جستجوی مقالات مرتبط با کلیدواژه « نماتدهای بیمارگر حشرات » در نشریات گروه « کشاورزی »

Tomato leafminer moth (Tuta absoluta) is a serious pest of tomato crops which could impose upto 100% yield loss. This study was designed to assess the pathogenicity of third stage juveniles (IJs) of Steinernema carpocapsae (Sc) and Heterorhabditis bacteriophora (Hb) on different instars of pest larvae in Petri dish and in a leaf bioassay. The most virulent nematode was selected for the following tests. The ability of different concentrations of the more efficient species in parasitizing the last instar larvae (L4) and pupae in Petri dish (50, 100 and 200 IJs/Petri dish) and pupae in soil (50, 100 and 200 IJs/cm2 soil) was determined. In greenhouse, the efficacy of the selected species against different larval stages of pest was examined and compared with chemical pesticide, indoxacarb. Hb was selected as the better species since its controlling ability was approximately 1.7 times more than Sc. 50 IJs of Hb per Petri dish parasitized 84% of pest’ L4. The highest mortality of pupae in Petri dishes (40%) and soil (28%) was achieved when IJs were respectively applied at a rate of 200 IJs/Petri dish and 200 IJs/cm2 soil. Increase in IJs’ concentrations resulted in higher mortality of pupae. In greenhouse, the most susceptible stage of pest to Hb was L4, while the chemical pesticide had a little effect on pest's larvae. According to the results, it seems that Hb could alleviate the damage and produce acceptable control level of the pest.

Antagonism of entomopathogenic nematodes (EPNs) on plant – parasitic nematodes (PPNs) has gained interest over the recent years. Therefore، the efficacy of live and dead infective juveniles of entomopathogenic nematode، Heterorhabditis bacteriophora Poinarwith concentrations of 5، 10، 25، 50 and 100 IJs/ml in 24 well plates was evaluated on egg hatching inhibition and second stage juveniles (J2) mortality of the root knot nematode Meloidogyne javanica Treub in concentrations of 50 eggs، 50 larvae and a combination of 50 eggs and larvae. The experimental design was split plot with six treatments and four replications. The whole experiments were replicated twice. The data recorded after 48، 72، 96 and 120 hours showed that both live and dead entomopathogenic nematodes have significant difference on root knot second stage juveniles (J2) mortality and egg hatching inhibition. The highest mortality was achieved in 100 IJs/ml and after 120 hours and the most inhibition of hatching in concentration of 100 IJs/ml and after 48 hours. Concerning the mixture of 50 eggs and larvae، the results indicated that the effect of live juveniles of H. bacteriophora on second stage juveniles (J2) mortality have no significant difference among the various time treatments.

To determination of thermal preferance range, the life cycle of an endemic isolate of eachcommon entomopathogenic nematode species in Iran, Steinernema feltiae Filipjev andHeterorhabditis bacteriophora Poinar was studied, separately. One isolate of each species collected from Tabriz and its suburb soils, were evaluated under four temprature levels viz 4±1, 15±1, 24±2 and 30±1°C on Galleria mellonella L. last instar larvae for 13 days. The experiment was carried out twice, for each isolate. The life cycle of H. bacteriophora was completed at 30±1 and 24±2 °C and IJs were appeared in 10th and 12th days post infection, respectively. At 15±1°C up to end of the experiment, only first generation (hermaphrodite females) of the species was appeared and after 312 hours, its life cycle was not completed. At 4±1°C, after 13 days (312 hours post infection) larval mortality due to nematode infectivity was not observed. For S. feltiae at 30±1°C despite insect infectivity, just first generation offsprings were emerged and second generation was not appeared. At 24±2°C the life cycle was completed and IJs observed in 8th day. At 15±1°C, mortality of G. mellonella larvae was occurred with one day delay compared to 24±2°C. The life cycle was completed and IJs appeared in 12th day. At 4±1°C, insect’s mortality due to nematode infection was not observed. Results of this study showed that the preference temperature for S. feltiae activity is lower than H. bacteriophora and the thermal preference ranges should be considered as they are used for biological control of insect pests.