Pests love the warm weather so be on the lookout! Caterpillars and aphids especially are on the move right now.
Check the plants in your greenhouse for aphids or red spidermites and take appropriate measures.
Check your apple trees: pests such as woolly aphids may be a problem! How to control woolly aphids: http://j.mp/LtiaWp
Ladybugs are beneficial insects as they are natural predators of aphids! More infos: http://bit.ly/r0pkqx