I have an indoor rosemary plant that I bought a month or so ago (It was never outdoors-zone 5 ) and it has grown new leaves and seems happy but it has a white "fluff" on its leaves. I washed it off all the leaves and stems but it returned 2 weeks later.
What is this and do I need to treat it and what is organically safe so that I can cook with this rosemary?
Thanks in advance!
White stuff on my indoor Rosemary plant
Fungus possibly. Without a photo it's hard to say.Your local garden center(s) should have some fungicides that are safe. Maybe Mealy bugs?
If this white stuff is kind of fluffy and in spots on the stems or leaves it might be mealy bugs. I find that herbs grown indoors are more susceptible to insect attack. You may just have to continue to wash them off of the leaves until they disappear entirely. The larvae might be in the soil so if this doesn't work re-potting might be the best option. Be sure to wash the pot well also.
For soil larvae get "Mosquito dunks" (at your garden center) and place one quarter of one in your watering can.
These work well for Fungus gnat larvae too.
Interesting. I have used dunks in my rain barrel but not heard of this use. I had a bad batch of root mealies on my Stapeliads and ended up dosing them with Bayer Advanced Tree & Shrub... As the residual effect of BATS is said to last a year, I would not use that on anything I might eat.
For mealy bugs, wiping them away with a q-tip or piece of paper towel dipped into rubbing alcohol will get rid of them... but as you said, you may need to repeat the treatment a few times before you get them all.
If the white is more flour-like, then you may have powdery mildew, which also often attacks rosemary indoors. Better air circulation can help (turn a fan on the plant). Often, rosemary plants indoors get stressed from over-watering, so check the soil with your finger before you water and keep them a little on the dry side... stressed plants seem more susceptible to mildew & other problems.
The DeBaggios included some good information about rosemary culture on this site (sorry, but they don't do mail order): http://www.debaggioherbs.com/growingtips.php#Growing+Rosemary+in+Containers
More fluffly than floury-will try the alcohol rub and look into the dunks for watering. Thanks everyone for your input and the herb website!
It is much cheaper and actually more effective to just buy Bacillus thuringiensis, the ingredient in Mosquito Dunks. *It is sold as "Thuricide" and works great for the larval forms of many insects/caterpillars. (Halt! See edit below)
The white stuff you have on your rosemary is most likely powdery mildew/mold, which can look "fluffy" if there is enough of it, and it the result of too much humidity (as someone above said). If so, a spray of baking soda and water will certainly go a long way to combat it if not alleviate it altogether. (It is quite common in our greenhouse environment if we aren't careful.)
Best,
Shoe
Edit: My mistake, Folks. "Thuricide" is a Bt product but is NOT the one you want for mosquito larvae/black gnat larvae/fungus gnat larvae. Thuricide is for leaf-chewing caterpillars only. For the larvae just mentioned Bt israelensis is the strain you are looking for (available in Mosquito Dunks as well as other products). See my post below for more explanations on these two strains. I apologize. Shoe
This message was edited Feb 26, 2008 5:07 PM
I wasn't sure if the Bacillus would work on mealy bugs that weren't in the soil... it would sure be worth a try, though! The q-tip and alcohol treatment is a suggestion I picked up over at the African Violet & Gessie forum... It's probably quicker to do on an AV than on a big rosemary plant!
If you look closely, you'll be able to tell if you have mealy bugs or powdery mildew. The mealy bugs really do look like bugs... white, fluffy bugs... LOL.
critter, you're right, Bt won't work on the mealy bugs. In my post above I was referring to the use of Thuricide over Mosquito Dunks and it was in reference to someone above mentioning it for fungus gnats.
For mealy bugs it is easier (for me) to use a soap spray (Safer's) but I have also resorted to q-tips and alcohol. (I'm not very patient for that technique though, being the lazy sort that I am!)
Shoe
I've diluted rubbing alcohol with a little water and spritzed it around... not recommended for something like an African violet, but for plants with tougher leaves (citrus, for example), it seems to work.
If it does turn out to be mealies, I'd suggest testing anything experimental like that on one or two stems, then waiting a couple of days before subjecting the rest of the plant to it -- just in case the cure turns out to be worse than the disease!
Obviously not on "food" plants but then would Bti work on root mealies on other plants?
Actually, I think Bt is safe on food plants.
OK, that was off the top of my head -- so check the label. But I seem to recall it's a recognized "organic" control.
Podster, you've just jogged my memory (and Folks, it is getting poorer by the year!). I need to go on record as correcting myself for an important mistake/post I made above. (I'll also go back up and correct it as well, for fear someone may one day take it, as it is written, as truth.)
When I read Podster's post above mentioning "Bti" it reminded me that although I've used Bt/Thuricide/Dipel (last two are trade names) for years at that time only Bt "kurstaki" was available. The kurstaki strain is aimed at, and only affects, leaf chewing caterpillars (armyworms, tomato worms, corn worms, etc).
Bt "israelensis " (Bti) is what kills mosquito larvae as well as fungus gnat larvae (and black fly larvae).
My statement above, "It is much cheaper and actually more effective to just buy Bacillus thuringiensis, the ingredient in Mosquito Dunks. It is sold as "Thuricide" and works great for the larval forms of many insects/caterpillars." is untrue, and I apologize. Well, actually it is "half true"!...
There is Bt in Mosquito Dunks but it is the israelensis strain and has an affect on skeeter larvae. Thuricide (Bt kurstaki) is a strain that only affect caterpillars and has NO affect on mosquito/fungus gnat larvae, etc.
So, to sum up my mistake I am sorry to have mentioned "Thuricide" as the product to combat skeeter and gnat larvae. I mis-typed/mis-spoke(?)
As for your last question, Podster, Bti is definitely safe for use on food crops. As for its use on "root mealies", and I am assuming you mean mealy bug "babies"(?), no. Mealy bug adults lay eggs which then hatch and are considered nymphs and are not considered larvae. Bti affects only larval forms of creatures, Btk affects leaf chewing caterpillars, and neither of those categories do the mealy bug nymphs fit into. (You'd be best off using Neem, insecticidal soap or parasitic wasps for large outbreaks or mealy bugs.)
Critterologist, your statement was correct above, questioning if Bt would work on mealy bugs above the soil.
And now, back to our regularly scheduled topic. "white stuff on rosemary".
Again, my apologies to have gotten off-track.
Shoe
Thanks for the clarification. I appreciate your knowledge and effort. Good explanation too.