Mitigating Plant Pests and Plant Disease With Stonewool Grow Media

Posted on August 3, 2021 by Red Rock Block

Nipping Plant Pests and Disease in the Bud: Tips for Control When Growing With Stonewool

Top 5 Most Unwanted Pests in Hydroponics and Stone Wool and How to Control Them

In the commercial greenhouse industry, not everything is sunshine and green. Lurking in the leaves of crops, roots, and other areas of the growing area may be a vicious pest waiting to prey upon unsuspecting and vulnerable crops. The top five most unwanted pests in a greenhouse are aphids, whitefly, spider mites, fungus gnats, and thrips. Even the most secure growing facility will have a bout of at least one of these criminal pests at some point. The question is, what hydroponic systems where there is no traditional growing media? Stone wool is sterile and clean. Can these pests still infiltrate the greenhouse and thrive? The answer may alarm a grower, but yes. The important thing is to know how to spot them, control them, and prevent them from spreading and becoming a major problem in the growing area.

Pests and Hydroponics-

There is a belief that pests can only really thrive when there is soil involved. Especially those that love to attack the root zone and lower vegetative levels of a plant. However, stone wool can have its fair share of pests that a grower will need to deal with throughout a growing season even with a great integrated pest management plan in place.


Aphids can be serious pests in the greenhouse as they are very persistent and can reproduce at very alarming rates. Aphids are also able to resist many traditional methods of chemical control and can become a very difficult problem to control during a growing season. Aphids are a sucking insect and damage crops through damaging tissues and draining plants of sap. Signs of aphids in a growing area are curling and distortion of young, new vegetative growth. If there is a high presence of nitrogen in fertilizers, recent transplanting of crops where plants become stressed, or other forms of stress on the plants aphids will appear.

Aphids can come in on young plants at the start of a growing season, through contact on clothing from the outside, or in the media. There are several forms of control for aphids in the greenhouse that range from chemical to organic. Spraying leaves with a mild solution of oil beating cleaner and water or introducing lady bugs into the greenhouse will adequately control aphid populations. At the end of each growing season, it is important to clean and sanitize all areas of the greenhouse including equipment, as well as having a short resting period before bringing plants in for the next cycle. This will help prevent the spread of aphids from season to season.


Whiteflies love to hang out in the vegetation and above the media. These white, small, moth-like insects can be spotted easily through rustling vegetation. Whiteflies are problematic at all stages of growth from larvae to adults. These pests like aphids, pierce the tissues of plants and suck the sap from the plants. Signs of whitefly beyond seeing the pest in the air or leaves, is the yellowing of plant leaves, a presence of a black sooty mold, and in extreme cases stunting and shedding of the leaves. Some key prevention methods to control whitefly population is through maintaining a weed free environment and monitoring the grow area and entry points. This includes inspecting new plants before they enter the facility, and monitoring HVAC systems. Inspecting the undersides of leaves for eggs and stealthy adults is also a method of control.

Fungus Gnats

Fungus gnats are difficult to control once established, but there is good news. Once the insect has reached the adult stage, they will not harm the crop. The issue with the gnats is the larvae. These infant gnats will prey upon the roots of plants and cause damage that will negatively impact the growth of the plant. Roots are one of the most important parts of a plant’s health. When these are not healthy, a plant will not flourish. These gnats can also carry soil-borne pathogens and bacteria that can further damage a crop if left unchecked. These insects flourish in damp and humid places where fungi can easily grow. The feeding wounds left by the larvae will also allow for soil borne pathogens to infiltrate a plant causing further health problems. One of the best approaches to controlling fungus gnats is through sanitation practices that eliminate the breeding grounds of the gnats. Standing water should be avoided if possible and the control of algae is essential. Just like whitefly control, the inspection of new plant material entering the facility will also help in preventing these gnats from infiltrating the greenhouse.

Spider Mites

Spider mites could be placed at the top of the most unwanted list because they are regarded as one of the most dreaded of pests in a hydroponic operation. Spider mites are super small- smaller than whiteflies and can easily go unchecked until a major infestation occurs. These mites stay under leaves where it shelters them from the sunlight and maintains a proper moisture level. Mites have a very quick life cycle and have a wide range of plants they like to munch on. The signs of a mite infestation vary depending on the specific species of mite but yellowing of the leaves or deadening of the leaves can occur with any mite. Spider mites can be controlled through chemical applications or through organic means. Conventional methods include the application of abamectin or bifenazate. One of the most common biological controls of mites is using a predatory mite known as Phytoseiulus persimilis.


Thrips can be found in growing areas that are primarily broadleaved evergreens such as citrus plants, avocados, and other ornamentals. Adult greenhouse thrips are black with white wings and legs, while the larvae and pupae are a pale yellow to white with red eyes. Signs of thrips in the greenhouse are tiny black pots on leaves and buds and leaf stippling. By using a microscope of a leaf with black spots or a magnifying glass, the presence of thrips can be confirmed. To control thrips in a greenhouse, the removal of injured vegetation or areas of a plant will help. Thrips on flowers can be eliminated as soon as signs of damage can be seen using a mild insecticide soap or neem oil. In extreme cases, the removal of the flower bud may be necessary.

Ways to Prevent an Infestation

Prevention is the best measure in the control of pests through an integrated pest management plan or IPM. There are several good practices that can help reduce the occurrences of pests in a greenhouse. Going a full growing season without a single pest is unheard of, however, instances of infestations can be controlled though prevention. A lot of good practices involve a working knowledge of the pests, and a huge dose of avoidance practices.

General Practices

There are several general practices that should be practices in all greenhouses regardless of the type of operation. These practices will greatly reduce the instances of pests in a greenhouse operation. The first is not going into a growing area dirty. Workers should be free of debris and should always wash hands before entering a growing area. If boots or shoes have media or other plant materials on them, these should be cleaned before entering a new area. In areas where sanitation is critical such as hemp facilities, workers may need to don suits over their work clothes.

The second approach is using a sanitized and clean system and growing media. In between growing seasons, all equipment and tools should be washed and sanitized. When working with stone wool, going with sterile and high-quality material is essential as it will be free from pathogens. Thirdly, entry points need to be monitored to ensure no pests or disease enter a growing area. By inspecting plants and equipment that enter a greenhouse before they enter the growing area ensures that pests do not make it through the door. Think of it like vampire pests. They can’t enter if you don’t welcome them in. Lastly, vulnerable crops such as those that are newly germinated, transplanted, or injured should be monitored closely and protected. These are the best targets for pests.

Hydroponic Practices

In addition to those mentioned in the general practices, hydroponics requires the control of humidity levels. Hydroponics use running water and has moisture all the time. This is very inviting to pests. However, if the humidity is controlled, they will be least likely to stay or survive. Constant monitoring of humidity can be done through the installation of monitors and through best watering practices.

For more information on pest control or stone wool inquiries, be sure to reach out to one of the many experts at Red Rock Block with decades of combined in industry experience. Call- 1-310-967-2025


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