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February / March 2024

Extension Briefs For February And March 2024

SA Fruit Journal: February / March 2024

By Hannes Bester, MC Pretorius, Wayne Mommsen, Coenraad Fraenkel, André Combrink, Natasha Jackson and Jan Landman (CRI)

Integrated pest management

Mealybug (S.D. Moore)

Growers should be scouting for mealybug regularly by inspecting underneath calyces, thereby determining the percentage of infested fruit. Where mealybug is under good biocontrol, infestation should peak during December or January in the northern production areas, and during February in the Cape production areas. If mealybug infestation does not decline during January/February and March, respectively, suppression with a corrective chemical treatment is advisable on early-maturing cultivars. The available corrective options are sulfoxaflor (Closer), spirotetramat (Tivoli) and fenpyroximate (Lesson), with the first two mentioned being the most effective. These products may not have a specific corrective registration, but their withholding periods do permit late-season use. Although registered, methomyl is not a preferred option, as it is not effective at the dose generally registered for mealybug, and methomyl is the only registered corrective option for red scale. It would be wise to restrict corrective usage to red scale alone, so the onset of resistance is not expedited. Ensure that the pre-harvest interval of any product used is complied with.
Another very important consideration in achieving and maintaining good mealybug control is diligent exclusion of ants from the tree canopy.
The species of mealybug present should also be determined, as it appears that the biocontrol complexes of mealybug species –
other than citrus mealybug – might not be as effective as that of citrus mealybug. Therefore, treatments can be applied more readily when other species are identified as the dominant species. The phytosanitary status of certain species must also be borne in mind. Note that colour plates, and a key for identification of the different mealybug species are available to order from Citrus Research International (CRI). If applicable, please also bear in mind the molecular identification service offered by the CRI diagnostic laboratory in Nelspruit, and the DALRRD Plant Health Diagnostic Laboratory in Stellenbosch.
A mealybug infestation can also attract a carob moth infestation. Therefore, if the fruit are to be exported to a market that is sensitive to carob moth, mealybug must be effectively controlled well before harvest.
Finally, if the fruit are to be exported to a mealybug-sensitive market, clear guidelines for pre- and postharvest management, as provided in Cutting Edge 298, must be followed. This includes stringent inspections, with zero tolerance for infestation with any quarantine species.

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