Population dynamics studies are very important for any area-wide control program as they provide detailed knowledge about the relationship of Medfly [Ceratitis capitata (Wiedemann)] life cycle with host availability and abundance. The main goal of this study is to analyse seasonality of C. capitata in Terceira and Sao Jorge Islands (Azores archipelago) using field and laboratory data collected during (2010–2014) CABMEDMAC (MAC/3/A163) project. The results from Sao Jorge Island indicate significantly lower male/female ratio than on Terceira Island. This is an important finding specially regarding when stablishing the scenario parameters for a sterile insect technique application in each island. The population dynamics of C. capitata are generally linked with host fruit availability and abundance. However, on Terceira Island fruit infestation levels are not synchronized with the trap counts. For example, there was Medfly infestations in some fruits [e.g., Solanum mauritianum (Scop.)] while in the nearby traps there were no captures at the same time. From this perspective, it is important to denote the importance of wild invasive plants, on the population dynamics of C. capitata, as well important to consider the possibility of having different densities of traps according to the characteristics of each area in order to improve the network of traps surveillance’s sensitivity on Terceira Island.
Three Nucleopolyhedrovirus (NPVs) originally isolated from Heliothis armigera larvae, collected from Portugal (HearNPV‐PO) and two places in Spain (HearNPV‐SP1 and HearNPV‐SP2), and three previously described NPVs were compared biochemically and biologically. Restriction endonuclease analysis of the virus genome with several enzymes revealed that isolates HearNPV‐SP1 and HearNVP‐SP2 are unique but closely related genotypes which represent two new strains of the NPVs of H. armigera. The DNA fragment profiles of HearNPV‐PO were distinct from those of the HearNPV‐SP1 and HearNPV‐SP2, with all the enzymes used, while they were identical to the Mamestra brassicae NPV strain present in the commercial product MAMESTRIN®. Bioassays in third‐instar H. armigera larvae showed that the LD50 value obtained for HearNPV‐SP1 (68 occlusion bodies/larva) was about two‐ and six‐times lower than those of HearNPV‐SP2 and a Russian isolate, HearNPV‐RU, respectively. The corresponding LT50 values were not found to differ significantly between these three virus isolates at comparable doses.
Larvae of the tomato fruitworm, Helicoverpa armigera, were surveyed for nucleopolyhedrovirus (NPV) infection (referred to as HearNPV) in three different locations from the Iberian Peninsula: Olivenza and Toledo in Spain and the Oeste region in Portugal. Twenty HearNPV isolates were obtained from single field-collected larval cadavers. Restriction endonuclease (REN) profiles of the collected isolates with BglII and PstI allowed identification of six different H. armigera single-embedded NPV strains in Spain (referred to as HearSP3, HearSP4, HearSP5, HearSP6, HearSP7, and HearSP8) and two in Portugal (referred to as HearPT1 and HearPT2). No strains were shared by isolates from different geographical regions except HearSP5, which was found in isolates from Olivenza and Toledo. Cluster analysis based on the restriction fragment length polymorphisms of these strains in relation to two previously identified strains from Badajoz (HearSP1) and Cordoba (HearSP2) in Spain, showed no correlation among the strains and their geographical origin. The biological activity of HearSP2, HearSP4, HearSP7, HearSP8, HearPT1, and HearPT2 was compared in terms of pathogenicity (50% lethal concentration, LC 50) and virulence (mean time to death). HearPT2 and HearSP7 were significantly more pathogenic than HearSP2, with LC 50 values 2.8 and 2.6-fold higher than the latter, respectively, on H. armigera second instars. HearSP4 and HearPT2 killed larvae significantly faster than HearSP8, whereas HearSP2, HearSP7, and HearPT1 showed intermediate mean time to death values.
The use of non-crop resources by natural enemies and their potentialities to enhance their effectiveness as pest control agents is increasing as a method for conservation biological control. Nevertheless, the effect of consumption of non-crop resources by pests has been generally overlooked being this knowledge crucial to favor natural enemies but not pests. In the present work, insect honeydews and flowers suitability as food resources for the olive tree key-pest Prays oleae were analyzed under laboratory conditions. The selected honeydews were excreted by Saissetia oleae and Euphyllura olivina, two olive pests, and the selected plants were seven abundant species in the olive grove agroecosystem that bloom simultaneously with the flight period of the anthophagous generation of P. oleae. In this work, some of these resources were identified as potential food sources for P. oleae. Despite the general findings, which indicate that honeydews have less nutritional value for insects than nectar, P. oleae reached the best survival and reproduction performance with the insects' honeydews. Several of the tested flowers were identified as potential food resources for P. oleae, being Malva sylvestris the one that originated the best performance. Moreover, our results suggest that P. oleae females are synovigenic and emerge with nutritional reserves for reproduction. We highly recommend accomplishing further research before establishing these resources in biological control methods in order to confirm their effect on pests in fields.
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