Diseases, pests,... of Hoyas, data collection thread

I'm at it again and this time I'm trying to collect things that trouble our Hoyas (and us for that matter) and ask our Hoya Maniacs for assistance to collect this data here. Might it be pests, diseases, reactions to unfavorable conditions,...etc. post it here, pictures are optional but would be good to have. Also give proposals on how to resolve/remedy the individual issues if you can.
It might get a bit chaotic within this thread and we may have to make a judgement call to divide the issues into seperate threads so that I later can index it on a "sticky threads".
I'm still not sure how I'll index it but I'm sure with your help we'll come up with the perfect index.

It would be good to use a basic form and below is my proposed format. Change it (add, rename,...) if you feel it necessary, I won't get upset :)

1. Name of disease:
2. Type of disease: (e.g. Viral, Bacterial, Insect, environmental,...)
3. Effected parts of Plant: (e.g. Leaves, Roots, Stems,....)
4. Type of damage: (e.g. Yellowing, dropping Leaves, rot, stunted growth,...)
5. Possible root cause: (e.g. too much light, not enough light, underwatering, overwatering, aliens,...)
6. Recommended cures/remedies: (e.g. increase humidity, use pesticide, squash them, ...)

You should also indicate on which species you saw the disease/pest and comment if you feel that certain species are more prone to it than others.
Write comments to your hearts content.

Thanks in advance for your help in this regard,

Milan

Oooops edited to add name of disease :)

This message was edited Dec 2, 2004 6:59 PM

1. Name of disease: Milkweed Aphids (aphis nerii)
2. Type of disease: parasitic insect
3. Effected parts of Plant: new stems and flower peduncles
4. Type of damage: stunted growth with heavy infections. secondary bacterial and/or viral and/or fungal infections possible
5. Possible root cause: seasonal
6. Recommended cures/remedies:
Biological: parasitic insects (Lacewing, Lady bug)
Non Chemical, Natural: soap/water mix spray
Chemical non systemic: Malathion,
Chemical systemic: Dimethoate (Cygon), Imadacloprid (Bayer advanced)

Easily seen and identified yellow to orange aphids with black eyes, legs and cornicles.
I've seen them on H. lacunosa, H. carnosa (any cv.) , H. pubicalyx, H. fungii


This message was edited Dec 2, 2004 10:31 PM

I would add to the above, Milan, that part of the root cause of aphids is ants, who farm the aphids. Getting rid of the ants is very important to keep the aphids away. Should also mention that Imidocloprid will not affect the flowers where the ants love to "herd" their aphids, so even if the plant is drenched and toxic to the aphids, they may still be in the flower. I have found this on H. carnosa and H. lacunosa. That is when I spray with an insecticidal soap on the flower.

So...how do we make bold type?

Thanks....and what a GREAT idea!

Carol

Good points Carol and they are noted.
This is the first round and this thread is currently the Brainstorming open discussion one and there will be several different opinions and proposals out there.
My small devious brain is currently envisioning to make individual threads with each disease/pest collected here and as much information as possible should be in the first post and other members opinions can then be posted freely thereafter. I might even go so far as to have individual/own threads for things like benficial insects (e.g Lacewing), special mixes,....etc. so that one only has to paste the link to it. That way discussions should get less confusing :).
If we do a good job there might be the possibility to go "Global" on DG but that's a long way out and maybe to much to expect.
I will need all the help I can get from you folks to just make this work in here.
A big hurray to teamwork :)

For the Bold, Italics, Underline check here in the DG FAQ: http://davesgarden.com/faq/forums/#131
Or here: http://davesgarden.com/forums/t/438534/

1. Name of disease: Dry Stem (My made up name for it)
2. Type of disease: unknown
3. Effected parts of Plant: Majure Stems
4. Type of damage: shriveled leaves, leaf loss on stems after effected area
5. Possible root cause: possible natural soil to epiphytic change
6. Recommended cures/remedies:cut stem after effected area and re-root the cut off section(s)

A short section of a stem dries out and bottlenecks down which does not allow water/nutrients to be transported by the stem to areas after the effected section(s). Can also occur on stem sections just above soil level. Often goes un-noticed for long periods of time (several weeks to several month) and one only sees it when leaves start to shrivel and/or fall off.
I have seen this happen relatively often and my theory is that this is the way of Hoyas in the wild where they seperate completely from their toots in the soil to a complete epiphytic growth.

Have seen it happen on many different Hoyas including but not limited to H. carnosa, H. pubicalyx, H. pottsii, H. cinnamomifolia.
May not occur on Hoyas which remain terrestrial in the wild like Eriostemmas or H. multiflora. I personally haven't seen it happen with those yet.

1. Name of disease: sun burn
2. Type of disease: environmental
3. Effected parts of Plant: Leaves
4. Type of damage: Yellow, brown areas on leaf/leaves, secondary fungal infections
5. Possible root cause: overexposure to direct sunlight, sudden change in sun exposure
6. Recommended cures/remedies:move plant or find ways to reduce direct exposure to sunlight

Many hoyas will get a redish coloration on leaves when exposed to direct sunlight (sun tan of hoyas) and coloration will reverse to green when direct sunlight exposure is reduced. Overexposure will burn the leaves irreversible and fungal infection will occur on the damaged section in high humidity enviroments. Also sudden changes from low light locations to direct sunlight locations can cause sunburn as the leaves do not yet have their natural "sun tan" (like we humans). Gradually adjust your plants to higher light conditions to allow them to build up their sun "defenses".




This message was edited Dec 2, 2004 8:52 PM

That's it from me right now., somebody else chime in :)
Do not have any pictures of mealies and can't find any on my plants right now. Where are they when you need them LOL (not complaining though :)


This message was edited Dec 2, 2004 8:56 PM

1. Name of Problem Root root
2. Cause of ProblemEnvironmental
3. Affected Parts of Plant Entire plant.
4. Type of Damage Leaves dry, become leathery and lifeless, stem dries also
5. Possible major cause Overwatering, letting plant get too dry before watering.
6. Recommended treatment Squeeze stem at soil level if it feels mushy, you know the rest of the plant below the soil is rotted as well. If the stem is firm, carefully unpot the plant and check the roots. One test is to clip the roots to see if there is sap/life. If none, keep clipping up the roots towards the soil level...you may come to healthy root/stem. If the plant is young, repot it and control the water, making sure it drains well. If the plant is old and there is little healthy root left, take cuttings and start over again.

Many times the small feeder roots out at the edge of the rootsystem next to the pot can get too dry, and then when watered they rot. One way to avoid this is to plant in the pot so that the area of the stem is a bit higher than the edges of the pot - another way is not to let your soil get so dry. It should be damp about 1" below the surface.

Milan...my change of wording is just a suggestion...as some problems are not diseases...and oft en the disease can only be found by a lab test...no?

Cheers,

Carol

No prob, like the sound of the changes :)

I hope I can't find a picture of the problem...but will try to create one!!! LOL.

There you go, create the problems on purpose just to take pictures, I like that :).
After a long time looking I finally found a few single mealies on ceropegia and caralluma cuttings that did not get treated with a systemic yet so maybe I'll be able to get some pics this weekend. Problem is they do not look too healthy so maybe I'll have to do the same and create an healthy environment for them just to get some nice pictures LOL.
Now if I only could get fungus gnats to sit still long enough to get a good shot of them :). Maybe I'll have to get them drunk like I did with katydids when I was a kid ;).

HA! I have H. imperialis growing up a StarFruit tree which has dropped a lot of fruit and has attracted every Fungal gnat on the island! I will send you a picture....NO problem!!!

Someone on this forum posted a picture of mealies....I am sure of it. And a picture of scale too. Scale I can get a picture of on the Gardenias...not problem there!!!!

This is my Hoya it is a "sweatheart"
Can someone tell me what is wrong with it? I got it from a trade and it was very healthy, I potted it up and notices it is getting this big spot on it. The soil is not wet or dry it seems to be just right. I have it under flouresent lighting with all my other plants I have been propagating. If you can help me figure out whats wrong, I would really appreciate it. The person who sent this to me is a very nice person and I want to be able to send her a pitcher of it in time when it has grown and is healthy.
Vicki

It seems like an onset of a fungal infection on the leaf. Try applying a fungicide or spray lightly with an Athletes Food spray (Tinactin).
Can't promise that it will save your single leaf cutting.
I personally never give out single leaf cuttings unless there is some new growth showing. Reasons for this are:
a) a single leaf cutting may never come true or may take a very long time to grow new shoots.
b) If the one leaf dies you are left with nothing.

Milan

This message was edited Dec 5, 2004 11:19 AM

Spot on, Milan. Leaves, for me,, are very problematic...may take years to do anything, or never. Everything depends on where the leaf is cut from, how it is cut etc. With some stem above or below it, you have a better chance. And it does look fungal to me, too. You might try cutting the leaf in half and taking out that spot before it spreads. HTH.

I' have seen virus spots on leaves, I don't think anything can be done about this except toss out the plant, soil, pot, so it doesn't spread. Brutal, but it works. Norma

Hello Gang:

I am very new to "The Garden" but I noticed you asking for a photo of Hoya infested with Mealybugs. I was just at my local Home Depot and noticed a plant there that could be a highrise apartment building for the little guys. I'll run back tomorrow and snap a few shots. It will most likely take a few days to come up here but I will be more than happy to get it for you. And who knows, with me taking photos I might even get someone to do something about the critters on their plant.

And this Thread? Great Idea to discuss the solutions to problems that will pop up. Great Idea!!!

Richard - aka - richteaz

Hi Richard and welcome to DG,
that would be really nice of you if you could get some nice shots of those pesky critters. Like I said above, the ones I have don't look too healthy (and I'm proud of that LOL) but I still may use them for a real close "close up".

Milan

1. Name of Problem: Mealybug
2. Cause of Problem: Parasitic Insect
3. Affected Parts of Plant:Entire Plant including roots
4. Type of Damage: stunted growth with heavy infections. secondary bacterial and/or viral and/or fungal infections possible
5. Possible major cause:contaminated soil and/or plant material, ants (harvesting)
6. Recommended treatment:
Biological: parasitic insects (Lacewing, Lady bug)
Non Chemical, Natural: Isopropyl alcohol (70-99%) direct or spray application
Chemical non systemic: Malathion,
Chemical systemic: Dimethoate (Cygon), Imadocloprid (Bayer advanced)
The most common one is the citrus mealybug (Planococcus citri) identifiable by a single dark stripe running along the back of the pink body and short, slightly curved filaments around the body. P. citri can infect arial plant parts as well as roots.

Picture: P.citri on Caralluma gracilipes

Sometimes little "cotton wads" are seen, and those are the eggs/nest. A light infestation can also be sprayed with an oil/soap...it suffocates the little monsters!!!! Another method, that I use for H. compacta is dunking the whole plant in a bucket of mild dishsoap (not ultra), let it stay for a min. or two and then pulling it out and hosing a lot of fresh water thru the soil. Then hosing off the plant.

Milan, back to aphids....another one of the damages they can produce is the Sooty Mold (looks like soot but is actually excess honeydew produced by the aphids where mold has formed). This Sooty Mold covers the leaves and prevents photosynthesis...stunting the plant. This isn't well said...but...you know what I mean!

:o{) Carol

If you are looking for a cause of the damage you called dry stem to the hoya, I would expect it to be the damage caused by tarnishbug or similar insect. The insect injects a substance that liquifies the stem inside and it poisons the growth above the injection site so that in most cases it dies outward from that spot. The only thing I have seen recommended for it is Malithion although there could be something newer. Jessamine.

Interesting...I have never heard that. Thanks, Jessamine!

I doubt that the cause is a tarnish bug as this happens with Hoyas even while they are indoors and these bugs would be clearly visible to the naked eye or at least would get stuck on my sticky traps. Nevertheless a good idea. Milan

My wild guess is that there is a lot of "stuff' that can be blamed on small insects. Sometimes they sting leaves which then turn into red spots, bite stems that can sometimes start rot (leaves too). Part of the game, I think!!!

Aloha

1. Name of Problem: Scale Insect
2. Cause of Problem: Parasitic Insect
3. Affected Parts of Plant: Leaves and Stems
4. Type of Damage: stunted growth with heavy infections. secondary bacterial and/or viral and/or fungal infections possible, mold growth due to exuded honeydew
5. Possible major cause:contaminated plant material
6. Recommended treatment:
Biological: parasitic insects
Chemical non systemic: Malathion,
Chemical systemic: Dimethoate (Cygon), Imadocloprid (Bayer advanced)

I personally didn't see any Scale insects on Hoyas until now but have heard about it from others.
The Pic shows soft scale insects (Coccus hesperidum I think) on an infected Aloe plant that I found in an office at work.

Also wanted to put this thread to the top again and see if some more input from others may appear this time around :)

Gardenias (at least around here) are favorites for scale...but they (the scale) don't seem to migrate to my Mother Plants outdoors. Another Scale I have found here is the Magnolia Scale...a soft bodied sale so it can be treated with Oil/Soap or Imidocloprid as a systemic. It is visible if you lift up tiny webs under a leaf (the eggs) and you see something moviing in there...that is the scale. I haven't found them on any hoyas...but they are all over the Michaela champaca!

Great thread!

I hope this thread is still active because I have a problem I would like some advice on.

My otherwise very healthy Hoya 'Chiang Mai' suddenly started to develop red spots/blotches, firstly in definite long lines (2 - 4 mm wide) around the outer sides of a couple of leaves. Some of these lines then started turning in irregular circular fashion, as though a caterpillar with a paint can was crawling around on the leaf, but there has been no sign of any living creature on the leaves. Then the spots/blotches more generally spread across leaves, without any sign of elongation or circular patterns. Now some of the elongated marks are becoming raised and starting to 'peel' - just the top thin silvery layer .

A nursery I showed one of the leaves to suggested it was sunburn, but this doesn't make sense as red spots have also started to develop under the leaves, and the plant was quite sun hardened to morning sun.

There is no sign of powdery pock marks underneath, like Red Spot Disease, but I'm wondering if I should treat this condition with a fungicide like copper oxychloride. I'm also wondering if all my other hoyas in the surrounding area will become infected if I leave this one where it is.

Please help.

Katranda,
I'm not sure, no I don't know what it could be, but I do know that some of my hoya's develop red spots on the back of there leaves from the sun. Also along the outer sides of the leaves. My H. verticillata var. comes to mind, as it is the most spotted. I know that doesn't help you much, but I'm sure some one on here will be able to answer your question. Do you have a photo?

Some of my plants will sport a red spotted leaf just for the heck of it...and I have a feeling it is a nutrient problem. Katranda...are all of the leaves doing this?

Yes, a photo would help....