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Description of the subject. The article deals with the study of compatibility of entomopathogenic nematode (EPN) species with insecticides currently used against diamondback moth (DBM) Plutella xylostella (L.) in northern BeninObjectives. The aim of this work was to determine the impact of five insecticides on the efficacy of entomopathogenic nematodes against DBM larvae.Method. Infective juveniles (IJs) of two EPN species (Steinernema sp. 83a and Heterorhabditis sonorensis KF723827) were exposed to five insecticides used against P. xylostella larvae in Djougou for 48 h. The number of surviving nematodes was used to infest DBM larvae. The experiment was carried out under laboratory and semi-field conditions.Results. The bioassays carried out in laboratory showed that the survival rate of nematodes exposed to KARATE 2.5 WG, LAMBDA SUPER 2.5EC or neem oil ranges between 95% and 98%. In the treated plots, Steinernema sp. 83a was the most virulent with the highest P. xylostella mortality (87% at 50 IJs·cm-2 after 24 h) while only 35% larval mortality was recorded for H. sonorensis applied at the same dose. Population density of nematodes which penetrated DBM larvae reached 9 ± 3I IJs·larva-1 for H. sonorensis KF723827 and 6 ± 2 IJs·larva-1 for Steinernema sp. 83a. In cadaver of DBM, nematode reproduction did not appear to be affected by the contact with insecticides.Conclusions. Based on our research, we conclude that the three insecticides did not affect EPNs efficiency and could be used in combination against DBM., Effet des insecticides sur l’efficacité des nématodes entomopathogènes contre les larves de la teigne des crucifères Plutella xylostella (L.) (Lepidoptera : Plutellidae) sur le chou au nord BéninDescription du sujet. L’article traite de l’étude de la compatibilité des nématodes entomopathogènes avec les insecticides utilisés contre la teigne des crucifères Plutella xylostella (L.) au nord du Bénin. Objectifs. L’objectif de l’étude est d’évaluer l’effet de cinq insecticides sur l’efficacité des nématodes entomopathogènes contre les larves de P. xylostella.Méthode. Des larves infestantes (IJs) de deux espèces de nématodes entomopathogènes (Steinernema sp. 83a et Heterorhabditis sonorensis KF723827) ont été mises en contact pendant 48 h avec cinq insecticides utilisés contre les larves de P. xylostella à Djougou. Ensuite les IJs exposées aux insecticides ont été utilisées pour infester les larves de P. xylostella en conditions de laboratoire et en milieu semi-contrôlé sur les plants de chou.Résultats. Les expérimentations conduites en laboratoire montrent que le taux de survie des nématodes exposés à KARATE 2.5 WG, LAMBDA SUPER 2.5EC ou huile de neem est compris entre 95 % et 98 %. Le taux de mortalité le plus élevé des larves de P. xylostella a été observé avec Steinernema sp. 83a (87 % à 50 IJs·cm-2 24 h après traitement), tandis que seulement 35 % de mortalité des larves a été enregistré au niveau de H. sonorensis avec la même dose d’application. Le nombre d’IJs ayant pénétré chaque larve de P. xylostella est de 9 ± 3 IJs·larve-1 pour H. sonorensis KF723827 et 6 ± 2 IJs·larve-1 pour Steinernema sp. 83a. L’exposition des nématodes entomopathogènes aux insecticides n’a pas affecté leur reproduction à l’intérieur des larves mortes.Conclusions. Ces résultats montrent que les trois insecticides testés contre P. xylostella n’affectent pas la survie ni l’efficacité des nématodes entomopathogènes et peuvent être utilisés en combinaison pour lutter contre P. xylostella.

In tomato, the only commercially available source of resistance to root-knot nematodes (RKN) is the Mi-1 gene that confers resistance to Meloidogyne incognita, M. javanica and M. arenaria. However, its effectiveness was limited at higher soil temperatures. A study was initiated with the objective to check the durability of the potential resistance genes found in some tomato breeding lines after screening in controlled glasshouse conditions ≤ 27°C by exposing them to higher soil temperatures at 28, 32 and 36°C for 24 and 48 h periods. The aggressive Jittu and Babile M. incognita and Jittu and Koka M. javanica populations originally collected from Ethiopia were used. When seedlings reached the four-leaf stage, each tube was inoculated with 50 freshly (≤ 24 h) hatched infective second-stage juveniles (J2). Immediately after inoculation, the seedlings were exposed continuously for 24 and 48 h in a warm water bath at 28, 32 and 36°C, respectively. A control was kept separately in ambient temperature (24°C ± 2°C). The external ambient temperature and the soil temperature inside the tube while in the water bath were simultaneously recorded using a TESTO data logger. Temperature, tomato breeding lines and time had a significant effect on the number of J2 of Jittu and Babile M. incognita and Jittu and Koka M. javanica populations that penetrated the roots. The utility of the potential resistance found in the breeding lines during the controlled growth chamber resistance screening experiment was limited at higher soil temperatures, especially at 32 and 36°C. At 36°C there was no significant difference found on the mean number of penetrated J2 of Jittu and Babile M. incognita and Jittu and Koka M. javanica populations inside the roots of all the tested breeding lines compared to ‘Marmande’ (a susceptible control) after 48 h of heat exposure after inoculation. More J2 were found in the roots of the tested breeding lines after 48 h compared to 24 h heat exposure after inoculation for each soil temperature level tested and for both populations of M. incognita. It is clear from our observations that local tomato breeding lines with resistance potential can be used when soil temperatures remain below 32°C. Differences were observed between breeding lines depending on the RKN population used at higher temperatures and this knowledge can help in further optimising the development of sustainable resistance under local Ethiopian circumstances.