PLANT PEST RESEARCH
Year:2017 | Volume:7 | Issue:2|Papers Count:7

This study examined the effects of prey stages on numerical reponses of Nephus arcuatus at different densities of four different sizes of Nipaecoccus viridis (four different stages including: the 1st, 2nd and 3rd instar nymphs and adult females of N. viridis). The densities of 2, 4, 8, 16, 50, 70, 90, 110 and 130 of 1st instar nymphs, 2, 4, 6, 10, 20, 30, 40 and 50 of 2nd instar nymphs, 2, 4, 6, 9, 15, 21 27 of 3rd instar nymphs and 1, 3, 5, 7, 9 of adult females of prey were considered as prey and introduced to mated female (10 day- old) during 24h. The results indicated that the number of eggs laid per female were nonlinearly increased with increasing prey density in all four prey stages. Comparisons of means eggs laid by females at highest densities of each prey indicated that females laid the highest number of eggs when exposed to small prey, 1st instar nymph (8.5± 1.2) and lowest eggs on 2nd instar (5.2±0.7), 3rd instar nymphs (5.9±0.8) and as well as adult females (4.7±0.7) with significant differences (P=0.0002). These findings showed that the numerical response of N. arcuatus is affected by different stage of N. viridis.

Stem borers are major pests attacking paddy fields during all its growth stages. In this study, the geographical distribution of moth stem borers (Lep.: Crambidae & Noctuidae) was determined in paddy fields of 16 provinces, Iran, during 2015-2016. The specimens were collected by light, malaise and pheromone traps. Six stem borer species in paddy fields; including five from Crambidae (Chilo partellus, C. luteellus, C. suppressalis, C. phragmitella and Scirpophaga praelata) and one belonging to Noctuidae, (Sesamia sp.) were recognized. The striped stem borer (C. suppressalis) and Sesamia sp. were identified as serious rice stem borers in Iran. Chilo suppressalis was recorded for the first time from five provinces: Khorasan-e Razavi, Qazvin, Zanjan, Chaharmahal Bakhtiari and Azarbayejan-e Sharqi. Damage by a Sesamia species was reported from Kohgiluyeh and Boyerahmad, Esfahan, Ilam and Ardebil provinces for the first time. According to the current results and unavailability of type specimens for this species, previous report of the presence of white stem borer (Scirpophaga innotata) in Iran is dubitable. The findings provided key and basic distribution information of all six stem borer species which can be used for controlling tactics through IPM programs against the pests in each region.

In present study, the maternal effect of temperature as an ecologic factor and the effect of Wolbachia infection as an inner-genetic factor on diapause percentage of Trichogramma brassicae Bezdenko (Hym.: Trichogrammatidae) were investigated. Maternal generation of both infected (asexual) and uninfected (sexual) populations were reared separately at 14 and 20oC. After maximum adult emergence (24 hours), asexual females and sexual-mated females (both 24h old) were separately selected and placed in glass test tubes. Each of them were supplied with a cardboard which included 100 eggs of Ephestia kuehniella Zeller (Lep.: Pyralidae) (6 hours old). The results revealed that Wolbachia infection and rearing temperature of maternal generation had significant effect on diapause percentage of T. brassicae. When rearing temperature increased, the diapause percentage had increased too. Diapause percentage in uninfected (sexual) population was higher than infected (asexual) ones which show the negative effect of Wolbachia infection. Probably, presence of Wolbachia causes energy reduction in facing low temperature.

Using resistant varieties is one of the suitable ways for controlling the potato moth, Phthorimaea operculella as one of the important pests of potato in field and storage. So that the resistance of six potato cultivars (Banba, Bellini, Jelly, Draga, Marfona, and Milva) to potato tuber moth was assessed by studying the biological and the demographic effect of the mentioned pest. This experiment was carried out in a growth chamber, 25 ±2oC, 65 ±5% RH and 14L:10D h photoperiod. According to the results, the potato tuber cultivars had a significant effect on the period of egg, larva, pupa, preadult, male life span, male and female adult longevity of this pest (P<0.05), but there was not significantly difference on the period of female life span (P>0.05). In addition, in this study, reproduction parameters of potato moth including APOP and total fecundity were not significant among the potato tuber cultivars (P>0.05), but they were significantly different on the period of TPOP and oviposition period (P<0.05). Also studying the life table parameters showed the least intrinsic rate of increase (r) on Marfona (0.141 day-1), the least net reproductive rate (R0) on Draga (34.56 offspring), the lest finite rate of population increase (l) on Marfona (1.151 day-1) and the highest period of generation time (T) on Marfona (28.06 days).

In superparasitism, a host is parasitized by one or more conspecific females, a phenomenon resulting in immature competition within the host’s body. In the present study, the competition between sexual and asexual strains of the parasitoid wasp, Lysiphlebus fabarum (Marshall) (Braconidae: Aphidiinae), was studied in simultaneous and successive introductions. The biological traits by both strains were determined in surviving individuals of superparasitized aphids as well. For this purpose, eight wasp females of each strain were introduced into 40 second instar of black bean aphid, Aphis fabae Scopoli, simultaneously or by a 24-hour priority. Our results revealed that the early introduction of each strain had a significant effect on the number of emerging adults of that strain. However, in simultaneous introduction, a greater number of sexual progeny emerged than asexual ones. The development time of sexual progeny was significantly decreased when their females were introduced earlier into the host aphids. Other morphological and biological traits (hind tibia length, head width, ovary area, egg load and egg size) of surviving individuals of superparasitized aphids were not affected by the oviposition sequence of the strains. The findings showed that sexual L. fabarum females were successful in competition with asexual females, the superiority of which could be more important in a host limitation conditions.

The striped stem borer is a serious pest of rice in the northern provinces of Iran, which is found in all stages of its growth from nursery to paddy field. It causes qualitative and quantitative damage on rice. Nowday, with the expansion the development of problems due to chemical control, other methods of pests management especially biological controlhas a special place in agriculture is rice. Accordingly, in order to study one factor affecting the role of biological control agents (Tricogramma) compared to other control methods. In this research, five different treatments, including biological control three, two and one-year-old, chemical control and cultural controlto reduce the population of rice striped stem borerin two city of Guilan province were evaluated in paddy fields. The results showed that rice striped stem borer population flactuations in three-year of biological control had a decreasing trend and its natural enemies population hadan increasing trend. Furthermore, results of this study indicated that the average number of natural enemies collected during the season in biological control of three, two and one year old, cultural and chemical controls, 679, 589, 469, 447 and 396 number was, respectively. This study also showed that all treatments in terms of yield levels had significantly different from each other. The highest yield on three-year biological and chemical control methods was observed. 3677 and 3650 kg per hectare, respectively. Based on the results obtained, two time release of Trichogramma in each generation of rice striped stem borer and during three consecutive years, had the highest effective compared to other methods used in the control of rice striped stem borer in paddy field.

Dung beetles play a significant role in mixing organic materials in nutrition cycle, dung recycling, adjustment of physical and chemical characteristics of soil and controlling arthropod pests (mostly Diptera). These beetles are distributed throughout the world. In order to collect and identify dung beetles in western part of Guilan Province, a faunal investigation was provided during spring to autumn of 2015. In total eight species belonging to four genera were found and identified from eight zones in western part of Guilan Province in Iran. Onthophagus formaneki Reitter, 1897 is reported for the first time from Guilan province. The list of identified species are as follow:Copris lunaris (Linnaeus, 1758), Copris hispanus (Linnaeus, 1764), Oniticellus fulvus (Goeze, 1777), Oniticel1us pallipes (Fabricius, 1781), Onthophagus taurus (Schreber, 1759), Onthophagus illyricus (Scopoli, 1763), Onthophagus formaneki Reitter, 1897*, Sisyphus schaefferi boschniaki Fischer, 1823.