slugs, snails... and the fungal development that follows the "slime"... best guess. Put out snail bait and remove the infected leaves. If it were mine, I would treat with a systemic fungicide.

Thanks for your input.

The surrounding earth is covered with landscaping rocks (plastic underneath) apart from where this tree is planted, so I wouldn't expect much snails/slugs in the area. At least I've never seen any.

ok great. I can hunt around for signs of slugs/snails. But I'm willing to try the fungicide after removing the affected leaves. I've never applied chemicals to my plants before (only been gardening for a year). I'm assuming there are a number of natural/organic options that are effective as a fungicide and snail repellent.

Do you have any recommendations?

google beer slug trap. Just basically - some beer in a small shallow cup/container. The slugs go in and drown. works on snails and slugs. Not sure if beer is natural/organic...but I'm sure someone sells an organic beer - but a cheapo beer works just fine.

You might fond this interesting/helpful http://www.gardenmyths.com/how-to-get-rid-slugs-with-beer/

I planted a grapefruit tree late summer

===>>> i cant rule out transplant shock .... what was the source.. how did you plant it.. whats the weather been since.. how do you water ...

i would also recommend removal of the plastic .... it interferes with water movement as well as soil heating ... and heat retention ...

can we have a pic of the whole plant ... loss or sacrifice of older lower leaves could be all stress related ... i would focus on the top new growth ...

imo .. NEVER use plastic or landscape cloth in your garden.. its against nature ... and since many weed seed is airborne.. frankly useless ...

ken

Hi Ken. I've added some pics below. I cut a ~2' diameter circle and planted a tree in 50/50 earth soil and compost as recommended by my nursery. I watered it twice a week except when it got cold and rainy (1-2 months ago). Now it's almost never since the soil is always moist at the top.

I suppose the infected leaves are concentrated in the bottom half, but there is an overall yellowing of the top half as well.

how hot do you think the rock gets in late afternoon ... and how long into the night.. do they stay hot ... you have to figure that all out.. im speculating ...

the problem is defined as cause and effect ... the leaves are stressed and damaged ... but what caused it.. the splotches you see .... could well be the effect ... and the following disease not the real cause of the problem ...

see link for info on planting .. perhaps for next time ... but more importantly.. proper watering ... basically you water a tree when it needs it.. not on some random schedule ... and when it needs it.. is a function of soil drainage .... as well as anything the interferes with such.. like landscape fabric or plastic ... etc ... bottom line.. insert finger and find out.. when it needs it ...

ken

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub

When planting a citrus tree in the ground NEVER dig a large hole, and NEVER ament the hole with anything other then the dirt that was removed while digging the soil. Dig a hole large enough to contain the tree's root ball, and then back fill using only the dirt removed when digging. When you make a large hole, thinking you are doing something nice for the tree, what you have actually done is create a lake every time you water the tree, and the roots set in this lake. Further roots will tend to stay in the compost and not move into the surrounding soil.

The yellowing in rather common for grapefruit this time of the year. The roots are not warm enough to take up nutrients.

Unless you've goosed the N during the year, i would expect exactly what is pictured. The tree is very young so it will take a while for the roots to grow and be able to take up enough nutrients.

The rocks are a good thing for heat stability ( I've done the same with one of my grapefruits), but... you will be moving them and expanding that diameter annually, or often!