Researchers used a chemical called NAA to stop apple and pear trees from growing unwanted sprouts on their trunks and branches. They found that applying 1% NAA was effective in controlling sprouting, with no extra benefit seen from using 2% NAA. The best results were seen after one growing season, with almost complete control of sprouting on certain types of apple and pear trees. However, 0.5% NAA was not as effective in preventing sprouting.