Warm winter days above 50 degrees make gardeners eager to get back out working in the garden. The warm temperatures also trigger many over-wintering insects and caterpillars to hatch and begin their development. Practitioners of Integrated Pest Management use “degree days,” or days above 50° to forecast when a garden pest might start doing damage and when management should begin. Some pests require more accumulated heat then others to complete their lifecycles. The variegate cutworm, for example, may start feeding as early as February during mild Northwest winters. Dedicated fruit and vegetable growers will want to download degree day calculators and spread sheets from Washington State University’s Entomology department.
Colorado State Cooperative Extension published an interesting article on the strategies pests use to survive cold winter days.