Stop the slime

Plant Health Secrets: The Underground Playbook from SePro - Advertorial

Algae in the greenhouse creates hazards to plants and people. Learn more about the best solutions to treat and prevent algae infestations.

Photos courtesy of sepro

Greenhouses can provide the perfect environment for the cultivation of sensitive and exotic plants due to the ability to regulate light intensity, moisture, and temperature. However, the control of these conditions often leads to the growth of unwanted photosynthesizers – algae. This should come as no surprise given that algae are also plants who thrive under the higher temperatures and controlled lighting provided by the greenhouse. Algae can also take advantage of the nutrients that are supplied by the irrigation system or leach nutrients from the soil.

The excessive growth of algae presents a few different challenges to greenhouse growers. The first and most obvious drawback is that algae growth on the flooring can make the surface slippery, presenting a hazard. Some algae, such as those in the genus Cephaleuros (Cephaleuros parasiticus and Cephaleuros virescens) are parasitic algae which can infect and cause leafspots on a variety of important tropical greenhouse crops. A more subtle issue with algae is that it can harbor a variety of pathogens such as bacteria, molds, and viruses. Algae can be a source of nutrition for many organisms including plant pathogens and insects. Algae have more permeable membranes compared to most other plants, which allows for the easy diffusion and transmission of plant viruses. Additionally, because algae grow so quickly in greenhouses, they are often the first organism in a biofilm, which is a group of different organisms that live symbiotically in a slimy film that remains attached to a rough surface. Biofilms are notorious for harboring the worst offenders of greenhouse sanitation – pathogenic bacteria, mold, mildew, and plant viruses. With all things considered, algae might not seem so bad themselves, but they can be the ideal means to harbor pathogens that can spread disease to greenhouse plants. Therefore, algae management in greenhouses is the key to maintaining sanitary conditions and reducing disease pressure.

Thankfully, there are a variety of solutions to treat and prevent algae infestation in greenhouses, regardless of the location. Classic algaecides (or chemicals that kill algae) are copper based. Copper inhibits catalase, the enzyme that protects algae from the damage caused by free-radicals which are produced during photosynthesis. Therefore, algae treated with copper-based algaecides will self-destruct when they are exposed to light. In low doses, copper is not only compatible with greenhouse plants, but a micronutrient required for growth. However, at higher doses it can inhibit the uptake of iron and cause toxicity to sensitive crops. Additionally, many growers are restricted from using copper-based algaecides if they discharge irrigation water. Peroxide-based algaecides are a newer development which directly damage the algae by exposing them to the free-radical, hydrogen peroxide. Algae membranes are much more permeable and more sensitive to hydrogen peroxide than terrestrial plants, which contain cuticles that serve as protective layers. Unreacted hydrogen peroxide also quickly decomposes into water and oxygen, leaving no biproducts or residuals behind. Copper-based algaecides are generally more powerful and cost-effective than peroxide-based algaecides, so a good rule of thumb is to pick a copper-based algaecide when on a budget and when efficacy is a priority. Choose a peroxide-based algaecide when dealing with sensitive crops or discharging irrigation water. Both peroxide and copper-based algaecides can be used proactively before algal growth is visible or reactively to target active growths. Routine proactive algae management is critical for growers that want to maintain optimum hygiene to promote ideal conditions for the highest quality crops. Additionally, proactive algae management is generally more cost-effective because new growth is much more sensitive to the effects of both peroxide and copper and therefore much lower rates can be used with improved efficacy.

Copper-based Algaecides

Captain XTR

Captain XTR is the most powerful algaecide available on the market. Captain XTR utilizes chelated copper, which prolongs the algacidal properties of the product after it is applied. Some algae, including the cyanobacterium Nostoc, form dense mats and protective sheaths that can make them significantly more resistant to algaecides. Captain XTR is an algaecide that was designed to address this resilience and comes formulated with infusion technology to quickly deliver copper into the algae cell membranes. The combination of chelated copper and infusion technology make Captain XTR the go-to solution for thick mats of resilient algae.

Algae can quickly destabilize a greenhouse and bring a variety of diseases with them.
Red rust lesion on the upper leaf surface of a Neoregelia hybrid caused by Cephaleuros parasiticus.


SeClear is the only EPA approved algaecide that also binds nutrients and prevents the regrowth of algae after the algacidal effect subsides, when the copper is bound up or washed away. SeClear comes in both liquid and granular formulations (SeClear and SeClear G). SeClear is the ideal solution for the growers who frequently see algae regrowth a few weeks after they use algaecides. In can be used in combination with Captain XTR. This allows for both the infusion technology to penetrate tough mats and the nutrient binding properties of SeClear to keep the algae from regrowing, saving time and labor.

Peroxide-based Algaecides

Leaf spot lesion on the upper leaf surface of Psidium guajava (guava) caused by C. parasiticus.


Phycomycin is the industry leading granular peroxide-based algaecide. It can be used in Chemigation, mixed into water before application, and applied as a powder to target thick algae mats or used for sustained release. The fast-acting oxidation reaction is effective against a broad range of algae including filamentous and planktonic blue-green algae, bacteria and fungi.

Oximycin P5

Oximycin P5 is the most innovative solution to date, with a formulation that kills on contact. This provides the algacidal power comparable to a copper-based formulation, but with the crop safety of a peroxide-based algaecide. Oximycin P5 is a liquid formulation with enhanced stability that is easy to apply and can be used in chemigation, diluted into water before application, or used directly in spot treatments.

Algae can quickly destabilize a greenhouse and bring a variety of diseases with them. Fortunately, SePRO has solutions to combat existing algae and prevent future algae from wreaking havoc on your greenhouse – liquids and ready-to-mix solids, both copper and peroxide-based products, as well as formulations with nutrient binding properties to keep algae from coming back. The range of powerful treatment options with excellent crop safety makes algae management an easy way to improve the health of crops, no matter what you grow.