Looking for advice for treating yellowing leaves and spider mites in passiflora incarnata

Question: Good afternoon,

I have a container passiflora incarnata that I am very fond of that is suffering two ailments (1) it has middle aged leaves that are yellowing and (2) it is relentlessly attacked by spider mites (or what I think are spider mites).  The plant is several years old (it has been cut back to the ground a couple times for various reasons.  It is in well-draining soil and a clay pot.  The root ball is maybe an inch or two smaller than the pot.  I use a 50-50-50 each watering per the instructions for continuous fertilizing.  For the spider mites, I have tried neem oil, homemade and commercial insecticidal soaps, and I've also used systemic insecticide (Imidacloprid .22%), following the directions.  The plant is very fragrant and the dew it releases is, I'm sure, extremely attractive to insects.  They attack all aged leaves equally, even the new growth that should be covered by the systemic insecticide.   Additionally, I have random middle-aged leaves yellowing and dying.  I suspect it might be that I use tap water, so I am going to try run filtered water through.  But the bugs are the chronic concern.  Unfortunately, I could not got a picture that was zoomed in enough to see whatever insects it might be.   I would sincerely appreciate any advice would be appreciated.

responder: The Question Asker Replied July 03, 2023, 5:17 PM EDT
response: Here are a couple additional pictures.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 05, 2023, 1:43 PM EDT
response: Thank you for the additional pictures. The foliage does not resemble that of Passiflora incarnata, but might be Passiflora caerulea instead (more images for comparison here), a more commonly-grown species that isn't reliably winter-hardy in our area. This may not matter much with regards to pest or disease susceptibility, but we thought we would mention it if it matters to you which species is being grown (especially if you intended to plant it outside some day).  Passionflowers are not usually grown indoors because of insufficient light, lack of good airflow, and low humidity. We would normally recommend you move the plant outside for the summer, but can see from the photos that this may not be practical or feasible since it looks wrapped around the pole. More light would increase its vigor overall and would allow the plant to retain more lower, older foliage instead of having them yellow and fall prematurely. Other causes of leaf yellowing and shedding can include insufficient nutrients, inconsistent watering (too much or too little), or stress from pests. You mention that the pot does have drainage, which is good; does it sit on a saucer, and if so, is any collected water in the saucer emptied promptly after watering, or does it soak back into the drain hole(s)? If the latter, this can run the risk of keeping roots too wet.  Spider mites can infest passionflowers but we can't see any mites clearly in the photos, though admittedly they are very small and hard to photograph. They will also tend to be found mostly on the backs of leaves and not the front. You can try tapping the foliage sharply over a piece of white paper, then folding or rubbing the paper over itself to squish and smear any mites present to make them more detectable. Mites can thrive in locations with limited air circulation and low humidity, and when leaves are not wet by rain since regular "rinsing" of leaves can reduce mite populations. For outdoor plants, this could be done with a simple hosing-down with plain water now and then, but in a trellis system indoors like this, that becomes difficult. (Though, so would using any sort of sprayed pesticide.)  The droplets of sap/nectar produced near the leaf base are probably "extrafloral nectaries," a normal phenomenon for a variety of plant species that produce this insect-attracting substance so the insects will then stick around to hunt for pests on the plant. The droplets don't attract pest insects, only those that are beneficial predators. Harmless and not necessary to remove/treat, these nectaries of course won't do a plant much good indoors since very few beneficial insects find their way inside. The production of extrafloral nectar doesn't necessarily mean that the plant is currently experiencing a pest problem as most plants capable of producing it do so all throughout the growing season.  Over-fertilized plants can be more vulnerable to pest outbreaks, plus some diseases and also root stress and dieback. Was the plant's potting mix refreshed within the past two years or so? We don't see salt buildup on the soil, but there appears to be some on the pot itself. ("Salts" in this context are fertilizer residues and any minerals in tap water that build up in the soil instead of being thoroughly rinsed out during watering. This is normal and problems with root sensitivity to them can be avoided by regular repotting to freshen the mix with new material to remove any salt-laded soil.) The fertilizer you are using sounds excessively rich, but the dose you're using and how often it's applied will impact how over-fertilized or not the plant may be. If it's not blooming well, that will mostly be due to lack of enough light, not lack of nutrition. When growing outdoors, passionflowers thrive in full sun (6-8 or more hours of direct light, which can't be emulated easily indoors).  The use of filtered or purified water isn't necessary as passionflowers are not very sensitive to water quality as far as we're aware. Purified water might help leach-out excess salts from the soil, but not completely.  Horticultural oil and insecticidal soap (used separately, not in combination) should work sufficiently well for mites without the need to use a different pesticide. Do not use a home remedy version of a soap spray as they don't work well or can risk further plant damage instead. Were they being applied as per label directions, with several repeat applications? It takes time to reduce a high population if pests are present. Plus, old plant damage won't heal, even if the culprit is removed, so the best indication of good control is the lack of ongoing damage on new growth the plant produces after treatment. Few, if any, products using imidacloprid as the active ingredient will affect mites; it is an insecticide chemical, not miticide, since mites are not insects and often don't respond to the same chemicals. Systemic granules (which we presume are what you've tried, as sprays are probably not labeled for indoor use) take time to be absorbed by the roots and moved into the rest of the plant, and here too, reapplication every few weeks (again, refer to label instructions) would be needed.  Miri

responder: The Question Asker Replied July 05, 2023, 2:14 PM EDT
response: Thank you so much for your response! It's much more thorough than my questions probably deserved; I really appreciate the advice.   I think I may try to cut the netting down and putting it outside.  I have put it outside during the summer in the past and it does flower; the flowers are purple.  Historically, it has been a rather traumatic experience for the plant because it has gotten itself wrapped around our balcony railing and the only way I could bring it in was to cut it back (though, it does always come back).  Sounds like it's worth the trouble, though.   To answer your questions, I probably did not use the oil and soaps or the systemic stuff consistently enough.  So, I will give those another try, and I will refresh the soil and everything else and reevaluate the fertilizer situation.  I do make sure the saucer isn't filled with water.  Thank you again for the help!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied July 06, 2023, 12:38 PM EDT
response: You're welcome! Indeed, passionflowers are very vigorous growers and they can scramble quite a ways around structures or sprawling over the ground by the end of the growing season. If you have a container that can accommodate a trellis, that might give it more room to climb without wandering over the railing also, or at least give you less to cut back for its move back inside.  Good luck!  Miri