The boxwood defoliator caterpillar reappeared. As expected, the mild winter and the absence of prolonged frosts favored the wintering of cydalima perspectalis, better known as box borer. At this point all that remains is to roll up our sleeves and intervene in a timely manner before the damage of the past year is redone. I confirm from experience that the foliar treatment based on deltramethrin kills the caterpillar, but the interventions must be repeated.
After going to an emergency last year, I personally re-ascertained the presence in my hedge of the box borer already at the beginning of March. In the middle of the month, the small fluffy honeycombs (concentrated in the points of the hedge most exposed to the sun) swelled and the canvases began to be seen. At the beginning of April I saw the first caterpillars-larvae, with the characteristic black-green color, and I also noticed that the boxwood was returning to suffering and the leaves to disappear (literally eaten).
In the first week of April, I implemented the first insecticide treatment against box borer. Personally, I used Bayer's Decis Evo solution that I found in the garden shop near my home after asking for a deltamethrin-based product. It is the same substance that I used last year on the advice of a plant pathologist, and it worked because the hedge recovered well after an attack that had completely stripped it of its leaves.
Here is the appearance of the box borer
I did the first treatment last year in September, the second in October. At that point, the arrival of the cold sent the box borer and no other interventions were necessary with the hedge which has returned to cover itself with leaves. But now with the arrival of spring we are point and head. The difference is that this time I noticed it before and I'm on him. The boxwood defoliator caterpillar it is very resistant.
Just fifteen days after the first treatment in early April, which I implemented quite intensively, I must say, the boxwood has returned to throw away the new leaves well but upon careful examination I still found some caterpillars (less than 1 cm) which evidently are survived or were born in the meantime. So I did a second deltamethrin treatment against the box borer, lighter this time. Now the attack seems to have been rejected, but I do not let my guard down: April and May, with the vegetative restart, are also the period in which fungal and parasitic attacks are most virulent.
This is what my boxwood hedge looked like after the first attack in the summer of 2013
To frame the situation, I specify that the boxwood hedge I am talking about is located in a location 900 meters above sea level in the province of Verbania, overlooking Lake Maggiore. It is sturdy and also quite old, I don't know exactly but it has been around for a few decades, and never before 2013 had it fallen ill or suffered attacks of this severity. From research I found that the box borer is originally from China and in Italy it appeared in Italy for the first time in 2011, on Lake Como.
Now I advise you to read: Bacillus thuringiensis effective against the box borer
Bacillus thuringiensis Aizawai from 500 gr
You can find the history of my battle against the boxwood defoliator here:
Caterpillar defoliator: how I take care of my boxwood
The care of the boxwood against the defoliator caterpillar
The boxwood defoliator caterpillar: my story
Lepidoptera: plant parasites