Bloomberg: Grain and oilseed crops may be threatened next year by a weather pattern known as La Nina, according to a private forecaster. La Nina conditions have developed rapidly across the equatorial Pacific Ocean during the past few weeks, said Drew Lerner, president of World Weather Inc. in Overland Park, Kansas. He said that may indicate more dry weather in parts of South America in the next three months and a wet, cold start to the U.S. planting season in March. La Nina, which means …