In recent years, the occurrence of *Bemisia tabaci* in certain regions of our province has led to serious plant diseases such as tomato yellow leaf curl virus. In addition to traditional control methods like agricultural practices, chemical pesticides, insect-proof nets, and yellow sticky traps, biological control using natural enemies has proven to be an effective and sustainable approach for managing whitefly populations.
One of the most commonly used biological control agents is *Encarsia formosa*, a species belonging to the family Aphelinidae, which is parthenogenetic. These wasps are attracted to honeydew secreted by whiteflies, which serves as their primary food source. Adult *E. formosa* can survive up to 28 days if they consume honeydew, but without this nutritional supplement, they typically only live about a week. In greenhouse conditions, their lifespan usually ranges from 10 to 15 days. Female wasps locate whitefly nymphs through touch and then parasitize them. Both active and inactive nymphs of *Bemisia tabaci* can be targeted, with the wasps preferring third- and fourth-instar nymphs. Once parasitized, the whitefly nymphs continue to develop but stop at the fourth instar stage, effectively preventing further reproduction and reducing pest populations.
This method is widely applied in protected agriculture, particularly for controlling whiteflies on vegetables and ornamental plants. Studies have shown that *E. formosa* has a high parasitism rate on infested whiteflies, with control efficacy exceeding 80%. The application is simple: after whiteflies colonize crops like tomatoes and cucumbers, the wasps are released by hanging the cards containing the adult wasps on the upper parts of the plants. The wasps actively search for and parasitize whitefly nymphs.
However, *E. formosa* has limited flying ability, so it's important to distribute the wasp cards evenly throughout the greenhouse. A recommended release rate is 1,500 to 2,000 adults per acre to establish a stable population. If the greenhouse is fully enclosed with insect-proof netting, feeding should be stopped to avoid unnecessary loss. It is advised to release the wasps every 7 to 10 days, repeating the process 5 to 6 times for optimal results.
To maintain the health and activity of the wasps, it’s crucial to avoid excessive humidity or moisture on the card, which can lead to suffocation or mold growth. The cards should not be exposed to direct water or rain. Greenhouses should be covered with plastic film during release, while still allowing for proper ventilation. The ideal temperature range is 20–35°C during the day, with nighttime temperatures above 15°C to maximize the effectiveness of the biological control.
MDVR Camera SystemsMDVR Camera SystemsMDVR Camera SystemsMDVR Camera SystemsMDVR Camera Systems
Mdvr Camera Systems,4G Vehicle Mdvr Recording System,Mobile Digital Video Recorder System,4G Mobile Digital Video Recorder
Vsstech Co.,Ltd. , https://www.vsstechcctv.com