Seaweed-based products from Ecklonia maxima and Ascophyllum nodosum as control agents for the root-knot nematodes Meloidogyne chitwoodi and Meloidogyne hapla on tomato plants

Two commercially available seaweed products, derived from Ascophyllum nodosum (An) and Ecklonia maxima (Em), were evaluated for their potential as control agents for the root-knot nematodes, Meloidogyne chitwoodi and Meloidogyne hapla. The effects of both products on hatching, host location and penetration by second-stage juveniles (J2) were examined. Continuous exposure of M. chitwoodi egg masses to 50 and 100 % An significantly reduced the final percentage hatch, but this result could not be confirmed. In a bioassay with pluronic gel, more J2 of M. chitwoodi and M. hapla were found within the 0.5-cm vicinity of a tomato root tip after 24- and 6-h pre-exposures to Em, respectively. On agar plates, J2 of M. chitwoodi pre-exposed to An or Em showed less attraction to tomato root diffusate compared with distilled water (DW). Moreover, J2 pre-exposed to An lost the ability to differentiate repellent and attractant solutions on agar plates, unlike J2 pre-exposed to Em or DW. A 24-h pre-exposure to An reduced the infectivity of M. chitwoodi and M. hapla, whereas pre-exposure to Em enhanced the infectivity of M. chitwoodi. In a glasshouse pot experiment, treatments with Em reduced M. hapla multiplication on tomato. For M. chitwoodi, no effect on the number of nematodes per gram root was seen. The root biomass significantly reduced for untreated plants infested with M. chitwoodi compared to Em- and An-treated plants. The results indicate that these seaweed products adversely affect hatching and sensory perception in in vitro assays, but assumptions about in vivo effects may be unwise as dilutions of the products when applied as soil drenches may compromise activity

Lure and starve: Host root exudates to suppress field populations of cyst nematodes

International audiencePlant parasitic nematodes are a burden to global food security, accounting for substantial yield losses in agricultural production worldwide. Increasing concerns over the environment and health issues have led to diminishing control options at the disposal of agricultural producers. Lure and starve, a strategy that is based on stimulating hatching of second stage juveniles (J2) of some cyst forming plant parasitic nematodes in the absence of their host plant seems a promising approach to maintain sustainability in crop production. Here we examined in-situ hatching of encysted eggs of the potato cyst nematode Globodera pallida and the carrot cyst nematode Heterodera carotae following exogenous applications of host root exudates in repeated field experiments during autumn and spring seasons. Population densities (viable J2 g-1 of soil) were assessed prior and post-application of root exudates. Results showed hatching induction of up to 83% for G. pallida and 54% for H. carotae in field plots drenched with their respective host root exudates. Spring season experiments were characterised by limited soil moisture and did not reduce nematode population densities for G. pallida. The potential for host root exudates in supressing field population of cyst nematode in lure and starve strategies looks promising for both cyst nematode species investigated

A Novel In Vitro Tool to Study Cyst Nematode Chemotaxis

International audienceThis study presents a novel three-dimensional (3D) tool "3D choice" for chemotaxis assays with cyst nematodes. The original 3D choice was customized through digital printing. Freshly hatched second stage juveniles (J2s) of the cyst nematode were used as the nematode model to illustrate chemo-orientation behavior in the 3D system. The efficiency and reliability of the 3D choice were validated with 2% Phytagel as navigation medium, in three biological assays and using tomato root exudates or potato root border cells and their associated mucilage as a positive attractant as compared with water. For each biological assay, J2s were hatched from the same population of a single generation glasshouse-cultured cysts. This novel easy to use and low-cost 3d-device could be a useful replacement to Petri dishes assays in nematode behavioral studies due to the ease of deposition of nematodes and test substances, coupled with its distinctive zones that allow for precision in choice making by the nematodes

Etat des lieux des connaissances sur les taupins (Coléoptères : Elatéridés) et des stratégies alternatives aux pesticides pour la gestion des dégâts

Alternatives aux néonicotinoïdes Rendu des projets réunissant des contributions des projets scientifiques d'Ecophyto et du Plan National de Recherche et Innovation-betterave avec, selon les projets, les soutiens financiers de l'Office français de la biodiversité (OFB), l’Institut national de recherche pour l'agriculture, l'alimentation et l'environnement (INRAE) et de l'Institut technique de la betterave (ITB).National audienceWhile many crops are attacked each year by wireworms (Coleoptera: Elateridae), knowledge on their biology is still fragmentary and limited to a few species. The acquisition of knowledge on the biology and population dynamics of wireworms, the improvement of damage risk assessment methods and the development of sustainable protection strategies are urgent scientific, technical and economic challenges. In Europe, damage is mainly attributed to the genus Agriotes, as shown by the bibliography that is almost exclusively dedicated to them. Very few studies have been carried out on the other genera of elateridae, some of which are carnivorous, others detritivorous and many of which are unknown. This article presents a synthesis of the current knowledge on wireworms, more particularly on the genus Agriotes, and alternative strategies to pesticides for the management of their damage. After an overview of the current knowledge on wireworms, we discuss risk forecasting, an important step before planting a sensitive crop such as corn or potato, action levers to limit infestations and strategies to limit damage.Alors que de nombreuses cultures subissent chaque année des attaques de larves de taupins (Coléoptères : Elatéridés), les connaissances sur leur biologie restent encore fragmentaires et limitées à quelques espèces. L’acquisition de connaissances sur la biologie et les dynamiques de populations de taupins, l’amélioration des méthodes d’évaluation du risque de dégâts et le développement de stratégies de protection durables constituent des défis scientifiques, techniques et économiques urgents à relever. En Europe, les dégâts sont principalement attribués au genre Agriotes, comme en témoigne la bibliographie qui leur est quasi-exclusivement dédiée. Très rares sont les études s’intéressant aux autres genres d’élatéridés dont le comportement alimentaire serait pour certains carnivore, détritivore pour d’autres et inconnu pour beaucoup. Cet article présente donc une synthèse des connaissances actuelles sur les taupins, plus particulièrement du genre Agriotes et des stratégies alternatives à l’usage de pesticides pour la gestion de leurs dégâts. Après un état des lieux des connaissances sur les taupins, nous abordons la prévision du risque, étape importante avant l’implantation d’une culture sensible comme le maïs ou la pomme de terre, les leviers d’action pour limiter les infestations et les stratégies pour limiter les dégâts

Hatching Induction of Cyst Nematodes in Bare Soils Drenched With Root Exudates Under Controlled Conditions

International audienceCyst nematodes account for substantial annual yield losses in crop production worldwide. Concerns over environmental and health issues due to the use of chemical nematicides mean alternative sustainable and integrated solutions are urgently required. Hatch induction of encysted eggs in the absence of host plants, i.e., ‘suicide-hatching,’ could be a sustainable alternative in reducing population densities of cyst nematodes in infested soils. Here we examined in situ hatching of encysted eggs of Globodera pallida, Heterodera carotae, and Heterodera schachtii at varying soil depths, following exogenous applications of host root exudates in repeated glasshouse experiments. Cysts were retrieved 30 or 43 days post-incubation depending on the nematode species and assessed for hatching rates relative to the initial number of viable eggs per cyst. Hatching of the potato cyst nematode G. pallida depended on both soil moisture and effective exposure to root exudates, and to a lesser extent on exudate concentration. The carrot cyst nematode H. carotae had over 75% hatched induced by root exudate irrespective of the concentration, with better hatch induction at 20 cm as compared with 10 cm soil depth. Hatching of the beet cyst nematode H. schachtii largely depended on the soil moisture level at constant temperature, rather than the type or concentration of root exudates applied. As a conclusion, exogenously applied host root exudates may play a major role in inducing in situ hatch of encysted eggs of potato and carrot cyst nematodes in the absence of host plant under favorable soil temperature/moisture conditions. To improve such strategy, the characterization of chemical profiles of the root exudate composition and field validation are currently ongoing

Diversity of lepidopteran stem borers on monocotyledonous plants in eastern Africa and the islands of Madagascar and Zanzibar revisited

Surveys were completed in Eritrea, Ethiopia, Kenya, Madagascar, Mozambique, Tanzania, Uganda and Zanzibar to assess the lepidopteran stem borer species diversity on wild host plants. A total of 24,674 larvae belonging to 135 species were collected from 75 species of wild host plants belonging to the Poaceae, Cyperaceae and Typhaceae. Amongst them were 44 noctuid species belonging to at least nine genera, 33 crambids, 15 pyralids, 16 Pyraloidea species not yet identified, 25 tortricids and three cossids. The noctuid larvae represented 73.6% of the total number of larvae collected, with 66.3, 3.5 and 3.8% found on Poaceae, Cyperaceae and Typhaceae, respectively. The Crambidae, Pyralidae, Tortricidae and Cossidae represented 19.8, 1.9, 2.5 and 0.1% of the total larvae collected, respectively, with 90.4% of the Crambidae and Pyralidae collected from Poaceae, and 99.7% of the Tortricidae collected from Cyperaceae. The lepidopteran stem borer species diversity in the wild host plants was far more diverse than previously reported