How to treat white and brown spots on potted vegetables?

[ELee]

hi - I am hoping someone can help me get to the bottom of what’s going wrong in my balcony garden (potted veg in normal and composta (pots with built in worm farm) pots).

My last crop of lettuce developed the marks seen below. They were grown from seed so I wanted to test if it was an issue with the seed but seedlings I planted developed the same issue within a week of being planted in the same pots.

I also added a mini cucumber and some pot friendly eggplants at the same time, and they have concurrently developed white spots on their leaves as well over the same timeframe. I notice my parsley is now also developing some discolouration. Interestingly the tomato and kale planted alongside are presently unaffected.

What is going on with my plants?

what can I do to treat them?

thanks in advance for any assistance you can give me!

Cucumber

Lettuce with brown marksEggplant with white and brown spotsParsley now developing white marks

[MitchellMc]

Welcome to the Bunnings Workshop community @ELee. It's wonderful to have you join us, and many thanks for your question about plant care.

It sounds like your balcony garden is facing a bit of a challenge. The white spots on your lettuce, cucumber, eggplants, and parsley could be due to pests like aphids or spider mites, fungal diseases like powdery mildew, or even nutrient deficiencies. Take a closer look at the undersides of leaves for any signs of pests. Consider using pyrethrum if pests are the issue, and make sure to remove any heavily affected leaves.

Check your watering routine, as overwatering or underwatering can cause problems. Also, ensure your plants are getting proper sunlight and protection from extreme weather conditions.

Let me mention one of our keen gardeners, @mich1972, to get her thoughts.

Please let me know if you have any questions.

Mitchell
 

[ELee]

Thanks @MitchellMc for your super quick response (and @mich1972 in advance for your input).

I did have an aphid issue a couple of weeks back on my pepper plant but (think 🤞) I got that sorted with some eco bug spray. I quarantined the affected plant (the benefits of pots that can moved to the other end of the balcony!) and haven’t seen the aphids on any of my other plants, nor on the spot-affected plants. 

That said on closer inspection there do appear to be some tiny black bugs on some of the affected plants, but not all. (See images below). Should I/Can I use the Ecobug spray on these?

Watering is with tap water every day or two, depending on how dry the soil gets in this summer heat. I have recently given them some seasol pellets as a fertiliser in case nutrient deficiency was contributing.

Also I should probably also have mentioned for context the balcony is 39 floors up in the CBD so wind factor can significant at times, and I suspect the air quality isn’t great up here at times when construction is going on, if that is relevant.

thanks in advance 

ELee

[Akanksha]

Let me also extend a warm welcome to the Bunnings Workshop community, @ELee. We're delighted to have you join us. 

@MitchellMc is currently away on a well-deserved break but let me call upon our horticulturalist and garden expert @Noelle in case she has any thoughts about your potted vegetables. 

Thanks for your patience in the meantime.

Akanksha

[Noelle]

Hi @ELee 

Wow, you are doing wonderfully well to be able to grow anything 39 floors up!

The small black flies look more like gnats than aphids, and they're unlikely to be responsible for the damage. Quarantining insect-infested plants to the other end of the balcony is probably not really sufficient as aphids and other similar pests can fly.  However, it's probably the best you can do given your location.

I suspect, from your most recent photos, it's a disease problem, may be more likely bacterial rather than fungal. As it is spotting on the leave only, and older leaves, I would not be too stressed. There is not a lot that can be done to treat leaf spot diseases but good plant hygiene can help. Do not water from overhead - water direct on to the potting mix and try to keep leaves dry. Avoid splashing leaves and don't water late in the afternoon or evening as humidity can make the problem worse. If a plant is really badly affected, then remove it.

[mich1972]

Good afternoon @ELee  Gee whiz , Growing pot plants on a balcony, 39 storeys up is certainly an achievement. Sounds like fungus gnats and the leaves look like a bacterial problem as @Noelle advised. Are you using self watering pots ? They can get too much water in them. 

[ELee]

Thanks @Noelle 

Humidity is likely contributing- its sticky in Brisbane- I kid you not my hygrometer is currently sitting. at 99% as we speak!!!

I’ve just taken pictures of the most obvious and easy to photograph parts, but the younger leaves also are affected, unfortunately. 

Watering is done directly to the potting mix around the plants vs on them but they will get the odd bit of overhead watering from the rain, and we’ve had a bit of it recently.

I’m a bit of a novice to gardening, but how would a bacterial infection get into my pots? Is it an unlucky batch of potting mix (though one composta was set up more than 6mths print to the second). The compostas with the worm farm included are by far the worst affected - could my worms have introduced the bacteria, or the scraps I’m feeding them? And I do use the rich run off from the worm farm as a fertiliser for my other plans so I’m probably spreading the bacteria that way?!

Is the bacteria self limiting or should I expect this to be an ongoing problem if I don’t get to the source of it and rid my potting mixes of it?

Thanks so much for your advice and expertise!

[ELee]

Hi @mich1972 

Only my mint is in a self watering pot, the rest rely on me or the weather for their moisture.

I have been watering every day or so in the summer, and maybe twice a week in winter. The composta pots have their water excess run off (with wormy goodness) that is re-fed to fertilise the pots or my other plants, though thinking through @Noelle’s thought on my situation I am questioning the wisdom of that presently!

Cheers and thanks!

[Noelle]

Hi again @ELee 

Bacterial infections are usually as a result of airborne and soilborne bacteria that are naturally occurring and mostly present all the time but the populations can explode when conditions are favorable. Sometimes bacterial diseases may already be present on the seedlings you buy. They generally don't arise from potting mix/growing media as the heat generated in their production kills off all the bad guys.

The scraps you are adding to your composta system may be a potential source, as they may be rotting rather than being decomposed and ingested by the worms. Rots are usually bacteria-caused. If you are using a 'closed loop' or close to it, then the problems you have may be self-perpetuating. I'd try eliminating the use of the worm farm run-off for a while and see if this breaks the cycle.

Just reading your reply to @mich1972 , there is a chance you may be over-watering, keeping the potting mix too moist, which will also promote the spread of diseases. Allow the pots/planters to dry out a bit, or at least the top 10cm or so of mix, before watering again.

[ELee]

Thanks @Noelle - that’s super helpful.

The issues have certainly gotten worse in the summer months so the combination of the humidity in Brisbane, me maybe overwatering the plants and maybe overfeeding my worms would certainly fit.

Thanks everyone for your help - I’ll give these suggestions a go and let you know how we go we can reverse this situation!

Thanks!

@ELee