Hi all,
I wanted to get you alls take on what is going on with the leaves on some of my roses. I have had to spray pretty aggressively to keep the spider mites at bay and have combined the miticide (I rotate Fobid, Avid, and Floromite) with propaconazole and macozeb on occasion, depending on the schedule. I always also use spreader sticker. After the last few sprays I have noticed an increasing number leaves which have black and bronzed spots, which then gives way to progressive yellowing, culminating in leaf death and drop. Any ideas? Doesn’t look like black spot to me. Phytotoxicity? Any input would be greatly appreciated. I have also attached a picture for clarity of the progression of leaf deterioration. Thanks!
I’d say phytotoxicity. I don’t know where you live nor what the weather conditions are there now, but if temps approach 80; the sun is BRILLIANT and HOT; it’s arid/windy; and/or the roses are close to any kind of surface which can act as a passive solar collector, resulting in high reflected/radiated heat, DO NOT SPRAY anything but WATER. A water wand turned upside down to wash off the foliage under sides will do more in most conditions to knock down spider mites than most chemical methods. They flourish in hot, dry, dusty situations so washing those off with water not only hydrates the plants which likely need it in those conditions, but also helps eliminate the mites. You need to be washing the various chemicals off the foliage before adding more to prevent build-up of too much “stuff” which can result in destroying the foliage as you’re experiencing. You already appear to need to use fungicides. I’d restrict the miticide use and replace them with water.
Why does it appear I need more fungicides? I’m not sure that is a fungus, based on the cadence and progression of the leaf deterioration. It starts 2-3 days after spraying and progresses through the stages in the photo. Besides, I am spraying with a rotating blend of contact and systemic fungicides every 7-10 days.
Also, I live in Mississippi. It’s humid and hot (above 80) from May through October
As an experiment stop using the spreader sticker, it may be causing the phytotoxicity. Do you have a lot of aphids? You are spraying the right things to prevent spider mites and black spot. What spreader are you using? How hot has it been?
Hi there,
Lately, it has been quite hot (80’s and 90’s) and I try and spray in the cooler parts of the day. The only pest I have ever really had is the two spotted spider mite. I don’t have aphids, but in years past I have had to spray aggressively at least weekly with rotating miticides to keep the mites extinguished. I have found this to be a common refrain from rosararians in south central Mississippi and eastern Louisiana. Right now, I have no pests at all and no fungus, but I do spray with contact and systemic fungicides as a preventative, as well as the miticides I mentioned. I use Hi-Yield spreader sticker which is recommended at 1-2 tablespoons per gallon. This particular spreader sticker is 90% alcohol ethoxylate and alkylphenol ethoxylate. I have included a picture of the label as well as some more of the leaves. Thanks again!
I’m sorry, I did not mean to imply you need more fungicides. I meant it appears you already need them so washing the foliage with water shouldn’t create any disease issues you aren’t already treating with them. Read the labels of your chemicals. I believe you’ll find many of them say not to use them when temps are 80 and above. It’s VERY easy to damage and even kill plant tissue with any kind of chemical spray when temps and sun are intense.
I think the spreader sticker is causing your leaf problem.
Thanks! What leads you to believe this is the culprit ? Is there a different spreader sticker that is less phytotoxic?
Because I have experienced this problem when I used them. But I do use a product known as Indicate 5, but now I purchase Tweak which comes from Southern Agriculture. This product lowers the pH, the water will turn color (pink), which also helps your chemicals to last longer. I know of another Rosarian that stopped using commercial spreader stickers because he was experiencing spray damage on the leaves of the gardens he was spraying.
I wash my 130 bushes with a very forceful spray twice every week, which killis or prevents colonization of mites. By brick or stones in other gardens that I care for, I may have to use
avid which is translaminar…the focus being specific around the leaflet junction and it penetrates the dermis for spot treatments in addition to washing. Even with Floramite, if you get the undersides and leaf junction, you will solve your mite problem. No need for a spreader/sticker which may create the spray damage that you see on your leaves.
Very cool. Do you have a particular high pressure nozzle and setup you would recommend? Is there a particular technique you have found particularly disruptive to the mites? How do you effectively cover the back of the leaf where they like to hang out?
Find a curved water wand, such as one Dramm makes for hanging baskets, attach one of the Fogg-It nozzles, they come in several gallons per minute. Then you will able to aim the water wand to hit the bottom of your rose leaves. Do this every three days for about 2 weeks. The hotter and dry it is, the faster spider mites multiply.
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Rosejoy below has a good recommendation of manufactured Dramm.
I put my thumb over my hose on full blast. I wash bushes systematically, down and up, then across and around. It is good exercise.
as with all things in rose care, staying ahead oof the curve makes for less work and good results.
