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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