There are multiple pests that can have a negative effect on our crops and ornamental plants. One of these pests are aphids. Aphids are small insects that are considered pests around the world. They have a soft body, shaped like a pear, and depending on the species, they can be of multiple colors such as green, yellow, red, brown, etc. You can see them without a microscope, but they are still very small, meaning some people may have them on their plants and not notice them. They are always in large groups, and their population increases rapidly without proper control. Most of the species are identified depending on the host plant they are infesting.
What are their feeding habits?
Aphids have a piercing sucking mouthpart, which means they have a tube-like structure that they use to extract plant sap. They feed off young developing leaves, buds, and shoots of multiple plants. When aphids feed, they excrete a sugary waste product called honeydew. This substance can be damaging to the plants because a fungus called sooty mold grows on the honeydew. This black fungus will block light coming from the sun affecting photosynthesis. Also, some ants will protect the aphids so that they can consume this honeydew. The ants kill any natural enemy of the aphids, such as lady beetles which feed on the aphids, allowing the population of the pest to grow.
Why are they so numerous?
Aphids have a gradual metamorphosis meaning, they have 3 life stages: egg, nymph (smaller version of the adult) and adult. Although aphids can reproduce sexually, they can also reproduce asexually. Meaning they don’t need to mate to reproduce. That is why most aphids are female. When a female uses parthenogenesis (non-sexual reproduction) she will give birth to live young, and these new young will already be pregnant with the next generation of aphids. Therefore, aphids can increase their population rapidly. After a few generations in a host plant, some aphids will develop wings and fly to another host plant where they are going to mate, and the reproduction cycle repeats again.
How can they damage my plants?
Plants that have an infestation of aphids can present symptoms like wilting, water stress, reduced growth, and reduced crop yield. As mentioned before, the presence of sooty mold can negatively affect the process of photosynthesis.
One of the biggest concerns of aphids is that they are vectors of diseases. Both nymphs and adults can transmit viruses, but the adults spread diseases more rapidly because they can move better around the host plant. These viruses can vary among species, but some of the viruses’ aphids transmits are mosaic viruses, carrot virus Y, Papaya ringspot virus, etc. These viruses are transmitted when the aphids used their piercing sucking mouthparts to extract plant sap. Plant juices are extracted, and viruses are introduced into the plant.
Managing Aphids populations.
The use of Integrated Pest Management (IPM) can be used to control aphids. IPM is the combination of all elements a person can use to control or suppress a pest. The first step in IPM is pest identification. Once the pest is identified, it is important to monitor the pest’s populations. If a small amount is presence and no major damage is observed, IPM may not be needed to control or suppress the population. On the other hand, if you monitor an increase in population and possible damage then control will be needed.
Aphids have some natural enemies that can help to control and suppress their population. Insects such as lady beetles, lacewings and parasitic wasp are examples of biological control that farmers or homeowners can use to suppress the aphids’ population. Some companies sell such insects with the purpose of controlling pests on crops. Other examples of control are traps and barriers (mechanical control), sanitation (cultural practices), and the use of plants that are more resistance to aphid’s damage (genetic control).
Aphids are insects, so the use of insecticides is adequate for their control (chemical control). There are numerous pesticides for aphid control. Some of these are systemic pesticides, which are effective for aphid control because of their ability to move across the plant, meaning that no matter where the aphid’s location is in the host plant, if the pesticide is applied correctly, the aphids will probably be exposed to the pesticide. In the end, the insecticide to use will depend on the host plant and personal preference of the applicator (following label instructions), but timing is essential to control aphids. Nymphs are easier to control than adults and eggs, and smaller infestation are easier to control than larger infestations.
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