Pests and Diseases
Hydroponics, upon eliminating the soil factor, also eliminates many diseases gateways. However, plants, as living things, are still vulnerable to certain diseases and infestations of pests. We must always be alert, as the proliferation of a disease might be fatal particularly due to the fact that there is a high density of plants, temperature and humidity have adequate levels (mainly inside a greenhouse) and the spread of diseases may occur quite quickly through the nutrient solution.
The best tool against pests and diseases is prevention, which can be the simplest steps presented as follows:
- Avoid using seeds from dubious origin and seedlings grown in nurseries or flower beds with soil or, if you do, wash them thoroughly to remove dirt before transplanting them to the system;
- Use good quality water;
- Treat irrigation water by filtration, UV radiation or ozonation;
- Use inert substrates;
- Use clean tools;
- Keep deposits protected from contaminations;
- Undertake a quick elimination of sick plants and plant material resulting from pruning and fallen leaves;
- Optimize the growth of plants: a healthy plant is less susceptible to pests and diseases;
- Avoid damaging plants;
- Find a balance between a proper density of plants and adequate aeration among plants.
Often, visible symptoms may mislead us and correspond to a nutritional disorder rather than a foreign agent.Learn here the most common nutritional needs and excesses.
When it comes to pests, we at Ecocenter have a principle: we do not use insecticides. They are harmful to the environment and to life in general, kill beneficial insects that protect vegetable gardens and are directly related to the decline of bees in Europe. Besides, they become useless after a while because insects develop defenses against them very quickly.
The best insect control is done by natural predators, as their efficiency is well proven. However, one downside is that they are expensive. Some effective alternatives are solutions made of tree oil extracts such as Neem or homemade solutions made from organic matter of all kinds such as onions, garlic and nettles, cayenne pepper, etc. cold water may be a powerful ally as it repels and breaks the breeding cycle of many insects.
It is also important to realize that good nutrition is the first step to make plants resistant to insects. For instance, a diet rich in calcium makes plants to have cell walls that are richer and more difficult to penetrate.
Possible infestations are of varying types, namely insects, nematodes, fungi, mites or viruses.
Above the ground, they are the spiders that cause most damage. They are small red dots to the naked eye and difficult to spot, they are usually on the underside of leaves, and when the infestation is at an advanced stage, they wrap flowers/leaves/fruits in webs. The first noticeable symptoms are small white spots on the leaves.
APHIDS / BUGS
Aphids breed at a high speed, may become a problem if they are not spotted in time and are found in a wide variety of colors (green to brown). By means of a good periodic inspection and manual removal, they should not become a problem; just move a sponge on both sides of leaves to remove them or crush them with your own fingers. Alternatively, you can use a homemade mixture of garlic, onion and pepper or even an insecticide soap or neem oil.
They are like small, 1mm traces and can be white, gray or brown. They are easy to identify because they have wings but do not fly and jump from leaf to leaf. A nice trick to identify them is shacking the plants and see how those insects react: if they do not fly, they are thrips, and are rarely a problem.
They are not very common, but they do make some damage. Just like aphids, whiteflies excrete substances on leaves leaving a trail that attracts fungi and ants. A homemade mixture of garlic, onion and pepper may help; insecticide soap and neem oil also work.
Caterpillars like kales and tomato plants and nay become a major problem if not controlled. The good news is that also like beer, so a few cups next to the plants will help capture them and manual removal works very well in hydroponics. It is advisable to avoid the piling of wood in the cultivation area because that is one of their favorite habitats.
FUNGI AND VIRUSES
There are many fungi capable of breaking into a cultivation area if the conditions for such are favorable (high humidity, poor air circulation/stagnant air and heat).
Fungi reproduce by spores, they are in the air and everywhere, and rarely grow if plants are healthy.
Most fungi attack the leaves, such as those of the Oidium genus, as well as the flowers and fruits, such as those of the Botrytis cinerea genus. Others attack the stem at the level of the substrate, causing plant death (damping-off). Regardless of the case, prevention is once again vital and the most effective ways used nowadays to reduce infection and prevent fungi from spreading are Bordeaux mixture (a blend of copper sulfate and calcium hydroxide / slaked lime) and silica / silicon dioxide.
Now, as for viruses, there is no cure for them but they are also very rare and are usually brought by other insects or by the introduction of an infected plant. If this happens, one then should burn the plants, replace the entire substrate and sterilize all the cultivation area.
As for the roots, these may also be attacked, albeit very rarely in hydroponics. Regarding pests, there may exist root aphids/bugs or nematodes and, regarding fungi, the two most common types are those of the Pythium and Fusarium genera. The spores of these fungi are always present and there is nothing we can do to avoid them, and these fungi only fully develop if plants are weak or when the solution lacks oxygen. The process is simple: when oxygen lacks to the roots, stress is generated and they release a gas (ethylene), which acts as a signal, thus attracting pathogens.
Pythium can be identified as a small black spot at the tip of the roots, while Fusarium attacks anywhere on the roots and looks like a brown, sticky stain. If nothing is done, plants die quickly.
It is very difficult to cure a fungal attack on the roots without harming the plants themselves, plants lose vigor and the crop is affected, so it is important to realize and consider thoughtfully what happened and find out the cause, which often boils down to the lack of oxygen in the nutrient solution, an unbalanced diet or an unstable climate.
Some of the methods applied to retard the action of fungi are the use of silica, cutting dead roots, replacing the nutrient solution with water containing a balanced pH level, even using a root enhancer and spraying the plants with an average nutrient solution to avoid nutritional deficiencies. This process should continue until the new roots begin to grow and the nutrient solution should be adjusted gradually. Humic or fulvic acids help in the recovery of plants at root level; earthworm compost and seaweed extract may be used to spray the leaves.
Using hydrogen peroxide is a common mistake and does not work; it may lower the population of pathogens but, at the same time, lowers the population of beneficial organisms. It does not distinguish “good” from “bad” organisms and ultimately weaken plants even more.