Low temperatures are now threatening the current and future avocado crops in the Tristate region but how low is too low?
Avocados are a sub-tropical tree that have been planted in a variety of Australia’s extreme climates. Avocado varieties originate from three race groups: Mexican, West Indian and Guatemalan. Mexican race avocado varieties have the highest tolerance for low temperatures, followed by West Indian race varieties and Guatemalan race avocado varieties are the most sensitive to low temperatures – See Table 1.
Moisture in the environment and duration of time at low temperatures will determine the extent of damage to the current crop and developing buds. Avocado trees despite their subtropical origins can survive at temperatures close to 0oC for short periods of time e.g. 1 hour but a dew point below 0oC increases the risk of frost damage to plants.
Mildura and Renmark avocado growing areas have been on high alert for low temperature damage. Figure 1 shows the temperatures for Mildura, last week on June 23-24, 2019. The temperature dropped below zero from 1:30 am - 7:30 am. It reached the ‘Hass’ temperature tolerance (-1.11oC) for a period of 30-45 minutes around 3:30am and again at 5am for 1.5hrs.
In my experience, if frost mitigation practices were not used during the recent low temperature, there is a high chance that some frost damage has occurred. It will most likely result in damage to tender leaves developed in late Autumn. I expect that there will be some fruit damage in areas that are naturally colder than the Mildura airport (e.g. low-lying areas). At the current stage of bud development, I believe there is minimal chance of bud damage because buds are closed and partially protected by the apex of the leaf. If further low temperature events occur, this could change quickly. If your avocados have been affected by frost or you are worried about specific temperature events, give me a call. I am happy to have a chat. Shane Singh – 0428 674 655