فصلنامه تحقیقات آفات گیاهی
سال پنجم شماره 4 (زمستان 1394)

Orange pulvinaria scale, Pulvinaria aurantii Ckll., is one of the most important pest on citrus in north of Iran. At present, the farmers use chemical control methods to prevent crop losses by the pest. Using effective natural enemies has a special importance in controlling of this pest. The present investigation was conducted to determine the efficacy of coccinelid beetle, Cryptolaemus montrouzieri Muls. (Col.: Coccinellidae), and it's releasing time against orange pulvinaria scale in screen house and citrus orchard. The treatments were conducted in three different experiments with a completely randomized design. The result revealed that the feeding rate of adult coccinelid beetle (each pair) from ovisac of orange pulvinaria scale was 35 in a month. The result indicated that the best treatment in these experiments was twice ladybird beetle releases (one pair in the beginning of oviposition and another in the peak of egg sacs) in controlling the population of this pest.

The false chinch bugs, Nysius cymoides appears in many canola fields of the country at harvesting time. Spatial distributions of different stages of the bug were studied in canola fields of the Broojerd Agricultural Research Station during years 2006-2007. Twenty to twenty five samples were randomly taken via an aspirator from a 25 cm2 rimmed-quadrate twice a week. Each sample was kept in alcohol and carried to the laboratory for counting number of eggs, different nymphal instars and adult females and males. Spatial distribution pattern of each stage was determined by both Taylor’s power law and Iwao’s regression method. Aggregated pattern was detected by both models for most immature stages and adults. However, the data showed a better fit to Taylor’s model. Both methods demonstrated different patterns for variance-mean model. Iwao’s method predicted larger or negative sample size for low densities of the bug, which is inapplicable. Overall, Taylor’s power law had a better estimation of spatial distribution parameters and predicted smaller sample size than those of Iwao’s regression method for N. cymoides.

Cotton whitefly, Bemisia tabaci (Gennadius) is one of the most important pests of agronomic in greenhouse’s crops and ornamental plants. In this study, the effect of sublethal dose of Fumria parviflora (Lamark) (Papaverales: Fumariaceae) extract on the age-stage, two-sex life table parameters of B. tabaci was evaluated. While insect was reared on sensitive (Ergon) and resistant (Cal j n3) tomato cultivars. A total of 30 adult insects of the same age were released into glass cage and the adults were removed after 24 hours. All less than 24 hours old eggs remained and the fecundity were recorded daily until the end of the last day of life. Experiments were done in greenhouse under controlled condition; 27 ± 2°C , 50 ± 5 %rh and 16 h light/8 h dark. Results showed lower intrinsic rate of increase, gross reproductive rate and net reproductive rate of pest on resistant varieties Cal j n3 with amount of 0.062 d-1, 37.2 egg/individual and 10.1 egg/individual respectively, than insects reared on susceptible cultivar, Eregon which were treated with Fumaria extract with amount of 0.071 d-1, 39.85 egg/individual and 13.82 egg/individual respectively. The intrinsic rate of increase reduction in control treatment of Cal j n3 cultivar showed the effect of resistant cultivars on pest population dynamic. Although extract of fumaria application increased a crash of population on both cultivars, coeffect of resistancy and herbal pesticide application showed a better result. The highest intrinsic rate of increase was observed in control and ergon treatments with 0.1 d-1 and the lowest rate was recorded on F. parviflora Cal j n3 (0.06 d-1) ones. Therefore, usage of resistant varieties beside the herbal pesticides application showe deeply effect on this pest population density and is very important in its IPM strategy.

Recently, the use of plant essential oil as natural compound for protecting crops and decreasing environmental pollutions has been considered. In this study, contact and fumigant toxicity of peel essential oil of Citrus sinensis singly and in combination with spirodiclofen and propergite were evaluated against adult females of two-spotted spider mite, Tetranychus urticae. Median lethal concentration (LC50) values of essential oil of orange peel in the contact and fumigant toxicity assay, were 11.48 μg/cm2 and 48/75 μl/l air, respectively. Contact toxicity of C. sinensis essential oil in comparison with the two chemical compounds showed that T. urticae was more sensitive to spirodiclofen (LC50= 2.76 μg/cm2) than the essential oil, while propargite was less efficient (LC50= 28.51 μg/cm2). Furthermore, mixture of propargite and essential oil of orange peel (both at LC25) showed a mortality less than the total expected mortality (50 %). In contrast, mortality of LC25 of spirodiclofen mixed with C. sinensis essential oil was much higher than that of the total expected mortality (96.66 %). According to co-toxicity coefficient (CTC) factor, mixtures of C. sinensis essential oil with propargite and spirodiclofen, exhibited antagonistic and synergistic effects, respectively.

Tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a quarantine pest in Iran that has recently distributed to most parts of the country and become one of the most important and dangerous pests of tomatoes, potatoes and eggplants fields. In this research, development, reproduction and life table parameters of this pest were studied on two varieties of tomato Mobil and Rio grand in laboratory conditions (27±2°C, 60± 5% RH and a photoperiod of 16 L:8hD). Life table data were analyzed using age-stage, two-sex life table theory. The duration of total pre-adultstage of this pest was calculated 20.85±0.301 and 21.4±0.37 days and oviposition period lasted12.81±0.58 and 12.16±0.43 days, on these two varieties of tomato, respectively. Females also laid an average of 210.29±11.24 and 120.95±10.8 eggs, on tomato varieties, respectively. The highest intrinsic rateof increase (r), finite rate of increase (λ), net reproductive rate (R0) and shortest mean generation time (T) were recorded 0.158±0.0058 (d–1), 1.1710±0.0068 (d–1), 73.6.4±10.44 (offspring) and 27.21±0.35 (days) on Mobil variety, respectively. Thus, according to the biological characteristics and life table parameters, the Mobil cultivar was determined more suceptible than Rio grand variety to the population increase of this pest.

Oenopia conglobata is an important active predator of pistachio psyllid in pistachio orchards. Alternative host or prey has an important role in the stability of natural enemies population in nature. In this study, prey preference of 4th larval instar, male and female of O. conglobata were examined in 10 replications. Nymphs and adults of Agonoscena pistaciae, Aphis fabae, Aphis gossypii and eggs of Ephestia kuehniella with corn pollen were used as preys. In order to study the effects of these preys on consumption rate of adult stage of O. conglobata when feeding only on the common pistachio psylla, it was reared on each diet separately and the feeding percentage was determined after 24 hours. The results showed that the larvae and adults of this predator prefer nymphs of pistachio psylla to other preys. They fed 87±1.52 and 85.5± 1.74 % of psyllid nymphs, respectively. The Manly preference index in the prey-preference test on different diets also showed more preference to nymphs of pistachio psylla compared to other diets. Those predators reared on psylla had more consumption rate on pistachio psylla nymphs (99.2±0.512 %) than to other preys. The results showed that O. conglobata preferred common pistachio psylla to other preys and the common pistachio psylla is a suitable prey for rearing of this predator, but due to feasibility and rearing expenses, A. fabae as a second prey is the most favourable prey for rearing of O. conglobata for biological control of A. pistaciae.

The fifth Neohydatothrips species, N. abnormis (Karny) is recorded from Kohgiluyeh and Boyer-Ahmad province, south west of Iran. A large number of both sexes of this species have been collected on Astragalus sp. Diagnosis characters as well as illustrations for N. abnormis are provided.