SoS: Pests and Diseases – Plant Doctor Needed!

My garden is plagued by pests and diseases. The latest victim is my beautiful Agave which is over twelve years old so I am hopping from foot-to-foot wondering what to do. When we are sick we go to the doctor, when animals are sick we take them to the vet… but where to go for advice on poorly plants? I search the net. Yellow leaves: Too much water, not enough water, nutrient deficient etc. etc. but which? As for the bugs, if they are not eating my plants they are eating me.

For my previous Six on Saturday I shared the best of my garden, but remove the rose-tinted spectacles of gardening on the west coast of Portugal, and I present you with just some of the challenges I face. Can any of my fellow gardeners offer any suggestions to rectify these problems?

Sickly Agave – Insect or Disease?

I first noticed lesions to the leaves a couple of months ago but so far I’ve not been able to identify the problem.

If anyone has ANY suggestions I would be grateful.

Strange markings on Agave
Strange markings on Agave



2. Queen of the Night – Is this my fault?

The leaves on the Queen of the Night succulent were turning yellow so after some research, I decided it needed nitrogen so I obliged. I think the problem now is over-fertilization. What do you think?

Queen of night with orange markings on leaves
Queen of the night with orange markings on leaves


Queen of night with orange markings on leaves
Queen of the night with orange markings on leaves

3. White patches on leaves

White patches on Agave leaves
White patches on Agave leaves

I thought at first it was scorching… but now I am not so sure. See cucumbers below.


White marks on cucumbers
White marks on cucumbers


4. Stunted Cauliflowers

The cauliflower seed plugs were planted on the 6th of February. Over three months later and I am left with…

Tiny cauliflowers - was it worth the effort?
Tiny cauliflowers

The cauliflower florets were starting to turn to flowers so I was left with no choice but to harvest them. Where do I go wrong?

5. Black Spots on Aloe Vera Leaves

I don’t have the first idea what’s caused this other than I wonder if it’s an airborne virus?

Black spots on Aloe Vera leaves
Black spots on Aloe Vera leaves

6. Mystery Problem with Pea Leaves

Again unsure if this is an airborne virus, thrips or? Any suggestions, please?


That’s it for this week.

Please don’t forget to click across to the Propagators blog to meet other keen gardeners

ETA: I like to end on a positive note so here is a picture of one of my container-grown strawberries.

Strawberries grow well in containers
Strawberries grow well in containers

24 thoughts on “SoS: Pests and Diseases – Plant Doctor Needed!

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  1. Tony, thank you so much for your considered reply! It is really appreciated. We do have VERY high humidity where we live so this probably causes a lot of the problems. You make a valid point re the cauliflowers and in hindsight, given the very hot weather in May probably exasperated the situation. I think I will pass on these next year. To much work/water for such a poor yield. We live to learn 🙂


  2. The foliage in the first picture was probably damaged by mildew, which is now desiccated. The insect damage is not as serious. If new foliage is as yellow as this damaged foliage is, there is likely some sort of nutrient deficiency as well, but it not easy to identify with this damaged foliage.
    The agave foliage seems to have been damaged by mildew of some sort as it was developing. It probably started before the leaves were completely unfurled. Such damage is merely cosmetic, although it could be a regular problem if the weather is normally humid or damp.
    Queen of the night is likely shedding old foliage in response to the nutrient deficiency. It was likely just trying to concentrate resources. Even if nitrogen is the remedy, old leaved occasionally shed naturally, although not so many at one time. Be careful with fertilizing. Too much can burn foliage, and almost too much can inhibit bloom.
    The white patches on the agave might have been where water puddled in the leaves. It could have suffocated the submerged or constantly damp part of the leaves, especially if the water heated up in the sunlight.
    However, the cucumbers really did get roasted by the sunlight. That is a different problem.
    Cauliflower is sometimes stunted by warm weather, which is why we grow it only from spring to autumn. If yours was planted late and the weather got too warm for it as it was blooming, development could have been stunted.
    Black spot on the aloe looks like a bacterial blight.
    The peas also seem to have been damaged by mildew, like the cucumber or squash foliage in the top picture.
    A few of these symptoms are typically caused by damp or humid situations mixed with warmth, which seems odd for Portugal. I really do not know the climate there though.

    Liked by 1 person

  3. Hi…I would say you have slug/ snail damage to the Agave…although that’s unusual!
    There definitely seems to be something very tiny munching on some of your plants!
    Hope you get it sorted ☹️

    Sent from my iPad

    Liked by 1 person

  4. Your strawberry looks tasty! I ate first tonight.
    About diseases , 2 solutions :
    * Cryptogamic diseases because of excessive humidity,….
    *or sunburn: Portugal is rather dry at this time of year … and you had a heat wave not so long ago … so it could also be sunburn. (Cold wet nights and hot temperatures during the day : leaves burned if there were droplets on them.)

    Liked by 1 person

  5. Thank goodness for the strawberry! I know my main nemisis at the moment. Lupin aphids. They make a satisfying pop when squished, better than bubblewrap.

    Liked by 1 person

    1. Lupin aphids and bubble wrap LoL… the only bug I dare squish between my fingers are cochineallas which attach themselves to my citrus trees. When you squeeze them they ooze red liquid which is used in cochineal dye

      Liked by 1 person

  6. Has it been unusually damp there? You said that you had blight on your potatoes the other week. These could be fungus or moulds of some sort. You could try a good general feed (seaweed perhaps) and then spray with a garlic solution. Could work. But your strawberry looks delicious. Does it still exist?

    Liked by 1 person

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