Male and female Trybliographa rapae (Hymenoptera: Figitidae) behavioural responses to food plant, infested host plant and combined volatiles

Parasitoids reach maximum reproductive success when responding to plant stimuli associated with food and host. We investigated the attraction of the parasitic wasp Trybliographa rapae Westwood (Hymenoptera: Figitidae) to volatiles emitted from plants infested by the cabbage root fly Delia radicum L. (Diptera: Anthomyiidae), as well as to volatiles from a nectar food plant. Behavioural choice tests showed that male parasitoids were not attracted to any volatiles from plants infested by D. radicum or from nectar plants, while females showed clear attraction to both volatile sources. Newly emerged females preferred combined volatiles of host and food plants over those from only the host plant, whereas older females showed no differences in attraction. This suggests that intercropping attractive flowers with host plants could potentially be used to recruit newly emerged parasitoids from surrounding fields while older parasitoids invest more energy in host allocation than in additional food search. Volatiles from a whole infested plant were preferred over those emitted from separated above- and belowground parts from infested plants, indicating that female parasitoids recognize a synergistic effect from plant volatiles. It is important to consider the availability of both energy and host resources for parasitoids when designing an eco-compatible management of a vegetable crop system

First report of "Candidatus Liberibacter solanacearum" associated with psyllid-affected carrots in Sweden

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Suppressiveness of 18 composts against 7 pathosystems: Variability in pathgen response

Compost is often reported as a substrate that is able to suppress soilborne plant pathogens, but suppression varies according to the type of compost and pathosystem. Reports often deal with a single pathogen while in reality crops are attacked by multiple plant pathogens. The goal of the present study was to evaluate the disease suppression ability of a wide range of composts for a range of plant pathogens. This study was conducted by a consortium of researchers from several European countries. Composts originated from different countries and source materials including green and yard waste, straw, bark, biowaste and municipal sewage. Suppressiveness of compost-amended (20% vol./vol.) peat-based potting soil was determined against Verticillium dahliae on eggplant, Rhizoctonia solani on cauliflower, Phytophthora nicotianae on tomato, Phytophthora cinnamomi on lupin and Cylindrocladium spathiphylli on Spathiphyllum sp., and of compost-amended loamy soil (20% vol./vol.) against R. solani on Pinus sylvestris and Fusarium oxysporum f. sp. lini on flax. From the 120 bioassays involving 18 composts and 7 pathosystems, significant disease suppression was found in 54% of the cases while only 3% of the cases showed significant disease enhancement. Pathogens were affected differently by the composts. In general, prediction of disease suppression was better when parameters derived from the compost mixes were used rather than those derived from the pure composts. Regression analyses of disease suppression of the individual pathogens with parameters of compost-amended peat-based mixes revealed the following groupings: (1) competition-sensitive: F. oxysporum and R. solani/cauliflower; (2) rhizosphere-affected: V. dahliae; (3) pH-related: P. nicotianae; and (4) specific/unknown: R. solani/pine, P. cinnamomi and C. spathiphylli. It was concluded that application of compost has in general a positive or no effect on disease suppression, and only rarely a disease stimulating effect.status: publishe

Suppressiveness of 18 composts against 7 pathosystems : variability in pathogen response

International audienceCompost is often reported as a substrate that is able to suppress soilborne plant pathogens, but suppression varies according to the type of compost and pathosystem. Reports often deal with a single pathogen while in reality crops are attacked by multiple plant pathogens. The goal of the present study was to evaluate the disease suppression ability of a wide range of composts for a range of plant pathogens. This study was conducted by a consortium of researchers from several European countries. Composts originated from different countries and source materials including green and yard waste, straw, bark, biowaste and municipal sewage. Suppressiveness of compost-amended (20% vol./vol.) peat-based potting soil was determined against Verticillium dahliae on eggplant, Rhizoctonia solani on cauliflower, Phytophthora nicotianae on tomato, Phytophthora cinnamomi on lupin and Cylindrocladium spathiphylli on Spathiphyllum sp., and of compost-amended loamy soil (20% vol./vol.) against R. solani on Pinus sylvestris and Fusarium oxysporum f. sp. lini on flax. From the 120 bioassays involving 18 composts and 7 pathosystems, significant disease suppression was found in 54% of the cases while only 3% of the cases showed significant disease enhancement. Pathogens were affected differently by the composts. In general, prediction of disease suppression was better when parameters derived from the compost mixes were used rather than those derived from the pure composts. Regression analyses of disease suppression of the individual pathogens with parameters of compost-amended peat-based mixes revealed the following groupings: (1) competition-sensitive: F. oxysporum and R. solani/cauliflower; (2) rhizosphere-affected: V. dahliae; (3) pH-related: P. nicotianae; and (4) specific/unknown: R. solani/pine, P. cinnamomi and C. spathiphylli. It was concluded that application of compost has in general a positive or no effect on disease suppression, and only rarely a disease stimulating effect

Assessment of the efficiency of different control programs to reduce Trioza apicalis

The control of carrot psyllid Trioza apicalis Förster largely relies on chemical measures, and the current integrated pest management (IPM) strategy is based on pest scouting. The number of active ingredients available for psyllid control will further decline in the coming years. The need for alternative control measures is therefore urgent. In this work the efficiency of different control programs including a kaolin particle film and plant‐derived, crude saponin extract, chemical control, insect net and IPM (kaolin in combination with insecticides) programs to reduce psyllid feeding damage, reproduction and the spread of “Candidatus Liberibacter solanacearum” (CLso) in carrots was studied. Each year in 2016–2018, four replicates of each treatment were randomised in a row‐column design on a commercial carrot farm. After the treatments were executed, the psyllid nymphs and eggs were counted. At the harvest, the carrot roots and shoots were weighed, damages assessed, and samples were taken for CLso detection from 50 plants at each replicate. Kaolin treatment alone and in combination with insecticides effectively reduced the number of psyllid nymphs and eggs in all the years studied. Saponin was applied only on the first year, since it significantly increased the number of T. apicalis eggs compared to other treatments. The insect net was superior to other treatments in all the studied aspects in all the years. Under normal weather conditions, the highest root weight was harvested under the insect net, followed by the chemical control program consisting of pyrethroids, kaolin treatment, untreated control and saponin treatment. During extreme weather conditions, chemical control programs were not effective at protecting the carrots from psyllid feeding, which was reflected as low root yield. In all years, the carrot leaf damage percent negatively correlated with the root weight. Similarly, the shoot:root ratio increased as the leaf‐curling percentage rose, which was even pronounced under drought stress. The effect of climatic stress should be considered when developing IPM strategies.202