JOURNAL OF CROP PROTECTION
Year:2012 | Volume:1 | Issue:1|Papers Count:8

This study was conducted to evaluate the age-specific functional response of Psyllaephagus zdeneki Noyes & Fallahzadeh (Hymenoptera: Encyrtidae) at different nymph densities of olive psyllid, Euphyllura pakistanica Loginova (Hemiptera: Psyllidae). Due to parasitoid behaviour of feeding and parasitizing the host, both traits were separately explored on a daily functional response. Results of logistic regression revealed a type II functional response of the wasp independent of their ages. The handling time (Th) and searching efficiency (a) were estimated using the Rogers equation. The highest searching efficiency for both parasitism and feeding was observed in the first five days of the adult age. The handling time for parasitism and host feeding increased with the age of female wasp. The highest searching efficiency and shortest handling time for host attacked (Parasitism and feeding) were gained in day 5 and day 2 and maximum parasitism and host feeding in days 2 and 3 of adult female age, respectively. We conclude that P. zdeneki demonstrated a reasonable performance as a potential biocontrol agent by feeding and parasitism of E. pakistanica which gained its maximum efficiency within 2 to 5 days of its life.

The cotton bollworm, Helicoverpa armigera (Hübner), which is known as one of the most important economic pests, can cause severe damage to different crops in Iran and many countries of the world. The effect of five maize hybrids: SC260, SC500, SC700, SC704 and DC370 on lysozyme activity in the hemolymph of sixth instar of H. armigera using lytic zone assay and its association with some fitness parameters of this pest was studied in growth chamber (25±1oC, 65±5% RH and a photoperiod of 16:8 (L: D) h). Our results indicated that except on SC260, the frequency of high immune-activated larvae on the other maize hybrids was lower than that of low immune-activated larvae. The mean lysozyme concentration in H. armigera larval hemolymph was the highest on SC260 (0.096±0.01 mg/ml) and lowest on DC370 (0.060±0.007 mg/ml). The longest pupal period was on SC500 (12.00±0.49 days) and the shortest was on SC700 (10.37±0.19 days). Daily and total fecundities of H. armigera were the highest on DC370 (61.68±9.85 and 196.89 ± 49.30 eggs, respectively) and lowest on SC260 (20.60±5.88 and 52.71±18.80, respectively). The results of this study can provide fundamental information for management of H. armigera on maize hybrids.

Subterranean termites are one of the most important pests of buildings, historic monuments and agricultural crops in some parts of Iran. Using entomopathogenic fungi as microbial insecticides is usually a part of biological control and insect pest management. The pathogenicity of entomopathogenic fungus, Metarhizium anisopliae (Metschnikoff) Sorokin (DEMI 001) isolated from Rhynchophorus ferrugineus (Oliver) was compared against two subterranean termites, Amitermes vilis (Hagen) and Microcerotermes gabrielis (Weidner) under laboratory conditions. Suspensions of the fungus spores at five concentrations of 101, 102, 103, 104, 106 spores ml-1 were prepared to define LC50 and LT50. To determine LC50 and LT50 of M. anisopliae, bioassays were carried out on worker casts of both termite species. LC50 values for A. vilis and M. gabrielis were 8.5×103 and 0.2×102 spores ml-1, respectively. LT50 value for M. gabrielis was shorter than that of A. vilis at all five concentrations tested. According to the results of the bioassay, M. anisopliae was more effective for controlling M. gabrielis than that for A. vilis.

The aphid parasitoids, Aphidius colemnai Viereck and A. matricariae (Haliday) (Hymenoptera: Braconidae: Aphidiinae) have high potential as the most effective biological control agents for controlling the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae). In this investigation, the effect of five constant temperatures (10, 15, 20, 25 and 30oC) on the reproductive parameters of the parasitoids was studied at 65±5 % relative humidity and a photoperiod of 16L: 8D hours. The newly laid (one- day old) eggs were reared on third instar nymphs of cotton aphid, and the pupal and adult stages of the parasitoids were recorded daily, until the last individual was found dead. The experiments were carried out with 15 replications at each temperature. The results revealed that the gross fecundity and fertility rates were significantly different at all tested temperatures for both species (P<0.05). The highest value for the mean fertile eggs per day were recorded at 25oC and 30oC for A. matricariae and A. colemani, respetively. The results of this research can be used for establishing integrated pest management (IPM) strategies against A. gossypii in cucumber greenhouses.

Fungi associated with ascocarps of Terfezia claveryi, Tirmania nivea, T. pinoyi, Picoa lefebvrei and P. juniperi in Iran showed a wide range of genera and species in 94 samples collected during 2005–2009 from different regions including Fars, Systan and Baluchestan, Kerman, East Azarbaijan, Khuzestan, Kermanshah and Hormozgan provinces. Thirty two species belonging to 21 genera were recovered from ascocarps of truffles on two culture media. Penicillium chrysogenum, P. citrinum, P. griseofulvum, P. brevicompactum, P. crustosum, P. oxalicum, Aspergillus carbonarius, A. niger, A. flavus and A. terreus were the most common fungal species isolated on glucose-Czapek agar medium. The number of fungal species recovered on 20% NaCl-Czapek agar were less (4 genera and 10 species). The most abundant fungal genera belonged to Penicillium and Aspergillus. Also, Paecilomyces lilacinus and Scopulariopsis halophilica could grow on Czapek agar medium amended with 20% NaCl. Other fungal species were not able to grow on this medium.

The entomopathogenic fungus Beauveria bassiana (Bals.) Vuill. is one of the important arthropod pathogens that can play an important role in the regulation of mite populations in agricultural ecosystems. In this study, the combined effect of a native isolate of fungus B. bassiana (EUT105) and ether-extract of plant, Ginkgo biloba was evaluated against the two-spotted spider mite, Tetranychus urticae Koch. At first, effect of three concentrations 5, 10 and 20% of G. biloba was evaluated on B. bassiana conidial germination and mycelial growth. Then, potential synergism between B. bassiana and G. biloba was investigated in order to incorporate both in the control of this pest. Only the 20% concentration of plant extract had significantly inhibitive effect on germination and mycelial growth. The mortality of adult female T. urticae increased significantly when B. bassiana was applied with 5 and 10% concentrations of G. biloba extract. Hence, there is a synergistic effect between this native B. bassiana and ether-extract of G. biloba in controlling the two-spotted spider mite.

Reproductive performance and life expectancy of the two-spotted spider mite (TSSM), Tetranychus urticae Koch were determined on seven eggplant cultivars (Isfahan, Dezful, Shend-Abad, Neishabour, Bandar-Abbas, Jahrom and Borazjan) at 25 ± 1oC, 60 ± 5% R.H. and a photoperiod of 16: 8 (L: D) hours. The results revealed that the TSSM gross hatch rate varied from 59% on Bandar-Abbas to 83% on Dezful. The gross fecundity rate was 59.726, 31.430, 31.443, 14.461, 19.328, 16.035 and 20.560 eggs/female and the net fecundity rate was 25.804, 17.496, 15.139, 7.620, 5.931, 7.526 and 11.947 eggs/female on the above-mentioned cultivars, respectively. The highest and lowest value of the net fertility rate was 20.735 eggs/female on Isfahan and 3.495 eggs/female on Bandar-Abbas, respectively. Also, the gross fertility rate was the highest on Isfahan (47.994 eggs/female) and the lowest on Bandar-Abbas (11.390 eggs/female). The values of the mean eggs per day varied from 2.040 to 6.560 eggs/ female, which was minimum on Neishabour and maximum on Isfahan. The life expectancy of one-day-old adults of the TSSM was estimated to be 7.550, 8.380, 5.820, 4.850, 5.440, 5.330 and 3.950 days on the above-mentioned cultivars, respectively. Comparison of the reproductive parameters of the TSSM on the examined cultivars revealed that Isfahan was the most susceptible cultivar and Neishabour was the most resistant cultivar to this pest. Using resistant host plants is one of the most important components of an integrated pest management program.

Soybean, Glycine max (L.) Merr is one of the most important oilseed plants in the world and Phythophthora root and crown rot is a significant limiting factor for its planting. In the present study the antagonistic effect of 12 Trichoderma spp. in vitro and these Trichoderma spp. in combination with Bradyrhizobium japonicum in vivo on Phytophthora sojae and soybean growth were tested. In laboratory tests the effects of Trichoderma isolates were studied in dual culture, volatile compounds and culture filtrate metabolites. The most hyphal growth inhibitions were obtained using T. virens, T. orientals and T. brevicompactum in dual culture tests and T. atroviride in volatile compounds test. The effects of Trichoderma culture filtrates on P. sojae hyphal growth were studied at six concentrations in CMA medium and the results showed that culture filtrates of all species inhibited the hyphal growth and that different concentrations had different inhibitory effects. The most inhibition was obtained by T. virens and T. brevicampactom culture filtrates. The greenhouse tests were carried out as two experiments. In the first experiment the effects of coated seeds with Trichoderma isolates and B. japonicum, alone and in combinations, on control of P. sojae and in the second experiment the effect of these two biocontrol agents on soybean growth, alone and in combinations, were assayed. In the first experiment, germination percentage, damping-off, seedling vigour index (SVI) and disease severity were measured and results showed that T. brevicompactum as alone and in combinations, was the most effective species. In the second experiment, coated seeds with Trichoderma isolates and B. japonicum, as alone and in combinations, significantly promoted the growth of treated seeds and the most effective species were T. orientals, T. brevicompactum and T. spirale. Hence, results indicate that T. brevicompactum, as the second most common species after T. harzianum in Iran, was the most successful species applied individually and in combinations with B. japonicum to act as biocontrol agent for P. sojae and was also able to promote plant growth.