It's a bad one. It's a carcinogen, for one thing. It's not likely you'll ever find a product with this active ingredient in the typical garden center but it is readily available as an agricultural pesticide. It belongs to the same group of pesticides as does Imidicloprid; they are both classified as neonicotinoids.

How bad was the infestation last year? I'm curious as to where you received the recommendation for Thiacloprid.

Psyllids, in general, can be controlled by Neem applications. Neem acts as an anti-feedant and therefore a repellant. Insects that do feed on a neem treated plant may experience its effects as a growth regulator, too. Neem disrupts the life cycle of insects that ingest it.

Here is a link that might be useful: Is this what you've observed?

Hmm. Completely different responses than in the other thread of same name at
http://forums2.gardenweb.com/forums/load/organic/msg04135641744.html?3

I suspect confusion among terms -- bay tree; bay suckers; and suckers (as in sucking pests)

Here is a link that might be useful: other thread

I don't see anything that different in the responses on the Organic Gardening Forum. Thiacloprid is a potential carcinogen and is known to be quite persistant in the environment and for those reasons should not be considered by anyone concerned about the environment and human health.

Rhizo,
I read about thiacloprid here
http://www.gardenaction.co.uk/fruit_veg_diary/fruit_veg_mini_project_september_3_bay_laurel4.asp
Here what i had on my bay tree last summer and summer before:
http://apps.rhs.org.uk/advicesearch/Profile.aspx?pid=505
I tried last summer soap and water but it did not help.

The term confusion is real, the differences in answers is not. Neem or insecticidal soap is the best choice.

Dan

The term 'bay sucker' is a British one, I believe. They are a psyllid.

Considering briergardener's zone, I strongly sense that the plant is Persea borbonia or other species. Persea is commonly attacked by this psyllid, causing those galls indicated by our poster.

My recommendation for neem stands.

Thanks everybody for recommendation.

Could you tell me when, how and how often should i apply neem oil?

The label has all the information you need.