Journal of Entomological Society of Iran
Year:2013 | Volume:33 | Issue:2|Papers Count:12

Mites of the family Pygmephoridae (Acari: Heterostigmata) consist of free-living species with phoretic or non-phoretic female forms. The free-living species of the pygmephorid mites are often associated with insects (primarily Coleoptera, Hymenoptera and Diptera) for phoretic dispersal. They are generally fungivorous in their habitats (Kaliszewski et al., 1995).

A hyperparasitoid was identified in a field study on larval and pupal parasitoids of diamondback moth, Plutella xylostella (L.) (Lep.: Plutellidae), in Isfahan province during May to October 2009. Mokrzeckia obscura Graham, 1969 (Hym.: Pteromalidae) was reared from an endoparasitoid, Cotesia plutellae (Kurdjumov) (Hym., Braconidae), which was obtained from P. xylostella larvae collected from Mobarakeh county. This is the first record of M. obscura from Iran. This species belongs to the subfamily Pteromalinae and has already been reported from the UK (Noyes, 2010).

The soybean pod borer, Etiella zinckenella (Treitschke) (Lep.: Pyralidae) is a key pest of pods and seeds of soybean (Marwoto & Saleh, 2003). This species is polyphagous attacking many cultivated crops such as medics, clovers, lucerne, field peas (especially blue boilers), vetch, lentils and soybeans (Hopkins, 2003). It is widely distributed in Asia, Europe, Africa, North America, Central and South America and Australia (Naito, 1960). This species causes up to 40% crop losses in the Lorestan province, Iran, and adjacent regions (Parvin, 1981).

Eulophidae is one of the largest families in the superfamily Chalcidoidea, including over 4472 species, placed in four subfamilies and 297 genera (Noyes, 2010). Some species are important biological control agent of pests. The first studies on eulophids in Iran were made by Herting (1973) and Davatchi & Shojaei (1989). Ebrahimi et al. (2009) and Hesami et al. (2010) have also recently collected and identified some eulophid species of Iran.

Mites of the family Tetranychidae (spider mites) include some of the important pests in agriculture and forestry, and can be found on many fruit trees, vines, berries, vegetables and ornamental plants (Zhang et al., 2002). They feed on most parts of plants, including the upper and lower surfaces of leaves, as well as on stems and sheaths of grasses (Jeppson et al., 1975).

The functional response of a predator is the base of prey-predator dynamics. Functional response of Serangium montazerii Fürsch at different egg densities (50, 100, 150, 200 and 250) of Dialeurodes citri (Ashmead) was studied in an open-patch experiment, in a growth chamber (25 ± 1oC, 65 ± 5% RH and a photoperiod of 16: 8 L: D h) on ‘Thompson’ navel orange (Citrus sinensis cv. Thompson) apical leaves. A type II functional response was obtained using logistic regression. The searching efficiency (a') and handling times (Th) of the female adults using nonlinear least-square regression were estimated as 0.0421 ± 0.00945 h-1 and 0.0896 ± 0.0362 h, respectively. Mean times required for the female predator to settle in a patch were 121.4, 140, 116, 83 and 78 minutes at above-mentioned prey densities, respectively. It was inversely density dependent (R2 = 0.740). The proportion of female predators remaining in open patches at the end of the experiment was directly dependent on prey density (R2 = 0.9). It was concluded that the type of functional response obtained here was in agreement with studies on this predator in closed patches.

Laboratory bioassays were carried out to study the insecticidal efficacy of two Iranian diatomaceous earths (DEs) and SilicoSecÒ formulation against Sitophilus granarius (L.). Four different particle sizes of DEs were applied at five concentrations. The mortality was counted 2, 5 and 7 days after exposure. The experiment was carried out at 27 ± 1oC and 55 ± 5% relative humidity in continuous darkness. For SilicoSecÒ and Mamaghan with less than 37 mm particle size, 500 ppm was sufficient to cause 100% mortality after 5 days of exposure. While in case of Maragheh deposit with the same particle size, complete mortality was recorded at 1000 ppm after 5 days. LC50 values indicated that SilicoSecÒ and Mamaghan with < 37 mm particle size were the most efficient DE samples against S. granarius. In most cases, the efficacy of DEs increased with decreasing particle size. The visual observation of scanning electron microscopy (SEM) images showed that SilicoSecÒ has more attachment to insects’ body. However, the adhesiveness of DE particles cannot be the main indicative of their insecticidal effectiveness.

A review of the genus Phasia Latreille in Iran is given. An identification key to the six Iranian species of Phasia and illustrations of their male and female terminalia are presented. The species Phasia obesa (Fabricius) and P. pusilla Meigen are recorded for the first time from Iran.

Searching efficiency (a') (attack rate) and handling time are two major components of natural enemies’ functional response and are usually used to evaluate their effectiveness. The age-specific searching efficiency of Aphidoletes aphidimyza (Rondani) was studied during its larval stage. The experiment was conducted in terms of age-specific functional response to the varying density (5, 10, 20, 40, 60 and 80) of third instar nymphs of Aphis craccivora (Koch) at 23 ± 1oC, 70 ± 5% R.H. and a photoperiod of 16: 8 h (L: D). Parameter estimates for logistic regressions showed a type III functional response at all larval ages to the varying density of A. craccivora. The age-specific handling times (Th) were estimated using Rogers random-attack equation, varied with the age of larval predator. The searching efficiency showed a similar and increasing trend at all predator larval ages. The estimated maximum rates of predation (T / Th) for the total larval stage were inversely related to prey density. It was concluded that A. aphidimyza, with type III functional response in all its larval stage, could be considered as a highly effective biological agent in suppressing and regulating A. craccivora population.

The tomato fruit borer, Helicoverpa armigera (Hubner), is a destructive insect pest of many host crops in Iran and worldwide. The effect of different tomato cultivars (SUN 6108 f1, Rio grande UG, Korral, CH falat, Hed rio grande and Cal JN3) was studied on life table parameters of H. armigera under laboratory (25 ± 1oC, 65 ± 5% RH and a photoperiod of 16: 8 (L: D) hours), and on the activity of some digestive enzymes of its sixth larval instars under field conditions. The larval period was longest on Hed rio grande (35.500 ± 1.340 days) and shortest on Korral (24.290 ± 0.688 days). The intrinsic rate of increase (rm) ranged from 0.094 ± 0.003 to 0.159 ± 0.002 (day-1), which was lowest on Rio grande UG and highest on Korral. The larvae reared on the leaves of SUN 6108 f1 showed the highest amylolytic activity (0.062 ± 0.00004 mU mg-1), whereas the lowest activity was in the larvae fed on the leaves of Cal JN3 (0.027 ± 0.00004 mU mg-1) and Korral (0.027 ± 0.0001 mU mg-1). The amylolytic activity of larvae fed on the fruits of tomato cultivars was highest on Cal JN3 (0.047 ± 0.0001 mU mg-1). Also, the highest general proteolytic activity of H. armigera was in the larvae reared on the leaves of Hed rio grande (3.235 ± 0.004 U mg-1) and fruits of Rio grande UG (2.757 ± 0.135 U mg-1). It could be concluded that Rio grande UG is unsuitable host for the growth and development of H. armigera.

Asian citrus psyllid, Diaphorina citri Kuwayama, is an important pest of citrus that transmits the bacterial pathogens responsible for citrus greening disease, also called Huanglongbing. The aim of the current study was to investigate the shape variations of the forewing among the Iranian geographic populations of D. citri, as well as one population from Pakistan. The adult psyllids used in this study were collected on Lime, Citrus aurantifolia (Christm.) Swingle, from orchards in Southern Iran in 2011. The forewings of 12 D. citri populations (30 randomly selected adult females from each population) were examined using geometric morphometric analysis. Multivariate and univariate analysis of variance indicated significant variation of wing shape and size among the examined populations. Based on forewing shape, Sistan-Baluchestan and Pakistan populations were different from other populations, including Hormozgan (Minab, Rudan, Fareghan, Hajiabad), Kerman (Manujan, Kahnuj, Jiroft-Anbarabad, Jiroft-Blook, Orzoiye), and Fars (Darab). Considering the following reasons, geographic variation was developed by the interaction of genetic mechanisms and environmental processes: (1) there was a significant difference in the shape and squared Mahalanobis distance between some populations, (2) the correlation between geographic distances matrix and Mahalanobis distances matrix was significant, and (3) the wings grew allometrically, and geographic populations had separate allometric direction but parallel to each others. It is suggested that wing morphology could be beneficial for the preliminary assessment of population structure and pest control methods of D. citri in Iran.

The parasitoid wasps of the genera Leiophron Nees and Euphorus Nees were studied in northern Iran (Guilan, Mazandaran and Alborz provinces). The specimens were collected using Malaise traps from different habitats during 2010-2011. Four species of both genera were collected and identified, of which three species, Euphorus pallidistigma (Curtis), E. similis (Curtis) and Leiophron fascipennis (Ruthe) are newly recorded from Iran. An identification key for these four species together with comments on diagnostic characters and geographical distribution of each species are presented.