Mass rearing of the larvae of Chironomus riparius (Dip.: Chironomidae)

Aquatic larvae of chironomid midge, Chironomus riparius Meigen, are one of the richest diets in fish rearing systems. The quantity and quality of food used to rearing these larvae, affect this developmental stage. This study was conducted to determine the effect of different diets (chicken manure, rice bran and soybean meal) with different weights (1, 3 and 5 gr) on larval development, the best time of harvesting at different constant temperatures (16-20, 22 ± 1, 24 ± 1, 26 ± 1, 28 ± 1 and 30 ± 1 oC) and the yield (larval live weight (gr) m-2 per week) based on the number of reared egg masses with the favorable diet. Results indicated that the highest weight of harvested larvae obtained when they fed on 5 gr of chicken manure (3.53 ï± 0.4, p < 0.01). The last larval instars were harvested at the shortest time (on 13th days), when reared at 24 ± 1 or 26 ± 1 oC feeding on chicken manure (compared to other temperatures). Mean yield of 131.38 ï± 13.99 gr m-2 per week obtained, when five egg masses were reared at 26 ± 1 oC on the chicken manure

Influence of different densities and nymphal instars of Aphis gossypii (Hemiptera: Aphididae) on developmental time and feeding rate of larvae of Episyrphus balteatus (Diptera: Syrphidae) under greenhouse conditions

Several aphidophagous insects such as predators and parasitoids are known to respond positively to aphid infested plants. This  study was intended to evaluate the effect of different densities (40, 60, 80, 100) and nymphal instars (1st, 2nd, 3rd, 4th) of the cotton aphid Aphis gossypii Glover (Hemiptera: Aphididae) as prey on developmental time and feeding rate of the larvae of the syrphid fly Episyrphus balteatus DeGeer  on cucumber leaves. The experiment was conducted at the greenhouse condition (22± 5°C, 55± 10% RH and 14L: 10 D h photoperiod) with 10 replications. Our study indicated that lower density and poor quality of prey caused higher larval mortality. Feeding on 3rd and 4th nymphal instars and higher density of prey (80 and 100 prey/day) caused shorter developmental time of E. balteatus. The larvae fed on densities of 40 and 60 prey, even though fed on higher nymphal instars, failed to complete their larval development. It is concluded that higher prey densities (80 and 100 prey) were highly suitable for predator's larval development and significantly reduced the developmental period of E. balteatus. These findings provide further evidence that E. balteatus has high predation capacity on aphids, and therefore can be used as a successful biocontrol agent against A. gossypii

Area dependent searching efficiency of Scymnus syriacus (Col.: Coccinellidae) feeding on Aphis craccivora (Hem.: Aphididae)

Searching efficiency is a key parameter of functional response which is in turn the major components in the selection of predators and parasitoids for biological control. Searching efficiency of Scymnus syriacus Mulsant feeding on Aphis craccivora Koch was determined at five different experimental arenas (i.e. 195, 247, 304, 385 and 650 cm2) on broad bean (Vicia fabae L.). To do this, functional response of the predator to different densities (i.e., 10, 20, 30, 40 and 60) of the third instar nymphs of A. craccivora was studied. At each experiment, one 48-h.-old female was introduced to the aphid density in a container (as an experimental arena) and replicated five times. The experiments were carried out at 25Ë Â± 1C, 65 ± 5% RH and a photoperiod of 16L: 8D h. Using the logistic regression, a type III functional response was determined for S. syriacus in the entire five experimental arenas. Searching efficiency was found to be area dependent as it decreased as the area of experimental arena increased. The maximum expected predation rates (T/Th) were 48.56, 42.44, 40.77, 38.09 and 34.88 in the five experimental arenas, respectively. The area searched as a function of prey density indicated that as prey density increased, the area searched by the predator decreased. It is concluded that the size of searching area and prey density, both influence foraging behavior of S. syriacus

Functional response of Serangium montazerii (Col.: Coccinellidae) to different densities of Dialeurodes citri (Hem.: Aleyrodidae): an open-patch approach

The functional response of a predator is the base of prey-predator dynamics. Functional response of Serangium montazerii Fürsch at different egg densities (50, 100, 150, 200 and 250) of Dialeurodes citri (Ashmead) was studied in an open-patch experiment, in a growth chamber (25 ± 1°C, 65 ± 5% RH and a photoperiod of 16: 8 L: D h) on âThompsonâ navel orange (Citrus sinensis cv. Thompson) apical leaves. A type II functional response was obtained using logistic regression. The searching efficiency (a') and handling times (Th) of the female adults using nonlinear least-square regression were estimated as 0.0421 ± 0.00945 h-1 and 0.0896 ± 0.0362 h, respectively. Mean times required for the female predator to settle in a patch were 121.4, 140, 116, 83 and 78 minutes at above-mentioned prey densities, respectively. It was inversely density dependent (R2 = 0.740). The proportion of female predators remaining in open patches at the end of the experiment was directly dependent on prey density (R2 = 0.9). It was concluded that the type of functional response obtained here was in agreement with studies on this predator in closed patches

Predation rate of Hippodamia variegata (Coleoptera: Coccinellidae) feeding on different densities of Aphis gossypii (Hemiptera: Aphididae)

Predation rate is basic to any investigation of prey-predator interaction and a major component in the selection of predators for biological control. The predation rate of variegated lady beetle, Hippodamia variegata (Goze), fed on different densities (20, 40, 60, 80 and 100) of third instar nymphs of cotton aphid, Aphis gossypii Glover, was studied under laboratory conditions (25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16L: 8D h). The net predation rates (C0) using age-stage, two sex life tables for 20, 40, 60, 80 and 100 aphids were calculated as 1547.50, 4011.91, 4450.78, 5300.20, 5305.73 prey nymphs, respectively. The mean consumption rates for male and female predators increased as prey density increased. The predation rate for both sexes also increased with increasing prey density. The lowest and highest predation rates for female were 1547.50 and 5305.73 prey nymphs at densities of 20 and 100 aphids, respectively. The transformation rate from prey population to predator offspring (Qp) decreased as prey density increased. It was concluded that any increase in the density of third instar nymphs of A. gossypii will result in significant effects on predation parameters of H. variegata

A comparative study on the population growth parameters of Coccinella septempunctata (Col.: Coccinellidae) and melon aphid, Aphis gossypii (Hem.: Aphididae) under laboratory conditions

Adult individuals of the ladybird, Coccinella septempunctata L., and also the melon aphid, Aphis gossypii Glover, were collected from cucumber fields in Rasht area, north of Iran. They were reared in a growth chamber at 26 ï± 2ËC, R.H. of 65 ï± 5% and a photoperiod of 16L: 8D. Ten mated pairs of two-day-old predators were separately transferred in to a plastic container (8 à 10 à 12 cm) that were covered with an organdy net. A demographic life table was constructed based on the daily fertility results. The intrinsic rate of increase (rm) and also the net reproductive rate (R0) of C. septempunctata were 0.159 and 373.916, respectively. The mean generation time (T) of ladybird was 37.25 days and the population was doubled (DT) in 4.35 days. The population of C. septempunctata was able to multiply 3.45 times per week (rw). In order to determine rm and R0 of the melon aphid, twenty wingless adults were put separately into a leaf cage (10 à 60 mm) on cucumber leaves. The R0 and rm values of the aphid were 49.256 and 0.471, respectively. The T was 8.27 days and the population of the aphid was doubled within 1.47 days. Female aphids were able to multiply 27.03 times per week. Adult longevity was 13.8 ± 1.09 days and mean number of offspring produced per female was 49.05 ± 2.32 and mean number of females per female per day (mx) was 3.22 ± 0.59

Reproductive performance of Chouioia cunea Yang (Hym.: Eulophidae) parasitizing fall webworm, Hyphantria cunea Drury (Lep.: Arctiidae)

The fall webworm, Hyphantria cunea Drury (Lep.: Arctiidae), is an important pest of forest and cultivated plants in Guilan Province, Iran. The reproductive performance of Chouioia cunea Yang (Hym.: Eulophidae), a gregarious pupal parasitoid of H. cunea was studied at 24±1°C, 70±5% (RH), and a photoperiod of 14:10 (L:D) hours. The pupal hosts were exposed to 1, 2, 4, 8, 12, 16 newly emerged adult parasitoids. The parasitoids remained in contact with host pupae for 24 hours in Petri-dishes (10x1 cm) until the death of all parasitoids. The results showed that parasitoid density influenced offspring production, as the higher parasitoid densities resulted in the lowest mean number of offspring per female (179.06± 6.29). The sex ratio was not influenced by parasitoid density, but the age of parasitoid affected sex ratio as a higher sex ratio (0.92±0.001♀) was observed in the progeny produced by younger parents. Rate of parasitism was higher at density of 4 wasps (33.33%). The mean percent parasitism by 1, 2 and 3 day-old female parasitoids were 21, 13 and 9, respectively (P<0.05). Maximum number of offspring produced per female was obtained at host/parasitoid ratio of 15 to 4. The female parasitoids survived 1-3 days after oviposition. The searching efficiency of the parasitoid decreased from 0.18 to 0.009h-1 with increasing its density. The survival rate for C. cunea was not significantly different at all densities of male or females, but a statistical difference was observed with increasing parasitoid age. It was concluded that the performance of C. cunea was mainly affected by its density and age

Olfactory response of the predatory bug, Orius niger (Hem.: Anthocoridae) to Tetranychus urticae (Acari: Tetranychidae) on cucumber leaves treated or untreated by Beauveria bassiana

Olfactory experiments were performed to study the predation behavior of Orius niger Wolff (Hemiptera: Anthocoridae) on the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) in presence or absence of Beauveria bassiana (Bals.). The experiments were carried out with six day old female bugs by recording the predator direction towards each of the Y-tube olfactometer arms and through three dependent replicates consisted of 15 replicates each. The predatory bug showed a significant preference towards the odors related to infested cucumber leaves by T. urticae in the absence of fungus and when the predator received odors related to T. urticae infested leaves v.s. B.bassiana fungus treated, spider mite infested leaves (72 hours). There was no significant difference in the predator olfactory experiment when the alternative arms consisted of treated v.s. untreated spider mite infested cucumber leaves (0, 24 and 48 hours after treatment). The results showed the capacity of the predatory bug to recognize the patches infected by B.bassiana fungus and successfully avoiding it

Temperature-dependent development of Habrobracon hebetor (Hym.: Braconidae) reared on larvae of Galleria mellonella (Lep.: Pyralidae)

The development times and the survival rates of different stages of Habrobracon hebetor Say reared on the last instar larvae of Galleria mellonella (L.) were compared at ten different constant temperatures (16 - 38 ºC). The development time of immature stages of the parasitoid, H. hebetor, decreased as the temperature increased in the range of 16 to 38 ºC. However, no larvae could survive and develop at 16 ºC. Development time from egg to adult females was the shortest (8.368 ± 0.069 days) at 35 ºC and the longest (32.667 ± 0.33 days) at 18 ºC. Egg incubation period, larval and pupal development times were significantly different at various constant temperatures. No significant difference was found between two sexes in their developmental periods from eggs to adult stage. The survival rate of the egg stage ranged between 94.90 and 100% at all temperature levels, but larval survival rates was significantly different at various temperatures. Although significant difference was found in the survival rate of pupal stage (P < 0.05), the trend of survival rate for pupae was similar to those of larvae. The relationship between temperature and the developmental rate of the parasitoid well described by linear regression model (R2 = 0.89, P = 0.0001, at the egg stage and R2 = 0.95, P = 0.0001, at the egg-adult stage). The lowest threshold temperature was obtained for all developmental stages of the parasitoid. Degree-days requirements (DD) for egg, larva, pupa and egg-female stages were 22.73, 56.82, 109.89 and 188.68, respectively. The results in this study showed that the temperature range between 25 and 32 ºC provide a favourable condition for mass rearing of this parasitoid