Question

Rose growers often spray their roses with insecticide to kill insecticide to kill greenfly. Explain why this can upset the food web? And suggest a way in which rose growers could control the numbers of greenfly without using chemical sprays

Answer 1

The greenfly, otherwise known as an aphid, is one of the most common insects affecting roses, according to the University of California Department of Agriculture and Natural Resources. This could include the melon and rose aphid, which although bothersome, doesn’t create a major threat to your rose bushes in small to moderate numbers. However, larger colonies of greenflies can produce copious amounts of honeydew, a sticky secretion that promotes the growth of sooty mold, which can blacken your rose’s leaves. Controlling greenfly infestations is possible without the use of potentially harmful pesticides.
1.
Knock the aphids from affected rose leaves with a strong spray of water from your garden hose. Spray the leaves several times a week, on both sides of the leaves, as the greenflies will often congregate on the leaves' undersides.

2

Increase the number of insects that consume aphids and keep their numbers under control without affecting your rose bushes, such as lacewings, lady beetles or soldier beetles. Plant flowers that naturally attract such insects, such as daises or lavender, or purchase larval insects at your local nursery.

3

Cover the area surrounding rose seedlings with a layer of aluminum foil mulch. According to the University of California Department of Agriculture and Natural Resources, the reflective surface will deter aphids from feeding on your growing rose bush's leaves.