Naturally occurring Trichogramma species in olive farms in Egypt

A survey of two-year studies (2001-2003) was carried out in two olive groves sited at two representative olive growing areas, namely Paradise Park (arid area) and Burg E1-Arab farm (semi-arid area) to monitor the frequency of endemic Trichogramma species on olive moth (Prays oleae) and jasmine moth (Palpita unionalis). The suspended host bait traps were found to be a more practical and effective tool for collecting Trichogramma wasps than the attached ones. Four naturally occurring Trichogramma species were collected for the first time in Egypt from the olive groves, where releases have never been conducted. T.bourarachae was collected exclusively from Burg El-Arab farm. It seems that this wasp species adapts well to the semi-arid area. Three species, namely T. cordubensis, T. nr.pretiosum and T. cacociae were isolated from Paradise Park farm. All of these wasps were also bred from naturally parasitized host eggs during favorable and even at unfavorable temperature conditions of June-August. However, these endemic species did not occur naturally in sufficient numbers to keep the pest populations from reaching damaging levels.The excessive usage of insecticides and the oophagous predators (e.g., ants and lacewing larvae) are some factors that affect the performance of Trichogramma wasps in olive farms.The presence of warm weather wasp strains suggests the existence of well-adapted wasp species or swains which may be appropriate candidates for the control of target pests in olive groves. Additional study is required to determine the best “habitat-specific” species/strains of Trichogramma for augmentative release of naturally occurring wasps and to incorporate them into integrated pest management programs. Efforts should be made to conserve these endemic species from oophagous predators, hot weather and insecticides.The olive and jasmine moth-larvae and pupae found under tree canopies were bred and emerged parasitoids were listed.     

CO2 Assimilation and Partitioning of Carbon in Maize Plants Deprived of Orthophosphate

In order to study the effects of inorganic phosphate (P1) starvationon C₄plants, 3-week-old maize plants (Zea maysL cv. Brulouis)were grown in a growth chamber on a nutrient solution withoutP1 over 22 d During the first 2 weeks, Pi-starved plants grewas well as control plants The Pi concentration in the planttissue decreased rapidly with time, which suggests that normalbiomass production can be maintained at the expense of internalP1 In addition, photosynthetic CO2 assimilation measured 4-6h after dawn was not affected, but the concentration of glucose,sucrose, and starch in leaves was much higher than in the controls¹⁴CO₂ pulse-chase experiments earned out on the ninth day oftreatment showed that ¹⁴CO₂ assimilation was perturbed duringthis initial period, resulting in a larger flow of carbon toboth starch and sucrose At the beginning of the third week ofP1 starvation (15 d after treatment) ¹⁴C incorporation intosucrose stayed high relative to controls but this was not thecase for starch At the end of the third week of P1-deficiency,shoot growth was considerably reduced and fresh weight was onlyone-third of that of the control plants. The P1 concentrationof both the leaf and root tissues was less than 1.0 µmolg^–1 FW compared to 20-25µmol g¹ FW in the controls.Photosynthetic CO₂ assimilation was reduced and the leaf concentrationof sucrose and starch, which had begun to decrease after theend of the second week of P1 limitation, became lower than inthe controls. These results obtained on maize plants show thatphotosynthesis and carbon partitioning between sucrose and starchwere strongly affected by P1 deficiency, similar to C₃ species. Key words: CO₂ assimilation, corn, orthophosphate deficiency, starch, sucrose     

Uncovering the tracks of a recent and rapid invasion: the case of the fruit fly pest Bactrocera invadens (Diptera: Tephritidae) in Africa

Phytophagous insects of the genus Bactrocera are among the most economically important invasive fruit fly pests. In 2003, an unknown Bactrocera species was found in Kenya. First identified as an ‘aberrant form’ of the Asian B. dorsalis complex, it was later recognized as a new species, Bactrocera invadens. Within 2 years of its discovery, the species was recorded in several African countries, becoming an important quarantine pest. As this invasive fly was discovered only recently, no data are available on its invasion pattern in Africa. This pilot study attempts to infer from genetic data the dynamic aspects of the African invasion of this pest. Using microsatellite markers, we evaluated the level of genetic diversity and the extent of common ancestry among several African populations collected across the invaded areas. A sample from the Asian Sri Lankan population was analysed to confirm the Asian origin of this pest. Genetic data cast no doubt that Sri Lanka belongs to the native range, but only a small percentage of its genotypes can be found in Africa. African populations display relatively high levels of genetic diversity associated with limited geographical structure and no genetic footprints of bottlenecks. These features are indicative of processes of rapid population growth and expansion with possible multiple introductions. In the span of relatively few years, the African invasion registered the presence of at least two uncorrelated outbreaks, both starting from the East. The results of the analyses support that invasion started in East Africa, where B. invadens was initially isolated.