Role of Biological Control Agents in Regulating Pests′ Populations on Cauliflower: A Field Study on Cabbage Aphid Brevicoryne brassicae and Diamondback Moth Plutella xylostella

The populations’ density of both of the cabbage aphid, Brevicoryne brassicae (L.) and also the diamondback moth, Plutella xylostella (L.), attacking cauliflower field, were recorded during season 2023/2024, in Qalubia Governorate. The field experiment was divided into two experimental areas; unreleased area and released one (where, the second instar larvae of the lacewing predator, Chrysoperla carnea (Steph.) were released). The obtained data showed that, the pest of the cabbage aphid on the cauliflower plants had covered the four months of the study (i.e., during the period from January, 2024 until April, 2024). The maximum total numbers of the pest individuals and the mummies of the surveyed aphid parasitoid, Diaeretiella rapae (M' Intosh), were recorded during the last week of February, 2024 in the two experimental areas. The synchronization of the increase of the pest numbers with the increase of its parasitoid numbers indicated that, the parasitoid, D. is as a suitable biocontrol agent against the aphid populations. The recorded reduction percentage in the total numbers of the cabbage aphid per season in the released area of the predatory larvae of Ch. carnea was 43.74%., in comparing with the unreleased one. Moreover, the occurrence period of the diamondback moth on the cauliflower plants was recorded from the second week of January, 2024 until the last week of April, 2024.The two hymenopterous parasitoidś species; Cotesia plutellae (Kurdjumov) and Diadegma semiclausum (Hellen) were surveyed parasitizing the diamondback moth. The percentages of the pest parasitism were simultaneously increased as the pest populations were increased. The percentages of the reduction in the total numbers of the diamondback moth (larvae & pupae) per season, in released area of the predator was 23.82%, in comparing with unreleased one. The field experiment was also included the measurements of both of the size and the diameters and also the weight of the resulted cauliflower after 103 days post plantation. Generally, such ecological information about the cabbage aphid and the diamondback moth and also the biological control experiment by releasing the predator must be included in future control applications against the two studies pests attacking cauliflower fields as well as other vegetable fields that suffer from the two pestś attack. Therefore, this situation will help to decrease the harmful hazard effects of the extensive uses of the chemical control methods, which will directly or indirectly decrease the environmental pollution for protecting the man health and his surrounding environment.