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The tomato leafminer, Tuta absoluta (Meyrick), is a major worldwide pest of tomato crops, both in the greenhouse and in open field cultivations. Since this pest’s new introduction in Iran, it has caused extensive damage. Chemicals have mainly been used to control this pest. The purpose of our research was to identify the indigenous predators of the tomato leafminer, associated with tomato in the Borazjan region of the Bushehr province, Iran. From March to May 2014, infested tomato leaves were collected from protected tomato crops. A predator species from the family Miridae was found, reared, and identified as Nesidiocoris tenuis (Reuter 1895). This species is reported for the first time on tomato leafminer in Iran. Identification of important natural enemies provides a scientific basis for including these predators in the biological programs against this pest.
Functional and numerical responses are basic to any investigation of predator-prey relationships and key components in the selection of predators for biological control. In this study, functional and numerical responses of the female and male ladybeetles, Scymnus syriacus Marseul to different densities of third instar nymphs of Aphis fabae (i.e. 5, 10, 20, 30, 40, 60 and 80) as prey, were studied in a growth chamber (25°C, 65±5% RH and a photoperiod of 16L : 8D h) on the broad bean, Vicia fabae Linn. Using the logistic regression, a type II functional response for both female and male ladybeetles was determined. Using Nonlinear least-square regression, the searching efficiency (a') and handling times (Th) of the female and male adults were estimated as 0.123±0.006 h, 0.434±0.012 h and 0.115±0.008 h, 0.514±0.016, respectively. The Rogers model was used to estimate the maximum theoretical predations (T/Th) for female and male, which were 55.18 and 46.64, respectively. These results indicated a higher efficiency in female ladybeetles. The reproductive numerical response, in terms of eggs laid, increased curvlinearly with increasing prey density. The reproductive response trend was similar to the shape of the type II functional response. This similarity means both responses are interlinked and function simultaneously. The efficiency of the ingested food conversion (ECI) of the females decreased with prey density, as females laid 25±0.65 eggs when exposed to the highest prey density (80) and 3±0.44 eggs at lowest prey density (5).
A life table can be used as an important and appropriate tool to evaluate the susceptibility or resistance level of different host plant cultivars to insect pests. In the current study, we determined the suitability or inferiority of five different canola cultivars (Hayula420, Hayula401, Hayula50, Hayula60, RGS) to Nysius cymoides, under laboratory conditions. Data were analysed based on the age-stage, two-sex life table theory. Nysius cymoides which fed on Hayula420 had the longest nymphal period, while those which fed on Hayula50 had the shortest nymphal period. Developmental times (sum of incubation and nymphal periods) was longest for those which fe d on Hayula420 and the shortest for those which fed on Hayula50. The adult pre-oviposition period (APOP), total pre-oviposition period (TPOP), mean fecundity, and adult longevity of adults reared on different canola cultivars showed significant differences. The highest and lowest net reproductive rates (R0) were obtained for those which fed on Hayula420 (11.40 offspring per individual) and Hayula401 (5.47 offspring per individual), respectively. The highest value (0.0395 d–1) for the intrinsic rate of increase (r) was obtained for those which fed on Hayula 60 cultivar and the lowest value (0.0261 d–1) for those which fed on Hayula401 cultivar. The shortest and longest mean generation times (T) were obtained for those which fed on RGS and H401 cultivars, respectively. The lowest and highest values of life expectancy (exj) were obtained for those which fed on RGS and Hayula420 cultivars, respectively. The results showed that Hayula401 and RGS were not susceptible cultivars to N. cymoides. These cultivars showed higher resistance to N. cymoides, while Hayula60, Hayula420, and Hayula50 were found to be suitable cultivars but with lower resistance to N. cymoides, respectively.
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