Is my white sapote sick?

[FigoVelo]

Hi everyone. I have 7 small white sapotes in the ground. They are young but have grown rapidly in the past year. Now, a couple of them are showing dark patches on their leaf ends. What’s going on? My soil is loamy clay, so it tends toward damp heaviness. But most fruit trees thrive on my property. - figs, mulberries, apples, stone fruits, etc all very productive. But I’m worried that the white sapotes are suffering from wet feet. What would the symptoms of this be? Though my soil is heavy, I am on a 10 percent slope with little or no ponding of water. The past 3 weeks have been very very rainy. I did not plant my white sapotes on mounds.

Photos are attached. If you think you know what’s going on, please offer advice. Thanks,
Alastair

[Gulfgardener]

It does look fungal. I'd try to move them up on small mounds in the spring. I don't think I'd do much until then besides spraying with copper.  Hopefully someone can ID the issue better than I.

[K-Rimes]

It would appear it's a classic wet foot look with the taco leaves, but there is also a bit of nutritional deficiency you can see with the browning tips.

I wouldn't be pulling the fire alarm on it yet, but it's certainly unhappy. Is it in a really wet part of your yard?

[Jack, Nipomo]

Recent fertilizing?  Have not seen that before, resembles avocado starting to drop last year's leaves, but the leaves look fresh.  I barely water my white sapotes, not at all with the recent rains.  The trees here (similar to your climate) are pretty bullet-proof, more like weeds. 

[Oolie]

It looks as you described, root tips succumbing to wet feet.

Once the trees establish themselves they will use that water up.

I've seen a roadside tree planted in a very similar situation, heavy soil, at the bottom of a steep drainage, but it is well established, and thrives for the extra water it receives.

[FigoVelo]

Even before I saw these replies I went outside and carved out a deep half moon ditch on the downhill side of the tree and backfilled with mulch-earth blend. Trying to create good drainage. This tree has been in ground for 3 years and over the summer and fall took off like a rocket. It's been loving the drought, I guess. Lots of rain now.

No, it's not a terribly soggy place.

Could this potentially kill the tree, or can it push through and eventually attain the size it needs to handle extra water?

And if I need to treat it, any suggested products?

Thanks.

[Oolie]

If you're really worried you can add lots of gypsum to the soil to help loosen the clay up, but it's probably going to grow through it either way.

That said the gypsum can only benefit the fruit quality, so it's your call.

The mulch will break down eventually, for good drainage things that can't break down like biochar have more favorable results, but that's only if you feel like replanting the trees. I wouldn't bother, once established the trees will take off.

[FigoVelo]

If you're really worried you can add lots of gypsum to the soil to help loosen the clay up, but it's probably going to grow through it either way.

That said the gypsum can only benefit the fruit quality, so it's your call.

The mulch will break down eventually, for good drainage things that can't break down like biochar have more favorable results, but that's only if you feel like replanting the trees. I wouldn't bother, once established the trees will take off.

I hear you on the organic matter as a soil amendment. I've often wondered about this, and I have my doubts about strategies that call for mounding with mulch and organic matter for avocado planting, for example. Quickly, it seems, the tree will sink.

[Gulfgardener]

Mulching in a hole that's going to be soggy is asking for problems. It will break down and can lead to rot issues. Just ask my avocado. It came in a mulch mix that I didn't swap out before planting. It died slowly over 4 months because the wood mulch would absorb and hold every drop of rain. Inorganic would be the better way to go. I mound with sand.

[FigoVelo]

I have been planting avocados with limited success, and recently I decided it was because of my soil. I am taking a variety of steps now to address this. I am filling holes (with outlet channels) with drain rock and mounding soil on top, planting at the edge of a 4-foot retaining wall where there is drainage built in by design, and -- most recently -- experimenting with a giant square planter box walled with corrugated metal sheets. I have filled it with mulch and still plan to add heaps of sand and soil, with the expectation that the tree will sink in significantly. It's exhausting.

"Sandy loam, sandy loam! My kingdom for some sandy loam!" 

Back to the unhappy white sapote. What should I treat the tree with? Is it obviously a fungus? Do I need to know what kind? Or is there an application that will cover a range of possibilities? I use virtually no purchased products for fertilizers or pest control, so I would benefit from a brand name or something.

And what if I just let it ride out the wet weather until it dries out?

[Jack, Nipomo]

The tip of the leaves being necrotic is usually a consequence of accumulated salts either from fertilizers or inherent dissolved solids in irrigation water. Transpiration takes the H2O out leaving the dissolved salts behind. The concentration of dissolved solids is usually greatest at the leaf tips.  Looks like the remainder of the leaf is healthy. The leaf petioles appear limp, if so that would indicate a root problem affecting the entire plant. During the quiescence time in the winter for plants they cannot utilize much nutrition nor water.  I would suspect that if you let the plant dry out, divert rainwater, by the middle of July you will have a happy plant.  Report back and let us know.

[Oolie]

"Sandy loam, sandy loam! My kingdom for some sandy loam!" 

The grass is always greener.

I have silty loam (similar to sandy), but it drains so well, water costs are high, also gophers. With softer soils, you get gopher activity in the extreme, and it's certain that you will lose trees each year, even established ones.

[K-Rimes]

"Sandy loam, sandy loam! My kingdom for some sandy loam!" 

The grass is always greener.

I have silty loam (similar to sandy), but it drains so well, water costs are high, also gophers. With softer soils, you get gopher activity in the extreme, and it's certain that you will lose trees each year, even established ones.

Same issue for me. Gopher and mole pressure is obscene. Caught 25+ last year. I keep dumping on organic material and think I'm winning, then realize it's only improved about 1".

[FigoVelo]

I have gophers galore, too, but I trap aggressively and have made rock filled trenches around some of my trees.

I should be clear that my soil is not pure clay. I had it tested a few years ago but the lab did not give me a reading on clay versus sand content, which was annoying. But it's loamier than pure clay. Gophers love it, and it clings to water. Double whammy. I have drowned a couple of avocados already. I was hoping white sapotes would be tougher.