Consumption rate, functional response and preference of the predaceous mite Iphiseius degenerans to Tetranychus urticae and Eutetranychus orientalis.

The functional response of females of the phytoseiid mite, Iphiseius degenerans (Berlese), to increasing densities of females of its prey, Tetranychus urticae Koch and Eutetranychus orientalis Klein, on bean leaves, were studied under laboratory conditions. Our results indicated that the predator consumed significantly more items of E. orientalis than of T. urticae at all densities treatments. Daily consumption of the predator increased with increasing prey density until a plateau was reached-maximum number of prey consumed was ca. 4 for T. urticae and ca. 12 for E. orientalis. A Type II functional response was determined by a logistic regression model. The highest estimated value a (instantaneous rate of attack) and the lowest value of T ( h ) (handling time) were found for the predator feeding on E. orientalis. Prey selection was evaluated by simultaneously presenting both prey species to the predator in various ratios and at increasing densities. I. degenerans showed a higher predation rate and higher preference for E. orientalis at all the ratios and prey densities tested. This may be due to the smaller size or the inactivity of E. orientalis and the inability of the predator to cope with the webbing of T. urticae. Our results suggest that I. degenerans can be considered a suitable biological control candidate based on its preference for E. orientalis in the Mediterranean region.

Temperature and diet effects on immature development of predatory mite Typhlodromus athenas Swirski and Ragusa (Acari: Phyotseiidae).

Temperature and food quality both can influence growth rates and developmental time of herbivorous insects and mites. Typhlodromus athenas Swirski and Ragusa is an indigenous mite in the Mediterranean region and data on its temperature dependent development are lacking. In the current study, temperature-dependent development and survival of T. athenas immature stages were evaluated on eggs and all stages of Tetranychus urticae Koch, as well as on almond (Prunus amygdalis Batsch) pollen, under seven constant temperatures ranging from 15 to 35°C, 65% RH, and a photoperiod of 16:8 (L:D) h. On both diets survival was considerably high at all temperatures. The longest developmental period of immature stages was recorded at 15°C, whereas the shortest was at 30°C. Female immatures on almond pollen had shorter developmental time compared to that on twospotted spider mites. Food had a significant effect on female total developmental time at temperatures lower than 25°C. The lower developmental thresholds, estimated by a linear model, for egg-to-adult of females and males fed on pollen were 8.60 and 8.77°C, respectively, whereas on T. urticae they were 10.15 and 10.62°C, respectively. Higher values of tmin for total development were estimated by a nonlinear model (Lactin-2), and ranged from 10.21°C for both females and males on almond, to 11.07 for females and 10.78°C for males on prey. Moreover, this model estimated optimal and lethal temperatures accurately. The results of this study indicate that T. athenas appears better adapted to higher temperatures that occur in the Mediterranean region and may be a useful biological control agent.

Effect of several different pollens on the bio-ecological parameters of the predatory mite Typhlodromus athenas Swirski and Ragusa (Acari: Phytoseiidae).

The development, survivorship, and reproduction of the predacious mite Typhlodromus athenas Swirski and Ragusa were studied in the laboratory by rearing the predator on nine different plant pollens [almond(Prunus amygdalis Batsch), apple (Malus domestica Borkh.), apricot (Prunus armeniaca L.), cherry (Prunus avium L.), pear (Pyrus communis L.), plum (Prunus domestica L.), walnut (Juglans regia L.), olive (Olea europaea L.), Typha sp.], and pollen collected from bee hives. All experiments were conducted in environmental chambers at 20 ± 1°C, 65% RH, and a photoperiod of 16:8 (L:D) h. Survival during immature development ranged from 81.1 to 96.0%. The shortest mean developmental time from egg to adult with respect to the range of pollen species was recorded for females and males fed on almond pollen (10.76 ± 0.18 and 10.45 ± 0.21 d, respectively), while the longest was on beehive pollen (26.97 ± 0.23 and 24.00 ± 0.25 d for females and males, respectively). Female longevity varied from 51.63 ± 5.52 d (olive pollen) to 102.81 ± 6.60 d (pear pollen), while fecundity ranged from 5.33 ± 2.35 eggs per female (beehive pollen) to 26.43 ± 1.73 eggs per female (almond pollen). The diet consisting of almond pollen resulted in the highest intrinsic rate of natural increase (r(m)) (1.00 d(-1)) and pollen collected from bee hives resulted in the lowest (0.013 d(-1)). These results showed that various pollen could favor the development of T. athenas, and also support the view that alternative food resources may play an important role in the field for sustaining and increasing the predator's population.

Genetic variation among Mediterranean populations of Sesamia nonagrioides (Lepidoptera: Noctuidae) as revealed by RFLP mtDNA analysis.

Restriction fragment length polymorphism analysis of two segments of mitochondrial DNA (COI and 16S rRNA) was used to examine genetic variation in Sesamia nonagrioides (Lefèbvre) populations from the Mediterranean basin. Four populations were collected from central and southern Greece, and five from northern latitudes: Greece, Italy, France and Spain. No variation was observed in COI, while 16S rRNA segment proved highly polymorphic and 28 different haplotypes were found. Lower intra-population polymorphism was found in the northern populations than in southern ones. Although no significant isolation by distance was found, the UPGMA tree based on Nei's raw number of nucleotide differences separated the populations into two major groups, i.e. one with the northern (40.6 degrees N-43.4 degrees N) and the other with the southern populations (37.3 degrees N-39.2 degrees N). Analysis of molecular variance revealed that most of the variation was between the two major groups (Phi(CT)=0.559), and all pairwise comparisons between the northern and southern populations resulted in high and significant F(ST) values (overall F(ST)=0.604). The high F(ST) values and the strong spatial genetic structure indicate that long-distance migration may be a rare event. The populations do not seem to have experienced a strong historical bottleneck. The occurrence of a few widespread haplotypes and the genetic similarity of the northern populations could be attributed to a historical expansion of certain haplotypes from the south towards to the northern borders of the species' distribution area.