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Abstract Laboratory studies were conducted at the Bollwonn Laboratory, Plant Protection Research Institute to detennine the effect of host species and different kinds of food on two Trichogramma species, i.e.; Trichogramma evanescens (native strain) and Trichogrammatoidea bactrae (imported from USA in 1992). Eggs of six lepidopterous species were used, three of them are considered as important economical pests for cotton (pink & spiny bollwonns and black cutwonn), however, the others (rice bran moth, angoumois grain moth and Mediterranean flour moth) are known as grain pests. The obtained results can be sunnnarized as follows: I. Host Inftuenceon Trichogramma spp.: a. Influence of rearing, hosts: 1. Occurrence of superparasitism: In the present results, the average number of the two parasitoids’ pupae/ egg and subsequently the percentages of. superparasitism were significantly correlated with the size of the host eggs. Regarding the present results of the two Trichogramma species, larger host eggs such as E. insulana and A. ipsilon have been shown to be able to support the development of more than one parasitoid larva. 6.36 & 7.2~!cJof eggs parasitized by T. evanescens and 8.73 & 2.810/0 of eggs parasitized by T. bactrae showed superparasitism in E. insulana and A. ipsilon eggs, respectively. Sometimes up to 3 pupae were observed! egg although host egg density was not limited (>80 host eggs! Trichogramma female). However, eggs of the remaining hosts supported generally the developing of only a single larva and rarely two in each host egg. 2- InDuence on recuD~ityand emerged progeny: In genera!, fecundity and emerged progeny per T. evanescens female (37.87 & 36.69/female) were significantly more than tIlose per T. bac””” female (32.172 & 31.12lfemale). while tile results varied significantly between tile six host species. T. evanescens and T. bactrae females produced significantly tile bighest nnmbers of adults (42.65 and 36.031 female) when reared on P. gossypiella and C. cephD/ollica eggs, respectively. However. the lowest nnmbers of progeny were produced when these two parasi toids were reared on S. cerea/ella eggs (23.67 and 23.621female,respectively). 3~InBuence on progeny survival: The percentage of survival (percentage of progeny emerging as living active adults) didn’t vary significantly between tile two parasitoids however it varied between tile six hosts. A1t1lough tile highest percentages of T. evanescens (99.89 & 98.10 %) and T. bac/rae (99.16 & 98.62~.) adults emergence occurred from tile larger hosts E. inslI/ana and A. ipsilon, no significant correlation was statistically obtained between the percentage of survival and the index egg size. r = 0.7910 and 0.79953, for the two parasitoi~ respectively. 4- laB.nce OB the Sex-ratio and Geaenl Productivity: Female progeny dominafed those of males, regardless of parasitoid species or hosts. The ovenill mean percentage of resulted females (68.1\ ± 0.42 and 68.56 ± 0.5 %- for T. evanescens and T. hac/rae females, respectively) didn’t differ, significant\y between the two parasitoid species. But rearing on differeIllhosts affiodedsigniticantly the pen:entage of produced females. Tric/togramma reared on E. imll/ana eggs (the largeSt host size) produced siglJilicant!Y _ feIna1es (74.54 ± 0.5 & 77.79 ± 0.60 %, respectively), while those reared on S. cereg/ella eggs (the smallest size) produced the lowest pereeniage offemales (61.82 ± 0.70& 62.67 ± 0.6%), General productivity of T. evanescens females (25.14femaleslfemale) was significantly higher than ilia! of T hac/rae females (21.20 female). Significantly the highest productivity values for T evanescens were produced under rearing on C. cephalonica. P. gossypiella and E. insulana (28.72~ 28.27 and 28.11 females/female~ respectively)~ while those per T. bactrae female were obtained under rearing on C. cephalonica (24.08), E. kuehniella (23.49) and E. insulana (23.17 females/female. 5. InftueDce ODsize of the parasite females: T. evanescens females were larger than those of T. bactrae, which reared from the same host, however, females reared on the larger hosts (E. insulana eggs) were larger than those reared on the other hosts; the abdominal width averaged 0.203 & 0.173 nun, while the head width averaged 0.228 & 0.218 mID, respectively. While~ females emerged from S. cerealella eggs (the smallest host) had the smallest abdominal and head width (0.131 & 0.124 and 0.148 & 0.149 mm, respectively). Statistically there was a close correlation between the e~’i’index size of the different rearing hosts and that of the parasites~ abdominal and or bead width sizes. 6. Fec.dity and longevity associated with the size of female parasitoid: For all females, which emerged from the same host, abdominal and head widths were found strongly correlated with both number of progenyl female and females’ longevity. Moreover. the abdominal width was more closely correlated with fecunditY and longevity than with head wid1h. thus. abdomen width appears to be a useful index of Trichogramma quality. In contrarY, the whole averages of female sizes (which emerged from each of the six mentioned hosts) correlated insignificantly with the averages of tbeir fecundity. However, females that had a medium size and reared from P. gossypiella and C. cepholonica eggs were more fecund than those had larger sizes and reared from E. insulana eggs. The longevities of T. evQll<scensfemales, of different sizes, reared from each of aforementioned hosts varied insignificantly (2.96 - 3.6 days). However, larger T. bactrae females lived significantly longer than the smaller ones (2.58 _ 3.84 days). Le.; T. /ractMe females from E. insulana eggs bad the longest life-span (3.84 daYs), wbile those emerged from S. cerealella eggs were smaller in size, less fecund and lived the shortest period (2.58 days). b. IFnrfolumencreesuoltfsthoef alttbeirsnstautdivye hiot sctouspldecbiees:conclnded that potentiality of the two parasi toids on each of the six alternative bosts varied according to the rearing host. For example, the potentiality of the two parasitoi ds when reared on the six aforementioned bosts and switched to parasitize P. gossypiella or E. insulana eggs, can be SlJ1llI1UI1’ize as the following: 1. T. evane scens ; the native parasitoid is generallY. more capable to parasitize more P. gossypiella OW than T. hac/Me; the introduced parasitoid (overall avernge of 49.19; 21-70 eggs! female in the former case opposed to 34.29; 2O-53eggs! female in the latter case). 2. E. _lana, E. /aJehniella and A. ip.<ilonmay be, fairly, considered the best for rearing T. evanesce’” (64.6,53.96 and 53.7 parasitized P. gossypiella eggs! female). While E. 1aJehniellaand C. cephalonico are considered lbe best for rearing T. /rae,””, (46.14 and 45.3 eggs! female) when the target pest (al\erDIIIiVChoot) is P. gossypiella. On contI8IY, S. cerealella gave poor capability ofparasitizingP. gossypiel/a eggs (36.3 and 26.5 e~ T. evanescens and T. bactrae female, respectively, compared to the fonner hosts. 3. It could be indicated that E. msulana is the best host for rearing T. evanescens to be used as a hiocontrol agent against P. gossypiel/a, while, E. kuehniella is the best for rearing T. bact rae for the same propose. 4. A. ipsilon eggs are the most suitable for rearing the two species of Trichogramma to be used as a control agent against E. insulana eggs. II. Host Preference: Two sets were designed to detennine the acceptance and preference of some lepidopterous hosts to be parasitized by T. evanescens and T. bactrae females which had been maintained on S. cerea/ella eggs (original culture) for more than 10 generations. In the first set, Trtchogramma female was offered the choice between S. cerealel/a eggs (the original host) and those of each of the other five hosts. Data revealed that the two parasite species accepted to parasitize eggs of the six lepidopterous species with different levels of preference (2.0 _ 2.9 contacts & 10.75 - 21.79 parasitized eggs by T. evanescens and 1.2 _ 3.0 contacls & 6.04 - 32.46 parasitized eggs by T. bactrae). The two parasitoid spefemales didn’t prefer S. cerealel/a over than each of the other five hosts. In the second set, in which the eggs of the six host species were exposed to Trichogramma females. Eggs of the six lepidopterous host species were accepted for parasitism, but with different levels of preference. The acceptance and preference behavior between the two parasitoid species took the same trend where the statistical analysis of data was not significant While, P. gossypiel/a eggs were the most preferred by females of the two species over those of the remaining five hosts. III. Effect of food kind and concentration on Trichogramma spp.: a. Fecundity: The lowest average of total progeny/ female of T. evanescens and T. bactrae (30.6 and 14.1 individual) were produced by the starved females. On the other hand. adding yeast to the 10% sucrose solution or to 100/0 bee honey enhanced T. evanescens female’s fecundity as they produced the highest total nwnber of progeny (56.4 /female). In case of T. bactrae, the highest fecundity of females (37.6 progeny/. female) was reported by offering 20% bee honey solution to the freshly emerged females with insignificant difference than . those reported from females fed on 100/0 bee honey with yeast added (33.9), 10% sucrose solution (32.9) and pure ~ee honey droplets (32.9 progeny/ female). Data revealed that T. evanescens females (native) has, generally, higher fecundity (overall mean 45.38 ± 0.82 progeny/ female) than those of T. bactrae (introduced from USA) which produced an overall mean of 27.68 ± 0.56 progeny! female b. Female longevity: By using all the tested foods and concentrations, it could be concluded that: 1. T. evanescens female’s life-span was always longer than that of T. bactrae (overall mean 3.25 ± 0.09 in the fonner case opposed to 1.71 ± 0.05 days in the latter one). 2. Females of the two species lived longer in the presence of nutrition than in its absence. Starved females of the two species lived for 1.95 and one day, respectively); however they lived the longest period when T. evanescens female was fed on pure bee honey followed; insignificantly; by 10% sucrose + yeast and 10% sucrose solution (4.6, 4.4 and 3.9 days, respectively), and when T. bactrae was fed on water only (2.7 days), followed by 10%bee honey + yeast (2.4 days) and pure bee honey (2.3 days ). 3. Adding yeast to water led to shorter life-span than providing the females water only (from 3.25 to 2.55 days in case ofT. evanescens and from 2.7 to 1.3 days in case of T. bactrae). While, on the contrary adding yeast to the 10% sucrose solution enhanced female’s longevity (from 3.9 to 4.4 days for T. evanescens and from 1.4 to 1.8 days for T. hactrae). c. Percentage of emergence: Insignificant differences were detected in the percentages of emergence from eggs of T. evanescens which were fed on either of the different nutrition treatments, while the opposite was true in case of results from T. bactrae which showed significant differences (86.2% from eggs of starved females - 97.3% when T. bactrae females were fed on pure bee honey). d. Sex-ratio (percentage of females): The sex-ratio was always female-biased and T. evanescens had an overall percentage of females (74.58 %) more than T. bactrae (66.36 %). Furthermore, the absence of nutrition did’ not influence the percentage of produced females in progeny. T. evanescens females fed on sucrose 2001c. + yeast produced the least percentage of females (64.1 %), however, those fed on 10 % bee honey solution + yeast produced the highest percentage (85.9 %). On the other hand; T. bactrae females fed on sucrose 5% + yeast produced the lowest percentage (59.6 %) and those fed on sucrose 100/0 + yeast produced the highest percentages (74.2 % females) e. General productivity: Productivity may be considered a very important measure of quality. However, the obtained data revealed the following: 1. The highest productivity by a T. evanescens, female averaged 46.6 females! an adult female fed on 10% bee honey solution + yeast followed, insignificantly, by 42.8 by feeding on either pure bee honey or 10 % ,sucrose solution + yeast. The lowest productivity (23 females) was produced from starved T. evanescens females and those fed on water + yeast (22.3 females). 2. As for T. bactrae, the overall productivity /female (17.4 females) was lower than that of T. evanescens (32 females). The highest productivity ofa T. bactrae female reached 23.4 by feeding the adults on 10% sucrose solution. Female productivity was drastically reduced to 8.1 females when T. bactrae females were kept without nutrition 3. Adding yeast to sucrose or bee honey solutions for feeding the parasitoids increased females productivity of T. evanescens but conversely caused a reduction on productivity of, T. bactrae females. 4. T. evanescens females appeared better to be fed on either of lOOIc. bee honey + yeast, pure bee honey or lOOIc. sucrose solution + yeast. While, T. bactroe females appeared better to be fed on either lOOIc. sucrose solution or 20 % bee honey solution. IV. Storage of Trichogramma at low temperature a. Storage of developmental stages: 1. Emergence of adult parasitoids from stored eggs: T. evanescens stored at the prepupal stage (3 days after parasitism) was the most tolerant to the adverse effect of the low temperature (79.5 ± 1.5% emergence), however, T. bactrae showed most tolerance when stored at the first larval stage (one day after parasitism) as the percentage of adults’ emergence averaged 74.3 ± 1.9 %. On the contrary, old pupae (7-days after parasitism) of the two species were the most susceptible stage to the adverse effect of the low temperature as the overall percentages of emergence averaged 47.7 ± 2.9 and 47.8 ±2.7, respectively. 2. Potentiality of Trichogramma females resulting from storage: It was clear that the higher percentages of females with successful parasitization and the higher numbers of parasitized eggs! female were produced in case of storing the prepupal stage. It is also worthmentioning that, by storage of the parasitized eggs after 7 days of stinging for 30 days, the resultant females were completely, unable to parasitize any P. gossypiella eggs Thus, when storage of Trichogramma is needed, the parasitized eggs are better to be stored when the parasitoid ·isin the prepupal stage (3 days after parasitism at 2S0C), as in this case, the resultant parasitoid adults are of higher potentiality than storage in either of the remaining stages. Also, it is, generally, advised not to expose the parasitoid to low temperatme when it is in the pupal stage. 3. Percentage of emergence from eggs of treated females: Results indicated high percentages of emergence from P. gossypiella eggs parasitized by T. evanesce”. and T. bactrae females 1hat resulted after storage at low temperature (8°C.) at different developmental immature stages of the parasitoid and for different periods up to 25 days. The overall percentages of the two species from stored parasitized eggs averaged 93.5 ± 0.177 and 92.5 ± 0.22?01c», while those from control eggs averaged 94.6 ± 0.32 and 94.5 ± 0.320/0,respectively. 4. Percentage .ffemales in the progeny (sex-ratio): In the present study, the sex-ratio in progeny was always female biased whatever the species, the stored age and the storage period. However, lower percentage of females in progeny of the two species were senera\1y recorded by increasing the storage period to 25 days. Generally, the overall percentage of females in T. evanescens and T. bactrae progeny from stored eggs averaged 64.8 ± 0.7 and 62.6 ± 0.75°/0, respectively, while those from control eggs averaged 65.8 ± 1.5 and 69.8 ± 1.33, respectively. b. Storage of adult females: 1. Potentiality .f’TrichogrlUfUlllJ females after storage: The potentiality of stored females for parasitizing P. gossypiella eggs was lower compared to the control feIDa1es. Females of the two species showed a degree of tolerant to the adverse effect of low temperature up to 3 days, however all females that stored for 6 days failed to parasitize any egg. 2. PI.Calf eDlltl’leaee: High percentages of progeny emerged from P. gossypiella eggs parasitized by T. ewmeseens and T. hac/rae females 1hat were stored at low temperature (8°C) up to 4 days. Generally, the overall percentages of emergence averaged 92.65 ± 0.5 and 90.22 ± 0.8 %, while those from control eggs averaged 94.7 ± 0.7 and 94.8 ± 1.1%, respectively. However, all progeny failed to develop in P. gossypiella eggs as the storage period was prolonged to 5 days. 3. Percentage of females in the progeny (sex-ratio): The overall percentage of females in progeny of stored T. evanescent female adults (67.36 ± 0.86 %) didn’t vary significantly than control (69.35 il.8 %). As for T. bactrae, a conflicted percentages of females in progeny were recorded after exposing their parental females to low temperature (8°C) for 2, 3, and 4 days, i.e.; percentages of females averaged 68.1 ± 1.6 and 63.8 ± 1.4 and 68.3 ± 1.06 %, respectively. According to the obtained results, it could be advised not to expose Trichogramma adults to low temperature more than three days. |