From BASF: The Chemical Company Website
By - Paul Pilon
As many greenhouses prepare for production this spring, it is beneficial to take steps to ensure the facilities are clean and ready for production. With proper preparations and sound cultural practices, growers can reduce the occurrence of many problems during the growing season.
In many instances, greenhouse pests over-winter in protected areas in unheated or minimally heated structures. Weeds and plant debris are notorious for harboring pests (insects, diseases, and viruses) during the winter months that could easily get moved to and possibly infect crops.
Cleaning involves physically removing existing pests from within and around the growing area. At the beginning of the season, it is important to thoroughly clean the production site by removing all of the weeds and plant debris, as well as cleaning the production surfaces by sweeping and/or washing them prior to moving in the new crops. Removing any growing medium left on benches and floors will reduce the breeding areas for such pests as fungus gnats, shore flies, and Western flower thrips.
Disinfecting involves applying anti-microbial agents to kill all pathogenic organisms. Disinfectants will control many fungal pathogens and bacteria which are likely to infect future crops. Additionally, many disinfectants are labeled for controlling algae which is a breeding ground for fungus gnats and shore flies.
There are a number of commercial disinfectants available to growers including hydrogen dioxide and quaternary ammonium compounds that are commonly used to disinfect the growing surfaces prior to crop production. It is beneficial to disinfect floors, bench surfaces, previously used plastic pots and trays, tools, and equipment between uses. Properly disinfecting greenhouses at the beginning of and between crop cycles is an important aspect of pest management.
Eliminating weeds from within the production site greatly reduces the potential for them to spread onto the crops later on. Weeds can also harbor insects such as aphids, spider mites, thrips, and whiteflies that may move onto newly planted crops. Additionally, weeds can harbor plant pathogens and viruses that may be vectored to the plants. In addition to removing the weeds from within the production houses, a weed free zone should be maintained within at least a 10 foot perimeter around the greenhouses.
There are several post emergent herbicides including diquat, pelargonic acid, glyphosate, and glufosinate-ammonium labeled for applications within greenhouse structures. These herbicides have very specific restrictions on their use within enclosed structures, often limiting applications to under benches, in walkways, and around the foundation of the greenhouse. Always refer to the herbicide label for proper application guidelines and restrictions before making applications within greenhouses to ensure spray drift does not move over the crops being produced.
Currently there are NO pre-emergent herbicides labeled for use in greenhouses as these products tend to be volatile and drift to non-target areas often causing significant crop injury.
Inspect Incoming Plant Materials
After the greenhouses are cleaned and free of all weeds and debris, a great deal of potential problems can be kept out of the production area by inspecting plant materials before they are moved into the facility. All new plant materials, such as unrooted cuttings, plugs, liners and newly transplanted containers, entering your facility should be free of any insects or diseases. Particularly look for the presence of brown, unhealthy root systems (root rot), swellings on the roots (root knot nematode), vein-bounded foliar discoloration (foliar nematodes), mosaic ring spots, dark lines and rings (viruses), and chlorotic leaves (nutritional disorders). These symptoms or the presence of insects, such as aphids, whiteflies, and spider mites, on incoming materials are all indications that a problem may be entering your facility.
One of the most important aspects of crop production is to start the growing season with few or preferably no pests in the greenhouses and to maintain this pest-free status throughout production.
Greenhouses should be thoroughly cleaned several weeks before new crops are grown. Be sure to remove all leftover plant debris, organic material, weeds, and ‘pet’ plants which all can serve as a source of insect pests, fungal spores, and plant viruses which may infect future crops. There is much to be said about the premise of starting clean and staying clean. These steps combined with good sanitary practices throughout the growing season will greatly reduce the occurrence of cultural problems during production.
The mention of specific active ingredients does not constitute an endorsement or recommendation of, or discrimination against similar products not mentioned. ALWAYS READ PRODUCT LABELS AND USE THEM AS DIRECTED ON THE LABEL.