نشریه نامه انجمن حشره شناسی ایران
سال سی‌ام شماره 1 (پیاپی 46، تابستان 1389)

Host plant resistance is an economic and environmental friendly method for controlling Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko). To evaluate resistance of 15 cultivars and advanced lines of wheat to RWA under field conditions, an experiment was conducted in a randomized complete block design with 4 replications in Mobarake region (Isfahan province, Iran) during 2001-2003. Four plants were harvested randomly from each plot in a weekly schedule and the numbers of settled aphids per plant were counted for both adults and nymphs, and the damage rate was estimated. Variance analyses were performed on pooled data from all samplings and correlation coefficients among resistance criteria were calculated. Results showed that maximum adult / plant was on Mahdavi, M-78-14, and M-78-19; and minimum adult / plant was on M-73-4, M-73-18, Alvand and M-75-7. Maximum number for nymphs was estimated on M-75-10 and M-78-20 and the minimum number on M-73-4. Mahdavi and M-75-7 had the highest damage rate and M-73-18, M-73-4 and M-78-7 had the lowest. Positive and significant correlation coefficients were found between damage rate with adult aphid / plant, and between the number of adults and nymphs. Therefore, damage rating could be used as a suitable criterion for evaluating resistance of wheat to RWA under field conditions. To assess influence of the pest on yield and yield components, a similar allotment was cultivated and sprayed two times with Metasystox. At harvest, yield and yield components were determined in sprayed and unsprayed allotments, and consequently, the means of yield and yield components between these two allotments were compared using t-student test. The mean comparisons showed that there was no significant difference between sprayed with unsprayed allotments for yield and yield components.

In the present study, virulence of three isolates of Metarhizium anisopliae (Ascomycota, Clavicipitaceae) were evaluated on the second instar larvae of the onion thrips, Thrips tabaci Lindman by using spray potter tower at six conidial concentrations of isolates (103-108 conidia/ml) with Thrips Entomopathogenic Bioassay System (TEBS) method. Causing the highest total mortality rate on thrips larvae and having the lowest LC50 value (2.3 × 104 conidia/ml), M. anisopliae EUT118 was selected as the highest virulent isolate. Afterwards, the susceptibility of female adults and 5th nymphs of Orius albidipennis (Reuter) was tested against this isolate of M. anisopliae without attendance of host. Results indicated that two stages of predator; female adults and 5th instar nymphs had similarly low susceptibilities to fungal infection. In general, our results revealed that the anthocorid predator, O. albidipennis was less affected by this isolate of fungus. As a result, these two biocontrol agents could be used both together in control programs of T. tabaci in greenhouses.

The peach-potato aphid, Myzus pesicae Sulzer, is a globally distributed, economically important pest of a wide range of field crops and ornamentals. Due to extensive and repeated use of insecticide, this species has developed many different resistance mechanisms to insecticides. The enzyme acetylcholinesterase (EC 3.1.1.7) (AChE) occurs widely in both vertebrate and invertebrate nervous systems and is the target of organophosphate (OP) and carbamate insecticides. One of resistance mechanisms to OP and carbamate insecticides is the insensitivity of AChE to these insecticides. In this study the possibility of mutation in insensitive AChE was surveyed. The complete coding sequences of acetylcholinesterases (MpAChE2) from susceptible and resistant populations were identified and sequences from resistant and two susceptible populations were compared. Consequently, one amino acid substitution (Ser431Phe) was detected within the resistant population at MpAChE2 gene. The Ser431Phe substitution is located in acyl pocket of acetylcholinesterase. Therefore, it seems that MpAChE2 is important as a target of pirimicarb. This substitution makes the acyl pocket narrower and pirimicarb can not have any access to this site. cDNA was obtained from individual aphids randomly and sequence of MpAChE2 indicated that MpAChE2 of the resistant population was heterozygous.

The predatory phytoseiid mite, Amblyseius herbicolus Chant has been collected from mulberry trees infested with two-spotted spider mite, Tetranychus urticae Koch and mulberry thrips, Pseudodendrothrips mori (Niwa) in Guilan province. Development and oviposition of this predatory mite was studied on two-spotted spider mite, mulberry thrips and date palm pollen as an alternative food in laboratory using the citrus excised leaf method in Petri dishes at 26 ± 1°C, 14L: 10D photoperiod and 70-80% RH. The results indicated that, mean duration of immature stages (day) of female predatory mite was the lowest on P. mori (4.86  0.19) and T. urticae (5.26  0.15) and the highest on date palm pollen (7.46  0.21). Fecundity (eggs/female) was the highest on P. mori (48.2  1.85) then on T. urticae (36.2  1.9) and the lowest on date palm pollen (19.13  1.72). Oviposition period (day) was the highest on P. mori (20.86  051) and T. urticae (20.33  1.19) and the lowest on date palm pollen (16.06 . 97). Lowest post-oviposition period (day) was on T. urticae (3.13  0.19) followed by date palm pollen (4.37  0.28) and then on P. mori (5.6  0.27). The mean generation time (day) of predatory mite was the longest on palm pollen (9.86  0.21), followed by mulberry thrips (7.13  0.21) and then two-spotted spider mite (6.86  0.16). Based on these results, A. herbicolus is a general predator. The date palm pollen may variously be used as an alternative food in absence of main food.

To detect the main mortality factors acting on the immature stages of Simyra dentinosa Freyer, a biocontrol agent of weedy spurges Euphorbia spp. in West Azerbaijan Province, multiple decrement life table was constructed. All field experiments were performed at Urmia in 2001-2004. The mortality factors in the population of S. dentinosa under semi-field conditions were assessed over its three generations. The analyses of the data obtained indicated that larval parasitoids and miscellaneous factors in pupal stage had the highest role in population reduction of the moth. The highest mortality was found in the larval stage and caused by parasitoids. The most common larval parasitoids observed were Cotesia spp. (Hym.: Braconidae), Hyposoter didymator (Thunberg) (Hym.: Ichneumonidae), Exorista larvarum (L.) (Dip.: Tachinidae) and also Pales pavida (Meigen) (Dip.: Tachinidae). Moreover, the dominant species of larval stage were Cotesia plutellae (Kurdjumon), H. didymator and C. plutellae during 2001-2002, 2002-2003 and 2003-2004, respectively. They parasitized 8.11, 6.59 and 14.85% of larvae during the mentioned years, correspondingly. Furthermore, the pupal stage had also significant mortality that was caused by a complex of miscellaneous mortality factors. The results showed that these factors annihilate 12.07, 16.21 and 10.33% of pupae during above mentioned years, respectively. The results also indicated that the survival curve of S. dentinosa were type II during its three generation. Furthermore, the net reproductive rate of this moth during three years of studies was 105.04, 82.16 and 95.68, respectively.

Cheilosia (Convocheila) cumanica Szilady is recorded for the first time from Iran. This species is similar to C. laticornis Rondani morphologically; however, is distinguished from this close species in male by hairy eyes (bare in C. laticornis) and in female by longer third antennal segment that is three times longer than the second segment (less than 2.5 times in C. laticornis). This finding increase the number of Cheilosia species known from Iran to seven.

Effects of four pesticides (imidacloprid, dichlorvos, pymetrozine and abamectin) were evaluated on life table parameters of Orius albidipennis (Reuter). Pesticides were used at the concentrations recommended by the manufacturers. The bioassays were carried out using drum-cell method, in a growth chamber at 27 ± 1ºC, R.H. of 65 ± 5% and 16 h photo phase. The net reproductive rate (R0) value for the populations treated with imidacloprid, dichlorvos, pymetrozine, abamectin and tap water as control was, 2.91 ± 0.48, 18.85 ± 2.55, 10.16 ± 1.21, 8.00 ± 1.05, 43.40 ± 7.64; the intrinsic rate of natural increase (rm) was 0.040 ± 0.005, 0.097 ± 0.018, 0.086 ± 0.012, 0.078 ± 0.010, 0.148 ± 0.006: the mean generation time (T) was 25.60 ± 1.12, 25.94 ± 1.85, 26.37 ± 0.25, 25.61 ± 0.21, 25.20 ± 1.16; the doubling time (DT) was 18.04 ± 2.76, 7.72 ± 1.60, 8.23 ± 1.11, 9.24 ± 1.37, 4.68 ± 0.18, and the finite rate of increase (λ) was 1.041 ± 0.006, 1.102 ± 0.019, 1.090 ± 0.013, 1.081 ± 0.011, 1.160 ± 0.007, respectively. Imidacloprid and dichlorvos, which revealed the most and the least effects on the life table parameters, were the most and the least harmful among the chemicals tested.

During a two-year (2004-2005) survey of alfalfa aphids and their natural enemies in Isfahan, a total of four aphid species and 58 species of their natural enemies comprised of 45 predatory species, 11 parasitoid species and two species of parasitic mites were collected and identified. Moreover, five hyperparasitoid species were collected. On each sampling date, six 20-sweep samples were taken using a 38cm-diameter sweep-net and also six 20-stem were sampled. The results showed that the mean percent of Hippodamia variegata Goeze, Nabis spp., Deraeocoris spp., Orius spp., Geocoris spp. and aphid parasitoids in strip-harvested field were 38%, 95%, 119%, 57%, 100% and 122%, respectively; higher than those in conventionally-harvested field. In contrast, the mean percent of Acyrthosiphon pisum (Harris) and Therioaphis trifolii (Monell) forma maculata (Buckton) were 24% and 28%, respectively; lower in strip-harvested field than in conventionally-harvested field.

The biological parameters of Sympiesis striatipes Ashmead, one of the most abundant hymenopterous ectoparasitoid of Phyllocnistis citrella Stainton in Ehime province of Japan, were studied under laboratory and field conditions. The mean immature developmental time and adult longevity at different temperatures (22 to 31°C), 50-70% RH and 12L: 12D photoperiod decreased as the temperature increased, and females survived longer than males. Offspring sex ratio from females provided with males was 84.7% males and 15.3% females. Presumably mated females began oviposition 2-3 days after emergence and continued up to 39 days. Each female laid a mean of 123.4 ± 13.97, and longevity reached 33.8 ± 1.5 days at 27 ± 1°C, 50-70% RH and 12L: 12D photoperiod. The intrinsic rate of natural increase (rm) was 0.312. Host feeding or stinging without oviposition killed 44.7 ± 4.2 host larvae per female parasitoid. Seventy five point eight percent of eggs were laid on third instar larva of host and the remainder on the prepupa. Under field conditions, superparasitism on the third instar larvae was 9.2% (n = 200) and up to 7 eggs per host were recorded. Under superparasitism lethal competition (n = 40), one adult parasitoid per host emerged from 87.5% of the samples and two adult parasitoids per host emerged from the rest. Superparasitism on prepupa was rare. The sex ratio (M: F) of the parasitoid oviposited on the third instar larvae of host and pupae was 2.2: 1.0, and 1.3: 3.0, respectively.

An account of the Iranian alticine fauna, comprising 59 species from 11 genera, is presented. Phyllotreta muehlei sp. nov. is newly described and 13 species are recorded for the first time from Iran.