Insect swarms or nests
Risks
Many species of insect will attack tree workers .
It can be hard to positively identify the presence of insects from the ground .
In environments where insects may be present , it is critical to ensure that tree access methods allow for quick descent or basal rescue , without a complicated transition from ascent to descent .
In some cases , swarms have caused deaths , either through allergic reaction or when climbers or EWP operators have been unable to quickly descend and have elected to jump from the tree instead .
Control measures
Conduct thorough tree inspections before working , particularly in areas where insect swarms are common .
Select access methods which allow for rapid descent ( preferably without any transition , if possible ).
Have insect swarms professionally removed prior to commencing work .
Lean
Risks
Pronounced lean is probably not a concern in isolation but will compound the effects of other structural defects if present .
All trees will grow toward available sunlight , and in many cases natural lean is nothing to be concerned about .
A pronounced or excessive lean will put additional strain on both the root system and supporting structure of the tree , and will exacerbate any other defects which are present .
Defects such as hollows , cracks or decay may be a significant concern when present in a tree which has a pronounced lean . The force applied in climbing or rigging will be exacerbated by the lean when applied to the area with the defect .
Control measures
Conduct thorough tree inspections before working , identify all other hazards and evaluate .
Use work methods which load the tree in compression to minimise the effect of lean .
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