Chemical trial comes to an end

Chlormequat To Be Removed From Spray Diary

A research trial into the efficacy of chlormequat on the berry set of currants has come to an end.

The results are in and the Dried Fruits Australia Maximum Residue Limit (MRL)/Chemical Committee and board has endorsed a recommendation to remove the chemical from the 2023/24 spray diary.

The research trial was in response to a reduction in the European Union MRLs in 2019, down to 0.05 mg/kg, compared to the Australian MRL of 0.75 mg/kg.

Various chlormequat application rates were trialled over three seasons – from 2020 to 2022 – in two commercial Sunraysia currant vineyards.

DFA field officer Stephen Kelly said the trials in these vineyards found no impact from chlormequat on bunch size and weight when applied at or below label rates.

“The residue level left from applications of chlormequat, even when applied at only 25 per cent of label rates, is significantly above the European Union MRL,” he said.

“These results were statistically significant in each of the three trial seasons.”

The DFA MRL/Chemical Committee and DFA Board has endorsed these results and chlormequat will be deleted from the 2023/24 spray diary to ensure access to market for currants.

DFA CEO Thomas Cheung said the removal of chlormequat from the spray diary was significant and would widen export market opportunities for Australia’s quality currants. v

Chlormequat was initially used after research completed on both Zante and Carina currant production systems in the late 1960s to the late 1970s showed it had a positive impact on the percentage of berries set by the vine.

The initial research work undertaken when the Carina currant variety was released in 1975 indicated that the caps may not fall easily from the flowers and hence not allow them to be fertilised properly.

Primarily, chlormequat reduces the vine’s natural production of gibberellic acid leading to reduced leaf and cane growth.

So, if applied just before berry set, it theoretically allowed the vine to divert its energy into setting berries. An application of gibberellic acid later in the season would assist in increasing the size of the currant berries, further enhancing overall production.