A study was carried out to map dispersal of TRICHOGRAMMA BRASSICAE Bezd. on tomato in a 0.5 ha field. First, 1, 5, 10, 15, 20 and 25 meter distances from the central point of the field were marked in form of squares. On each square, 8 points were selected and a wooden stake of 1.5 m length was vertically secured into the soil at each point equal to plant height and bearing a yellow sticky trap (YST, 10 x 20 cm) on the top. Moreover, three egg batches each containing ~200 freshSitotroga cerealella Oliv. eggs on cardboards (SEC) were stapled on top leaf of three plants around the wooden stake arranged in a 0.75 m arch. Evaluation was done two days before and 2, 4, 6 and 8 days after a release of 50000 newly emergedT. BRASSICAE (~1: 1 Male: Famale) from the central point. The number of T. BRASSICAE trapped by YST, and number of parasitised eggs on SEC were counted under a stereomicroscope and noted down. The coefficient of fitting YST data to the model (R2) for all 4 sampling dates was as high as 86%. The average diffusion coefficient was equal to 16.89 m2/day for four times sampling. In general, the distance encompassing 98% of trapped T. BRASSICAEpredicted by the model was up to maximum 29.9 m from the central point 8 days after the release. The mean percent parasitism was 44.7, 5.5, 5 and 0.9 per SEC during 2, 4, 6 and 8 days after release, respectively. It is concluded that, the farther the distance from the releasing point and the longer the time elapsed after release, the less number of wasps were recaptured. Therefore, multiple releasing points are required to achieve even distribution and enough population of parasitoids in the field.

Learning ability and memory duration are two inseparable factors which can increase the efficiency of a living organism during its lifetime. Trichgramma brassice Bezdenko (Hym.: TRICHOGRAMMAtidae) is a biological control agent widely used against different pest species. This research was conducted to study the olfactory associative learning ability and memory duration of T. BRASSICAE under laboratory conditions. According to our results, T. BRASSICAE showed olfactory learning ability in response to conditioned odors, and this learned olfactory stimuli lasted for 20 hours. In a second experiment, the effects of frequent experiences on the memory duration of females were studied. A direct relationship between frequent experiences and memory duration was observed. When exposed to a conditioned odor, wasps’ memory duration increased in response to the number of experiences. Memory was observed at 28 h after one extra conditioning. The duration of the associative memory lasted 42 hours when 2 extra experiences were given, 50 hours after 3 experiences, and 58 hours after 4 extra conditioning experiences. Our results showed that T. BRASSICAE can associate new odors to host existence, and they will show increased memory duration after multiple experiences.

Dispersal of TRICHOGRAMMA BRASSICAE Bezd. was studied in 2 rice fields by a single release of 50000 adult wasps from a central point and recapturing them using yellow sticky traps and egg cards of Sitotroga cerealella (Oliv. ) Results revealed that in rice field 1, dispersal coefficients were 3. 04 and 1. 07 m2/day at 1st and 2nd sampling turns. However, it reached to a level of 11. 28 m2/day at 3rd sampling turn. In contrast, T. BRASSICAE dispersed with a speed of 3. 93 m2/day at 1st sampling turn and had the highest dispersal coefficient (29. 76 m2/day) at 3rd sampling turn in rice field 2. Similarly, the distances that encompassed 98% recaptured T. BRASSICAE was highest in field 2 (53. 45 m) compared with that in field 1 (15. 11 m) at 3rd sampling turn. Number of wasps remained in fields 1 and 2 were recorded as 630. 67 and 272. 18 individuals, respectively, for total sampling turns. Moreover, the highest parasitism rates (64. 75 and 91 mean parasitized eggs/card in fields 1 and 2, respectively) were observed at 1 meter distance from release point at first sampling turn and it decreased wi th time and distance elevation. It is concluded that more release points of T. BRASSICAE per rice field is required to achieve universal dispersal in successful rice stem borer biocontrol. It needs innovation in packing and release method of the wasp.

Integration of different pest control tactics is a principle in modern pest management. Interaction between different tactics and possible antagonism between them then will become important. A common integration is integration of egg parasitoid, TRICHOGRAMMA spp. and larvicidal microbial agent, Bacillus thuringiensis against some field crop moth-pests, particularly in bollworm-cotton system. Although sequence of application allows avoiding direct antagonism, but indirect effects on the next generation of the parasitoid via treating the target pest’ s larvae is not impossible. Some direct effect via overlapping of different stages of the pest is also possible. Therefore, studying possible maternal effects on parasitoids of the next generation that are developing on B. t.-treated host larvae is required. In this study, response of T. BRASSICAE, was studied on two kinds of hosts; first bollworm, Helicoverpa armigera eggs laid by those females that treated by LC20 of B. thuringiensis in third instar. The second one control (untreated) individuals. Life history parameters were compared between the two groups by two-sided t-test. No significant difference was observed between the two groups. It means that B. t. had no undesirable effect on T. BRASSICAE. The mean value of R0, rm and T were 41. 22 ± 3. 85 female/female/generation, 0. 3545 ± 0. 009 /d and 10. 49 ± 0. 19 d as average of the two treatments. Thus, B. t. is safe for integration with TRICHOGRAMMA application programs.

The effects of long-term rearing of TRICHOGRAMMA BRASSICAE (Bezdenko) on host preference and switching behavior was examined when parasitizing two common factitious hosts, including Mediterranean flour moth (MFM), Ephestia kuehniella Zeller and Angoumois grain moth (AGM), Sitotroga cerealella (Olivier) over 45 generations. Both host species eggs were offered to the parasitoid over 24 h. Significantly more MFM eggs were parasitized in all generations, but a distinct negative switching behavior was found in all experiments. The parasitoid negatively switched from MFM when they became abundant compared to AGM and vice versa. The preference coefficient (c) estimated using Murdoch's index ranged from 2.056 (in G5) to 1.734 (in G45) for MFM and 0.486 (in G5) to 0.577 (in G45) for AGM. The linear regression indicated that despite preferring MFM, the intensity of the preference decreased over 45 generations. Negative switching behavior in T. BRASSICAE may be advantageous for this species in controlling pests in given situations.

Most natural enemies have low maintenance capabilities so they are often cultivated shortly before release. In the case of parasitoids, their hosts can be stored instead of parasitoids. Since storage of host eggs can increase the efficiency of the mass production units of TRICHOGRAMMA wasps, this approach has been suggested by various researchers as a suitable method for mass production of TRICHOGRAMMA species. As regards that there are few studies on the effect of low temperatures on the growth population parameters of parasitoid, so in this study the effect of cold storage of Phthorimaea operculella (Zeller) eggs at 4° C for 0, 1, 4, 7, 15 and 30 days on biological and population parameters of TRICHOGRAMMA BRASSICAE Bezdenko were investigated. This experiment was conducted in a completely randomized design with 25 replications. Mean comparisons were performed using Duncan's test. The results showed that developmental time, longevity, parasitism rate, percentage of emergence, fecundity and oviposition period of T. BRASSICAE were significantly different between treatments and the all parameters decreased when the storage period increased. It was also determined that all population growth parameters had a significant difference between the control and cold treatments. Due to the parasitism and adult emergency rate, longevity and fecundity of T. BRASSICAE on stored host, eggs of P. operculella can be stored at 4° C for up to two weeks without significant negative effect on the efficiency of the T. BRASSICAE. However, based on population growth parameters, maintenance of host eggs for up to one week are most recommended.

The flight and walking activities of the second, forth, sixth and eighth generations of Trichogramm BRASSICAE reared on Sitotroga cerealella eggs were compared under laboratory condition. The parasitoid wasps were obtained by collecting egg masses of Naranga aenescens from rice fields and Sitotroga cerealella egg traps. The experiments of flight and walking activities was carried out using black P.V.C. tubes and the percentage of inactive, flying and walking wasps to light were calculated. Results showed a reduced flight and walking activities and increased percentage of inactive wasps with the increasing number of generations. In second generation, 41.9±2.88, and 36.7±2.65 of wasps population had flight, and walking ability, respectively, and 21.4±2.45 of them was not able to fly and walking. The highest percentage of inactive wasps were observed at eighth generation, whereas wasps showed significantly better flight and walking activities at second generation. Based on the results, flight and walking abilitiies of T. BRASSICAE were gradually decreased at continuous laboratory rearing.

Parasitism rate of TRICHOGRAMMA BRASSICAE Bezdenko at laboratory conditions with six constant temperatures of 15, 20, 25, 30, 32 and 35±1oC, relative humidity of 65 ± 5% and a light period of 16 h. was evaluated on the eggs of gelechiid moth Sitotroga cerealella (Olivier). Parasitism rate of T. BRASSICAE was significantly affected by different temperatures. The highest (40.257 hosts) and the lowest (3.731 hosts) values of net parasitism rate (C0) was obtained at 32 and 15oC, respectively. The transformation rate of host population to parasitoid offspring (Qp) was equal to 1 at all temperatures. The values of stable parasitism rate (y) increased from 0.074 to 0.451 (host/parasitoid) with increasing temperature from 15 to 30oC, but the values for this parameter at 32 and 35oC significantly decreased. The highest recorded value for finite parasitism rate (w) was obtained at 30oC (0.654 day-1). The temperature thresholds for finite parasitism rate of T. BRASSICAE were estimated by nonlinear models of Briere-1 and Lactin-2. The Lactin-2 better fitted the related data (SSE=0.004833, R2adj=0.977, AIC=-38.7438). The obtained values for the lower temperature threshold (Tmin), optimum temperature (Topt) and upper temperature threshold (Tmax) of parasitism activity of this parasitoid were 13.20, 31.20 and 35.40oC, respectively.