فصلنامه گیاه پزشکی
سال سی و هشتم شماره 4 (زمستان 1394)

Flea beetles (Chrysomelidae: Alticinae) are the pests of vegetative phase of oilseed rape (Brassica napus). Adult flea beetles feed on cotyledons and young leaves of the crop causing damage. In order to investigate the efficacy of Cruiser and Gaucho insecticides as seed treatments to reduce the pest damage, this project was conducted in a randomized complete block design with 5 treatments and 4 replications at Sari during 2009-10 and 2011-12. The treatments were control (untreated seeds), treated seeds with imidacloprid (Gaucho WS70%) 12 g/kg and 14 g/kg, treated seeds with thiamethoxam (Cruiser FS350) 7 ml/kg and 10 ml/kg. The coefficient of infestation (the number of healthy, slightly and seriously damage plants over 1 m2) was determined. The number of flea beetle larvae in the plant tissue, the yield as well as 1000 kernel weight was calculated. The results showed that both Gaucho and Cruiser with the applied doses for seed treatments had good efficacy in control of the flea beetles compare with control. Among those, thiamethoxam (Cruiser FS350) 10 ml/kg and imidacloprid (Gaucho WS70%) 14 g/kg were found to be more beneficial.

Verticillium wilt disease of potato is soil-borne pathogen that causes problems in potato plant all over the world and is difficult to control. In this research, the effect of Basamid granulate (Dazomet 98%) at different concentrations (266, 333, 400 gr/m3) was tested in vitro and greenhouse conditions for their ability in order to control Verticillium wilt of potato. The results showed that application of basamid granulate at the rate of 400 gr/m3 caused complete death of colony and microsclerotia of pathogen in vitro and greenhouse conditions. Similar to untreated control, disease severity and vascular discoloration in this treatment were reduced to zero. All treatments showed significant differences at 1% according to Duncan’s test. Therefore, results indicated that not only is soil fumigation by basamid granulate cheaper, easier and safe, but also it is an acceptable alternative for other fungicides in control Verticillium wilt of potato.

In order to replace pesticides with less hazardous compounds, plant essential oils are widely investigated. In this study, the effects of essential oil of Citrus aurantium L. leaves was tested for fumigant, contact and repellent effects against adults of Rhyzopertha dominica, Tribolium castaneum and Oryzaephilus surinamensis. The experiments were conducted in completely randomized design with 5 replications in 27±2oC, 65±5% R.H. and dark condition. The essential oil were extracted using Clevenger-type apparatus and analyzed by GC-MS. Fumigant toxicity was studied in 50 mL containers and contact toxicity experiments were performed using petri-dish method and five different concentrations and the mortality was investigated after 24 h. Repellency of the oils was studied using the choice bioassay system in petri-dish with five concentrations, at 2 and 4 h exposure times. Analysis of chemical composition showed high amounts of monoterpenes in essential oil, mainly linalool (32.41 %). Probit analysis showed that the LC50 of C. aurantium essential oil against O. surinamensis was 262.93 µL/L air but there was no fumigant toxicity against R. dominica and O. surinamensis. Results of contact toxicity showed that C. aurantium had more toxicity for R. dominica (LC50=0.13 µl/cm2) and O. surinamensis (LC50=0.11 µl/cm2) than T. castaneum (LC50=1.84µL/cm2). Percent repellency (PR) increased with increasing exposure time and concentration of the essential oils. After 2h exposure time the PR of C. aurantium oil was 48, 90 and 84 % at the highest concentration of essential oil (1.194×10-1 µL/cm2) for R. dominica, T. castaneum and O. surinamensis.

Seedling damping-off caused by Rhizoctonia solani is one of the most important diseases of sugar beet resulting in substantial economic losses to the producers of this crop. In this study, the biocontrol capability of 16 Trichoderma isolates and one Piriformospora indica isolate against R. solani AG-2-2 was evaluated in vitro and in vivo. Among the tested isolates, Trichoderma harzianum 65 and Trichoderma viride 60 were the most effective antagonists in vitro and could inhibit mycelia growth of the pathogen in dual culture and culture filtrate assays. However, the maximum damping-off disease control in greenhouse experiments was achieved by T. harzianum 65 with 73.6% disease control that was as effective as fungicide treatment (carboxin-thiram) and followed by P. indica with 69.8% disease control. Moreover, sugar beet seeds treatment with these fungi promoted plants growth and increased root fresh weight. In addition, the efficiency of different concentration of three resistance inducer compounds BABA, MeJA, and SA to control R. solani AG-2-2 in greenhouse was assessed. The maximum disease control was observed when seeds treated with 10 mM BABA and 1 mM MeJA, probably these compounds by induction of defence mechanisms in sugar beet have increased seedlings resistance to R. solani AG-2-2. Herein, for the first time we report control of Rhizoctonia seedling damping-off by using P. indica and resistance inducer compounds BABA, MeJA and SA.

Rhopalosiphum padi L. (Hem.: Aphididae) is one of the most important pests damaging cereals specially wheat and lowering the quality and quantity of the production directly and indirectly each year. In this study, the toxicity effect of two extracts of Rubia tinctorum L. (Rubiaceae) and Lawsonia inermis L. (Lythraceae) is compared with two conventional insecticides, imidacloperid and pirimicarb. The study was conducted in petri dish of 8 centimeter diameter using a completely randomized design with five different concentrations for each set with four repetitions on 15 adult insects of R. padi L. (Hem.: Aphididae) 25±2 degree Celsius, relative humidity of 70±5 percent and in photoperiodic of 16 hours lightness and 8 hours darkness. All biometric studies were performed on similar and identical leaves of barley with the method of leaf immersion. The number of dead insects was counted after 24 hours. The results indicated that the insecticide imidaclorperide with fatal effects of 50%, 0.0318 and the methanol extract of henna L. inermis L. with fatal effects of 469.532 micro liter per milliliter were the most and least effective, respectively. Comparison of the results revealed that the extracts of the two plants, especially methanol extract of madder (R. tinctorum L.) with insecticide imidaclorperide and pirimicarb, have especial toxic potential to control the above said insect. Accordingly, as the extracts had less potential insecticidal potential, they should be used in conjunction with other methods.

The strawberry spider mite, Tetranychus turkestani (Ugarov & Nikolski) is one of the important pests of agricultural crops especially within grean houses. Biology ane life table parameters of Orius albidipennis (Reuter) feeding on strawberry spider mite at three different temperatures (20, 25 and 300C) was studied under laboratory conditions. Preimaginal developmental time of this predator at 20, 25 and 300C was 34.54, 16.82 and 11.68 days for females and 31.83, 16.1 and 11.89 days for males, respectively. Preimaginal mortality was 30, 28.12 and 17.25% at above mentioned temperatures, respectively. Sex ratio (female %) was 46, 51 and 48 % at at above mentioned temperatures, respectively. Adult longevity of female and male at 20 and 250C was 26.22 16.7 and 22.43, 13.22 days, respectively. Total egg production of females at two above mentioned temperatures was 50 and 39 eggs, respectively. Intrinsic rate of increase of this predator at two respected temperatures was 0.124 and 0.165, respectively. Generation time of O. albidipennis was 23.59 and 16.37 days, respectively. Our results showed that O. albidinnis has enough potential to control T. turkestani.

Tomato leaf miner Tuta absoluta is one of the key and dangerous pests of solanaceae crops specifically tomato. Larva feed on leave, stem and fruit of host plant. To develop a successful IPM program, detailed information on the population parameters and life table of pests is critical. Because lack of previous studies on the population parameters of tomato leaf miner on Potato and Tobacco, the porpose of this study was determination of biological parameters and life table of the pest on Potato and Tobacco. Adult moths were collected from fields in Khuzestan province and were reared on Potato and Tobacco pots for two generations. The cohort eggs of third generation were used the expeiments. Chi theory and TWO SEX - MS Chart program were used to determine life table parameters. All trials were conducted under laboratory conditions with temperature 25±1ºC, humidity 60±5% and the light: dark 16: 8h in germinator. According to results of the study, r, λ, T, Ro and GRR for Potato and Tobacco were(0.07 and 0.065 day-1), (1.078 and 1.066 day-1), (38.70 and 35.40 day), (12.78 and 9.92 offspring) and (18.68 and 15.06 offspring) respectively. The results can be used for a successful IPM programs against the tomato leaf miner in the fields for the cultivation of solanaceae plants.

Parasitoid wasps usually encounter hosts of different ages or sizes and they select the most suitable hosts to maximize their reproductive fitness. In this study, a sexual population of Lysiphlebus fabarum was reared on different instars of the black bean aphid, Aphis fabae Scopoli, to evaluate some biological components. The results showed that pre-adult development times were decreased with increasing the host body size (from first to third instars), but the longest period was observed in the fourth instar. There was no significant difference in the rate of parasitism of the different treatments, while sex ratios in wasps reared in first and third instars were the most. The largest wasps were observed in wasps reared in second instar as well as, these wasps had a high egg load and egg size. Moreover, a survey on lifespan of parasitoids reared in different host instars showed that the maximum longevity was observed in the wasps reared in second and fourth nymphal instar, in the presence of host aphids. Totally, the greatest fitness was achieved when the wasps were reared in second nymphal instar of aphids, although the wasps reared in other instars obtained some biological components.