Is your nutrient solution healthy part 2
This is part 2 of the following article: Is your nutrient solution healthy, Part 1
Problems with a generally trouble free hydroponic system happens to most growers on occasion. Algae growth is the most common and easy to detect in the nutrient reservoir. But problems can also be hidden down in the root zone where their not always obvious. Fungus gnat larvae (fly larvae), nematodes (microscopic worms) and algae are all hydroponic parasites. They take advantage the nutrients, the plants roots and the favorable growing/living environment to grow and multiply. They all can cause a great deal of damage to your plants. The microscopic nematodes and fungus gnat larvae can even do considerable damage to the plants roots in a hydroponic system without a grower even knowing that it’s going on. Recognizing these types of growing medium, root and nutrient problems is important, as well as planning and maintenance to prevent these parasites from settling in, in the first place.
Fungus gnats are small dark short-lived flies, with long legs and distinctive wings, the adults are 2-5 mm long and are weak fliers. Usually seen flying around the base of the plants, and around the growing media or foliage. The females lay their eggs in the moist growing media or potting soil. Then the larvae hatch and begin to feed on the plants roots system. In sufficient numbers they can cause significant damage to the plant root systems. They cause many crop problems by weakening the root system of a large number of plants. The larva are white or transparent with a black head. Most fungus gnat larvae feed on fungi or dead plants tissue in the growing media and/or soil, though some species also feed on the living tissue and will attack young seedlings or cuttings. Fungus gnats can also spread plant disease and pathogens in the media or soil.
Shore flies look similar to fungus gnats but live in, or on algae growth and/or on very wet, decomposing organic material. This is common in growing areas where conditions are damp. Shore fly larvae don’t feed on the root systems, but they are frequently confused with fungus gnats because they look similar and like the same moist soil/media conditions, so they often occur together. The adult flies are attracted to yellow sticky traps, but identification of fungus gnats and shore flies can be difficult because many species look similar.
Prevention of fungus gnats can be difficult but some things can help like screening of doors and vents, as well as reducing moisture of the media and organic material in the area. Also allowing the surface of the hydroponic media or substrate to dry out between watering cycles can help to prevent infestations. Also good drainage of growing beds and/or ebb and flow systems will reduce moisture. Removal of all the dead leaves and organic matter that has fallen onto the surface of the growing media will reduce the material that the fungus gnat larvae feed on.
Algae is a form of plant life and is usually green, but it can also be brown, reddish brown and/or even black in color. Algae naturally grows when exposing water with nutrients (that’s dissolved in it), with a light source. It sticks to the sides of the reservoir, inside gullies and channels. It also clings to pumps, tubes and even forms on the top of damp growing media. When in sufficient amounts algae usually has a moldy or earthy smell to it, especially when it’s decomposing in your nutrient reservoir. It can also clog emitters, return lines, drippers.
Except for it’s appearance and smell, algae also creates a problem with dissolved oxygen. As it grows dies and then decomposes it uses up the dissolved oxygen in the nutrient solution, then the plants can suffocate from a lack of enough oxygen. When the algae decomposes it also can release toxins, it also provides a food source for pathogens, fungi and bacteria, causing them to multiply out of control. Also if algae forms directly on the growing medium and on plants roots, it can suffocate the root system. That will also make the plants prone to attack by opportunist pathogens. But algae can’t grow without light. so the simple answer to preventing algae is stopping light from reaching the nutrient solution where ever possible. If not, frequent nutrient changes and cleaning may be needed.
Nematodes (also called eelworms roundworms and even needle worms) are basically microscopic worms. You can only see them with a microscope, that makes identifying them very difficult. But not all nematodes are a problem to plants, many of them are even beneficial to them and feed on other tiny insects, as well as clean up decaying organic matter in the root zone. some nematodes are even natural predators of plant pests. Nematode infestations damage the root systems of the plants. Some symptoms of nematode infestations are swellings, stunting, galls, and root knots. In general, root death and low vigor of the overall plant. Root systems damaged by nematodes are very prone to infection by fungi and bacteria by entering the nematode injured root tissues and then cause other diseases.
The most common source of nematode infestation in hydroponic systems is in situations where soil has been used to raise the seedlings or plants, then the seedlings or cuttings were introduced into the hydroponics system. Generally nematodes are soil born pathogens but in cases where the system has been contaminated with soil, nematode damage of hydroponic crops can be a common problem. Although nematode contamination can also be present in the water supply. Well water, dams, streams and lakes can all contain nematodes, anywhere that the water has been in contact with soil can contain nematodes and become a source of infection. The water can be sterilized before use to kill the nematodes.
Nematodes can also be spread from soil to hydroponic systems on equipment, on tools, by wind, and even by humans and animals. Even fungus gnats and fungus gnat larvae can also carry nematodes and spread them from infected plants to healthy plants. Nematodes can even cause more damage to hydroponic plants because they can also transmit a number of plant viruses. In hydroponics, a severe nematode infestation will mean the system needs to be stopped and cleaned out with infected plants and media removed and destroyed to prevent re-infestation. The nutrient solutions reservoir will also need to be cleaned, and the nutrient solution replaced. Then new sterile growing media, and nematode free seedlings replanted. Also Identifying how nematodes entered the system in the first place is important to prevent a re-infestation.