crepe myrtle leaf problems

[FruitTrees]

Spring is here: the leaves are coming out in my crepe myrtle. Whoot!

But some of leaves seem to have a problem - they are white and fuzzy. Perhaps a fungus. Please see the picture. How to treat this problem?

 

[zigs]

Welcome to the forum

Looks like mildew, spraying with Bordeaux mixture should do it

 

[Chuck]

@zigs is correct. What you have is called powdery mildew. Very common on CM's. I doubt seriously if you can find Bordeaux in the US, I don't know why but I have never seen it. What you can try is 2 TBS baking soda, 1 TBS vinegar and a squirt of dish soap in a gallon of water and spray it every other day. It's caused by humidity and dampness. It won't kill the tree but it will make it ugly for some time. The leaves will become deformed, turn brown and fall off.

 

[DirtMechanic]

you could try 1 or 2 Tbsp of betadine per gallon of water with 1Tbsp soap like baby shampoo. Betadine is a fungal wipeout used on human skin.

 

[DirtMechanic]

Would milk or some food source promote an antifungal fungi or bacteria? While common and easily corrected, the mildew treatments also kill off the beneficial activity on the exterior of the plant, leaving it open to further invasion by food seeking pathogens.

 

[Chuck]

Would milk or some food source promote an antifungal fungi or bacteria? While common and easily corrected, the mildew treatments also kill off the beneficial activity on the exterior of the plant, leaving it open to further invasion by food seeking pathogens.

There are a bunch of different strains of powdery mildew. I have used milk on cucumbers and squash and it did work, sort of. I believe that milk works best in acidic or neutral conditions but I can't prove or disprove this as I only used my alkaline well water in the mix and I don't get the mildew often enough to try distilled water. When I lived in the Houston area powdery mildew was much more prevalent than it is here and I used all sorts of things, garlic, oil, hydrogen peroxide, sulfur and other homemade remedies s I can't recall. All of them worked to some degree. I found that regular spraying made things better no matter what was used except for oils. They just never worked as well as the others. In my experience I have not seen any of the remedies act as a pathway for other pathogens. Only if the plant was weakened significantly did any other harmful insect or pathogen cause further damage. All in all, out of list of antifungal agents, baking soda followed by milk, then sulfur, then garlic, then hydrogen peroxide have proved to be the best in the area of powdery mildew. Downey mildew is another story.

 

[DirtMechanic]

I understand it takes about 6 inches of water to leach salt from soil. If one sprays a salt, like baking soda, every 3 weeks, then the 1 inch of water per week rule becomes challenging to my understanding. It obviously would be related to your needs in your soil. Here, in heavy clay with low potassium, I would chose potassium bicarbonate instead of sodium bicarbonate. Milk yes, but I cannot use sulfur generally, and I use thyme oil, instead of garlic oil, and it is very successful. H2O2 is a strong oxidizer, and I have not used it. Oxygen is good for growth generally, so I am asking to what many purposes can I use hydrogen peroxide? Here where the deeper soil is 5 pH and the upper crust is 5.5 pH, could I not use a spray made of water from wood ashes inasmuch as the alkaline lye in the ash would separate fungi from its soul as easily as the acidity of Sulfur or is there more to it?

 

[Chuck]

I understand it takes about 6 inches of water to leach salt from soil. If one sprays a salt, like baking soda, every 3 weeks, then the 1 inch of water per week rule becomes challenging to my understanding. It obviously would be related to your needs in your soil. Here, in heavy clay with low potassium, I would chose potassium bicarbonate instead of sodium bicarbonate. Milk yes, but I cannot use sulfur generally, and I use thyme oil, instead of garlic oil, and it is very successful. H2O2 is a strong oxidizer, and I have not used it. Oxygen is good for growth generally, so I am asking to what many purposes can I use hydrogen peroxide? Here where the deeper soil is 5 pH and the upper crust is 5.5 pH, could I not use a spray made of water from wood ashes inasmuch as the alkaline lye in the ash would separate fungi from its soul as easily as the acidity of Sulfur or is there more to it?

Sodium bicarbonate is a salt and too much of a good thing is bad. IMO it would take a lot of baking soda to affect soil in any harmful way. Non-organic fertilizers are full of salts of which I am not a fan, but, it takes a lot of it and over an extended period of time to be harmful to the soil. In your case of acidic soils potassium bicarbonate actually dilutes the acid somewhat although I don't know if it shares the same properties of sodium bicarbonate when it comes to plant fungus and baking soda's other beneficial properties.

Hydrogen peroxide is very useful in the garden. You can use it as a drench as it kills young root worms and juvenile cut worms. On indoor container plants it kills fungus knats. As a foliar spray it helps control aphids and spider mites. And if you have heavy clay soils it provides oxygen. Hydrogen peroxide actually does all of the above but not quickly. Other products do a better job but it is another tool in organic gardening that has its place IMO

 

[FruitTrees]

I assume "copper fungicide" is similar to the 'bordeaux mixture' mentioned above. That is what they have on hand at the local hardware store. I will try that first.

 

[DirtMechanic]

Of all the toxic materials on the planet, metals are high on the list. Personally it freaks me out that my house water pipes are copper. Its toxic as hell. Only because it is stabilized is it useful. But should it be introuduced to a low pH material, the acid will dissolve it and it becomes trouble. In my low pH soil I avoid it as a result. 3ppm is a criteria for dissolved copper on water testing. That is a small amount to be considered trouble.

 

[DirtMechanic]

I stand corrected again.

"In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime with an adequate margin of safety, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water.

The MCLG for copper is 1.3 mg/L or 1.3 ppm. EPA has set this level of protection based on the best available science to prevent potential health problems.

For most contaminants, EPA sets an enforceable regulation called a maximum contaminant level (MCL) based on the MCLG. MCLs are set as close to the MCLGs as feasible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. However, because copper contamination of drinking water often results from corrosion of the plumbing materials belonging to water system customers, EPA established a treatment technique rather than an MCL for copper. A treatment technique is an enforceable procedure or level of technological performance which water systems must follow to ensure control of a contaminant. The treatment technique regulation for copper (referred to as the Lead and Copper rule) requires water systems to control the corrosivity of the water. The regulation also requires systems to collect tap samples from sites served by the system that are more likely to have plumbing materials containing lead. If more than 10 percent of tap water samples exceed the copper action level of 1.3 milligrams per Liter (mg/L), water systems must take additonal steps to reduce corrosiveness.

EPA promulgated the Lead and Copper Rule in 1991, and revised the regulation in 2000 and in 2007. States may set a more stringent regulation for copper in drinking water than EPA."