Spring Insects – Scale

Scale insects – so called because that’s what they look like. The young insects are small, soft-bodied and mobile. When the eggs hatch the young, six-legged scale insect “crawlers” disperse throughout the new tissue seeking suitable sites in which to feed. They attach themselves to the plant with long, threadlike mouthparts (stylets) which are six to eight times longer than the insect itself. Once attached, they lose their legs and antennae, and begin to secrete a waxy layer over themselves.

The immobile, “shell stage” of scales are adult females; males are small, fly-like and infrequently seen. Scale insects can be basically divided into two groups: soft scales and armored scales. Soft Scales generally secrete an attached, thin, waxy layer over themselves. The soft covering they secrete cannot be separated from the scale’s body. Soft scales typically move between branches and leaves during their lifecycle. Armored Scales shed skins and wax that is unattached to their body to form their hard, shell-like cover. These covers can be separated from the scale’s body. Hard scales typically do not move to leaves during their lifecycle. Most species of armored scales overwinter as eggs beneath the female cover. In spring, these eggs hatch into tiny mobile crawlers which migrate to new feeding sites.

Scale insects feed on plant sap slowly reducing plant vigor. They can occur on leaves, twigs, branches or trunks. Heavily infested plants grow poorly and may suffer dieback of twigs and branches. Their small size and general lack of mobility make them difficult to notice by the casual observer. Large colonies remove substantial quantities of plant fluids and cause wilting, but seldom kill their host.

As Scale insects feed on plant sap they secrete a sugar-rich sticky liquid called honeydew. Armored scales do not produce honeydew. This honeydew serves as food for ants and wasps and supports the growth of black sooty molds. It often falls on leaves or needles, branches, fruits or anything else immediately underneath the infested area of the plant. The sooty mold fungi grow on the honeydew.Sometimes plants not actually infested by insects may be affected if a tree above them is being attacked by a honeydew producing insect and the honeydew drops onto them.

Scale insects can be controlled by using dormant oil treatments generally applied in very early spring, before bud break. Summer oils can also be very effective but some plants are sensitive to these treatments. Check labels to make sure your plant is not harmed by the treatment you are considering. Many other insecticides, including insecticidal soaps, can be used only against the mobile crawler stage of scales since adult scales are protected from insecticides by a waxy covering. Natural enemies to scale include tiny parasitic wasps and predators such as ladybugs. It is very common for ladybugs to move onto a plant with a growing scale infestation; before deciding upon a treatment, look for adult and immature ladybugs on your plants.

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Spring Insects – Aphids

Warm winters are is to blame for an early onslaught of pest in the summer. A plethora of pests can survive warm winters. Some of the most common insects are scale, whiteflies, Lace bugs, garden aphid, Leafminers, and Japanese Beetles. Some of the most prevalent diseases affecting plants this season are black sooty mold and black spot.

We have posted information to help you define and eliminate your pest problems. Three posts are already available to help you. Check these out:

Let’s begin this series with one of the most common garden pest insect, Aphids!

What are Aphids

Aphids feed on both garden crops and ornamental plants. There are around 250 species that in essence “specialize” in feeding on different types of plants, everything from pine trees to your strawberries. Aphids may be green, yellow, brown, red, or black depending on the species and the plants they feed on. They vary in length from 1 to 10 millimeters. The basic mug shot of an aphid shows a plump, pear-shaped body and two tubes, or cornicles, which project from their abdomens. Most adult aphids are wingless, but many species also exist in winged forms, especially when populations are high or during spring and fall. This provides the pest with a way to disperse to other plants when they run out of food.

Aphids feed by using special mouthparts to pierce plant tissues and suck the sap out of tender plant shoots and leaves. Their feeding causes leaves and stems to become distorted and cause wilting and sometimes even dieback of shoots and buds. This distorted growth may be mistaken as herbicide injury. Aphid’s ability to transmit plant virus diseases may be more harmful to some plants than any direct feeding damage.

Aphids feed in colonies, part of the reason that they are so destructive. Generally, if you see one aphid, there are lots more to be found as well. Aphid populations are largest during the spring, on the flush of new growth. During this time these insects excrete large amounts of a sticky, sugary substance commonly called “honeydew”. The excreted honeydew coats leaves, stems, and fruit, stimulating the growth of sooty mold. With a big enough infestation of aphids, leaves below the aphid colony begin to grow fungi from the aphid honeydew, this is black and brown in color and called sooty molds, these molds cover leaves and other objects below aphid colonies where the honeydew collects. To get rid of the sooty mold requires getting rid of the aphids.

Aphids often work in a symbiotic relationship with ants. Some species of ants “farm” aphids, protecting them on the plants they eat, eating the honeydew that the aphids release. Some species of dairying ants manage large “herds” of aphids that feed on roots of plants in the ant colony. Queens that are leaving to start a new colony take an aphid egg to found a new herd of underground aphids in the new colony. These farming ants protect the aphids by fighting off aphid predators.

Aphids are unlike most insects in that the large majority are female which reproduce without mating; and many seldom lay eggs, but give birth to living young.

How do I control Aphids?

Early detection is the key to reducing aphid infestations. Small numbers of individual colonies on small plants can be crushed by hand or removed by pruning as they are found. In some cases, this may provide adequate control. Insects that attack aphids include predatory lady bugs, hoverfly larvae, parasitic wasps, aphid lions (the larvae of green lacewings), crab spiders and lacewings.

Most products used for aphid control work as contact insecticides. This means that the aphids must be hit directly with spray droplets so that they can be absorbed into the insect’s body. Sevin is not effective against many aphids so it is generally not a good choice for control unless recommended specifically. In fact, applications of Sevin may reduce the number of beneficial insects, such as lady beetles, and increase the potential for aphid outbreaks. You can kill aphids by spraying, especially under the leaves, with a solution of 2 tsp mild dish or laundry soap to a bottle of luke warm water. The soap washes off the aphid’s protective waxy coating and causes dehydration. You can also mix three parts luke warm water to one part vegetable or horticultural oil and a couple drops of dish soap.

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