Research supports use of Actigard post-harvest

Post-harvest is a high-risk period for Psa in Kiwifruit, with cooler, wetter weather conditions favouring infection. Around 300,000 to 500,000 wounds per hectare are created at harvest on fruit stalks, providing entry points for Psa.

Psa infection that occurs post-harvest may not be visible until the following spring, but applications of Actigard® post-harvest can help reduce Psa pressure.

Actigard is unique in that it interacts directly with the plant, triggering its natural self-defence mechanisms to help protect against Psa infection.

Until recently, most of the research into the effectiveness of Actigard has been focused on spring applications prior to flowering, where visual effects can be measured by how well leaf spotting and shoot dieback are controlled a few weeks after application.

In 2019 Syngenta, Zespri, Kiwifruit Vine Health (KVH) and Plant & Food Research collaborated to design a research programme to get a better understanding about post-harvest use of Actigard and what impact (if any) it was having on kiwifruit vines at this later
growth stage.

As Tony Reglinski, Senior Research Scientist at Plant & Food Research explains, “the best way to understand the effect of Actigard in the post-harvest window, is to look for changes in the defence gene expression in Actigard treated vines compared with the untreated vines. An increase in gene
expression is likely to equate to an increase in protection against Psa.”

The good news is the vines were responsive to Actigard on both early and late harvested Hayward vines and the gene response patterns were similar. This is good supporting evidence of the value in using Actigard post-harvest to help protect vines
against Psa infection, occurring from fruit scars and leaf fall after harvest. It also indicates good flexibility in the application timing of Actigard in relation to leaf condition after harvest.

Further work is being carried out on Gold- 3 this season and hopefully new data will be available in the coming months.

A maximum of four sprays of Actigard can be applied on kiwifruit each season at 21-day intervals. This normally allows two sprays if the first spray is applied immediately post-harvest. To avoid the risk of residues, extreme care must be taken to prevent spray drift into unharvested fruit in adjacent blocks.

Leaves need to be actively photosynthesising for Actigard to be properly absorbed. Actigard is likely to be less effective if applied to leaves at an advanced stage of deterioration, or after a significant frost event.

For more information on how best to use Actigard in your kiwifruit orchard for Psa control, contact your local Farmlands Technical Advisor.

Article supplied by Syngenta