JOURNAL OF ENTOMOLOGICAL RESEARCH
Year:2012 | Volume:3 | Issue:4 (12)|Papers Count:8

This pest strongly demonstrates resistance against chemical pesticides and decreases the yield of cotton and worsens its quality as well. Since Biorational pesticides are generally desirable, believing to have less disturbance of the environment; this research covers the study of susceptibility of different developmental stages of Bemisia tabaci Gennadius to pyriproxyfen, citowett oil and their mixture too. Citowett oil and pyriproxyfen have been used in 5 concentrations and control treatment. The LC50 value of pyriproxyfen for adult, egg, and immature stages was 1086, 45.04 and 11.47 PPM, respectively. This criterion to citowett oil for adult, egg; and immature stages was 1554, 884.79 and 684.70 PPM in the same order. To evaluate the synergistic effect of citowett oil on pyriproxyfen we used the mixture of LC25 of either compound. The results revealed that there are 52.36%, 62.32% and 69.19% mortality rate for adult, egg, immature stages respectively. The experiments showed that citowett oil is able to enhance efficiency of pyriproxyfen.

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Host-plant resistance is one of the effective and sustainable strategies in pest management programs against diamond-back moth, Plutella xylostella (L.) (Lepidoptera, Plutellidae). In this regard, the effect of host plant type on life-history parameters, such as survival and developmental period of P. xylostella was determined under the constant environmental condition. The experiments were carried out with five host plants, including Brassica pekinensis (Chinese cabbage) cv. Hero, B. oleracea var. botrytis (cauliflower) cv. Royal, B. oleracea var. capitata (common cabbage) cv. Globe Master and cv. Red Dynasty, and B. napus (rape) cv. SLM046.Batches of 10 neonate P. xylostella larvae were placed on leaf discs within individual Petri dishes (6 cm dia.) containing a moistened filter paper. To prevent starvation of larvae, the leaf discs were replaced every 24 h. Pupae were transferred to Petri dishes and kept until eclosion. Life stage and mortality were recorded every 24 h until all the insects had either died or emerged as adults. Each treatment (plant) was replicated 17 times (in total, 170 host larvae for each plant). The results showed that there were significant differences between host plants for life-history parameters measured. The highest and lowest developmental times (from neonate larva to eclosion) of the host occurred on Red Dynasty (17.3 days) and Hero (10.5 days), respectively. The most survival (from neonate larva to eclosion) of the host was observed on Hero (72%), whereas the least survival happened on Red Dynasty (16%) and SLM046 (20%). The mean pupal weight of the hosts fed on Hero (4.3 mg) was significantly greater than that on Royal (3.8 mg) and Red Dynasty (3.7 mg), which in turn, were significantly greater than that on SLM046 (2.9 mg). These results indicated that Hero was the most susceptible host plant to be attacked by P. xylostella, whereas Red Dynasty and SLM046 were partially resistant compared to other host plants. These findings emphasize on using the partially-resistant varieties such as Red Dynasty and SLM046 in pest management programs against diamondback moth.

Two spotted spider mite, Tetranychus urticae Koch is the most important pest of common bean in most areas of Iran, including Lorestan province. In this study the geostatistical charachteristics of this pest were evaluated in Borujerd common bean fields in 2009. To do this research, two red common bean (Goli variety) fields that each one was about four hectares were selected. In each field, about 300 points (stations) were identified and marked. Sampling was started in mid July. At each station on three point of plant height (bottom, middle and top) three leaves were sampled. In the laboratory, the samples were observed and mite population density were counted with respect to each life stage. Results showed that the spherical model provided the best fit (based on r2-values) for the semivariogram data in 20 data sets out of 25 at the beginning of the pest attak in late July and early August. In this time, nugget/sill ratio was very low and by passing the time this ratio increased so that the spatial dependence among points decreased. Thus in August and early September more semivariogram curves fitted with the model of pure nugget effect and did not show any spatial corrdation among points selected in the fields. The effective range of spatial correlation of this pest were relatively high at the beginning of the pest attack. This range for adult females, nymphs and eggs were 357-641, 510-710 and 610-711 meters respectively. These distances were reduced by passing the time and by approaching end of season. Based on these results, application of geostatistics is recommended to monitoring and forecasting of two spotted spider mite, T.urticae in common bean fields at the beginning of the pest attack.

One of the most important pest of vineyards in Iran is the Lobesia botrana Den & Schiff (Lep., Tortricidae). Damage from this pest on grapes has considerable economic importance.Currently, the most common method of control is using chemical pesticides. According to this fact that spraying of pesticides makes serious problems with health care and environment, so controlled spraying using the effective estimation of pest due to growth period by pheromones traps are the important manner in combating. In our present research, we used pheromones traps in 5 villages of Urmia city in West Azerbaijan at various heights as selected points in study. Hunted insect was counted twice in a week at the same intervals of time. Results show that this pest has three complete generations in Urmia city region. The first appearance of moths was accrued in first half of April and three moth peaks were seen in first half of May, third decade of June to first half of July and second half of August, respectively. According to the obtained results, the best time to chemical control of pest was 7-10 days after appearance of the first generation peak and for the second and third generations were 5-7 days after generations peaks are considered.

The full text of this article is the Persian language, please for the view full text, refer to Persian Please click here to view the full text of this article

The full text of this article is the Persian language, please for the view full text, refer to Persian Please click here to view the full text of this article

The full text of this article is the Persian language, please for the view full text, refer to Persian Please click here to view the full text of this article