skip to main content

Begonias Garden Clinic House Plants

How do I treat powdery mildew and potenital leaf spot on my begoinas?

3 years ago

last modified: 3 years ago

I recently discovered powdery mildew on my Begonia Maculata Wightii. I'm SO upset! I have wanted this plant for so long and I finally got one from Etsy. Not even a month after receiving it, I discovered the mildew. I also think it may have leaf spot. There is no way I am able to take a healthy cutting, but the plant is still putting out new leaves so I hope I can rescue it!

My Begonia Maculata Wightii was sitting next to my Begonia China Curl. I know, I probably should have quarantined the new plant, but we live and learn I suppose. I have started to see reddened spots on the China Curl, so I believe I need to treat this one for powdery mildew and leaf spot as well.

I am particularly interested in using homemade fungicide to treat. I have read that a potassium bicarbonate solution is great for killing and preventing all kinds of plant ailments. Does anyone have a go to recipe for homemade fungicide? I am especially interested in those using potassium bicarbonate since I already have it on hand, but I will take any advice I can get!

Thanks for your help!

Sort by:Oldest

Comments (7)

hc mcdole
3 years ago
Milstop is a brand of fungicide that uses potassium bicarbonate (a tad expensive) and I've used it in the past with pretty good results. If I recall the ratio is one TBSP per gallon of water.

Mildew is the bane of begonias - especially the polka dot canes and many others as well. The spores are everywhere so it isn't your fault or the store's or the grower's. The spores are just waiting for the perfect conditions to start growing and reproducing - usually cool, damp conditions. Remove the worst affected leaves. You may have to completely remove all the leaves if they are really infected and spray the stems all around, the soil, maybe the pot. New leaves will come out and eventually new stems from the roots if all goes well. This pattern occurs every year unless you have a really "clean environment" with no mildew spores present or very low levels. Once you realize this, life gets a little easier as you know what to expect in future seasons.

It is a great grower in summer but a bit of a prima donna in winter. I wished I had known that over 10 years ago. It did its best the first year I bought it in 2009.
Crystal Ransom
Original Author
3 years ago
Thank you so much for the info! I’m new to plants and this has been a huge help. Your begonias are BEAUTIFUL! I did look into the Milstop and it’s a little out of my price range unfortunately. And I don’t believe I need a 5lb bag. I’m considering using potassium bicarbonate mixed with water to see how that does. Hopefully my begonias will make it through to be as big and beautiful as yours!
Related Discussions
squash had wilt & powdery mildew, how to prepare for next year?
Q
Comments (4)
Homebody, your suspicion about bacterial wilt is probably correct, if you have cucumber beetle problems. You should also inspect the stem of any dying squash vines, to see if squash vine borers are responsible. If you find their larvae, or the holes left by them, then prevention next year is your best hope for success. And if your "white aphid looking creatures" look like this, then you should try to kill them before they reach adulthood. The symptoms of squash bug infestation can appear very much like bacterial wilt. Butternut squashes (Cucurbita moschata) are more resistant to beetles & borers than C. pepo (pumpkins & summer squashes) and C. maxima (buttercup, hubbard, banana squash). I quit growing zucchini for that reason, and now grow Tromboncino (a butternut relative) instead. It has few problems... but it does take up a bit of space, unless trellised. You can protect young squash plants with floating row cover, until they either blossom, or outgrow it. This gives the plants time to build up strength, so they have a fighting chance. For me, this prevents SVB, and by delaying the start of attack, reduces the population of cucumber beetles & squash bugs. I could not grow most winter squash successfully without the use of row covers - I highly recommend their use. The use of nylons or some other impenetrable wrap (around the base of the squash stem) can prevent the SVB moth from laying their eggs there. Also, try to grow squash varieties that root at the nodes; bury the stems early, to encourage early rooting... this will help the plants to survive, if SVB does kill the main stem. The last thing that you should do (after killing the squash bug nymphs) is to eliminate any pests that might otherwise over-winter. SVB pupae lay dormant underground, so a Fall tilling will kill many of them. Cleaning up any debris in or near the garden will help to reduce the population of squash bugs the following year.
...See More
Powdery mildew--how much to cut back?
Q
Comments (4)
Chris, not to minimize the possible damage the mildew has already done, have you tried other formula..other than the fungicides to treat this problem. The mildew can indeed cause damage in that it obscures sunlight and photosynthesis from the leaf of the plant. Usually we are told to try to improve the air circulating thru the bed and it is caused from the hot temperatures and the moisture laden air. Unfortunately the advice is to remove any and all damaged or covered portions of the plant. If this includes the stems, then ...sorry, them too. There are a number of remedies and one is two TBSP baking soda.....to 1/2 tsp vegetable oil...to a quart of water. (in Canada...that's a litre) You can add 1/2 tsp dishsoap to help the oil emulsify when shaken---not stirred. You might also consider trying to increase the plant's drainage capability by adding an amount of builder's sand to the soil under the plant.
...See More
How to prevent Powdery Mildew on large Zinnias?
Q
Comments (5)
To Ken_adrian: Thanks for the advice, but I am not one to give up on a plant because I had a problem with it for a little while during 1 season. I have dealt with issues with dahlias as well from time to time, like slugs, spider mites and tree hoppers, but I stiIl grow them. I think some things are worth a little extra effort, and its really not that much more effort anyway to be honest. I grew the same variety of zinnias about 2 years prior to last year's powdery mildew, and at that time I had more zinnias in a more shaded area that tended to hold moisture/humidity moreso than this new area does, yet I didnt have any problem with powdery mildew at that time. I dont mind having to take 10-15 minutes 2-3 times a season mixing up some spray solution and coating the plants with a safe, relatively non-toxic spray that helps prevent fungus if it means having 5-6 foot tall flowering plants that continuously flower from June til early November. I will also try to keep them more ventilated. Maybe they were too close last year. But we also had a generally wet first half of summer.
...See More
What's wrong with my Dracaena? (Mealybug or Powdery Mildew?)
Q
Comments (4)
I wouldn't assume that the browning leaves are a result of the scale infestation, either.. Scale on houseplants can be controlled by the use of a horticultural oil spray. You can find oils at any garden center.....read, understand, and follow the directions. You can apply hort. oils with a simple plant sprayer. As to the dying leaves and stems, I'd look very carefully at your watering practices and the quality of the potting medium for answers.
...See More
hc mcdole
3 years ago
I went through 2 or 3 buckets of Milstop. Yeah, it is a tad high. Neem oil is another one you can use but it is pungent smelling so I swapped it out for Orchard spray (sulfur which has its own odor). You can look through old threads on mildew as there are many helpful suggestions.

If you had a huge greenhouse like the Atlanta Botanical Garden then you can grow it like this - I think the height is over 12 feet tall.
ken_adrian Adrian MI cold Z5
3 years ago
if you havent already.. separate the plants as best you can ...

read a bunch of these: https://duckduckgo.com/?q=potassium+bicarbonate+homemade+fungicide&t=ffcm&ia=web

by the time you read thru a couple.. you ought to get the jist ...

do not spray in sun ... or on hot days ... etc .. all the general rules .. adding actual leaf damage/burn to your problems wont accomplish much ....

and here is a truism.. many say.. you arent a green thumb.. until you have killed every plant.. 3 times ... so if you lose ... so be it ... try again.. and trust me.. you will have learned something for the next time you try ...

welcome to the forums... plz come back often ...

ken

ps: it is usually helpful to include your location.. big city name ... in this case.. im not sure if you are still holding these indoors ... as i would be here in MI ... or if they are already outside ... and if they are outside .. did you harden them off before they went outdoors ... can we rule out leaf damage from shipping.. transplanting.. sunburn ....etc ... there are many things that should be ruled out.. before we start spraying them ...

a pic might help ....
hc mcdole
3 years ago
I finally watched this YouTube video on treating powdery mildew on begonias. I have had it cued up for weeks and decided today is the day to sit through it. About ten minutes long. Cute in a way but annoying in another. She uses Neem oil, dish soap, and baking soda for her cure-all. Pick your poison.

https://www.youtube.com/watch?v=dgKosjWq8RY&feature=youtu.be&fbclid=IwAR1bnq8l3HU0W2lw3RTFbfdIiLAabUtA5d3nn8XB7dCyTCAqJ2e3-mSFgk8
ken_adrian Adrian MI cold Z5
3 years ago
Cute in a way but annoying in another.

==>>> thats why i said to read multiple articles at the link i provided ...

and if you hit the VIDEO link.. there are a couple of those ...

when you find your muse.. the one that speaks to you ... then you will feel comfortable in taking action ....

one of the problems with the WWW ... theres a lot of stuff.. that wouldnt qualify as a muse.. lol .. and too many that should just have their internet taken away .. lol ... [im talking about peeps who comment on news or politics.. not us here.. lol ...]

ken
hc mcdole
3 years ago
Oh yeah, there is a "lot of stuff" on the WWW aka the internet. And you are right that some stuff is full of junk-science. Thank goodness there isn't an internet police so everyone has a voice even if some like it and some don't. Today's political environment has spilled over into every facet of life which is a shame.

Back to mildew issues, B. maculata is one that is very prone to this dreaded fungus and there are many ways to treat it. Whatever method you choose, don't let it fester to the point of death.

My own seed grown hybrid from Mrs. Hashimoto X maculata in late December, 2019. Then mildew set in and I removed all infected leaves but others dropped off by themselves.

I sprayed with Orchard Spray twice now and the plant has recovered somewhat.

Related Stories

GARDENING GUIDES New Ways to Think About All That Mulch in the Garden

By Benjamin Vogt / Monarch Gardens

Before you go making a mountain out of a mulch hill, learn the facts about what your plants and soil really want

LANDSCAPE DESIGN Great Design Plant: Sun-Loving Ninebark Puts on a Color Show

By Jay Sifford Garden Design

This tall, dark and handsome native shrub is equally at home in jeans and boots or in a suit and tie

SUMMER GARDENING How Are Your Roses Doing? A Complete Summer Guide

By Noelle Johnson Landscape Consulting

Follow these tips to keep your roses healthy and beautiful throughout the warm season

GARDENING FOR BUTTERFLIES Great Design Plant: Lungwort

Yes, the name is unfortunate. But the flowers and foliage are delightful, and this perennial is easy to grow and shunned by deer

FLOORS 5 Benefits to Concrete Floors for Everyday Living

By Natalie Myers

Get low-maintenance home flooring that creates high impact and works with home styles from traditional to modern

WINTER GARDENING Pruning Secrets for Exquisite Roses

By Annie Thornton

Encourage gorgeous blooms year after year with this time-tested advice on how to prune your rosebush in winter for health and shape

GARDENING GUIDES What Kind of Roses Should You Grow?

By Noelle Johnson Landscape Consulting

Want to add the beauty of roses to your garden? Find out which ones, from old-fashioned to modern, are right for you

FLOWERS Great Design Plant: Lilies

By J. Peterson Garden Design

Try these delightfully exotic stunners for paintbox colors, deep fragrance and intricately detailed petals

GARDENING GUIDES A Beginner’s Guide to Growing Succulents

By Carol Bucknell Garden Design

Their easy-care reputation is well-deserved, but a little TLC will turn succulents into star plants

EDIBLE GARDENS How to Add an Apple Tree to Your Edible Garden

By Marianne Lipanovich

Readily available, beautiful and fragrant, apple trees offer four-season interest along with crisp, juicy fruit

Sponsored

Sotheby Floors, Inc.

1 Review

One-Stop-Shop for All of Your Floor Coverings Needs in Virginia