White Mealybugs On Plants: How To Get Rid Of The Cottony Mealybug

Today we will talk about one of the most common pests of horticultural and fruit trees: the cottony cochineal, cotonet or «flour mealybug». As we will see, there are several types of mealybugs of different shapes and sizes, but today we will focus on those peculiar little white bugs, with the appearance of bits of cotton.

We will see what the cottony mealybug is, what the damage of this pest is, and the best insecticides for mealybugs and ecological remedies that prevent and help eliminate the cottony mealybug on plants.

What is the cottony mealybug

There are several types of mealybugs. In the first place, it is worth distinguishing between what are known as «ball bugs» or sow bugs, which are crustaceans, and coccoids or scale insects, those bugs that stick to the stems and fruits of plants, which are homoptera (in the case of the cottony mealybug, of the pseudococcida family). We will talk about the latter today.

There are thousands of species of mealybugs or scale insects, of different shapes and colors, but today we will focus on one of the most common types of pests in the garden: the cottony mealybug or white mealybug. (There are also other coccoids that are quite common, such as the ribbed mealybug, which is also white, or the waxy mealybug, but we’ll leave these pests for another blog article).

Cottony mealybugs are insects that move very little and have a body covered by a kind of white wool or dust that protects them, so they are quite easy to recognize despite their small size.

As you can see in the photos, where you can compare their size with the thickness of a pencil, these white bugs are very small, barely measuring about 3 millimeters.

The mealybugs that become pests of crops are the females, since the males (different in appearance and with wings) do not feed during their adult lives and live for a very short time, only until they mate with a female.

After laying, in which a single female can lay hundreds of eggs, the female mealybugs move around on their little legs until they find a good place to settle. It is in that place where they will remain sucking the sap of the plant practically the rest of their life (from 1 to 2 months). Before they die, they will mate with a male and the cycle will begin again.

What plants does the cottony mealybug attack?

The plague of mealybugs can affect both outdoor and indoor plants.This pest is very common in citrus fruits such as lemon or orange trees, so be careful if you have these fruit trees in your garden because they could harbor mealybugs that can spread to the rest of the plants in the garden. Mealybugs can also appear on other fruit trees such as apple trees, banana trees, pomegranate trees, fig trees or vineyards.

Also be careful if you have a small garden, because mealybugs are very common on ornamental plants such as cacti, palm trees, conifers and also on some flowering plants such as rose bushes, geraniums or oleanders.

Among the plants in the garden, mealybugs mainly affect cucurbits such as cucumbers or melons and solanaceous plants such as aubergines, peppers and tomatoes. It is also very common in some aromatics such as rosemary.

Symptoms and Damage of Mealybugs on Plants

The main damage caused by mealybugs is that, by penetrating their biting-sucking mouthparts and absorbing the sap, they weaken the plants, and may even lose their leaves and fruits, if the attack is serious and continued over time. They will fade and fall to the ground.

In addition, the substance secreted by mealybugs (molasses) can attract other pests such as ants, and is also the perfect breeding ground for the appearance of one of the most dangerous fungi in the garden, the bold. The bold is a fungus whose symptom is a black or grayish powder that covers the leaves and that will prevent the plants from carrying out photosynthesis correctly, and can die in a short time.

How to combat the cottony mealybug

Below we will see some ways to prevent mealybugs in the orchard and in the garden (because prevention is always better than cure…) and some of the best ecological treatments for mealybugs, such as home remedies, insect traps or biological control.

The most effective ecological methods to eliminate a cottony mealybug pest if we already have it on our plants.

Prevent the appearance of mealybugs in the orchard

As we always say, the most important thing for integrated pest control is prevention. We must be aware and monitor crops often to prevent harmful insects from multiplying and becoming pests. If you find mealybugs on your crops, try to manually remove them with a cotton swab or cloth soaked in alcohol before it’s too late.

Also, here are some ways to prevent mealybug:

• Keep away and control ants, as they can often carry mealybugs. In addition, the molasses or sweet and sticky substance that mealybugs secrete (it is clearly seen in the second photo above) also attracts ants, so if we see them in the garden we must be alert.
• Avoid excess moisture. Through, for example, the use of localized irrigation that does not wet the aerial part of the plants or by pruning to favor aeration in the most leafy crops.
• Maintain hedges and flowers in the garden that attract or harbor beneficial insects (such as the natural enemies that we will see later).
• Placing traps or capsules of sexual confusion pheromones specific for mealybugs that attract and capture them before they colonize the plants.
• Place yellow chromatic traps, where the male cochineals will stay stuck and thus prevent them from mating with the females and giving rise to another generation.

How to eliminate the cottony mealybug with ecological remedies

Biological control or, what is the same, the use of natural enemies of pests, is one of the best methods to eliminate mealybugs from plants. These insects feed on mealybugs or parasitize them, thus helping us to eliminate the plague. Some of the natural enemies of the whitefly are:

• Trichogramma wasp: its larvae feed on cottony scales (and also on aphids, another common garden pest).
• Ladybug Cryptolaemus: as we have already seen in other Agrohuerto articles, ladybugs are one of the most desirable beneficial insects in the garden, since these insects feed on such common pests as aphids or mealybugs. It can be a very good idea to catch some and build a shelter for beneficial insects.
• Leptomastix dactilopii and Anagyrus pseudococci: these are parasitoid wasps that lay their eggs inside mealybugs and, when they hatch, the larvae kill the plague because they feed on them and grow inside them.
• Cryptolaemus montrouzieri – This friendly beetle is one of the most effective predators or natural enemies to eliminate the cottony mealybug pest from plants.

Frogs and toads in the garden are also good predators of the cochineal, so if you have a pond nearby, do not hesitate to take advantage of this utility.

Another way to eliminate mealybugs is by applying natural or ecological insecticides. The natural remedies for mealybugs that we can apply to plants are:

• Neem tree oil
• Paraffin oils and other mineral oils, such as the well-known «summer oil». (Caution: it can be applied as long as the temperature does not exceed 30ºC and sulfur has not been used to control other pests in the last 40 days).
• Potash soap
• Powder or diatomaceous earth

These are just some of the treatments for the cottony mealybug. If you know other tricks or natural remedies to eliminate mealybugs from plants in an ecological way or you have experiences or anecdotes about this pest, do not hesitate to share it with everyone in the comment thread below, where you can leave your photos and comments about the treatments. for cottony mealybug.

References

1. Martínez Ferrer, MT, 2003. Biology and control of the cotton wool Planococcus citri (Homoptera: Pseudococcidae) in citrus orchards. doctoral thesis Polytechnic University of Valencia (Spain).
2. O’Farrill-Nieves, H. & Medina Gaud, S., 2007. Common garden pests, identification and integrated management. University of Puerto Rico, Agricultural Extension Service.
3. Jacas, JA & Urbaneja, A., 2010. Biological Control in Citrus in Spain: From Classical to Conservation Biological Control. Integrated Management of Arthropod Pests and Insect Borne Diseases, vol. 5, p. 61-72.
4. Moreno Salmerón, J. 2011. Prospecting and identification of cottony mealybugs (Hemiptera: Pseudococcidae) and search for associated parasitoids in protected horticultural crops in western Almeria. Final Year Project for the Degree in Agricultural Technical Engineering, University of Almería (Spain).