PLANT PEST RESEARCH
Year:2015 | Volume:5 | Issue:1|Papers Count:7

Olfactory response of Encarsia formosa to odors produced by untreated and treated whitefly that were infested by fungi Lecanicillium longisporum was determined in an airflow Y-tube olfactometer. The results indicated that the parasitoid response to odors from cucumber plants infested by whitefly compared to whitefly and fungi free cucumber plants showed no significant differences. Also in other test, cucumber plants infested by whitefly compared with the cucumber plants infested by whitefly that were treated by fungi no significant differences was observed in the selection rate of parasitoids as seen in the olfactometer tubes. Parasitoid response to odors of non-infested plant (no whitefly and fungi) against clean air and the whitefly infested plant against clean air, the parasitoid was significantly attracted toward the arms having non-infested and whitefly infested plant. Based on the present result in spite of parasitoid attraction to some of the treatments there was no absolute response to plant-whitefly combination compared to non-infested plant. In fact the presence of whitefly is no indication for attraction of parasitoid toward its host.

The Sunn pest is the major insect problem of cereal, especially wheat and barley in Iran. Chemical control is the most effective and frequently used control method against sunn pest. Most treatments to control of this pest are done when adults and nymphs are in fields with the highest number. It means chemical materials are used against overwintering adults and nymphs. For several years, two commercially insecticides, deltamethrin and fenitrothion, have used for achieving control of sunn pest were. A new project was designated to evaluate efficiency of a newly introduced chemical insecticide to control the pest. Insecticides were tested in two locations in Ghazvin and Kermanshah provinces. For comparison, two formulations of Deltamethrin, Deltamethrin EC 2.5%, Deltamethrin SC 2.5% , a formulation of Fenitrothion, Fenitrothion EC50% and lambda cyhalothrin ( Karate zone CS100® ) were tested based on a randomized complete block design with four replications. All chemicals were tested against both 2nd nymphal stages and overwintering adults. Two concentration of Deltamethrin SC 2.5%, 250 and 300 ml/ha, and two of Karate zone CS100, 75 and 100 ml/ha, were tested. Average mortality percent of overwintered adults in two locations, were 84.94, 88.2, 87.93, 92.2, 90.65, 93.11 respectively and for nymphal stages 85.92, 92.18, 95.37, 90.35, 92.14 and 94.32 respectively. The results of the experiment showed no statistically significant difference between treatments and all insecticides can be effective in reducing the percentage of quantitative and qualitative damage. The efficiency of treatment by two insecticides, Deltamethrin SC 2.5% and Karate zone CS100 for 20 days after spraying was more than 70 percent so these insecticides are recommended to be included in a pesticide rotation with others for reducing the probability of resistance biotype formation in sunn pest.

Proliferation and virulence of entomopathogenic fungi can be affected by exposure to pesticides. Compatibility of Metarhizium anisopliae (Metschnik off) Sorokin (DEMI 001 strain) with imidacloprid (IMI) was assayed by evaluating IMI effects on conidial germination, mycelial growth and sporulation. SDAY fungal cultivation medium was amended with IMI at concentrations of 10, 100 and 500 ppm. SDAY medium without insecticide was used as control treatment. The medium was inoculated by conidial suspension and the number of germinated conidia was counted after 24 h. Mycelial growth and sporulation were also measured. Results showed that IMI had no negative effect on conidial germination or mycelial growth. However, sporulation was progressively reduced as IMI concentrations increased. At the highest concentration of IMI, sporulation was reduced to 2.40×107 conidia ml-1, compared with control at 4.93×107 conidia ml-1. According to these results, IMI is reasonably compatible with strain DEMI 001. Additionally, mortality of M. diversus caused by either M. anisopliae or IMI alone, and in combination with different sublethal concentrations of IMI, was evaluated in laboratory bioassays. Mortality in combined treatments was significantly higher compared with non-combination treatments, indicating possible synergistic effects.

Lack of quality control methods during the mass rearing of natural enemies may lead to failures in biological control. Body size has important effects on fitness components of parasitoids, and often use as a standard measure of quality control. In the present study, the most appreciate morphological feature that provides the best correlation with body size and egg load in a sexual population of the parasitoid wasp, Lysiphlebus fabarum (Marshall) was determined, when females reared on different nymphal instars of the host aphid, Aphis fabae Scopoli. The experiments were performed under standardized conditions in a growth chamber (21± 1oC, 60–70% RH, and 16L: 8D), and candidate metrics were head width, length of the right forewing, and length of the right hind tibia. According to results, head width emerged as the most suitable proxy for total body length of females that were reared in the 2nd nymphal instar (the most suitable host growth stage for mass rearing), while length of the right forewing yielded the highest correlation with total body length, when the data of wasps reared in all four nymphal instars were pooled. Egg load increased linearly with body length across all host growth stages, and the forewing length had the highest correlation with females reared in all four nymphal instars, so it may serve as a better predictor of egg load than other measurements. The results suggest that forewing length can be used as a proxy of quality control in mass rearing of this population of L. fabarum.

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most important and devastating pest of tomato crops throughout South and Central America, Europe and recently Iran that caused severe damages to tomato crops in greenhouses and fields. Since antixenosis and antibiosis are the two important resistance mechanisms in Lycopersicon hirsutum to tomato leafminer, these mechanisms were evaluated on 12 tomato cultivars of Lycopersicon esculentum Mill. (Petomech, Mobil, superstain-B, kingstone, Redstone, Early urbana-Y, Early urbana, Riogrande, Cal-J-N3, Primo early, Falat-111 and Dehghan) in greenhouse with daily temperature fluctuations of 18–27oC during November and December 2013. The first experiment was carried out to appraise the oviposistion preference of tomato leafminer on different parts of those 12 cultivars. Survival and duration of eggs, larvae and pupae, weight of pupae, sex ratio of progeny, visual injury rating and number of mines of tomato leafminer on 12 tomato cultivars were examined in the second experiment. The higher and lower ovposition were observed on Falat-111 (30 eggs) and Kingstone (5.33 eggs), respectively, on the fourth day of the experiment. Incubation period, larval and pupal stadia, pupal weight, visual injury rating and number of mines were significantly affected by tomato cultivars. Based on all examined characteristics, tomato cultivars were clustered into three main groups. We concluded that three cultivars Mobil, Riogrande and Cal-J-N3 appeared to be relatively more resistant to the damage inflicted.

The olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a serious insect pest of olive crops in many parts of the world. There is no study on population structure of this insect In Iran. In the current research, to investigate morphological variations, geographic populations of olive fly, were collected from five localities in Guilan province. Fourteen landmarks were selected on wing and the shapes were compared among populations using geometric morphometric method. Multivariate analysis of variance and Discriminant Function Analysis were performed on partial warps. The relationship between geographic populations was investigated through UPGMA algorithms. The geometric morphometric analysis showed significant variations in the wing shape and size, among geographic populations.

Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruitcrops worldwide, and its outbreak has recently been reported in fruit orchards of northern Iran. In this study, the values of some important developmental and reproductive parameters, including percent daily oviposition (in both choice and non-choice tests), larval and pupal developmental times, egg hatch percent of adult emergence and sex ratio were estimated on six different host plants (persimmon, citrus Unshiu, Thomson orange, Golden Delicious apple, red apple and peach) under laboratory conditions. Among the studied fruits, peach was determined as the most suitable host for Mediterranean fruit fly due to its high mean daily oviposition (4.74 egg/female/day), egg hatch (79.62 percent) as well as short larval (10.4 day) and pupal developmental times (7.76 day). In contrast, Thomson orange was suggested as the least suitable host plant because of low mean daily oviposition and amount of egg hatch (0, and 67.49 percent, respectively). Golden Delicious and red apples were also considered nutritionally poor hosts because of low mean daily oviposition (0.56, and 1.15 egg/female/day, respectively) and long larval developmental period (14.84 and 24.08 days, respectively). Because of high susceptibility of peach fruits to this pest, it is recommended to impose more restriction on establishing new peach orchards especially where mixed with citrus.