Recovering from hail
Minimising secondary damage will be the key task facing orchardists recovering from hail storms.
Queensland Department of Agriculture and Fisheries extension officer Simon Newett said it was important for all growers to be prepared for potential hail damage.
“Physical damage to trees lays them open to attack by fungi and insects that take advantage of the wounds, and the loss of canopy exposes the branches to severe sunburn damage,” Mr Newett said.
“In the case of insects, tree wounds release chemicals such as ethylene that appear to act as magnets to some opportunistic insects such as borers.”
For this reason, Mr Newett said it was a good idea to apply a fungicide and insecticide treatment.
“A registered avocado fungicide such as one of the coppers is suitable. The insects most likely to be attracted are borers of various types such as the auger beetle (Xylopsocus gibbicollis) and other ambrosia or pinhole borers.”
The advice from Department of Agriculture and Fisheries (QDAF) Mareeba’s Ian Newton and NSW Department of Primary Industries entomologists Craig Maddox and Ruth Huwer is to consider the registered insecticide chlorpyrifos, which is effective against beetles, or trichlorfon which will also be effective and treat spotting bug at the same time if you have fruit present.
“Once the borers are inside the tree it is too late so an application within a few days then a follow up perhaps a week or two later is suggested,” Mr Newett said.
“The advice is to try and avoid using pyrethroids at this early stage of the season for their potential to result in a build-up of other insects such as scale.
“An azoxystrobin fungicide could be used instead of copper but shouldn’t be applied at the same time as chlorpyrifos because of incompatibility.
“The other thing to take action on as soon as possible is sunburn protection. With branches exposed as a result of the loss of leaf cover some sort of sunblock such as white acrylic paint or a proprietary sunburn protection product should be applied to newly exposed branches especially on the northern and western aspects.”
Mr Newett said these products could often be applied in diluted form through orchard sprayers but multiple applications may be necessary to get enough protection. To speed up the canopy re-growth you may also want to apply some extra nitrogen.
“With the loss of crop it does present an opportunity carry out some canopy management, just remember to protect the newly exposed branches and trunks from sunburn before the fast approaching hot weather arrives,” he said.
If you have any queries or want to discuss your particular situation, please contact Simon Newett on 07 5381 1326, 0400 565 784 or email@example.com.
Thanks to Chris Searle, Ian Newton (QDAF entomologist at Mareeba) and the NSW DPI entomologists Craig Maddox and Ruth Huwer for their advice.
This article is based on one first published in the Spring 2018 Talking Avocados and has been reproduced for the 18 October 2019 Guacamole.
Date Published: 16/10/2019