Plant characteristics mediated by growing conditions can impact parasitoid’s ability to attack host aphids in winter canola

Abstract

Winter canola (Brassica napus) is an important crop in various parts of the world. It is planted in fall, vernalized during winter and oVers higher yields than spring canola. One of the key aphid pests of this crop is Myzus persicae Sulzer (Homoptera: Aphididae). Recent surveys in Europe showed that M. persicae in winter canola is parasitized by Aphidius matricariae and Diaeretiella rapae, but not by other aphidiine parasitoid species known to attack M. persicae in other crops. During vernalization, winter canola plants acclimatize to survive speciWc climatic conditions of winter, e.g. through the formation of epicuticular waxes on leaves. These waxes could aVect eYciency on natural enemies. In this study, we characterized (1) the ability of aphidiine parasitoids to locate and attack M. persicae on winter canola, and (2) how plant vernalization inXuences parasitoid ability to attack suitable hosts. In the laboratory, the ability of A. ervi, A. matricariae and D. rapae to orient toward odors of the M. persicae-winter canola complex was studied in an olfactometer, as well as their ability to attack M. persicae on winter canola. In addition, the impact of plant species and plant vernalization on the ability of A. colemani to attack and locate M. persicae was evaluated. The results show that A. matricariae and D. rapae readily locate and attack M. persicae on winter canola as does A. ervi, albeit to lesser extent. Aphidius colemani shows low ability to parasitize M. persicae on this plant species. Vernalization of canola is an important factor mediating the ability of A. colemani to attack M. persicae and it likely results from the presence of Brassica's waxes that reduce parasitoid mobility and impact foraging behavior. These results show that aphid parasitoids diVer in their ability to locate and attack M. persicae on winter canola, the latter being a function of parasitoids' capacity to cope with plant characteristics that are mediated by growing conditions.

Performance of four Trichogramma species (Hymenoptera: Trichogrammatidae) as biocontrol agents of Heliothis virescens (Lepidoptera: Noctuidae) under various temperature regimes

“…A similar program has been implemented with T. achaeae, which is currently used against Tuta absoluta in Europe, despite a parasitism rate of about 50% on this pest . Multiple abiotic and biotic factors can directly affect parasitoid efficiency (Mulatu et al 2006;Emana 2007;Desneux and Ramirez-Romero 2009;Rousse et al 2009) and therefore they should be considered and carefully studied. Difference in important biological traits related to Trichogramma species effectiveness can vary among strains of a same species (Klug and Meyhöfer 2009;Pizzol et al 2010;Tabone et al 2010).…”

Resistance of some canola cultivars to Myzus persicae (Hemiptera: Aphididae)

“…The low population of this aphid on these five cultivars might result in less damage and yield loss. Biotic and abiotic factors in field conditions could be affecting the population density of M. persicae on canola cultivars (Athanassiou et al, 2003;Desneux and Ramirez-Romero, 2009); therefore, we investigated the preferences and performance of M. persicae on Zarfam, RGS003, Opera, Elite, Okapi and Ebonite cultivars under controlled conditions. This study demonstrated that the host preference of M. persicae varied among the tested canola cultivars, and Zarfam was the most preferred, whereas Opera was the least preferred cultivar in terms of attraction.…”

“…The slowest development rate and lowest intrinsic rate of the natural increase of M. persicae on Opera would result in a lower population growth that in turn should lead to lower subsequent infestations by this pest. Also, plants responsible for antibiotics may have an indirect effect by increasing the exposure of the insect to its native natural enemies as a result of a prolonged develop-mental time (Desneux and Ramirez-Romero, 2009). Using resistant cultivars has an important role in the IPM of M. persicae in Iran, but the resistance level of Opera cultivar reported in this paper is not sufficient to achieve adequate control of M. persicae.…”

“…Using resistant cultivars has an important role in the IPM of M. persicae in Iran, but the resistance level of Opera cultivar reported in this paper is not sufficient to achieve adequate control of M. persicae. Using resistant cultivars in combination with biological control agents and novel insecticides could be a useful strategy in the integrated pest management of M. persicae (Tatsumi and Takada, 2005;Desneux and Ramirez-Romero, 2009). Therefore, further research is required to investigate the potential of using Opera cultivar in combination with novel insecticides and biocontrol agents, especially for the dominant native parasitoid, Diaeretiella rapae (McIntosh), in the integrated management of M. persicae.…”

Parasitism of different Trichogramma species and strains on Plutella xylostella L. on greenhouse cauliflower

“…However, given the artificial conditions of this primary screening, parasitoid efficiency waits to be determined under more realistic conditions. Under natural conditions, various factors like crop architecture, plant morphology, prey distribution and climatic conditions could affect the efficiency and behaviour of natural enemies and may affect the efficacy of biological control (Andow and Prokrym 1990;Rutledge et al 2003;Desneux et al 2006;Tabone et al 2006;Carrillo et al 2008;Desneux and O'Neil 2008;Desneux and Ramirez-Romero 2009). For Trichogrammatidae, parasitism levels vary greatly among different habitats, plant species and plant structures, and plant spacing, odour and chemistry all play a role in moulding the efficiency of Trichogramma spp.…”