Ask Mr. Smarty Plants

The tree in the previous answer was a pecan, not an almond. Here is an excerpt from that answer:

"Well, I think this is the first time that Mr. Smarty Plants has been asked how to stop a tree from producing desirable fruit.   I can find you lots of information about keeping the pecan trees healthy (fertilization, watering, protecting from insects and diseases, etc.).  Here are some links to pecan tree care from Arizona Cooperative Extension Service, Alabama Pecan Growers Association, and Texas Pecan; and, I suppose if you didn't follow the guidelines for keeping your trees healthy, you might see a reduction in the size or the quality of the crop of pecans.  Nut production on pecan trees (as well as other nut trees) is generally cyclical with some years producing large crops and alternate years producing very few fruits.  The US Forest Service says that Carya illinoinensis (pecan) produces a good crop at intervals of 1 to 3 years.  However, I don't know of any way,  short of cutting it down, to completely stop the tree from producing for a season."

If the question had been about an almond tree, we would not even have been answering it, as Prunus dulcis (almond) is non-native to North America, but rather originates from Saudi Arabia, Israel, Jordan and Lebanon.  It is a member of the Prunus genus, family Rosaceae, and therefore related to peaches, plums and cherries.  Carya illinoinensis (pecan) is a native to North America, and a member of the  Juglandaceae or hickory family.

Not only is there no way to keep the chinaberry tree from producing seeds, it is a prolific producer, and an alien invasive tree, native to India, Southern China and Australia. California, in particular, is vulnerable to non-native invasive plants. Read this website from the Plant Conservation Alliance Alien Plant Working Group "Least Wanted" Melia azedarach (chinaberry tree). Whoever told you it could be sprayed to keep it from being super prolific with seeds was having you on, as the British say. The primary command in any organism's genetic structure is to reproduce itself, and the chinaberry does far too good a job at that. In answer to your question, no, that's not true that a spray will prevent the formation and distribution of seeds. Our recommendation would be to have it cut down and hauled off. If you want the shade more than you want an environmental friendly, less messy native tree, then you will be stuck with the chinaberry.