Quality control of the parasitoid wasp Trichogramma brassicae(Hymenoptera:Trichogrammatidae)over 45 generations of rearing on Sitotroga cerealella

Trichogramma brassicae(Bezdenko)is an important biological control agent that has been used widely against many lepidopteran pests.Commonly,colonies of Tri-chog...     

Two new species of Chrysis Linnaeus (Hymenoptera,Chrysididae) from Iran

The Iranian species in the Chrysis pulchella and C. varidens species groups are investigated. Six species are recognized, two of which are described for the first time: Chrysis gamberoonensis Farhad, Rosa and Talebi sp. nov. and Chrysis brunneamarginata Farhad, Rosa and Talebi sp. nov.. Chrysis gamberoonensis Farhad, Rosa and Talebi sp. nov. belongs to the C. pulchella group and is recognizable within this species group by its unique blue body coloration, scattered mesosoma punctures, polished pit row with elongated pits, and a small median tooth on the lateral edge of metasomal tergum 3. Chrysis brunneamarginata Farhad, Rosa and Talebi sp. nov. belongs to the C. varidens group and is recognizable by the usually colorless apical rim of metasomal tergum 3, and the unique shape of the anterior corners of the scutellum which are enlarged, thickened and directed backward covering the axillary trough. Dichotomous keys and distributional data for Iranian species included in these species groups are provided. Chrysis schwarzi Linsenmaier, 1968 is raised to species rank. The number of Iranian Chrysis species and subspecies is raised to 122.www.zoobank.org/urn:lsid:zoobank.org:pub:F419F860-3B90-4679-9A19-2CF5C255AE6B     

Increased food utilization indices and decreased proteolytic activity in Helicoverpa armigera larvae fed sublethal Bacillus thuringiensis‐treated diet

The cotton bollworm Helicoverpa armigera is one of the most devastating insect pests. A set of protease enzymes allows this species to feed on different host plant species. Control measures in agriculture often involve the application of the pathogenic bacterium Bacillus thuringiensis subsp. kurstaki (Btk). In the present study, the effects of sublethal Btk doses are evaluated with respect to the food utilization indices and proteolytic activities of Helicoverpa armigera. Accordingly, the H. armigera larvae are fed with artificial diet containing sublethal Btk doses (LC₅, LC₁₀, LC₁₅, LC₂₀ and LC₂₅) and a Btk‐free diet as control. All but one of the food utilization indices we measured is observed to increase significantly with increasing Btk doses. By contrast, the specific activity of total protease, chymotrypsin and elastase enzymes decrease significantly with an increasing Btk concentration. We conclude that Btk was not toxic to H. armigera larvae and any damage that it causes can be compensated for by H. armigera larvae via various mechanisms. In conclusion, increased nutritional indices in the larvae fed with Btk diet represent an important issue that needs to be considered to avoid the pest establishing Bt resistant populations. Meanwhile, the lack of effect of Btk sublethal concentrations on trypsin enzyme specific activity can bolster this challenge.     

A rapid and non leaky way for preparation of the sharp intracellular recording microelectrodes

To fill microelectrodes using backfilling method needs excessive time approximately 4–6  h. It is often difficult to fill microelectrodes without damage or leakage. A main problem is bubble formation in microelectrodes which has an impact on the electrical properties of the electrode and thus it influences the quality of the recording. Based on Archimede's principle there is a force within a solution which pushes insoluble material with a lower specific gravity upward and outside of the solution. Centrifugation can increase the force to eliminate the bubbles.

We designed a microelectrode holder to protect microelectrode sensitive tips from mechanical damage due to the gravity tensions; it can help to eliminate the bubbles easily and simultaneously in 10  min or less.

The tests were performed for 2000, 4000, and 8000  rpm centrifugation each one for 3, 6 and 12  min duration respectively, it was found that the bubbles were completely eliminated at 8000  rpm for 6–12  min and there were no significant differences for resistance, and the number of leaky or damaged electrodes between the two methods.

In the new design of devices, the materials used and the design of the holder are simple and the approach is applicable to many laboratories worldwide.     

Thermal requirement for development of Sancassania rodionovi (Acari: Acaridae) on mushrooms

The free-living mite species Sancassania rodionovi (Zachvatkin) (Acari: Acaridae), is a serious pest of mushrooms in Iran. Studies were conducted to examine the development of this mite in relation to temperature on two mushroom species: Agaricus bisporus Lange (button mushroom) and Pleurotus ostreatus Kummer (oyster mushroom). The developmental time of this acarid mite was studied at eight constant temperatures, ranging from 5 to 40 degrees C, and developmental rates were modeled as a function of temperature. Sancassania rodionovi completed immature development in 17.35 +/- 0.58 and 20.17 +/- 0.88 d at 25 degrees C on button and oyster mushrooms, respectively. When the mite fed on button mushroom, the rate of development increased gradually from 10 to 35 degrees C. Using a linear model, the developmental zero was estimated to be 3.50 degrees C with a thermal constant of 357.14 degree-days. The Logan 10, Briere 1, and Thermodynamic models adequately described the data for this mite and yielded R2 values >0.95; these models provided estimates of optimum temperature for development of 33.244, 32.145, and 32.148 degrees C, respectively. Understanding the influence of temperature on development of S. rodionovi is discussed with respect to pest management in mushroom production.     

Bottom-up effect of different host plants on Plutella xylostella (Lepidoptera: Plutellidae): a life-table study on canola

The effects of 10 commercial canola, Brassica napus L., cultivars widely grown in Iran--'SLM(046),' 'Opera,' 'Okapi,' 'RGS(003),' 'Modena,' 'Sarigol,' 'Zarfam,' 'Licord,' 'Hayula(420),' and 'Talaye'--on the demographic parameters of diamondback moth, Plutella xylostella L. (Lepidoptera-Plutellidae), were determined. The experiments were conducted in a growth chamber at 25 +/- 1 degrees C, 65 +/- 2% RH, and a photoperiod of 16:8 (L:D) h. The comparison of intrinsic rate of natural increase (r(m)), net reproductive rate (R0), and the survival rate of adult stage of P. xylostella on 10 canola cultivars suggested that this pest performed best on SLM(046). The r(m) value of P. xylostella ranged between 0.241 on RGS(003) and 0.304 on SLM(046). The R0, finite rate of increase (lambda), mean generation time (T), and doubling time (DT) values of P. xylostella on SLM(046) were 52, 1.35, 13.4, and 2.35 and on RGS(003) were 31, 1.27, 14.4, and 2.94, respectively. The Weibull model adequately described the shape of the survivorship curve of adult P. xylostella from life-table data. A significant fit was obtained with the Weibull model for P. xylostella in all experimental canola cultivars. As a result, SLM(046), Opera, and Hayula(420) were the most suitable hosts and had least negative impact on life-history statistics of the pest.     

Effect of cotton cultivar on performance of Aphis gossypii (Homoptera: Aphididae) in Iran

Cotton aphids, Aphis gossypii Glover (Homoptera: Aphididae), obtained from cotton, Gossypium hirsutum L., fields in the Gorgan region of northern Iran, were colonized on 'Varamin' cotton plants in a growth chamber. The development, survivorship, and life table parameters of the cotton aphid were evaluated at 27.5 +/- 1 degrees C, 65 +/- 10% RH, and aphotoperiod of 14:10 (L:D) h of artificial light on five commonly growing cotton cultivars: Varamin, 'Sealand' (relatively resistant cultivar), 'Bakhtegan', 'Sahel' (both relatively susceptible cultivars), and 'Siokra' [resistant to Bemisia tabaci (Gennadius)]. The developmental times of immature stages ranged from 4.6 d on Bakhtegan and Varamin to 6.3 d on Sealand, whereas the immature survival was 97.5 to 65% on Sahel and Siokra, respectively. On average, there were 28.7, 28.3, 23.5, 20.1, and 16.8 nymphs produced per female on Sahel, Bakhtegan, Varamin, Sealand, and Siokra, respectively. The intrinsic rate of natural increase (r(m)) for cotton aphids on Sahel was the highest, whereas the values for r(m) varied from 0.284 (nymphs per female per d) on Siokra to 0.368 on Sahel. Jackknife estimates of generation times (T), net reproductive rate (R(0)), doubling time (DT), and finite rate of increase (lambda) on these cultivars were as follows: 9.79-10.84 d for T, 9.23-23.81 nymphs per female for R(0), 2.17-3.19 d for DT, and 1.28-1.38 nymphs per female per d for lambda. Cotton aphid performance was at its highest on Sahel and lowest on Siokra.     

Functional response,switching, and prey-stage preference of Scolothrips longicornis (Thysanoptera: Thripidae) on Schizotetranychus smirnovi (Acari: Tetranychidae)

The objective of this study was to evaluate the efficiency of Scolothrips longicornis Priesner (Thysanoptera: Thripidae) as a biocontrol agent of Schizotetranychus smirnovi Wainstein (Acari: Tetranychidae), a key pest of almond trees in the southwest of Iran. To achieve a strategy for the control of this pest, it is important to understand foraging behavior (Functional response, switching, and prey-stage preference) of S. longicornis. The predator exhibited a type III functional response when it was offered S. smirnovi protonymphs at seven densities (2, 4, 8, 16, 32 .64 and 128). Based on the random predator equation, the estimated attack rate (a), handling time (T_h), and maximum rate of predation were 0.0048 h^?1, 0.4816 h, and 49.84 per day, respectively. Using the Murdoch's model, switching behavior was observed in S. longicornis. The predator switched from one stage when it becomes rare to another more abundant stage. S. longicornis fed on all stages but preferred S. smirnovi larvae and protonymphs. The results of this study revealed that S. longicornis could be used in the integrated management of S. smirnovi. However, further field studies are needed to verify this hypothesis.     

Assessment of metals in agricultural soil of surrounding areas of Urmia Lake,northwest Iran: A preliminary ecological risk assessment and source identification

The aim of this study was to quantify the levels of toxic heavy metals and sodium in topsoil of farmlands around the Urmia Lake. A total of 96 topsoil samples were collected, pre-treated, and analyzed for metals using ICP-AES.

Median concentrations of As, Cd, Cu, Ni, Pb, Zn, and Na in sampling sites were 5, 0.26, 30, 40, 13, 84, and 251 mg/kg, respectively. The enrichment factor, geoaccumulation index, and contamination factor of the metals ranked them in the order of: Na > Pb > Cu > As > Cd > Zn > Ni, indicating minor contamination for them except Na and Pb with moderate contamination. Furthermore, the spatial analysis indicated that Cd, Cu, Pb, Ni, and Zn had similar distribution patterns in the north and northwest lands of the lake. Principal component analysis revealed anthropogenic sources for Cd, Cu, Ni, Pb, and Zn in the soil, whereas, sources of As and Na were most likely related to the dust emitting from the dried bed of Urmia Lake and from a cement industry. Potential ecological risk index in 7% of the sampling sites was at serious or considerable pollution level, and Cd and Pb were identified as the main pollutants.     

Finish line plant–insect interactions mediated by insect feeding mode and plant interference: a case study of Brassica interactions with diamondback moth and turnip aphid

There are gaps in our understanding of plant responses under different insect phytophagy modes and their subsequent effects on the insect herbivores’ performance at late season. Here we compared different types of insect feeding by an aphid, Lipaphis erysimi, and a lepidopteran, Plutella xylostella, and how this affected defensive metabolites in leaves of 2 Brassica species when plants gain maturity. Thiocyanate concentrations after P. xylostella and L. erysimi feeding activities were the same. Total phenolics was higher after the phloem feeder feeding than the folivore activity. The plants compensatory responses (i.e., tolerance) to L. erysimi feeding was significantly higher than the responses to P. xylostella. This study showed that L. erysimi had higher carbon than P. xylostella whereas nitrogen in P. xylostella was 1.42 times that in L. erysimi. Population size of the phloem feeder was not affected by plant species or insect coexistence. However, there was no correlation between plant defensive metabolites and both insects’ population size and biomass. This suggests that plant root biomass and tolerance index after different insect herbivory modes are not necessarily unidirectional. Importantly, the interaction between the folivore and the phloem feeder insects is asymmetric and the phloem feeder might be a trickier problem for plants than the folivore. Moreover, as both plants’ common and special defenses decreased under interspecific interference, we suggest that specialist insect herbivores can be more challenged in ecosystems in which plants are not involved in interspecific interference.