Xylella fastidiosa subsp. multiplex
What could be wrong with an attractive, compact, bushy peach tree? Plenty! Your tree could have the incurable bacterial phony peach disease (PPD).
This disease came out of nowhere and struck peach trees in Georgia in 1900. And it had spread all the way to Texas by 1933.
A century later, this pathogen is still a pernicious problem.
No peach tree is safe – every cultivar, form, and hybrid is susceptible.
Your tree won’t die, but it will stop producing fruit over a 2- to 4-year period.
However, there are steps you can take to prevent PPD, and we at Gardener’s Path will advise you on these steps, to keep your peach from becoming another victim.
What You Will Learn
Read on to learn about PPD and how to control it.
What is Phony Peach Disease?
The cause of phony peach disease is a type of bacterium known as Xylella fastidiosa subsp. multiplex that lives in the plant’s xylem – the tubes that transport water and nutrients from the roots to the leaves. The infection is closely related to the dreaded Pierce’s disease that limits the types of grapes that can be grown in the southeast.
Aggressive leafhoppers known as sharpshooters and spittlebugs suck out the liquid and become infected in the process, and then infect surrounding trees.
Unfortunately, these leafhoppers can live on a number of different types of weeds, so they are probably residing in close proximity to your peach tree.
What can be done at this point? Not much. If your tree is infected, you should remove and destroy it.
You do not have to worry about phony peach disease if you live in the northern US. PPD is a creature of the South.
This disease has been confirmed to occur from Florida north to North Carolina, and west as far as Missouri and eastern Texas.
It is severe in Alabama, Florida, Georgia, Louisiana, New Mexico, and South Carolina.
In fact, the situation in southern Georgia is so bad that PPD frequently kills whole orchards.
There are reports that PPD has struck in Montana and Nebraska, but they have not been confirmed definitively by plant pathologists.
Rare cases as far north as southern Ohio and southern Missouri have also been reported and confirmed.
How PPD Spreads
The bacteria that cause PPD can live in a variety of plants, including common weeds and wild trees like plum, apricot, and almond.
Unfortunately, insects like the dreaded glassy winged sharpshooter (a kind of leafhopper) are very aggressive feeders and can transmit the disease from wild hosts to peaches. And the insects can transmit the bacteria for their whole adult lives.
According to an article by DL Hopkins and AH Purcell in the journal Plant Disease, PPD is rarely spread between trees. Yours is most likely to become infected by transmission from wild plants.
However, it can spread by root grafts between trees that are next to each other.
Infected trees usually don’t show symptoms until a year and a half or more after they have been infected.
The first thing you might notice is that your tree will be bushier and more compact. This is because the terminal growth and the internodes are shortened.
Blooming will occur several days earlier than it normally would, and the fruit will ripen more quickly.
The leaves will be a darker green, too, and they will stay on the tree longer in the fall.
The xylem in the woody tissues will look black because that is where the bacteria live.
The most significant problem is the response of the fruit. Over time, the size of the mature fruit will continue to decrease until they grow to only be the size of silver dollars.
If immature trees are infected, they will never bear fruit.
Confirm Your Diagnosis
Plant disease experts in Georgia report that some growers have been removing trees that they thought had PPD. However, these problems were shown to be caused by weevils or root nematodes.
The difference is that trees infested with weevils or nematodes will not be as green or have the short internodes.
While trees infected with these organisms will be stunted, they will continue to produce fruit.
Removing a tree that could keep producing would be a very costly mistake, so if you are not sure of your diagnosis, check with your local extension agent to confirm that your tree does have PPD.
How to Prevent Phony Peach Disease
The primary mode of prevention is to eliminate vegetation that could harbor the disease or the vector – or both!
Control the weeds around your tree or orchard, and remove nearby trees that could serve as hosts for the insects that transmit the bacteria.
Carefully check for signs of infection in the early summer.
Also avoid the urge to prune in the summer. This way, you will be able to recognize any symptoms of PPD. Also, your tree won’t produce the vigorous new leaves that draw in the leafhoppers.
If your tree is infected, be merciless. Remove it and burn it, so the disease will not spread.
A Problem Throughout the South
This insidious disease has been a problem in the southern US for over a century, but information on it is limited.
What is known is that every type of peach is susceptible.
Take measures to prevent this infection by removing weeds and alternate hosts like wild plum. If your tree shows the classic signs of being bushy and compact with shortened internodes and tiny fruit, prepare to remove it and destroy the remains.
Have you had a tree infected with phony peach disease? Let us know how you diagnosed it in the comments.
And read on for more information on peach tree diseases:
- How to Identify, Prevent, and Treat Gummosis on Fruit Trees
- How to Identify, Prevent, and Treat Scab in Stone Fruits
© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Uncredited photos: Shutterstock.
About Helga George, PhD
One of Helga George’s greatest childhood joys was reading about rare and greenhouse plants that would not grow in Delaware. Now that she lives near Santa Barbara, California, she is delighted that many of these grow right outside! Fascinated by the knowledge that plants make chemicals to defend themselves, Helga embarked on further academic study and obtained two degrees, studying plant diseases as a plant pathology major. She holds a BS in agriculture from Cornell University, and an MS from the University of Massachusetts Amherst. Helga then returned to Cornell to obtain a PhD, studying one of the model systems of plant defense. She transitioned to full-time writing in 2009.