Suitability of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae) as host for two local Trichogramma species (Hymenoptera: Trichogrammatidae) and possible implications on biological control programs

In this study, laboratory tests were conducted to evaluate the suitability of Ectomyelois ceratoniae (Zeller) eggs as host for the development of two Trichogramma species: Trichogramma cacoeciae (Marchal) and Trichogramma bourarachae (Pintureau and Babault) (Hymenoptera: Trichogrammatidae) collected in Tunisia and reared on Ephestia kuehniella Zeller eggs. We also studied effects of five different temperature regimes (15, 20, 25, 30 and 35°C) on the biological traits of these two parasitoids. Results showed that eggs of E. ceratoniae were more suitable for the development of T. bourarachae. The number of parasitized eggs (15.46±2.04) as well as the emergence rate (95.78±5.10) was significantly higher compared to T. cacoeciae. For both Trichogramma species, the highest parasitism rate was observed at 30°C. At 35°C, the mean number of parasitized eggs (32.06±13.32) and the longevity (4.03±0.56) of T. bourarachae females were significantly higher compared to T. cacoeciae. The developmental time of both Trichogramma species was shorter at higher temperatures. The emergence rates were similar and relatively high in all tested temperature ranging from 80.48% to 97.92% for T. bourarachae and from 92.03% to 99.33% for T. cacoeciae

Effect of cold storage on the performance of Trichogramma bourarachae (Pintureau and Babault) (Hymenoptera: Trichogrammatidae)

6 p.-3 fig.-2 tb.In Tunisia, the use of the egg parasitoid trichogrammatid wasps to cope with several economic pests is gaining increasing attention. Trichogramma bourarachae (Pintureau & Babault) is among the Trichogramma wasps naturally present in Tunisia and regarded as a potential natural enemy to be used in biological control programs of many lepidopteran pests that cause economic losses. The propensity of T. bourarachae to cold storage with and without diapause induction was studied. The effect of this technique on its emergence rate and parasitic activity was investigated. The study showed that wasps of T. bourarachae treated at the induction temperature of 15 °C for 5 days can be stored at 4 ± 1 °C for more than 30 days without significant loss of their performances. By using this prestorage temperature, T. bourarachae could keep its emergence capacity (77.5%) up to 60 days of cold storage at 4 ± 1 °C. However, its parasitic activity decreased significantly (37.16%) after 45 days of cold storage. These results are promising for its mass production, transport, and release in the framework of national campaigns to control several agricultural pests of economic importance.Peer reviewe

Suitability of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae) as host for two local Trichogramma species (Hymenoptera: Trichogrammatidae) and possible implications on biological control programs

In this study, laboratory tests were conducted to evaluate the suitability of Ectomyelois ceratoniae (Zeller) eggs as host for the development of two Trichogramma species: Trichogramma cacoeciae (Marchal) and Trichogramma bourarachae (Pintureau and Babault) (Hymenoptera: Trichogrammatidae) collected in Tunisia and reared on Ephestia kuehniella Zeller eggs. We also studied effects of five different temperature regimes (15, 20, 25, 30 and 35°C) on the biological traits of these two parasitoids. Results showed that eggs of E. ceratoniae were more suitable for the development of T. bourarachae. The number of parasitized eggs (15.46±2.04) as well as the emergence rate (95.78±5.10) was significantly higher compared to T. cacoeciae. For both Trichogramma species, the highest parasitism rate was observed at 30°C. At 35°C, the mean number of parasitized eggs (32.06±13.32) and the longevity (4.03±0.56) of T. bourarachae females were significantly higher compared to T. cacoeciae. The developmental time of both Trichogramma species was shorter at higher temperatures. The emergence rates were similar and relatively high in all tested temperature ranging from 80.48% to 97.92% for T. bourarachae and from 92.03% to 99.33% for T. cacoeciae

Diagnosis of "maladie des feuilles cassantes" or brittle leaf disease of date palms by detection of associated chloroplast encoded double stranded RNAs

The “Maladie des feuilles cassantes” (MFC) or “Brittle leaf disease” of date palms is associated with the accumulation of two populations of small, chloroplast-encoded RNAs. A plasmid vector containing a cDNA with partial sequences of both of these RNA populations was used to synthesize a DIG-labeled bifunctional probe by PCR. The probe has been tested to detect, by molecular hybridization, MFC-associated RNAs from dsRNA-enriched palm leaflet preparations. Leaflet samples from MFC-affected date palm trees consistently gave a positive hybridization signal regardless of the date palm cultivar, severity of symptoms, or geographical location, whereas samples from date palm trees affected by other biotic and abiotic stresses tested negative. The assay is specific for MFC and can be used for early diagnostic purposes

"Maladie des feuilles cassantes" or brittle leaf disease of date palms in Tunisia: Biotic or abiotic disease?

“Brittle leaf disease of date palms”, known in southern Tunisia since the 1960s, has assumed epidemic proportions from 1986 on. The symptoms are associated with manganese deficiency and the presence of a small double stranded RNA of host origin. Even though no pathogen has yet been found, some observations do not fit a purely abiotic cause of the disease. In particular, affected trees seem to cluster into foci, and mineral analyses show no significant differences between the soils of affected and unaffected trees. Further work is required to understand the etiology of the disease