National Public Radio: We all know about the drought in California, but farmers there have more to worry about than a lack of water. There's also the looming threat of Asian citrus psyllid (ACP), an invasive pest that flies from tree to tree, feeding on tender leaves. By itself, the psyllid is not particularly harmful, but it can carry citrus greening disease, which kills trees within a few years of infection. There is no cure. In 2005, ACP spread citrus greening disease all over Florida, devastating the state's $9 billion...