Aphids on Sunflowers

Sunflowers

• Sunflowers (Helianthus annus) are widely used in gardening and as freshly cut flowers. The flowers are available in a number of styles and sizes, and make excellent and hardy additions to the garden. Helianthus varieties are natives of Central America, but are now available around the world. To thrive, plant them in a sunny location with well-draining soil and balanced nutrition.

Identification

• Aphids are small, though they are visible to the naked eye. They come in a number of colors, including green, yellow, red and black, and their colors often vary, depending on the species of plant being eaten. They have pear-shaped bodies that may have a furry or sleek texture, and some species have wings, while others don't. All species have a functionally modified jaw called stylets, which aid in helping them feed, and serve to damage plant foliage.

Damaging Effects

• Aphids feed on the sap of sunflowers, obtained by ripping open foliage on the cellular level. When present in low numbers, aphids are not a serious problem. When the population grows, they take over the plant and damage it. Early symptoms include leaf curling and discoloration, usually yellow or brown. Some species produce a toxin, which stunts growth when injected into the plant. Aphids may spread viruses from infected plant to uninfected plants, which may cause more crop losses.

Natural Enemies

• One of the easiest ways to prevent aphid populations from becoming a problem is to introduce a few of their natural enemies to the garden. This is an especially important step in gardens that aren't sprayed with pesticides. Lady bugs, though not their primary enemy, are easy to bring into the garden to eliminate aphids. Additionally, parasitic wasps, crab spiders and lacewings are all important steps in controlling aphids. Aphids are susceptible to a few fungal diseases, particularly during humid times of year.

Control Methods

• Sunflower growers should look into chemical and cultural methods to control aphid populations. These are often the most effective ways to keep these pests from ruining a crop. Remove any weeds, fallen leaves or other debris where populations may begin. In the early stages of infestation, before the population spreads, growers should remove infected leaves as soon as possible. Excessive amounts of nitrogen encourage aphid reproduction. Nitrogen content may be adjusted by utilizing a less-soluble form of nitrogen. Time-released organic fertilizers are available to eliminate this problem. In small spaces, a thorough dose of insecticidal soap over infested foliage is ideal for getting rid of aphids. For larger crops, a dose or two of insecticide may be necessary. Either option provides long-term protection against aphid problems.