Rowan (Sorbus): growing guide

Aphids are small, soft-bodied, pear-shaped insects (1/16 to 1/8 inch long) that feed by sucking nutrient-rich sap from plants. They reproduce rapidly and can quickly weaken plants, causing distorted growth and transmitting plant viruses. Aphids come in various colors including green, black, red, yellow, brown, and gray. They secrete honeydew, a sticky substance that attracts ants and encourages sooty mold growth.

Scale insects are small sap-sucking pests that appear as brown, shell-like bumps on plant stems and leaves. There are over 25 species, divided into armored (hard) and unarmored (soft) scales. They feed by piercing plant tissue and extracting sap, which weakens the plant and can lead to yellowing, stunted growth, and even death if left untreated. They also excrete honeydew, which attracts ants and promotes sooty mold growth.

Eriophyid mites (family Eriophyidae) are extremely small, worm-shaped mites that feed by piercing plant tissue and sucking out the contents. They live on young leaves, buds, and sometimes fruit. Typical signs include tightly curled or blistered leaves, felt-like patches (erineum), small galls, bronzing or rough “russeted” fruit skin, and stunted or distorted new growth. They do not make the obvious webbing seen with spider mites, and you often need a hand lens to spot them. Many ornamentals and edibles can be affected, including roses, maples, grapes, apples, pears, birch, and viburnum. Some species can also spread certain plant viruses (for example, on roses).

Spider mites are tiny arachnids (less than 1/20 inch long) related to spiders and ticks that feed on plant sap. They thrive in hot, dry conditions and can cause significant damage to ornamental and vegetable plants. During severe infestations, crop losses can reach 14% or higher as these pests disrupt vital plant processes including photosynthesis, carbon dioxide absorption, and transpiration.