Avocado is struggling

Question: We have an Avocado tree which was started from seed approximately two years ago which has done well, but is now struggling. The plant is approximately four feet high. The mature leaves are turning brown around the edges and drying out (please see attached photos). Growth of new leaves continues, but the mature leaves are dying. We have survived a Mealybug infestation (which now appears to be eradicated with the use of Cryptolaemus montrouzieri Mealybug Destroyer Beetles).  The tree is being grown indoors in a greenhouse type environment at an elevation of 9000'.  Any help and / or suggestions will be appreciated. Thank you.  Steven Smith Support Services Specialist   US Forest Service  Dillon Ranger District, White River National Forest   c:<personal data hidden> o:<personal data hidden> <personal data hidden>   680 Blue River Parkway; PO Box 620 Silverthorne, CO 80498 www.fs.fed.us     Caring for the land and serving people

responder: Cassey Anderson   Replied July 11, 2023, 3:08 PM EDT
response: Hello,  Thank you for your question. It looks as though there could be several issues at play here. You could have an accumulation of fertilizer or other salts (calcium is common from our water) in your soil which are causing death at the tips of the leaves. This is common in houseplants if they are watered lightly and the nutrients are not "flushed" through regularly. The container could also be getting small and the roots are unable to take up enough moisture. Finally, the tree could be getting over or under watered. Your goal is to water frequently, but allow the soil to dry out in between irrigation events.  How long has it been since you potted this up in size? The container does look a little small for the size of the plant. If you like this size you can practice some pruning both on canopy and on the roots to keep it restrained in size. Replace the potting soil at replanting if possible.  I'm happy to answer further questions should they arise.

responder: The Question Asker Replied July 11, 2023, 4:07 PM EDT
response: Hi Cassey, THANK YOU for your response! It has been very difficult finding anyone who knows anything about citrus trees and Avocado trees up here in Summit County. I re-potted the Avocado tree last year to a pot that I was hoping would be large enough to hold the tree for a while, but it may be that it has already outgrown the pot.  As for water, I try not to overwater.  I do not want root rot.  I use a moisture meter to see if the soil is dry. Would it be better to try to let the soil get dried out and then “flush” the plant - to not only water the planet but flush minerals and / or nutrients through the soil?  I have also struggled with Mealybugs (which are a scourge) so that may be causing some problems, but I am usually able to go through and eliminate the bugs pretty well since I bought some Mealybug Destroyer Beetles.  They worked well, but there are still a few Mealybugs in our greenhouse, and they are VERY difficult to eliminate. If you are ever up in Summit County, please stop by our U.S. Forest Service office. I would enjoy meeting you, and showing you our tropical greenhouse – at 9000’! Thanks, and have a great week!     Steve Smith Support Services Specialist   US Forest Service  Dillon Ranger District, White River National Forest   c:<personal data hidden> o: <personal data hidden> <personal data hidden>   680 Blue River Parkway; PO Box 620 Silverthorne, CO 80498 www.fs.fed.us     Caring for the land and serving people                   From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension Sent: Tuesday, July 11, 2023 1:08 PM To: Smith, Steven - FS, CO <<personal data hidden>> Subject: [EXTERNAL: Suspicious Link]Re: Avocado is struggling (#0109242)     CAUTION: This message triggered warnings of potentially malicious web content. Consider whether you are expecting the message, along with inspection for suspicious links, prior to clicking. Any concerns with known senders, use a good contact method to verify.  Send Questions or Suspicious messages to: <personal data hidden>

responder: Cassey Anderson   Replied July 11, 2023, 5:34 PM EDT
response: Steve,   I'd love to come see, I'll let you know if I'm up that way some time.   Regarding soil moisture -- the inexpensive moisture meters you can buy at nurseries tend to be inconsistent. I prefer to test soil moisture with our fingers up to the first knuckle or so. Also I realized I forgot to ask if you have drainage in your container. Also is the whole pot filled with soil? I've seen rocks or other materials used to "increase drainage" at the bottom of a pot, this actually just reduces the soil volume and increases the likelihood of root rot.   It's entirely possible that the tree is still good in it's pot, if you pull it out slightly and see roots circling around the edge that is usually a sign it's time to re-pot.   Mealybugs are a tough one without systemic insecticide treatments. In some cases a q-tip dipped in alcohol can penetrate their waxy outer layer and help reduce populations, but vigilance is necessary for sure.