-leaf vegetables. In the spinach production, diseases cause a significant loss in both yield and quality. Improving disease resistance is one of the major challenges in spinach breeding. Arabidopsis nucleoporin CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5 (CPR5) functions as a negative regulator of plant cell death and immunity as cpr5 mutant exhibits spontaneous cell death and heightened immunity. In addition, CPR5 play a role in trichome development as the majority of cpr5 mutant trichomes are branchless whereas wild type trichomes are often three-branched. In the spinach genome, we identified a homolog of Arabidopsis CPR5, referred to as Spinacia oleracea CPR5 (SoCPR5). To investigate the function of SoCPR5, we introduced SoCPR5 into Arabidopsis cpr5 mutant. Our data showed that both spontaneous cell death and heightened immunity were suppressed in the SoCPR5-transgenic cpr5 mutants, verifying that SoCPR5 functions as its Arabidopsis counterpart in plant cell death and immunity. SoCPR5 also fully restored wild type trichome phenotype of the cpr5 mutant. Our study therefore indicates that the function of SoCPR5 is conserved between plant species and SoCPR5 can be applied for genetic manipulation of plant immunity in spinach.     

Multiple facets of response to fungicides – the influence of azole treatment on expression of key mycotoxin biosynthetic genes and candidate resistance factors in the control of resistant <Emphasis Type="Italic">Fusarium</Emphasis> strains

The spread of fungicide resistant and/or tolerant phytopathogenic fungi is an important factor affecting crop protection. However, the mechanisms of fungal response to fungicide application are not entirely characterised. In particular, the contribution of previously known resistance factors and the final influence of fungicide treatments on metabolism of surviving mycelia (e.g. mycotoxin increased release and biosynthesis potentially causing contamination of the crops) merit investigation, in order to improve future molecular diagnostics of fungicide resistant strains. The performed experiments have shown distinct expression changes for homologs of a known fungicide resistance factor Flr1 (yeast; DHA1 family of major facilitator superfamily transporters) after azole application in cultured fusaria. Two distantly related homologs of that gene were selected, based on the unsupervised clustering and phylogenetic analysis of transporter sequences. One of these (FGSG_02865), was found to occur across the Fusarium sambucinum complex (F. graminearum, F. culmorum, F. cerealis) and was upregulated starting 24 h after fungicide treatments. This delayed response may point to possible involvement of DHA1 antiporters in a generalised response to stress resulting from fungicide treatment. Additional expression profiling was conducted for the mycotoxin biosynthetic genes (trichothecene and zearalenone gene clusters) in strains of Fusarium sambucinum complex cereal pathogens. The expression changes, when subjected to treatment with the fungicides (flusilazole, carbendazim), show that even an effective treatment (in this study, the benzimidazole fungicide carbendazim) applied to the grown mycelium, can result in enhanced activation of mycotoxin biosynthetic genes in fungal cells which survive the treatment. Our results suggest that increased mycotoxin contamination can be strongly influenced not only by the amount or the type of antifungal compound, but also the timing of fungicide exposition (stage of infection).     

Susceptibility of eight Algerian olive cultivars to <Emphasis Type="Italic">Bactrocera oleae</Emphasis> infestation – a pomological and nutritional quality perspective

The olive fruit fly, Bactrocera oleae (Rossi), is the major olive pest in the Mediterranean Basin, being responsible for high losses in olive production. The objective of this work was to study the influence of B. oleae infestation on the pomological parameters and nutritive value (lipids, proteins, carbohydrates and ash) of eight olive cultivars (Abani, Aellah, Blanquette de Guelma, Chemlal, Ferkani, Limli, Rougette de Mitidja and Souidi) from Algeria. The results displayed different degrees of susceptibility of the studied cultivars to this pest. Fruit size (weight) and the Fruit weight / stone weight ratio are significantly correlated with the attack. The statistical treatment of the results (PCA and HAC) highlighted different behaviors from the cultivars, concerning the attack. There are some cultivars more susceptible, being the nutritional value also affected. The lipid and protein contents were positively correlated with the attack and the carbohydrates negatively, suggesting a careful choice by the B. oleae. Ovipositional preference of olive fruit fly females and the success of larval development in different olive cultivars are crucial to establishing new approaches in Integrated Pest Management (IPM) against this pest.     

Effects on the aphid parasitoid <Emphasis Type="BoldItalic">Aphidius ervi</Emphasis> of an insecticide (Plenum<Superscript>®</Superscript>, pymetrozine) specific to plant-sucking insects

The use of a selective insecticide is highly recommended for Integrated Pest Management programs. Plenum (a.i.: pymetrozine; Syngenta Agro), a systemic insecticide, is regarded as a good candidate for use in situations where plant-sucking insects have to be controlled and where natural enemies can play a substantial role as biological control agents. In this context, the effects of Plenum on a host–endoparasitoid relationship were investigated. Potato aphids Macrosiphum euphorbiae were reared for 4 days on an artificial diet supplemented with a low concentration of Plenum (sublethal concentration inducing 15% aphid mortality) before parasitization by the endoparasitoid Aphidius ervi. The development of A. ervi larvae was negatively affected, especially during the early stages of development, and the sex ratio of the progeny was strongly male-biased. Moreover, the host-choice experiment showed that A. ervi was not able to discriminate between control and Plenum-contaminated aphids. These results show that Plenum may not be as selective as it was previously thought to be, and the observed effects need to be considered when developing IPM systems.     

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.     

Integration of Calneem® oil and parasitoids to control <Emphasis Type="BoldItalic">Cadra cautella</Emphasis> and <Emphasis Type="BoldItalic">Corcyra cephalonica</Emphasis> in stored grain cereals

The compatibility and protectant potential of Calneem® oil derived from the neem tree Azadirachta indica and two parasitoids, Habrobracon hebetor and Venturia canescens, for the control of the rice moth Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) and the tropical warehouse moth Cadra cautella Walker (Lepidoptera: Pyralidae) in stored rice and wheat, were evaluated in the laboratory. Calneem® oil (= neem oil) is a biopesticide produced, registered and marketed in Ghana by AQUA AGRIC Community Projects (AACP/Caldor Ghana Ltd., Tema). It contains 0.3% azadirachtin as its major active ingredient. The oil was emulsified with water using 0.07% soap. Fourth instar moth larvae were held in grain treated with neem oil only, grain treated with one of the parasitoids only, grain treated with a combination of neem and one of the parasitoids, and a control with untreated grain. Neem oil was applied at concentrations from 5,000 to 30,000 ppm. All samples were kept in growth cabinets maintained at 25°C and 65–70% r.h. Adult emergence was recorded after 4 weeks. Parasitoid or neem treatments alone reduced the emergence of C. cephalonica and C. cautella. In general, parasitoid releases were as effective as a combination of neem oil and parasitoids. At the lowest dose, 5,000 ppm, the combination of neem and parasitoid was more effective than the neem alone. The number of adults of H. hebetor and V. canescens that emerged in rice containing either parasitoids alone or in combination with neem oil was similar. This indicates minimal or no adverse effect of neem oil on the two parasitoids. It is thus possible to incorporate neem oil in a well-designed pest management program with parasitoids.     

Functional response of <Emphasis Type="Italic">Geocoris ochropterus</Emphasis> Fieber (Hemiptera: Geocoridae) to different egg densities of <Emphasis Type="Italic">Helicoverpa armigera</Emphasis> (Hübner) (Lepidoptera: Noctuidae)

The biology and predatory efficiency of Geocoris ochropterus Fieber (Hemiptera: Geocoridae) has been studied extensively against many insect pests, but information on functional response of different stages of G. ochropterus to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is lacking so far. The functional response of different stages of G. ochropterus to varying densities of eggs of H. armigera was investigated in the laboratory at 26?±?2°C, 65?±?2% RH and 12 L: 12D. Immature stages i.e. 3rd, 4th, 5th instar and adult predator exhibited type II functional response. Handling time decreased with increasing predator’s developmental stage. Adult G. ochropterus followed by fifth instar exhibited highest egg consumption and attack rate compared to other stages. Functional response parameters indicate that the adult and fifth instar of G. ochropterus were more voracious and efficient than other juveniles and might be useful as promising biocontrol agent against H. armigera.     

Resistance to metalaxyl-M and cymoxanil in a dominant clonal lineage of <Emphasis Type="Italic">Phytophthora infestans</Emphasis> in Huánuco,Peru, an area of continuous potato production

Fifty-eight isolates of Phytophthora infestans were evaluated in vitro and on detached leaves of potato for their sensitivities to metalaxyl-M and cymoxanil. The isolates belonged to the clonal lineage, EC-1, which is dominant on potato in Peru and Ecuador. All isolates were collected in Huánuco, Peru, an area of year-round potato production, where the potential for development of fungicide resistance is high. All isolates were resistant to metalaxyl-M, with in vitro EC₅₀ values ranging from 468.30—813.57 mg l⁻¹. In contrast, we found no evidence for resistance to cymoxanil for which in vitro EC₅₀ values ranged from 0.03—1.11 mg l⁻¹. Resistance to each fungicide was also evaluated for five isolates in a detached leaf assay in which the fungicide was sprayed on the leaf surface prior to inoculation. With metalaxyl-M, the range of EC₅₀ values was 158.85—828.29 mg l⁻¹, similar to that for the in vitro assay. For cymoxanil, EC₅₀ values ranged from 1.41 to 2.31 mg l⁻¹, which was higher than in the in vitro assay but still two orders of magnitude lower than the concentration applied by farmers in the field.     

Effect of Combined Treatment of Pasteurisation and <Emphasis Type="Italic">Coniothyrium minitans</Emphasis> on Sclerotia of <Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> in Soil

Integrated control of soil-borne plant pathogens such as Sclerotinia sclerotiorum is becoming more important as the soil fumigant methyl bromide is being phased out of use. Two alternative methods of control that have been found to reduce viability of sclerotia are steam sterilisation (pasteurisation) of soil or the application of the mycoparasite Coniothyrium minitans. This work investigated the possibility of integrating these two control measures. Soil was pasteurised in an autoclave, using a temperature of 80 °C for 3 min to simulate the possible temperatures reached by soil steaming machines for field use. Coniothyrium minitans was subsequently applied to the pasteurised soil to assess the effects of the combination of control measures in reducing sclerotial viability of S. sclerotiorum. Similar results were found in two soil types. Either method used individually was effective in decreasing the number of viable sclerotia, but no further reduction in sclerotial viability was seen when the two methods were combined. Coniothyrium minitans was found to colonise pasteurised sclerotia significantly quicker than untreated sclerotia, and it was seen that there was an increase in number of C. minitans in pasteurised soil in the presence of sclerotia. Experiments were also conducted to investigate the effect of application timing of the biocontrol agent to soil following pasteurisation, in relation to sclerotial infection. Here, two different isolates of S. sclerotiorum were used, with similar results. Application of C. minitans to soil immediately following pasteurisation resulted in sclerotial infection by the mycoparasite, but application 7 days or more after soil pasteurisation resulted in low recovery of the biocontrol agent from sclerotia, possibly due to the mycoparasite being masked by the presence of other fungi which colonised the sclerotia first.     

The stereoisomerism of second generation anticoagulant rodenticides: a way to improve this class of molecules to meet the requirements of society?

Second generation anticoagulant rodenticides (SGAR) are generally highly efficient for rodent management even towards warfarin‐resistant rodents. Nevertheless, because of their long tissue‐persistence, they are very associated with non‐target exposure of wildlife and have been identified as ‘Candidates for Substitution’ by the European Union's competent authority. A promising way to reduce ecotoxicity issues associated to SGAR could be the improvement of SGAR based on their stereoisomery, and due to this improvement, positioning about SGAR might be reconsidered. © 2018 Society of Chemical Industry     

Induced resistance in potato to <Emphasis Type="Italic">Phytphthora infestans</Emphasis>—effects of BABA in greenhouse and field tests with different potato varieties

We have investigated to what degree induced resistance with β-aminobutyric acid (BABA) can protect potato from late blight infection under Swedish field conditions and if synergistic interactions occur if BABA is applied in combination with a commonly used fungicide, Shirlan. In greenhouse experiments we also investigated the durability of BABA induced resistance, the dose-response relationships in susceptible (Bintje) and partially resistant (Ovatio, Suberb) cultivars and effects of combined applications of BABA and fungicides. We found a clear effect of BABA on P. infestans infection of greenhouse grown potato plants. The lesion sizes were reduced by on average 40–50% compared to untreated control. However, this effect lasted for only 4–5 days after BABA treatment and then the efficacy was lower. When BABA was given in combination with the fungicides it appeared to have an additive effect both in greenhouse and field experiments. Higher concentrations of BABA gave a stronger protective effect. The partially resistant cultivars Ovatio and Superb reacted to lower concentrations of BABA where no effect was found in susceptible Bintje. According to our field data, 20–25% reduction of the fungicide dose in combination with BABA gave on average the same result on late blight development as full dose Shirlan alone; while reduced dose of Shirlan alone sometimes resulted in less effective protection. Our results indicate that induced resistance could be used in practice in combinations with fungicides in order to reduce the amount of toxic compounds under north European conditions.     

A selective barrier in the midgut epithelial cell membrane of the nonvector whitefly <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> to <Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> uptake

We studied the presence of a potential transmission barrier that blocks Tomato yellow leaf curl virus in the nonvector greenhouse whitefly, Trialeurodes vaporariorum. Because T. vaporariorum can ingest and retain the virus after acquisition feeding on an infected plant, comparable to the vector whitefly Bemisia tabaci, circumstance evidence suggested that a transmission barrier presents at location(s) where the virus moves from the digestive tract lumen to the hemolymph. To provide direct evidence for the site of a transmission barrier in the nonvector insect, we compared the accumulation levels and localization of the virus between the two species of whiteflies. Quantitative real-time and conventional PCR analysis showed that accumulation of the virus during acquisition feeding and retention after a short acquisition period were indistinguishable between the two species, but the circulation of the virus within the whiteflies differed significantly between the species. In an immunofluorescence analysis using an antibody specific to the coat protein of the virus, the virus was restricted to the luminal surface of the midgut epithelial cells and did not enter their cytoplasm or that of the salivary glands in T. vaporariorum. In contrast, the virus was localized within the cytoplasm of the midgut epithelial cells and in the paired salivary glands of B. tabaci adults. This direct evidence shows that a selective transmission barrier at the luminal membrane surface of midgut epithelial cells in the nonvector whitefly blocks entrance of the virus into the midgut epithelial cells, resulting in incompetence as a vector of the virus.     

Clove-transmissibility of <Emphasis Type="Italic">Pseudomonas salomonii</Emphasis>, the causal agent of ‘Café au lait’ disease of garlic

Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial disease, known as ‘Café au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources such as crop debris, soil or alternate hosts in order to develop successful control strategies.