The fecundity of the aphid Rhopalosiphum padi during the first ten days of reproduction was measured on five wheats at three growth stages. The wheats were of UK and Iranian origin, but also involved both spring and winter wheats as well as hexaploid and tetraploid types. Aphids which had already been reared on the respective variety for at least one generation were transferred to the experimental plants. The tetraploid Emmer showed some resistance in comparison with the hexaploid UK varieties at later growth stages, whereas the Iranian variety Moghan 2 appeared relatively resistant only at the tillering stage. The other Iranian variety, Ommid, was resistant at all growth stages, and appears to be the most resistant hexaploid wheat variety t o R. padi so far identified.Correlations of aphid fecundity with plant chemistry were attempted with total phenolic compounds, hydroxamic acids and amino acids. All three of these chemical groups have previously been reported as correlated with plant resistance to cereal aphids. Even just for the results at the tillering stage, no correlation could be found for phenolics or hydroxamic acids, but a multiple regression based on the levels of alanine, histidine and threonine accounted for over 95% of the variation in aphid fecundity at all 15 data points (5 wheats X 3 growth stages). No cause or effect relationship is necessarily implied.

Purpose Successful implementation of construction projects is one of the crucial factors for the economic development of every country. The main part of the countries’ capital is allocated to civil and infrastructure projects annually, most of which are accomplished with delay. Construction projects are often criticized for overrunning time and budgets. Analyzing the factors causing delay is essential for omitting them and timely implementation of these projects. Due to the importance of oil projects, this study aims to investigate and analyze the factors causing a delay in Iran’s oil construction projects. Design/methodology/approach In this research, after a broad literature review, using the fuzzy Delphi method, a total of 75 delay factors were identified under 11 major categories of owner, contractor, consultant, equipment, labor, materials, design, contract and contractual relations, laws and regulations, environmental factors, and managerial factors. Then, by using the best-worst method, the factors were prioritized. Findings The results showed that sanction, governmental management systems, weak project management by the contractor, technical and managerial weaknesses of the consultant, financial problems and delay in payment by the owner, low efficiency of the equipment, low productivity of the workforce, changes in laws and regulations, inappropriate organizational structure linking to the project, changes in the design, and changes in the price of materials are the most crucial factors causing a delay in Iran’s oil construction projects. Research limitations/implications These findings are expected to have significant contributions to Iran’s oil construction industry in controlling the time overruns in construction contracts. Originality/value The main contribution of this study is to develop a comprehensive framework in which, causes of delay in Iran’s oil construction projects are addressed and prioritized.

Calculation of Skid Trail Spacing (STS) is an important option to minimize the total costs of skidding. Construction of many skid trails increases the construction cost, it also results in more degradation on different levels in forests. On the other hand, by constructing less skid trails, winching cost will increase, and in many cases, the skidders will exit from skid trails. This research was carried out in four districts under management of Mazandaran Wood and Paper Industry Company with the aim of determination of Optimum Skid Trail Spacing (OSTS) for an HSM skidder. In this study, a continuous time study method to the nearest second with stop watch was used. The results indicated that the time modelling of winching was mainly affected by load volume and winching distance. By using the time modelling of winching, the winching cost is estimated and then by combining that with the skid trail cost graph, the OSTS graph is calculated. Finally, 95 meters is calculated as optimum skid trail density in this study.

Problem Statement: Psyllids as a small group of insects with plant feeding adult and nymphal stages, not only could have direct feeding damages but they could also transmit plant diseases especially viruses. Bactericera tremblayi had recently increased to high densities in onion fields in East Azarbaijan province in Iran and the pest had become widespread. This was the first study of the biology of the pest in Iran and probably in the world. Approach: After collection of the adult insects from infested onion fields, they were then reared in laboratory under controlled conditions (at 21±3°C, 60±10% RH and under a 14:10 (L: D) light regime) and different life stages of the pest were studied. Results: The lifespan of adult male and female psyllids was 33.63±2.36 and 39.94±2.64 days respectively. The preoviposition period was 3.75±0.14 days. The total number of eggs laid per female was 625.5±53.9. Egg incubation took 7.44±0.15 days and a mean of 90.3% eggs hatched. The nymphs passed through five instars before reaching the adult stage and the development time for the nymphal stage was 17.71±0.61 days. The sex ratio was estimated as 1:1. Conclusions: The results of the present study could successfully be applied to future IPM strategies in order to effectively control this pest with relatively unknown biological characteristics and decrease the damages observed in onion fields.

Habrobracon hebetor Say (Hymenoptera: Braconidae) is one of the most important natural enemies that has been used for biological control of lepidopteran pests, so the sub-lethal effects of imidacloprid, abamactin and Bacillus thuringiensis Berliner (Bt) on progeny sex ratio (male/total) and adult longevity of H. hebetor were examined under laboratory conditions. It was found that the progeny sex ratio changed to male bias significantly by Bt treatment. Also, the adult longevity of the wasp was affected adversely by insecticides treatment and it was longest in Bt treatment. In conclusion, the current results indicated that the sub-lethal concentration of these insecticides affected the progeny sex ratio and adult longevity and the best strategies for reduction of hazard to the H. hebetor in combination with Bt is to avoid their application before Bt spraying.