Argentine Saguaro Black area - Ask Extension
We have a 3-4 foot Argentine Saguaro in our yard that was planted in February 2015 after our house in Green Valley was built.. It has a black substanc...
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Argentine Saguaro Black area #276742
Asked September 08, 2015, 10:52 PM EDT
We have a 3-4 foot Argentine Saguaro in our yard that was planted in February 2015 after our house in Green Valley was built.. It has a black substance on one side at the bottom near the ground. Also, it seems to be missing a lot of spines in the middle part of the cactus as well as having numerous gray spotty areas. Can you advise us on what this might be and if it is something that can be treated/removed? Thank you.
Pima County Arizona
Expert Response
Hi,
Your saguaro appears to be suffering from bacterial necrosis. The initial symptom is a small, light-colored spot with a water-soaked margin on the surface of the trunk or branches that may easily go unnoticed. The tissue under the infection site soon becomes brown or almost black. As disease progresses, the tissue may crack and exude a dark brown liquid. If decay is slow, the tissue may not have the liquid exudates. As infected tissue breaks down the woody skeleton is exposed. The pathogen, Erwinia cacticida, survives in soil or plant tissue for long periods of time. The bacterium is spread by insects and in infested soils. Infections take place at wound sites on roots, trunks and branches, especially those made by insects, weather-related events, or rodents. Dead and dying plants serve as reservoirs of the bacterium and as sources of bacterial inoculum for new infections. In large natural stands where disease occurs, proximity of saguaros to dead and dying plants significantly influences mortality. If noticed in time, new infection sites can be treated when very small (less than two inches (5 cm) in diameter) by carefully removing the infected tissue, along with a small margin of healthy tissue, using a clean sharp knife. Allow the wound to heal on its own. Older infection sites exuding dark liquid, especially those at the base of the plant, are not treatable. Plants with advancing decay should be removed to prevent infection of nearby saguaros and damage or injury of persons or property. All infested plant material should be completely removed from the site and away from any other saguaros.
Peter
Your saguaro appears to be suffering from bacterial necrosis. The initial symptom is a small, light-colored spot with a water-soaked margin on the surface of the trunk or branches that may easily go unnoticed. The tissue under the infection site soon becomes brown or almost black. As disease progresses, the tissue may crack and exude a dark brown liquid. If decay is slow, the tissue may not have the liquid exudates. As infected tissue breaks down the woody skeleton is exposed. The pathogen, Erwinia cacticida, survives in soil or plant tissue for long periods of time. The bacterium is spread by insects and in infested soils. Infections take place at wound sites on roots, trunks and branches, especially those made by insects, weather-related events, or rodents. Dead and dying plants serve as reservoirs of the bacterium and as sources of bacterial inoculum for new infections. In large natural stands where disease occurs, proximity of saguaros to dead and dying plants significantly influences mortality. If noticed in time, new infection sites can be treated when very small (less than two inches (5 cm) in diameter) by carefully removing the infected tissue, along with a small margin of healthy tissue, using a clean sharp knife. Allow the wound to heal on its own. Older infection sites exuding dark liquid, especially those at the base of the plant, are not treatable. Plants with advancing decay should be removed to prevent infection of nearby saguaros and damage or injury of persons or property. All infested plant material should be completely removed from the site and away from any other saguaros.
Peter
Peter,
Thanks for the information. As this Argentine saguaro was planted in our yard in Feb, 2015, the landscaper gave us a 1 year warranty. Do you suggest we have him remove this cactus and go with another one in that spot or is the soil possibly contaminated? We have 3 non- Argentine saguaros in the front yard (the one in question is on the back yard) and a couple of them have skin issues unlike the Argentine. I have posted pictures of them. The small front yard saguaro has a few inches at the base where the surface is woody. The Large and 4 foot saguaros have what look like tears near the base where the skin looks like parchment paper. Any issues with these that you can see. Thank you.
Hi again,
It's your call whether or not to take advantage of your warranty. The soil could be a problem or it could have been an insect vector or weather extremes such as sunburn may have caused the initial wound. Newly planted cacti can be sensitive to their new surroundings. In the wild, they often grow in the shade of nurse plants. Two things that can be done to mimic that kind of help are making sure the cactus is planted facing the same direction as it was at the nursery and shading it for a few weeks to reduce the chance of sunburn. Planting in the fall or early spring allows the cactus to adapt before the summer sun is in play and may allow you to skip the shade cloth.
Peter
It's your call whether or not to take advantage of your warranty. The soil could be a problem or it could have been an insect vector or weather extremes such as sunburn may have caused the initial wound. Newly planted cacti can be sensitive to their new surroundings. In the wild, they often grow in the shade of nurse plants. Two things that can be done to mimic that kind of help are making sure the cactus is planted facing the same direction as it was at the nursery and shading it for a few weeks to reduce the chance of sunburn. Planting in the fall or early spring allows the cactus to adapt before the summer sun is in play and may allow you to skip the shade cloth.
Peter
