This is the eight article in a series where I present selected tricks and advanced growing techniques. My name is Franco, and I work at Green House Seed Company, in Amsterdam, since the year 2000. Over the last 10 years I have learned from Arjan countless tricks and advanced techniques, and I developed a few of my own as well. And now it’s time to share some of this knowledge with growers worldwide. If we share the knowledge, everybody wins.
Last month I explained some of the best tricks for flowering indoors. This month, I give you...
Franco’s tricks on pest & disease control indoors
The single most likely cause of crop failure, in any indoor grow operation, from large to small, are pests. Working in a clean indoor environment and applying logical, strict rules are the only ways to prevent pests and diseases from harming your crop. But sometimes even with many precautions it gets necessary to fight the problem. Prevention and cure are the two expressions of the same philosophy: monitor your crop carefully in order to prevent problems, or to cope with existing ones quickly and effectively enough.
Prevention begins by sterilizing the growroom before putting any plant inside. The best way to sterilize a growroom is to use water peroxide (H2O2-35%) diluted 1/10 in water. With this mix it is possible to spray the entire room, at lamps off, including the entire equipment inside (pots, tables, buckets, tanks, lamps, controllers, fans, hangers, nets, bamboo sticks...). When spraying, apply the necessary protection (mask, goggles, coat with head protection) and after spraying wait until the room is perfectly dry before switching on any electrical appliance. Lights and ventilation should then run for 12 hours before putting plants inside). The sterilized room is only a good start. After that comes a proper prevention plan. Try to use sterilized mediums (or pasteurized ones) as purely organic compost can contain lots of bugs, and is most indicated for outdoor grow but a real nightmare to work with indoors. The ventilation should intake air from a filtered pipe (most of the mites and other bugs enter growrooms from the outside, through ventilation intake).
When bringing plants in, the best is to make sure that the plants that are introduced to the room do not carry diseases already (if starting from cuttings) or that the seedlings are pathogen-free. Unfortunately this is rarely possible, as often the source of the plants or seeds is not offering any certification. So it is often the case that the plants themselves carry some sort of problem already. As a preventive step, all young plants in the room should be treated with 3 sessions of Vertimec (or equivalent) spray (available from Bayer or Syngenta in Europe), at half the normal dosage (1 ml per each 5 liters of water). Vertimec can be sprayed every five days, so in 10 days time it is possible to treat the plants 3 times and to make sure that any spider-mite egg or other bugs are killed on the spot. It is effective against most bugs, and it attacks the eggs as well. The active components inside the Vertimec brake down with exposure to light and air, and disappear completely after 15-20 days of the last treatment. For this reason, Vertimec should only be used on plants that are in the vegetative growth stage, and avoided on plants that are flowering, especially after the buds form resin.
The most common threats to crops are bugs and fungi. Once the plants finish growing and turn to flowering, they become more attractive to bugs. Furthermore, the medium is getting older, and less air gets to the root system. At this stage monitoring the plants frequently is the only way to prevent problems. Experienced growers rotate the plants inside their growroom periodically, so to have the chance to check each plant individually and to avoid plants being left abandoned unchecked in a corner. If plants grow on fixed systems (slabs, rockwool blocks, acquafarms or similar) they are impossible to move but this should not be an excuse not to check regularly. When checking for trouble, it is best to start from the medium and the root system.
The roots must be white and hairy, if they turn yellow and brownish they are likely rotting or they have some fungus infection. This is most likely due to excessive watering, or lack of air to the root system. The medium should never smell rotten (unless special organic feedings are applied) and should be free from bugs. Fruit-flies on the surface of the medium are common even in healthy environments, but if they are present in large numbers it can be that the surface of the medium is forming a crust (it should be avoided, otherwise transpiration is majorly affected).
After checking the root system it is good to have a look at the lower part of the stem, making sure that it is free from small branches and leaves touching the medium. When this happens the leaf material tends to break and rotten, creating a way in to fungi and diseases.
When checking for the presence of bugs and pests, it is good to look under the oldest leaves of the plant, and on the stems. Look for the most common bugs: ants, white fly, aphids, scale, mites. And for the most common diseases: algae, powdery mildew, botrytis, leaf spot. For the algae, the best is to deprive them of light (cover the medium surface), while powdery mildew can be treated organically using vinegar, or cinnamon oil.
For botrytis it is necessary to apply a fungicide, or a specific product, but once botrytis appears it is almost impossible to get rid of it, so it is really a matter of prevention (controlling the humidity of the room and the watering is the first step). Each of these diseases or pests has a proper way of being targeted, but the most important factor is to spot the problem on time, take immediate action, monitor the success of the process, and evaluate the consequences so not to have any bad surprise.
All over the Internet nowadays it is possible to find accurate information on pests and diseases, so it is really only a matter of applying common sense and be vigilant. And these principles go well with any aspect of growing pot.
Franco – Green House Seed Co.
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