Six indeterminate plants in the ground, mulched, drip line twice a week for about 40 minutes. Over the last ten days the upper leaves on four of them have rolled up along the midrib and feel thick, almost like plastic. No yellowing, no black spots, no visible bugs under the leaves. Fruit is setting normally. We have had a run of 33C days. I sprayed nothing. Should I be worried or is this the heat?
Leathery upward roll with normal colour and normal fruit set is physiological leaf roll and it is not a disease. The plant is limiting transpiration in heat, and indeterminates that are growing fast do it more. The tell is exactly what you described: no chlorosis, no lesions, no wilting at dawn. Compare with herbicide damage, which twists and cups the new growth into a fern shape, and with viral curl, which comes with mottling and stunted fruit. Neither is what you have.
That pattern is textbook physiological. Do nothing except keep the mulch deep and stop watering more, which is the usual panic reaction and gets people into root problems.
New growth is flat and normal green, it is only the older upper leaves. So heat then.
Two things worth checking anyway. Did you prune hard recently? Heavy suckering in the same week as a heat spike triggers this reliably for me. And is your drip actually wetting the whole root zone? Twice a week for 40 minutes could be plenty or could be a wet stripe 15cm wide, depending on emitter spacing. Dig down 15cm an hour after a cycle and see how wide the wet band is.
The dig test is underrated. I thought I was watering deeply for two seasons and my wet zone was about the size of a mug.
Mine do this every July and still out-produce everything else in the bed. I stopped treating it years ago.
@metronome_mel · last mo.
If it were herbicide drift you would usually see it on the youngest growth first and on nearby plants that are unrelated species. Worth a walk round the garden to check whether anything else looks strange, particularly if a neighbour has been spraying a lawn.
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