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Tag Archives: agricultural pest

Controlling Whiteflies

All whiteflies suffer from somewhat of an identity crisis, as they are not flies at all. Their tiny, white appearance resembles moths, but they are, in fact, most closely related to sap-sucking aphids. Aphid-cast skins are easily mistaken for that of the whitefly, but whiteflies will quickly fly away if disturbed.

The fact that they hide on the undersides of the leaves, coupled with a quick flight pattern, makes them challenging to manage. Whiteflies are also fruitful because their numbers rapidly increase from two to four, four becomes eight, eight becomes 16, and so on. During the hottest weeks of summer, whiteflies may mature from the egg stage to a reproductive adult in as little as 16 days.

Damage

Whiteflies cause two types of damage to a plant, the first being direct. Whiteflies seriously injure plants by extracting juices from them, causing leaves to yellow, wither, and fall early. If the number of whiteflies per leaf is significant enough, it could lead to plant death. The second, or indirect, happens by way of adult whiteflies. They are able to transmit several viruses from diseased plants to healthy through their mouthparts.

Whiteflies (again like aphids) excrete “honeydew,” which is a sweet substance that forms a sticky coating on leaves. A fungus called “sooty mold” also quickly colonizes, which makes leaves look dirty. Generally speaking, sooty mold is harmless except when it is incredibly expansive, thus preventing light from reaching the surfaces of leaves, which stresses the plant. Sooty mold washes off easily with a forceful stream of water on sturdy plants.

Detection

Like many insects, whiteflies have nymphal and adult stages. Females lay their eggs in arcs or circles on the underside of the leaves that they spend their entire life cycle on. Whitefly nymphs have wingless, oval bodies and no apparent legs or antennae. The adults that emerge from mature larvae are winged and look like a very tiny moth.

Prevention

  • Attract beneficial enemies to your garden.
    • Plant a wide variety of flowering plants or individual insectary plants can provide beneficial insects with the habitats they require. Natural enemies of whiteflies are spiders, small birds, lacewings, ladybugs, and big-eyed bugs.
  • Scrutinize new plants. Make sure you aren’t purchasing infected plants.
  • One way to detect an invasion early is to hang sticky traps above the plants at the beginning of the season.
  • Use slow-release, organic fertilizers.
    • Maintain healthy plant growth, but make sure you do not over-fertilize with high nitrogen fertilizers. Too much nitrogen can overstimulate lush plant growth, prompting aphids to reproduce more quickly. Organic fertilizers are superior because they slowly release the proper levels of nutrients.
  • Avoid excessive pruning
  • This stimulates whitefly-attracting growth.
  • Use a row cover to exclude whitefly and other pests while still allowing light, air, and water to reach all plants.
  • Control ants by painting or spraying a 4″ wide sticky barrier around woody shrubs or trees.
    • For many sensitive trees, such as citrus, apply a protective barrier of white latex paint to the trunk before the sticky wall.

Less-Toxic Control

  • Use a syringe of water on the undersides of leaves on sturdy plants to wash off whiteflies and honeydew.
  • Use a vacuum to suck up whiteflies in the early morning when they are cold and slow-moving.
    • After vacuuming, empty into a sealed plastic bag and remove it from the premise.
  • Prune away any severely infested portions of the plant.
    • Place and seal material in bags and remove them from the premise.
    • Dispose properly and do not compost.
  • Use insecticidal soaps to kill whiteflies while causing the least harm to beneficial insects.
    • Even coverage of the underside of leaves is essential for effective use. These products do not leave toxic residues, sparing injury to the natural enemies.
  • Use spray (horticultural) oils to control whiteflies minimizing adverse effects on natural enemies.
  • To protect bees, avoid applying imidacloprid during the period one month before or during bloom. Removing blossoms before they open on young trees will prevent honey bee exposure to imidacloprid in the nectar/pollen.

Garden Pests

Spring is an exciting time for everyone, but especially gardeners. The time to begin their yearly botanical endeavors is quickly approaching. However, it is not all smooth sailing no matter how skilled of a gardener one is— there are dangers in the form of garden pests lurking around the corner. Garden pests lay in wait for your new plants to begin growing, which when they’ll come out in full force, hungry from winter dormancy. By diligence and taking preventative action, you can stop these pests from wreaking havoc on your garden.

Aphids

Aphids can come in many colors and species, all of which can cause damage to your plants. These pests use their piercing mouthparts to feed on plant sap and juices. They can be found feeding in groups on new plant growth or the undersides of leaves, which kills them, as well as stems and buds. An aphid infestation can actually be exacerbated by over-fertilization with nitrogen. The plants most affected by aphid damage include geraniums, roses, tomatoes, peppers, lettuce, carrot crowns, kale, and cabbage. You can plant certain herbs that will attract wasps, who prey on aphids, to help control an infestation; however, spraying them off with a garden hose is most effective.

Corn Earworms

Corn earworm is a pest that migrates to Michigan every year carried on weather fronts; it overwinters in the southern United States, where it is also a pest of cotton and soybeans. Aptly named, corn earworms feed on ears of fresh corn. These worms are the biggest threat to sweet corn in Michigan because once they enter the ear, they become impossible to remove.

The worms attack corn silk, which results in moldy and deformed ears. Controlling corn earworms can be a difficult task that requires year-round vigilance.

Colorado Potato Beetles

Potato beetles have a yellow shell with ten narrow black stripes. In the spring, the females lay their eggs on the undersides of leaves.

When the larvae hatch, they feed on plant vegetation for 10-30 days before reaching adulthood. Potato beetles continue to feed on the foliage, which leads to the death of the plant. Use a floating row cover on potato plants to prevent these beetles from reaching the plants. Hand pick adults and larvae from the leaves and drop them into a cup of soapy water.

Cucumber Beetle

Cucumber beetles cause severe damage to crops like cucumbers, watermelons, and cantaloupe. These yellow-green beetles don’t limit the extent of their damage to feeding; they also cause bacterial wilt.

The bacterium that causes bacterial wilt lives in the stomachs of the cucumber beetles— in the spring when they emerge to feed, they spread the bacterium from their mouthparts and through their excrement. Once inside, the bacterium quickly multiplies which produces blockages that cause the leaves to wilt and die. The beetles unwittingly pick up the bacteria from the exterior of the plant and transfer it. There is, unfortunately, nothing that can be done to save a plant infected with wilt. Early preventative measures are essential to halt the spread of bacterial wilt. Cover crops with a row cover and remove as plants flower to help control these beetles.

No gardener wants their hard work to be compromised by garden pests. Knowing what to look for is the first step toward protecting the fruits of your labor!