THE AGRONOMIST ANSWERS ON HOW TO GROW AND CARE FOR PLANTS
Sticky, white parasitic leaves on my Photinia
QUESTION FROM MICHELA
I ask her for advice on a parasite that populates our garden Photinya. I enclose 2 photos. The bottom sheet shows the parasites in the photo, and the top page is sticky.
What is it about? How can I fight it? Thank you very much.
it is not serious what yours has Photinia, it's just very annoying and you need to be patient to get rid of it. Yours Photinia in fact it has a floury cochineal infestation. That white formation you see is the female insect that lives under that kind of shield, in this case silky and whitish. The damage they cause with their mouthparts as they insert their stilettos into the tissues of the plant to suck the sap they feed on.
They prefer warm and dry climates and these two conditions are an important element for the proliferation of the insect.
As for their physiology and the damage they can cause, I refer you to the article The scale insects, where you can find all the information you need to learn more about this insect.
The sticky you feel is caused by their excrement and is called honeydew. It is a substance that is very popular with other insects, especially ants. In fact, an "invasion" of ants is usually associated with a cochineal infestation. Honeydew is also appreciated by bees so much that, if they can find it in good quantity, they also make honey. On the market you can find in honeydew honey. That said, let's see what you can do to eliminate these annoying unwelcome guests.
If the infestation involved a plant that was in the apartment and with a mild infestation, you could simply eliminate them with a cotton swab dipped in alcohol passed over the insect. In your case, since these are plants in the garden and of a certain size, it is necessary to intervene with pesticide products such as white oils, which are nothing more than mineral oils obtained from the refining of petroleum. The white oil acts by contact, forming a patina on the plant and therefore killing the insects by simple suffocation.
Since the infestation is quite important, I would recommend using activated white oils. that is to say a white oil added with a specific insecticide to increase its effectiveness which can act either by contact or enter the plant's circulation and therefore the insect assumes it with nutrition. In a good nursery you will be able to find these ready-made products without any problems.
Surely it will be necessary to do more treatments to eliminate the different generations of cochineal. Follow the directions on the product packaging.
A recommendation: be careful to do the treatments in the evening, when the pollinating insects are no longer present to avoid causing a massacre.
If you do not like to intervene with chemicals, you can use insect antagonists of the cottony cochineal what is the Cryptolaemus Montrouzieri, a ladybug very fond of this cochineal that you can find without problems on the market and also on the internet. Obviously this ladybug is used as an alternative to chemical treatment and never together.
I hope I was clear.
Dr. Maria Giovanna Davoli