Biological responses of Tetranychus urticae (Acari: Tetranychidae) to sub-lethal concentrations of the entomopathogenic fungus Beauveria bassiana.

Tetranychus urticae (Acari: Tetranychidae) is one of the most important pests of agricultural crops with worldwide distribution causing considerable damage to different products. Application of chemical acaricides is one of the most important strategies used for the control of this pest. Entomopathogenic fungi, however, have been proposed as alternative control agents. In this study, sub-lethal effects (LC10 = 6.76 × 102, LC20 = 8.74 × 103, and LC30 = 55.38 × 103 conidia ml-1) of Beauveria bassiana strain TV on the life table parameters of T. urticae were evaluated under laboratory conditions. The results demonstrated that by increasing the concentration, a significant decline was observed in adult longevity of both male and female individuals. Total fecundity of T. urticae was calculated as 45.16, 36.28, 23.98, and 18.21 eggs in control, LC10, LC20, and LC30 treatments, respectively. Sub-lethal concentrations drastically affected the population parameters of this mite pest. The intrinsic rate of increase (r) ranged from 0.1983 to 0.1688 day-1 for the mites treated with distilled water and LC20 treatments, respectively. The net reproductive rate (R0) was affected by the sub-lethal concentrations (lower value at LC30 concentration: 11.19 offspring/individual). Considering the detrimental effects of B. bassiana on some biological parameters of T. urticae, it can be concluded that this product can be used to develop targeted interventions aimed at integrated pest management of this pest.

Supplementation of natural prey with pollen grains exerts an influence on the life table parameters of Neoseiulus californicus.

Better performance of generalist predators, as well as an increase in their density, may be an incentive factor in the ability of the predators to exploit more than one food item or mixed diets. In this study, the effects of four pollen grains (cedar, pear, apricot, and pistachio) when provided to Neoseiulus californicus in mixed diets with prey, Tetranychus urticae, were evaluated. The result indicated that the fastest female developmental time was observed on pistachio pollen + T. urticae, together with apricot pollen + T. urticae. Females reared on the mixed diet comprising pistachio pollen reflected the longest total life span duration, while the shortest total life span was observed in those on the diet that included pear pollen. Furthermore, the lowest fecundity, as well as the shortest reproduction period, was determined on the diets that included pear pollen, while the highest fecundity and the longest reproduction period were observed in pistachio pollen + T. urticae. In addition, the intrinsic (r) and finite rate of increase (λ), net (R0) and gross (GRR) reproductive rates were highest in pistachio pollen + T. urticae. These findings have important implications for developing a comprehensive biological control program of T. urticae, which will be discussed.

Suitability of Pollen from Different Plant Species as Alternative Food Sources for Neoseiulus californicus (Acari: Phytoseiidae) in Comparison with a Natural Prey.

Alternative foods such as pollen may help predators to maintain their populations even when their prey is scarce or absent. In order to develop an appropriate spider mite management strategy using Neoseiulus californicus McGregor and optimize laboratory rearing, its biological parameters on four types of pollen (cedar, pistachio, pear, and apricot) were determined and compared on Tetranychus urticae Koch. Our results indicated that the developmental times of females and males varied from 6.06 to 7.32, and 6.00 to 7.15 d, respectively. The highest fecundity was obtained on pistachio pollen, followed by apricot pollen and T. urticae. Feeding on cedar pollen caused the lowest fecundity. In contrast to T. urticae and pistachio pollen, which resulted in the highest intrinsic and finite rates of increase, feeding on cedar pollen produced the lowest value. Pistachio and apricot pollen appear to have the highest nutritional value. From an ecological perspective, in the presence of pistachio pollen, a more rapid population increase of N. californicus could be expected, when the prey is scarce or absent in greenhouses or fields. This may provide valuable information for the design of a comprehensive program for conservation and/or mass production of N. californicus to control T. urticae and other pests.

Sublethal effects of fenazaquin on life table parameters of the predatory mite Amblyseius swirskii (Acari: Phytoseiidae).

Knowledge of the impact of acaricides on predatory mites is crucial for integrated pest management programs. The present study evaluated the sublethal effect of fenazaquin (Pride(®) 20 % SC, Behavar, Iran) on life table parameters of the subsequent generation of the predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae), fed on Tetranychus urticae Koch under laboratory conditions [26 ± 1 °C, 70 ± 3 % RH and 16:8 (L:D) h]. The sublethal concentrations including LC10, LC20 and LC30 were determined using a dose-effect assay. The total development time of both sexes enhanced with an increase in concentration. The oviposition period and total fecundity decreased in dose-dependent manner. The intrinsic rate of increase (r) and finite rate of increase (λ) significantly descended with concentration enhancing from LC10 to LC30, compared with the control. The net reproductive rate (R 0) ranged between 2.76 and 7.37 offspring. Overall, the results indicated that fenazaquin had negative effects on development and life table parameters of the subsequent generation of A. swirskii. In conclusion, fenazaquin is not a compatible acaricide with A. swirskii and should not be used with this predatory mite in integrated management of T. urticae.

Effect of temperature and button mushroom varieties on life history of Lycoriella auripila (Diptera: Sciaridae).

Temperature-dependent development and population growth parameters of the fungus gnat, Lycoriella auripila (Winnertz), on button (737 and A15) mushroom were evaluated at nine constant temperatures, ranging from 8, 10, 12.5, 15, 20, 22.5, 25, 27, and 30 degrees C and developmental rates were modeled as a function of temperature. At 25 and 27 degrees C, an average of 20.89 and 22.43 d was needed for L. auripila to complete its development from oviposition to adult eclosion on 737 and A15, respectively. The population failed to survive at 8 and 30 degrees C. The developmental times of males or females on each variety at various constant temperatures differed significantly. The regression and Ikemoto and Takai linear models, in the absence of 10, 12.5, and 27 degrees C, described the relationship of developmental rate to temperature for male and female of L. auripila very well. Data were fitted to various nonlinear temperature-dependent models. The Logan 6 and Briere 1 nonlinear models provided the best estimation for Topt and Tmax and are highly recommended for the description of temperature-dependent development of L. auripila on 737 and A15, respectively. On 737 variety, significant differences were observed among all growth parameters at various temperatures. The intrinsic rate of natural increase (r(m)) for L. auripila was 0.134 on 737 variety at 25 degrees C, which was significantly >0.052 on A15 variety at the same temperature. No other data are available in using linear and nonlinear models to describe the relationship between temperature and L. auripila development. Understanding the influence of temperature on development of L. auripila is discussed with respect to pest management in mushroom production.