JOURNAL OF CROP PROTECTION
Year:2013 | Volume:2 | Issue:2|Papers Count:12

Plant extracts, such as phytoecdysteroids, are currently studied because of the possibility of their use in plant protection. Phytoecdysteroids are insect steroid hormone analogues, and they are believed to deter invertebrates from plants, either by acting as antifeedants or by being toxic through hormonal disruption upon ingestion. We describe here the effects of extract from Spinacia oleracea L. (Chenopodiaceae), a plant producing phytoecdysteroids, on the demographic parameters of Plutella xylostella L.(Lepidoptera: Plutellidae). Spinach is one of the very few crop plants which produce large amounts of phytoecdysteroids. Ecdysteroidal extracts of leaves from this plant were incorporated into food given to third instar larvae for two days. Then the larvae were reared on untreated leaves. The eggs from the emerging adults were picked up for demographic experiments. The rearing of the newly hatched larvae was continued individually on untreated leaves. All experiments were performed at 25±oC, 65±5% RH and a photoperiod of 16: 8 (L: D) h in a growth chamber. Data analysis demonstrated that the fecundity of the females was strongly affected by ecdysteroidal extract. Values of intrinsic rate of increase and net reproduction rate decreased significantly as concentration of the extract increased. However, doubling time increased significantly as concentration of the extract increased. The present study demonstrated that the ecdysteroidal components of spinach are effective on the demographic parameters of P. xylostella. Therefore, this extract may be a potential protectant as botanical alternative agent.

Hippodamia variegata is an efficient and most abundant predatory coccinellid in many countries. Understanding the ability of long-term low temperature survival in beneficial insects can be used to make better predictions about subsequent abundance and hence the biological control potential in the next spring and summer. So in this study, effects of long-term low temperatures were investigated on mortality and supercooling point (SCP) of field collected (pre-diapausing) and overwintering aggregations of H. variegataadults. Unlike the pre-diapausing insects, aggregated coccinellids could easily survive at -3 and 0oC for one month. One month acclimation at 10oC caused more than 80% mortality in overwintering adults, indicating that higher temperatures were not appropriate for overwintering aggregated coccinellid. In December and January, when diapause was in its highest level, changing the habitat temperature did not affect SCP. Acclimatization at 5 and 0oC for one month decreased SCP of pre-diapausing adults, collected from aphid infested plants in October. Our study revealed that long term exposure to temperatures below 0oC that usually happen in natural conditions may be necessary for overwintering of the coccinellid.

Edaphic Mesostigmata are important, because these feed on arthropods and other invertebrates which may affect natural equilibrium of other living micro-organisms. In order to study the fauna of mesostigmatic mites, samples of soil and litter were collected from different parts of Esfahan region. Mites were extracted by means of Berlese funnel, cleared in Lactic acid and mounted in Hoyer's medium. In this research, the world and Iranian distribution of species with some information about their habitats are provided.Two genera and 3 species were recorded as new records for Iran mite fauna that are marked by an asterisk. The list of identified genera and species is as follows: Ascidae: Arctoseius cetratus (Sellnick, 1940), A. pristinus * Karg, 1962, A.venustulus(Berlese, 1917), Gamasellodes bicolor (Berlese, 1918); Blattisociidae: Lasioseius sugawarai Ehara, 1964, L. youcefi Athias-Henriot, 1959; Melicharidae: Proctolaelaps pygmaeus (Muller, 1860); Parholaspididae: Proparholaspulus * angustatus * Ishikawa, 1987 Trachytidae: Uroseius* traegardhi * (Hirschmann & Zirngiebl-Nicol, 1969).

Soybean, Glycine max, is susceptible to a large number of disease agents such as seedling and root pathogens that cause serious damages to this crop plant. One of these soil-borne pathogens is Macrophomina phaseolina, the causal agent of charcoal root rot. In this study, two bacteria, Pantoea agglomerans and Bacillus sp. BIN, and a fungus, Trichoderma harzianum T100, as potential biocontrol agents, and maneb fungicide, were evaluated against soybean charcoal rot disease in In Vitro and greenhouse conditions. All antagonists inhibited growth of the pathogen in dual culture test by 73.8, 63.3 and 55.3%, respectively. Data from greenhouse experiments showed that in the presence of pathogen all antagonists increased the growth indices of soybean in both pasteurized and non-pasteurized soil. Reductions of microsclerotia coverage on soybean root and stem by P. agglomerans, Bacillus sp. and T. harzianumwere up to 62.5, 87.6 and 62.5%, respectively and for maneb fungicide was 87.6% in pasteurized soil. The overall results of this study show high capability of used antagonists in reduction of initial inoculums for next season of this monocyclic disease.

Banana Xanthomonas wilt is a systemic disease of banana plants. We investigated the risk of spreading Xanthomonas campestris pv. Musacearum (Xcm) through asymptomatic mature bunches. Samples of banana fingers and rachis from markets within Kampala, Uganda and at border points of Uganda with DR Congo, Tanzania, Rwanda and Kenya were tested for the presence of Xcm through recovery of the bacterium onto semi-selective media. Fingers and rachis infected with Xcm were sampled weekly to determine survival duration in such materials. Characteristic colonies of Xcm were observed in 89 bunches. Within Kampala, various levels of Xcm were detected in the local markets at 21% from Kalerwe, 50% in Nakawa and Nakasera and 53% from Kasubi. At international borders, Xcm was detected at 17% in Malaba, 32% at Mutukula, 33% in Busia, 42% at Katuna/Kamwezi, 44% Mpondwe and 62% Mpanga. About 13% of the inoculated plants exhibited symptoms typical ofXcm infection. Xcm survived for up to six months, with colony counts of 25.3 cfu/gm, 23.1cfu/gm and 20.0 cfu/gm in the peel, pulp and rachis, respectively. This study demonstrated that Xcm is carried in traded banana materials over long distances and across borders. The pathogen can survive in the peel and rachis from markets up to 6 months and therefore these organs may act as sources of inocula for new infections. Consquently, there is need to improve on phytosanitary issues to manage spread of Xcm and spread of contamination to new areas.

A survey was conducted to identify the fungus gnats (Diptera: Mycetophilidae) in Kermanshah province (west of Iran) during 2010-2011.The specimens were collected from nine different localities. Adults were reared from the fruiting bodies of agaric fungi. Five species are recorded for the first time from Iran: Mycetophila strigatoides (Lundrock), Allodia ornaticollis (Meigen), Rymosia pseudocretensis Burghele-Balacesco, Synplasta gracilis (Winnertz) and Sciophila eryngii Chandler. Eight host associations (gnats-fungi) are also reported for the first time. The diagnostic characters, host range and geographical distribution of each species are given.

Life table of almond moth, Cadra cautella Walker was studied on four main dry and semi-dry date palm varieties (Deyri, Zahedi, Piarom, and Rabbi) of Iran under laboratory conditions. Data were analyzed based on the age-stage, two-sex life table theory. Duration of total preadult stages was 42.54, 45.79, 51.48 and 50.41 days on Deyri, Zahedi, Piarom, and Rabbi, respectively. The highest fecundity of female almond moth on date palm varieties was 245.29 eggs on Zahedi. The intrinsic rate of increase (rm) on different varieties of date palm ranged from 0.069 d-1 (on Piarom) to 0.105 d-1 (on Deyri). The highest net reproductive rate (R0) was on Deyri (95.81 offspring) and the lowest value was on Rabbi variety (42.37 offspring). Our results showed that the highestrm, the largest fecundity and the shortest generation time of almond moth were observed on Deyri variety. It was concluded that among date palm varieties, Deyri was the most favorable host plant for almond moth reproduction performance.

The melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most important pests of agricultural products in Iran. In this study, susceptibility of melon aphid populations collected from seven regions (Yazd, Varamin, Mohammadshahr, Esfehan, Karaj, Hashtgerd and Ramsar) 24 h after exposure to pirimicarb and malathion in 2009 was compared. Bioassay experiments on adults were carried out using leaf dipping method. Squash (Cucurbita pepo) leaves were dipped in different concentrations of insecticides in laboratory conditions (25±0.2oC, 60±5%, 16: 8 [L: D] h). Control treatment was dipped in distilled water. Each test was replicated three times. The results showed that LC50 values of malathion for Ramsar, Karaj, Mohammadshahr, Hashtgerd, Varamin, Esfehan, and Yazd populations were 162.99, 159.19, 117.94, 79.96, 38.81, 36.32, and 20.25 ppm, respectively. Also, LC50 values of pirimicarb for Yazd, Mohammadshahr, Kararj, Hashtgerd, Ramsar, Esfehan, and Varamin populations were 1414.16, 1359.34, 1057.62, 970.33, 881.87, 806.14, and 601.98 ppm, respectively. According to results, aphid populations of Varamin and Yazd had the most susceptibility to pirimicarb and malathion, respectively. Also, aphids of Yazd and Ramsar populations had the least susceptibility to pirimicarb and malathion, respectively. Regarding the fact that Yazd and Ramsar populations had the least susceptibility to pirimicarb and malathion, respectively, there is a possibility that melon aphids in these regions are susceptible to other organophosphate and carbamate pesticides with similar mode of action. Therefore, in the pest management program, careful chemical control measures for melon aphid in these regions is recommended.

The effect of various host plants including chickpea (varieties Arman, Hashem, Azad and Bivanij), common bean (variety Khomein), white kidney bean (var. Dehghan), red kidney bean (var. Goli), cowpea (variety Mashhad), and tomato (var. Meshkin) on the reproductive performance and growth indices of the cotton bollworm, Helicoverpa armigera (Hübner) was determined under laboratory conditions (25±1oC, 65±5% RH and a 16: 8 h light: dark photoperiod). The highest rate of gross fecundity, gross fertility, net fecundity, net fertility, mean daily eggs and mean daily fertile eggs were observed on chickpea Arman (2947.8±7.8, 2933.0±7.8, 2404.2±7.1, 2392.2±7.1, 170.9±0.4, and 170.1±0.4 eggs female-1, respectively), whereas the lowest values of these parameters were on tomato Meshkin (847.5 ± 9.2, 673.8±7.3, 225.5±2.6, 179.3±2.1, 67.9±0.7 and 54.3±0.5 eggs female-1, respectively). The development index of overall immature stages varied from 1.10 to 1.57, with the minimum on tomato Meshkin and the maximum on chickpea Arman. Also, the fitness and standardized insectgrowth indices were highest (0.349±0.009 and 0.058±0.001 gr day-1) and lowest (0.052±0.001 and 0.013±0.000 gr day-1) on chickpea Arman and tomato Meshkin, respectively. The Weibull model sufficiently described the shape of the survivorship curve of adult H. armigera from life-table data. A significant fit was obtained with the Weibull model for H. armigera in all experimental host plants. The results of reproductive performance, growth indices and the cluster analysis showed that tomato Meshkin was partially resistant to H. armigera.

Medicinal plants have been used from the past to present. Different small arthropods such as Acari were found on these plants. Therefore a study on the Acari fauna associated with some medicinal plants (Family: Asteraceae) in Hamedan region was carried out during 2008–2009. In this survey, 23 species belonging to 18 genera from 15 different families of the subclass Acari were collected and identified. Two spotted spider mite (Tetranychus urticae Koch) was determined as an abundant phytophagous mite species in this study.

The calling behavior of virgin carob moth females, Ectomyelois ceratoniae (Zeller) (Lep.: Pyralidae) was evaluated under two different thermal regimes, cycling and constant temperatures under laboratory condition. The period of calling activity under cycling temperature was prolonged and the total period of calling activity of an individual female was increased. Although moths maintained under cycling temperature started calling later for the first time significantly in the scotophase than those maintained at 25oC, but the calling activity at cycling temperature was higher than at 25oC. At two temperature regimes, the mean onset time of calling (MOTC) advanced from about 441 to 189.5th min after the onset of the scotophase, and the mean time spent calling (MTSC) increased by>120 min during eight days. MTSC and MOTC for cycling thermal regime were 96.8±6.5 and 275.9±9.3 min respectively. We assumed that the extension of the calling period under cycling temperature might be due to potential similarities of the temperature regime to natural thermal fluctuations which could lead to an increased proportion of females mated; apart from its importance in efficacy of sex pheromone extraction under laboratory conditions.

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is one of the most important diseases of canola (Brassica napus) in Golestan province, the leading canola producer in Iran. In order to assess the yield loss of canola caused by SSR, 80 fields were surveyed in four different regions of the province (Gorgan, Ali Abad, Kalaleh and Gonbad) during 2006-2007, and SSR intensity was recorded weekly in the fields. Study of yield loss-SSR severity relationships by linear, nonlinear and multiple regression analyses with final intensity (S f), time to initial symptoms (t is), Gompertz rate of disease progress (r G), and standardized area under disease progress curve (SAUDPC) as independent variables indicate that single point and integral models were significant (P<0.05) only in three cases. Results of multiple point models which were performed using weekly recorded SSR intensities (S1, S2, …), were significant in two cases and a general model for 2007 survey was developed using S 3 to S 6. Eventually, response surface models were developed for each region by integratingt is with SSR intensity variables (S f or SAUDPC).