This work was initiated for the first time to identify parasitoid species associated with the immature stages of Pieris rapae (L.) inhabiting cabbage plantations in Assiut governorate, Upper Egypt during the 2018 and 2019 cabbage growing seasons. Attacking periods and parasitism percentages (PPs) of the identified parasitoid species were calculated. One solitary parasitoid species, Hyposoter ebeninus was found to attack P. rapae larvae in the field 110 days after transplantation. However, one hyperparasitoid species Baryscapus galactopus was recorded as an internal gregarious hyperparasitoid of H. ebeninus. The solitary larval parasitoid H. ebeninus strikes were recorded throughout the last five weeks of the season with a marked decline before harvesting. Although H. ebeninus revealed 42.00% abundance, it presented 21.69% PP on P. rapae larvae during the entire period of study. One solitary, Brachymeria femorata and two gregarious parasitoid species [Pteromalus puparum (L) and Tetrastichus sp. (Haliday) were recorded as P. rapae pupae parasitoids on October, 2 nd . Parasitism peak was recorded on October, 16 th with an average of 56.25%. The first appearance of the gregarious pupal parasitoid P. puparum was recorded on October, 9 th . Four weeks later, the second gregarious parasitoid (Tetrastichus sp.) was recorded on November, 6 th . Both pupal gregarious parasitoid species were found to be active until harvesting. The gregarious parasitoid P. puparum presented high PP (23.73%) as compared with Tetrastichus sp. which exhibited 6.96% PP during the entire period of study. In conclusion, two solitaries, one hyperparasitoid, and two gregarious parasitoid species were identified. Pupal gregarious parasitoid species together reduced P. rapae pupae populations by 30.69%. These parasitoids could be used in the IPM programs for this pest in the future. At the same time, the effect of hyperparsitoides must be taken into consideration.
The small white cabbage butterfly, Pieris rapae (L) is one of the most serious insect pests infesting cruciferous plants especially cabbage. Comparison between the potency of certain chemical and safe alternative compounds in reducing, P. rapae larval populations in the field was the corner stone of this investigation. Also, their potency to reduce the pest infestation levels and yield loss (unmarketable plants) has been taken in consideration. The pest larvae were recorded in very small numbers; 14 days post application (round up the economic threshold) by using most of the tested compounds. Potency of the tested compounds indicated that, Broact 5% SG (Emamectin Benzoate) showed the highest reduction percentages, (93.29% for larvae populations; 52.13% for infestation percentages and 36.04% for unmarketable plants). It followed by the newly introduced European compounds, Karate ® Zeon (Lambda cyhalothrin Sc 9.4%) and Evure ® (Tau-Fluvilonat). However, Melody 24% SC (Metoxyfenozide) and Biosad 22% SC (Spinosad) appeared as the least effective compounds. In general, it can be concluded that, Broact 5% SG in the rate of 8 gm. /100 Litter water, was the most effective against P. rapae larvae, providing an increase of marketable cabbage plants by 36.04% with one application per season. Therefore, it can be recommended to use Broact 5% SG , Karate ® Zeon and Evure ® in the Integrated Pest Management (IPM) programs for controlling the small white cabbage butterfly, P. rapae in the future
This work was carried out at the experimental farm of the Faculty of Agriculture, Assiut University during the 2017-2018 and 2018-2019 cabbage growing seasons. Evaluation of the seasonal abundance of the cabbage aphid Brevicoryne brassicae L in cabbage fields and responsibility of certain biotic factors for managing populations of this insect pest was the cornerstone of this investigation. Cabbage aphid, B. brassicae was found to be active on cabbage plantations and recorded in low numbers (99.71 individuals / 12.5 Cm 2 / leaf / infested plant) at the beginnings of the season (November) with gradual increase until harvesting. Three amongst the six evaluated cabbage cultivars and/or hybrids were appeared as susceptible (S) and harbored so high numbers of the pest. However, the remaining cultivars showed some sort of resistance to this insect pest. The local cultivar (Ganzory) harbored the least aphid numbers and appeared as moderately resistant (MR) cultivar. This finding could be attributed to the antixenosis and/or antibiosis phenomena presented by this local cultivar. Proteins and amino acid contents showed a highly significant positive correlation (r) with B. brassicae populations, however, chlorophyll showed highly significant negative (r). The obtained data reflect the role of the cabbage aphid parasitoid Diaeretiella rapae (McIntosh) to manage B. brassicae populations. Mummified aphids (parasitism rate) before harvesting were found to be equal 6.16 fold of that recorded before ripening stages. High percentages of D. rapae were succeeded to emerge from the mummified B. brassicae with diverse extrusion rates. Multiple increases were recorded on the percentages of infested plants when cabbage undergo toward ripening at the 9 th stage till harvesting. No or less existence of unmarketable plants (through the periods of the low infestation) before cup formation and/or plant ripening period was recorded. So, it can be concluded that cabbage cultivar, plant age, and stage in addition to plant metabolites combined with the naturally occurring biological control agent (Aphid parasitoid) can be affected and manage the population trend of cabbage aphid B. brassicae infesting cabbage in the field.
The main goal of this study was to determine the seasonal abundance of the white butterfly Pieris rapae L. (Lepidoptera: Pieridae) on several local and imported cabbage cultivars in old and reclaimed lands. The impact of certain cabbage metabolites on P. rapae populations was examined, as well as the relative susceptibility of different cabbage cultivars. Damage caused by P. rapae Varies. During the first two months following transplantation, P. rapae can cause economic damage to cabbage plants in both areas. One month later, its population had multiplied several times in the old land. Three of the six tested cabbage cultivars were appeared as susceptible (S) cultivars and harbored high numbers of the pest with an average of 0.63, 0.60 and 0.53 Kenz, Crossina and Ganzory cultivars, respectively. However, the imported white cabbage hybrids, 728, 730 and 747 showed sort of resistance and appeared as low resistant (LR) hybrids and harbored 0.40, 0.41 and 0.45 individuals/plant, respectively. Chlorophyll only showed highly significant negative correlation with P. rapae populations. However, the remaining metabolites showed non-significant positive correlation. In a comparison between P. rapae populations in Assiut (the old area) and El-Fath province (the reclaimed area), it can be note that the pest populations, the damaged (infested and unmarketable) plants were multiplied several times in the later. It can be noted that the general mean of the pest numbers recorded in the reclaimed area (2.14 individuals/plant) was found to equal 4.28 folds more than that recorded in the old area (0.50 individuals/plant).
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