Dormex for managing budbreak in plums & prunes

Plum and prune growers in areas with insufficient chilling for satisfactory budbreak and flowering can now use the plant growth regulator Dormex to advance or schedule and concentrate blossoming, and to advance foliation.

Already registered in Australia for regulating budbreak in apples, kiwi fruit and grapevines, plums and prune trees were added to the Dormex label late last year.
Crop Care technical consultant Glen Tucker said Dormex would also be useful on plums and prunes in areas with chilling less than the required level of 400 to 1000 hours (depending on the variety), where delayed foliation reduced budbreak, prolonged flowering, lowered fruit set and produced uneven fruit size.
“Prolonged flowering also creates inefficiency in blossom-blight control,” Glen said.
Glen added that there were other potential advantages for Australian prune growers in manipulating flowering date and duration.
“High temperatures (more than 28C) can lead to poor fruit set in prunes. Advancing flowering to a lower-temperature period could improve prune yields, particularly in the Murrumbidgee Irrigation Area (MIA).
“Manipulating flowering and maturity could also lead to better scheduling of prune harvesting for dehydration.”

Dormex trials

Glen said that from 2005–06 to 2012–13 there had been many Australian trials and demonstrations to examine the use of Dormex for regulating budburst in plums and prunes.
The trials were conducted in the Riverland in South Australia, the MIA in southern NSW and in the Murray Valley in northern Victoria—representing Australia’s plum and prune moderate-chill (800–1000 hours) production areas.
“Trials were conducted with one common variety of plum and four common prune varieties: Autumn Giant, GF 698, GF 707, D’Agen and Moyer.
“Time of application in relation to budburst (defined as blossom start in untreated trees) varied from trial to trial, based on historical data for each area.”
Bud growth and flowering were monitored in all trials from the commencement of budburst to petal fall. Fruit set and weight-of-fruit per tree were assessed in some trials, and in one trial, return blossom assessment was conducted in the year following the trial.
In all trials, natural budburst in untreated trees occurred during September: early September in plum trials in the Riverland; and mid-to-late September in prune trials in the MIA and Cobram, depending on the season and the variety.

Trial results using Dormex

  • Applied 35 to 60 days before blossom budburst (DBBB), Dormex advanced budburst by 2 to 10 days across a range of plum and prune varieties and climatic conditions.
  • The extent of advancement varied from site to site, with applications between 35 and 45 DBBB generally providing a more consistent and (in most cases) greater advancement.
  • When applied at less than 35 DBBB, there was less or no effect on date of budburst.
  • Dormex applied at a low rate of 1L/100L from 29 to 39 DBBB produced satisfactory results on both plums and prunes, significantly advancing leaf budburst (foliation) of prunes compared with untreated trees.
  • Dormex applied at 35 to 45 DBBB reduced duration of flowering most consistently compared with untreated plum and prune trees.
  • In most cases, Dormex did not significantly affect fruit set and yield of plums and prunes.
  • However, in two prune trials conducted in 2007–08 at Cobram and Yenda in the northern MIA, fruit set and yield were increased when Dormex was applied 44 to 46 DBBB.
  • There was no detectable effect on return blossom or shoot growth in the year following Dormex application.

Summary of recommended use
Glen summarised the recommended use of Dormex in Australian plums and prunes:

  • Apply 35–45 days before expected budburst.
  • Apply 1L/100L as a fine spray to the point of runoff for complete coverage of buds
  • Apply no later than 30 days before expected natural budburst, as budburst will not be advanced and buds may be damaged
  • Warmer weather 3–5 days after application will improve the response; cold weather following application will reduce the response
  • Be aware that early blossoming may increase the risk of frost damage
  • Advancing and shortening the flowering period may also affect cross pollination, so ensure pollinators are also treated.

Contact Glen Tucker, Technical consultant, Crop Care Australasia phone 0427 004 435 This email address is being protected from spambots. You need JavaScript enabled to view it.

Get your orchard manual

The latest orchard management, tree training and fruit production methods.
Easy to follow instructions, illustrations and photos.

Go to Orchard Manuals

Subscribe to receive Tree Fruit every month