PLANT PEST RESEARCH
Year:2017 | Volume:7 | Issue:1|Papers Count:7

The cotton mealybug, Phenacoccus solenopsis Tinsley is an invasive pest species in tropical and subtropical regions and recently has caused severe infestations on Hibiscus rosa-sinensis L. in southern Iran. In the present study, field biology of this pest was investigated on Chinese hibiscus shrubs as its important host plant in Ahvaz during 2013-2014. Results indicated that P. solenopsis has completed 11 generations per year. The shortest generation times were 3rd, 4th and 5th from early May to early July which lasted 21.63±0.84, 21.48±1.01 and 23.11±1.55 days, respectively, with no significant difference. The 11th generation was the longest and occurred from early December to late March for 90.20±19.61 days. The reproduction mode in all generations was bisexual and none of unmated females did parthenogenetic reproduction. The highest fecundity was calculated as 432.15±35.00 offspring / female for 8th generation in September and the lowest belonged (10.58±1.33 offspring / female) to 10th generation in winter. The highest and lowest sex ratio of females in total population were obtained in 11th generation (%96) and 9th generation (%69), respectively. According to present results, the cotton mealybug has high reproductive potential on Chinese hibiscus shrub and is able to develop well in unfavorable hot summers of Ahvaz. These results can be used in control management of this pest.

In this research, the efficiency of diazinon and edifenphos extraction from two paddy soils with different organic contents was investigated using a modified QuEChERS extraction method. The methods included extraction of 10 g soil using acetonitrile with or without the addition of water to the samples, extraction of 5 g soil using acetonitrile with the addition of water to the samples, and extraction of 5 g soil using ethylacetate with the addition of water to the samples. The clean-up was carried out using dispersive solid phase extraction (dSPE). The pesticides quantification was performed using a liquid chromatography system equipped with a UV/VIS detector. According to the results, soil organic matter contents affected the recoveries of the two pesticides significantly. Factors such as reducing the sample size to 5 g, hydrating of the samples prior to extraction, and using ethylacetate as the solvent increased the extraction efficiencies of the two pesticides significantly. Best recoveries (70-100%) and relative standards deviations (RSDs) (˂20%) were achieved using 5 g soil as the sample with the addition of water and extraction using ethylacetate. The method had a good linearity within the range of 0.5-10 mg g-1. The sensitivity of the method was confirmed by the estimated method detection and quantification limits between 0.07-0.54 mg g-1.

Essential oils of some plant species have shown suitable insecticidal properties against stored-product pests, which are one of the main factors affecting post-harvest food losses. In this study mortality, repellent effects and durability of fumigant toxicity of the formulated essential oils of golpar (Heracleum persicum), thyme (Thymus vulgaris), eucalyptus (Eucalyptus globules), peppermint (Mentha piperita) and rosageranium (Pelargonium roseum) as 2.5 gr sticks (10%), were studied on two important pests of stored products, Oryzaephilus surinamensis and Trogoderma granarium in laboratory at 28±1oC, 70±5% RH and dark condition. The results showed that sticks of rosageranium and golpar had the lowest toxicity and sticks of peppermint and thyme had the highest toxicity effects especially on O. surinamensis. The highest repellency effect was observed in peppermint and eucalyptus on O. surinamensis (94 and 91.6% respectively) while repellency of rosageranium sticks was observed below 20% on both pests. Sticks durability in comparison with pure essential oils of plants was significantly different so that from the fourth day by the end of the eighth week the mortality rate was approximately constant while the durability of pure essential oils decreased after 2-3 weeks represents the slow-releasing of essential oils in stick formulation.

Seven- spotted ladybird (Coccinella septempunctata L.) is a common and widespread natural enemy in the agroecosystems that serves as an important biocontrol agent against harmful aphids on various crops. This research was conducted to study the biology and feeding diversity of C. septempunctata in alfalfa fields of Badjgah area, located at north of Shiraz. This was done during 2013-14 by sampling from the fields using a standard sweep net. Population changes were recorded weekly and midgut contents of adult beetles were also determined for each month. Based on the results, C. septempunctata had three generations per year in Badjgah area. Overwintering of Seven- spotted ladybird under the environmental conditions of Badjgah started at early November. Studies conducted on the food composition of adult ladybirds in this area revealed that aphids represented main proportion of the total diet in April and May. Decrease in number of aphids afterwards pushed the beetles to feed on Alternaria spores during June and July. In September, when their aestivation terminated, the beetles shifted to available pollens from different plants. Throughout the fall a balanced mixture of spores and pollens composed the metabolic needs and energy reserves for overwintering of the coccinellids.

Since plant quality could affect biological performance of natural enemies (bottom-up effects), compatibility of parasitoid wasp, Trichogramma brassicae Bezdenko with susceptible ("Infinity") and resistant ("Goldy") tomato cultivars to Tuta absoluta (Meyrick) was evaluated in laboratory conditions with 25±1oC, relative humidity of 65±5 % and a light period of 16 h. Data analysis was performed using Age-Stage Two Sex Life Table theory. The value for total immature stages of T. brassicae on the cultivar "Infinity" was 12.80±0.06 (days), which was significantly different from the recorded value of this parameter on "Goldy" (12.31±0.07 days). The mean number of parasitized eggs of T. absoluta by this parasitoid wasp on the cultivars "Infinity" and "Goldy" was not significantly different and the obtained values for this parameter on the above-mentioned cultivars were 36.28±2.67 and 39.30±2.65 (eggs/female), respectively. Immature mortality of this parasitoid wasp was not significantly different on the cultivars "Infinity" and "Goldy" (65.97±3.95 and 64.00±4.05 (%), respectively). Furthermore, the values for net reproductive rate (R0), intrinsic rate of increase (r) and finite rate of increase (l) of parasitoid wasp T. brassicae on the cultivar "Infinity" was 7.31±1.33 (offspring/individual), 0.139±0.013 (day-1) and 1.150±0.015 (day-1), which was not significantly different from those obtained on the cultivar "Goldy" (8.36±1.47 [offspring/individual], 0.154±0.013 [day-1] and 1.167±0.015 [day-1], respectively). Furthermore, the cultivars "Infinity" and "Goldy" had significant effects on the mean generation time (T) of T. brassicae and the recorded value for this parameter on the above-mentioned cultivars was 14.26±0.08 and 13.76±0.09 (days), respectively. Regarding the results obtained in the present study, partially resistance of cultivar "Goldy" had a relative compatibility with parasitoid wasp T. brassicae and therefore, these two control procedures could be combined together for integrated management of T. absoluta.

The diamondback moth, Plutella xylostella (L.), is an important pest of canola in Iran. In this study, the effect of four treatments including strip-intercropping of two, four and six rows of canola with two rows of clover (2Ca: 2Cl, 4Ca: 2Cl, and 6Ca: 2Cl) and canola monoculture were studied on the population density of P. xylostella, species diversity of its predators, parasitism on eggs, larvae and pupae, and associated yield of canola under the field conditions in Ardabil region during 2015 and 2016. The density of eggs, larvae and pupae were significantly higher in monoculture than in intercrops. Moreover, the density of larvae and pupae was lower in 2Ca: 2Cl than in 6Ca: 2Cl. Shannon diversity index (H') for predators' species composition of moth was higher in intercrops than in monoculture. The values of Morisita–Horn index (CMH) for predators species composition of moth between canola monoculture and each of the three intercrops (CMH ≤ 0.897) were lower in comparision with the values of this index among the three intercrops (CMH ≥ 0.957). The percent parasitism for eggs, larvae and pupae was significantly higher in intercrops than in monoculture. Moreover, the percent parasitism for eggs and larvae was higher in 2Ca: 2Cl than in 6Ca: 2Cl. The dry seed weight loss was also lower in 2Ca: 2Cl and 4Ca: 2Cl in comparison with other two treatments. Thsese results indicated that intercropping 2Ca: 2Cl and 4Ca: 2C could be useful in integrated management of P. xylostella in canola fields.

The White peach scale (WPS), Pseudaulacaspis pentagona (Targioni-Tozzetti) (Hemiptera: Diaspididae) is a polyphagous pest that feeds on many plants from 120 genera in 55 families. This survey was carried out in order to identify parasitoids of the WPS, in Mazandaran province. Infested branches of Kiwi trees were cut using gardening scissor. Each branch was placed into disposable cups with 12 cm height and 5 cm width, with wet cotton at the end of the branches. The cups were stored under room temperature until emergence of parasitoids. Among the identified specimens, Encarsia perniciosi (Tower) (Hym.: Aphelinidae) is here recorded for the first time as parasitoids of WPS in Iran.