Aphids are sap-sucking bugs. It is usually easy to see aphid infestations with the naked eye; they colonise shoot tips, flower buds and the underside of younger leaves. Aphids cause stunted growth with curled or distorted leaves. This can weaken the plant. Many aphids also excrete a sticky honeydew, which allows the growth of black sooty moulds. Insecticides should be used regularly and thoroughly.