Red scale online phenology and spray timing tool - 2018 12

Practical application of the red scale tool

Dr Jianhua Mo and Andrew Creek, December 2018

There is current uncertainty over the use of chlorpyrifos in Australia. The United States Federal Appeals Court ruled that all chlorpyrifos residue limits will be banned in the USA. Europe may take a similar stance. These international rulings may influence the current chlorpyrifos review by the Australian Pesticides and Veterinary Medicines Authority. Australian growers are advised to consult with their packer before using chlorpyrifos. Sheds that pack for export to the USA are ensuring growers do not apply chlorpyrifos to citrus varieties that individual packers may export to the USA.

An interactive online tool has been developed as a recent outcome from an industry supported project lead by NSW DPI. The red scale tool predicts when crawlers are most abundant. Crawlers and the following whitecaps are the most vulnerable stages in the red scale lifecycle. Similar to the gall wasp prediction tool, the red scale tool also has tabs for description, crawler, Aphytis and notes on controlling scale.

A trial version of the red scale tool can be found online at NSW DPI also seeks your feedback on this tool.

Time insecticide application

Chlorpyrifos and oil application is not recommended during flowering due to risk with foraging bees.  Research trials on the timing of the commonly used chlorpyrifos plus oil treatment showed that application with the first post-winter peak of red scale crawlers gave the highest proportion of red scale control in Valencia oranges (Figure 1).

Bar graph showing the timing of red scale hatching

Red scale spray treatments are more effective when applied during the first post winter, crawler peak period. Use the online red scale timing tool (Figure 2) for a single, well timed insecticide application. Red scale has a history of developing resistance to repeated poor insecticide applications.

Time Aphytis release

Aphytis are tiny wasps that parasitize red scales. They are commercially available and routinely used in red scale management. Aphytis prefers to parasitize virgin females, whose number peaks around similar dates as adult males. The red scale phenology tool also predicts adult male flight peaks for the chosen weather station data. Red scale male flight peaks can be used to time Aphytis releases.

Screen shot of the red scale online tool


The prediction tools are outcomes from ‘Development of national strategies to manage citrus gall wasp (CT15006)' project and ‘Development of phenology models and a timing guide for the management of Californian red scale in Australian citrus (CT15006)’ funded by Hort Innovation using the citrus levy with co-investment from NSW Department of Primary Industries and funds from the Australian Government.