Viruses can be a major setback, reducing vigor and growth, and invariably producing discoloration. They are often spread by sap-sucking insects, one very good reason to create natural habitats for birds, ladybugs and other natural aphid predators. You can also grow plants like marigolds that attract parasitic wasps, which feed on aphids. If you decide to spray the aphids, it may kill their predators, giving the next generation of these pests a free run. Wait and see if the predators tackle the problem before spraying. Group 9 Rembrandt tulips are particularly prone to a virus that produces \"broken\" flowers with wonderfully attractive white and feathered markings, but it can also be transmitted to other tulips.