PLANT PEST RESEARCH
Year:2018 | Volume:8 | Issue:1 |Papers Count:7

This study was conducted to evaluate the compatibility of some plant essential oils in combination with entomopathogenic fungus, Beauveria bassiana against Callosobruchus maculatus. Lethal effects of three essential oils including Petroselinum sativum, Satureja sahendica and Heracleum persicum against the adults of C. maculatus were studied. The biological activity of two fungal isolates, IS-1 and IS-75, as alone and in combination with the essential oils for insect pest control was evaluated. Results showed that S.sahendicaessential oil was the most toxic agent on adults than other oils, and IS-75 isolate showed more virulence against the pest compared to IS-1 when applied alone. Results of percent inhibition of sporulation and mycelial growth of the fungus showed P. sativum essential oil with 100 percent inhibition completely inhibited fungal growth and sporulation and S. sahendica essential oil with 24 percent inhibition had more compatibility compared to two other essential oils. Combined application of three essential oils and IS-75 isolate of the fungus in lethal and sublethal concentrations showed that H. persicum essential oil has the least LT50 value in combination with the fungus. Essential oil-pathogen interactions of sublethal concentrations of plant essential oils and IS-75 fungal isolate revealed that the synergistic effects on percent adults’ mortality only belongs to the combination of LC25 concentrations of each of the agents, and other sublethal combinations had additive and antagonistic effects.

The Mulberry white scale, Pseudaulacaspis pentagona (Targ.-Tozz.) is a polyphagous pest with a wide range of hosts and is one of the most important pests of mulberry trees in Northern provinces of Iran. It is said to be one of the restricting factor in commercial sericulture. In the present study, efficacy of the specialist parasitoid wasp of this pest, Encarsia berlesei, was investigated under three distinct experiments: (1) percentage parasitism on different developmental stages of the host (choice testvs no-choice test); (2) adults' longevity, daily and overall mean rate of parasitism; and (3) functional response to host density changes. In no-choice test, the average parasitism in the presence of first and second instars and adult female were 0.0%, 11.02% and 3.84%, respectively. In choice test, the mean parasitism in the presence of second instars and adult females were as 10.26% and 2%, respectively. Mean longevity of adults in the presence and absence of the host were 4 and 10 days, respectively. The egg laying had an ascending order in early period and a descending order in the late period of adult stage. Overall, the mean parasitism was 28.4 hosts per female parasitoid. The wasp parasitism rate followed a type III functional response. The searching efficiency was 0.0003 ±0.000057h-1 and the handling time was 3.695 ± 0.520 h. According to the results, especially considering the adult parasitoid longevity, it seems thatE. berlesei is an efficient natural enemy for biological control of the Mulberry white scale.

The common Pistachio psylla, Agonoscena pistaciae, is one of the most important pests that feeding on the sap both in nymphal and adult stage. In this study, the effects of spirodiclofen, spinosad, azadirachtin and Thymol soap were studied on the psyllid nymphs. At the same time, the impact of these pesticides on the activity of esterase and glutathione S-transferase (GST) enzymes were studied. In this research, three doses of each pesticide were selected (Recommended dose, 2-fold recommended dose and 1/2 recommended dose). The results showed that thymol soap had better performance in controlling pistachio psylla with concentration of 2000 mg/l compared to other pesticides. The populations of nymphs were reduced to 95.40, 94.12, and 82.30, 55.51 and 29.48 percent at 1, 3, 7, 14 and 21 days after application. The biochemical results of this study showed that spirodiclofen, spinosad, azadirachtin and Thymol soap, had the greatest impact on the inhibition of esterase enzyme in concentrations 120, 120, 200 and 2000 mg/l, respectively in different days after spraying. Most of the inhibition in glutathione S-transferase was observed in spirodiclofen, spinosad, azadirachtin and Thymol spraying soap in concentrations of 180, 240, 200 and 1000 mg/l, respectively. Because of the effectiveness of Thymol spraying soap, its competitiveness with other pesticides, and reduction in production costs (cost-effectiveness) and compatibility with environment, it seems that this insecticide could be a good candidate for psylla control.

In this study, the population density and survival of overwintering larvae ofChilo suppressalis (Walker) (Lep: Crambidae) was compared between single- and double cropped rice fields in north of Iran (Amol) during winter months (November-March) of 2016-2017. According to the results, a significantly higher frequency of overwintering larvae was observed in double cropped fields in both growing seasons and during all overwintering months. Additionally, larval mortality in double cropped fields was significantly lower than those in single cropped fields. The efficiency of three pesticides, diazinon (with two formulations G 10% and EC 60%), hexaflumuron (EC 10%) and fipronil (G 0.2%) as well as an integrated pest management approach (IPM) using mechanical, physical, and biological methods for control of Ch. suppressalis in double cropping fields of Amol was investigated during growing seasons of 2016 and 2017. According to fields experiments, a single application of hexaflumuron or diazinon EC at a concentration of 1.5 L/ha against the first instar larvae resulted in the most decrease in dead heart and white head damage and the highest crop yield in both growing seasons. The effect of IPM approaches on damage and crop yield was also considerable among treatments. Results of this study indicate that hexaflumuron, as an insect growth regulator (IGR) can be efficiently integrated in management programs of Ch. suppressalis. Besides environmental advantages, the integration of insecticides with novel modes of action in rotation with convenient pesticides can decrease the rate of resistance development by the pest in double cropping systems.

Pomegranate aphid, Aphis punicae (Passerini) (Hem.: Aphididae), damages pomegranate trees through feeding and producing considerable amounts of honeydew. The effect of drought stress on fertility-life table parameters of A. punicaewas studied by using leaf cages on plant in three treatments including control (irrigation at 100% of field capacity), moderately (at 75% of field capacity) and highly (at 50% of field capacity) drought stressed pomegranate plants (Robab cultivar) in greenhouse (natural photoperiod, 30±5°C and 50±10% RH). Life table parameters and their pseudo-replication were calculated by a computer program for the age-stage two sex life table analysis and bootstrap technique (10000 replications), respectively. The highest mean number of nymphs per female (16.54 nymphs), female adult longevity (7.14 days), the intrinsic rate of increase (0.39 day-1), the finite capacity for increase (1.74 day-1) and the net reproductive rate (15.19 nymphs) were observed in aphids that reared on moderately drought stressed trees. The highest mean generation time of A. punicae was 8.02 days in aphids reared at control condition.Amount of proline, phenol and soluble carbohydrate in leaves increased by increasing drought stress and the highest amount were measured in plant under highly drought stress. Considering that the highest population growth rate of pomegranate aphid calculated in plants under moderately drought stress, it seems that the highest quality of host plant for aphids obtained under this irrigation condition. Also, highly drought stress can lead to a decrease in aphid population growth by increasing the level of plant defensive compounds.

The Indian meal moth, Plodia interpunctella H., Mediterranean flour moth, Anagasta kuehniella Z., and Greater wax moth, Galleria mellonella L. are the most important pests of stored products and beehives. Chemical pesticides are commonly used to control them. Inappropriate using of pesticides caused serious environmental problems and also chronic effects on human health. Pest damage can be reduced by the optimum use of these materials. The purpose of optimum use is selection of the correct pattern and applying appropriate methods for use of pesticides. In this study Response Surface Method was used in order to determine optimal points to achieve maximum mortality with minimum concentration. The effect of factors such as temperature (25-35°C), humidity (60-80 %) and the concentration (1400-2000 μL) was evaluated on the mortality of fifth instar larvae of three pests. The experiments were performed according to Central Composite Design. Temperature and dosage had significant effect on mortality of fifth instar larvae of three Pest. The Optimum conditions in minimum dosage to obtain the maximum mortalities were determined 7.9 fifth instar larvae of Indian meal moth are: 35°C, humidity 80% and 1400 microliter of chlorpyrifos in the 1000 ml of water and for Mediterranean flour moth 7.1 fifth instar larvae are: 35°C, humidity 75% and 1400 microliter in the 1000 ml of water and for Greater Wax Moth are7.9 fifth instar larvae are: 35°C, humidity 80% and 1500 microliter in the 1000 ml of water. Results show leaner and significant effect of concentrations and term on lethal fifth instar larvae of three pests.

Fall webworm moth (Hyphantria cunea Drury) was observed in Guilan province in 2002 for the first time. Now it has spread in a wide area and has been observed on many species of plants. The larvae of this pest after hatching lives and feeds in grouping form. Younger larvae soon produce a silken web and feed on the upper surface of the leaves.. As larvae grow webs are enlarged and cover more foliage. With respect to its wide range of host plants and the rate of damage, it was essential to survey and determine an appropriate chemical compound to control this pest. The refore, in this research during 2004 to 2006, insecticidal effects of five safe pesticides including three kind of B.t. (Lepinox Ò-kurstaki and B.t.produced in Iran), Dimilin Ò and Neem Ò on webworm moth were investigated in the form of a completely randomized design. Experiments were performed at the second larval instar of pest. Sampling was done three days after spraying. Final results showed that biological compounds based on Bacillus thuringiensis, specially Lepinox Ò and Kurstaki were successfull for controlling of the fall webworm and in many experiments they ranked in high level with high effect (65-97%). Dimilin Ò (45-98%), Iranian product of B.t. Talphigh Daneh Ò (37-80%) and Neem Ò (47-79%) with lower effect and higher fluctuation ranked in lower level.