TOKYO—Toyota is scaling its production back 40 percent, affecting 14 auto assembly plants in Japan, as coronavirus pandemic-related lockdowns in Southeast Asia crimp parts supplies. Japan’s top automaker said Thursday production will halt completely next month at some plants and partly at others, affecting a wide range of models, including the Corolla subcompact, Prius hybrid, and Land Cruiser sport utility vehicle. Global production for September will decline by 360,000 vehicles, according to Toyota Motor Corp. But it stuck to its annual forecast to produce 9.3 million vehicles, as lockdown risks were figured in. Of the lost production, 140,000 vehicles are for Japan and 220,000 for overseas, with 80,000 in the United States, 40,000 in Europe, 80,000 in China, 8,000 in the rest of Asia, and about 10,000 in other regions. The move follows smaller production halts announced for this month and July. “We sincerely apologize for the inconvenience caused to …