The current method of controlling immature wheel cactus is to squash them completely underfoot if they are very small or to dig them up and remove them. In some infested areas there is a “sea” of immature cactus and digging them up is extremely time consuming. Some infestations are also in difficult terrain and/or accessible only on foot. Carrying buckets in and out can be quite difficult. A system of follow up control using a spray would be most valuable in such areas. Australian soils are deficient in copper and a couple of members of the group decided to experiment with sprays of copper solutions to determine the impact on immature wheel cactus.
Pilot study with copper sprays 2011
In 2012 a pilot was conducted with sprays of three copper solutions (copper sulphate, copper carbonate and copper hydroxide). The trial yielded promising results for copper sulphate in the form of Bluestone (see Cactus_copper_spray_trial_2012 short form).
Copper sulphate sprays 2013
A second trial with 3 doses of sprayed copper sulphate on immature plants was followed up every 4 weeks for 12 weeks with documented records of damage and kill rates plus photographic evidence (see TCCG Cu sulphate spray record sheet 2013). Unfortunately, there was little impact except in the area where the excess spray was emptied onto the ground. In that area some immature plants had yellowed and a few had died. This prompted the third trial with copper sulphate, which is currently in progress.
Copper sulphate top dressing 2013
This third trial used copper sulphate in the form of Bluestone as a top dressing sprinkled over an area of immature wheel cactus (new recruits). The final results were collated at the end of July and the results indicate that close to 45% of the plants were very damaged and 5% had died. The site will continue to be monitored in case 3 months is not long enough for all the damaged plants to die. The results can be viewed in TCCG cu Sulphate granules trial sheet 2013