Extrafloral nectaries in cacti
Re: Extrafloral nectaries in cacti
Yes Mrs Green, an interesting article, many do not realise extrafloral nectaries are found on quite a few cacti. It's one way for cacti to get ants to protect them by keeping other sap sucking or chewing pests off them. Unfortunately mealy bugs and aphids have developed the same ruse to get around it and also provide the ants with honeydew, meaning they "farm" and "milk them" so do not remove them. Some also claim ants can actually carry mealies from plant to plant, but how true that is I do not know? You can see the drop of honeydew in the ants jaws here:-
https://www.flickr.com/photos/rainforests/5917674016
https://www.researchgate.net/post/Do-an ... 579e0699a4
https://www.youtube.com/watch?v=h8CpCrTvIqo
One of the main problems with extrafloral nectaries is if not regularly washed off black sooty mould can forms on the sticky honeydew on the epidermis. Though it is unsightly it does not damage the plant. Although this link mentions mealies the extrafloral nectaries can produce the same sooty mould problem, but it can easily be washed off with a small artists brush and soapy water, or if a recurring problem treated with a fungicide.
https://gardeningcalendar.ca/articles/w ... a516e31fe9
https://www.flickr.com/photos/rainforests/5917674016
https://www.researchgate.net/post/Do-an ... 579e0699a4
https://www.youtube.com/watch?v=h8CpCrTvIqo
One of the main problems with extrafloral nectaries is if not regularly washed off black sooty mould can forms on the sticky honeydew on the epidermis. Though it is unsightly it does not damage the plant. Although this link mentions mealies the extrafloral nectaries can produce the same sooty mould problem, but it can easily be washed off with a small artists brush and soapy water, or if a recurring problem treated with a fungicide.
https://gardeningcalendar.ca/articles/w ... a516e31fe9
Re: Extrafloral nectaries in cacti
Thank you DaveW for the links 
I am aware of the fact that some ant species farm what we sees as pests. Fascinating that such small creatures probably developed the consept of farming or keeping livestock, long before the ‘most intelligent’ species on earth did.
I wasn’t aware of the extrafloral nectaries produced by some cacti before last summer though. I noticed small clear ‘balls’ on one of my cacti and small flecks of sothy mould, further down the plant. I posted a pic and a question here and was enlightened The forum really is a great place, especially for newcomers in the hobby and I will take the opportunity to say a heartfelt thank you to you and all the others, who kindly shares your experience and knowledge with us who are new in the hobby. 
I am aware of the fact that some ant species farm what we sees as pests. Fascinating that such small creatures probably developed the consept of farming or keeping livestock, long before the ‘most intelligent’ species on earth did. I wasn’t aware of the extrafloral nectaries produced by some cacti before last summer though. I noticed small clear ‘balls’ on one of my cacti and small flecks of sothy mould, further down the plant. I posted a pic and a question here and was enlightened
The forum really is a great place, especially for newcomers in the hobby and I will take the opportunity to say a heartfelt thank you to you and all the others, who kindly shares your experience and knowledge with us who are new in the hobby. 