The vampires of the insect world

The brown marmorated stink bug has become a pest in recent years. It gets its food by injecting leave and buds and vegetation and extracting the nutrients. Insects with mouthparts that allow them to pierce and suck are the vampires of the insect world; they have mouthparts that enable them to pierce the plant and obtain their nourishment by siphoning off water, sugars and other nutrients. Some have chemicals in their saliva that enable them to liquefy plant tissue so that it can easily be consumed.

The piercing and feeding activity can impact the health of the host plant. In some cases, the damage inflicted on the plant is merely cosmetic, resulting in no serious damage. In others, the feeding activity will remove enough water, nutrients, and fluids to stunt a plant’s growth and development, impact the development of fruit and flowers, or cause early leaf drop. Sometimes these insects can spread disease from an infected tree to a healthy one, which can damage or even kill the host plant.

Here are some of insects that impact trees by piercing and sucking activity:

  • Hemlock wooly adelgid: This insect has severely impacted hemlock stands throughout the eastern part of its range. The wooly Adelaide attaches to the smaller twigs and needles to suck the juices of the tree, causing the general defoliation and death of this evergreen within 3-7 years. During periods of hot dry weather, the weakened hemlocks can also be attacked by mites and hemlock scale insects which speed up their demise. Many of the hemlock groves that have sheltered cold water trout streams in our county have declined to the point of rising water temperatures in these streams, to the detriment of the trout populations. There is an active program nationwide to restore hemlocks to their native range by controlling the adelgid with insecticides, introducing beetles that feed on them, managing the forest to encourage hemlock growth, and replanting strains of hemlock that are resistant to the adelgid.

  • Aphids: Aphids are small sap-sucking insects that, on a global scale, are one of the most damaging groups of insects of crops, ornamentals, and trees. There are nearly 5,000 species of aphids identified around the world. These insects reproduce in great numbers and have multiple generations throughout the growing season, with some of the greatest reproductive potential of any insect. Aphid feeding can result in stunted growth, browning of foliage, mottled leaves, wilting of plant part, gall formation, and the spread of disease from one infected plant to another. As part of their metabolism, aphids excrete a sticky substance known as “honeydew. “ Honeydew can cover the tree, lawn furniture, automobiles, or other plants with a gooey mess. Sometimes parasitic fungi and molds can grow on honeydew, spreading these diseases to other plants. Some ants will actually herd aphids and direct their honeydew production to obtain this material for food. Aphids generally have soft bodies and they serve as a food source for many birds, animals, and other insects. The ladybird beetle is a celebrated predator of aphids. When attempting to control aphids, it is wise not to apply an insecticide that kills all of the natural controls, because in the absence of predators, the bountiful aphid will take over, given its enormous reproductive potential. White pine aphid is an insect that attaches to the trunk and branches of white pine, giving heavily infested trees an almost whitewashed appearance. White pine aphids seem to build up in dense pine plantations where airflow is limited. This insect causes a general decline in tree vigor but it normally does not result in the death of the pine tree.

  • Scales: Scales are small, mostly immobile insects that attach themselves to plants and feed on the sap of the host. There are nearly 300 species of scales found in our region and they are very common, although sometimes their small size does not make them very noticeable.

  • Scales produce an outer barrier that helps provide them protection. There are two families of scale insects: the soft scales and armored scales. Soft scales produce a waxy substance as protection. This outer coating is directly attached to the body. Armored scales produce a hard, shield-like cover composed of shed skins and wax that conceals, but is not attached to the body. Scales hatch from an egg inside the protective covering, then the young nymph, also called a crawler, leaves the shell, striking out on its own. Once the crawler finds a suitable place to feed, it inserts its stylet into the plant and begins developing its covering. Female scales remain immobile from this point on, while the male develops wings at maturity and strikes out to find a mate. The feeding activity of scales causes discoloration, leaf color change, and a stunted or weakened appearance to the host plant, dieback, and sometimes it results in the death of the plant, although this is not very common in large trees. Some scales produce large amounts of honey dew which can create a sticky mess and spread diseases among plants, especially sooty mold fungus. Some of the more common armored scales found in this region include pine needle scale, hemlock scale, oyster shell scale, obscure scale, and San Jose scale. Some of the more common soft scales include cottony maple scale, lecanium scale, Indian wax scale, tortoise shell scale, and mealy bug scale.

  • Lacebugs: Lacebugs get their name from the delicate appearance of their body. There are nearly 2,000 species of lacebug worldwide, and these insects tend to be host specific. Lacebugs usually feed on the underside of a leaf, causing leaves to turn bronze to silver. If you notice leaf discoloration on a plant and turn the leaf over, you may see lacebugs at work. Observe the holes they made or their fecal matter on the underside of the leaf. Lacebug damage can be seen on oaks, hawthorn, rhododendrons, and especially azaleas.

  • Spittlebug: Spittlebugs are not very harmful to large growing trees. These insects normally attach to a plant, live inside, then excrete a frothy spittle substance. Spittle bugs are very common in white pines, their spittle very distinct during late May and June in this area.

  • Leafhoppers: Leafhoppers are one of the largest and most diverse groups of insects, with nearly 20,000 species identified worldwide. Leaf hoppers are general feeders that quickly move among plants, briefly stopping to feed. Most leafhoppers have very large back legs in proportion to the rest of their body that they utilize to jump. Leaf hopper feeding activity does not normally damage plants. It is the spread of disease by leafhoppers that causes the greatest damage. Two serious diseases of local trees are spread by leaf hoppers, elm yellows, and bacterial leaf scorch.

  • Stink bug: Not only is the brown marmorated stink bug a general nuisance, its feeding activity is impacting many agricultural crops and local orchards. This feeding deforms leaves and buds, stunts growth, ruins crops, and has the potential to spread plant disease. After stinkbug injects its stylet and begins feeding, it injects its saliva which denatures the tissue, causing a general pitting or scarring.

  • Spider Mites: Spider mites are not insects; they are members of the arachnid family. Spider mites are very tiny creatures that feed on the sap of various plants, causing many of the aforementioned problems. Spider mite populations generally increase during hot dry periods, and their damage seems to intensify during the dog days of summer. Spider mites attack a number of trees, especially hemlock, Alberta spruce, and other spruce trees. The use of a product that has mite-controlling properties is necessary to control these creatures; most common insecticides do not control spider mites

Article by FCFCDB member

Nature Note for 4/3/2016