We were surprised by how many questions were going to be generated by readers of our last article, “Buying Nematodes” but it’s good to know we have readers. Nobody wrote, even though we are always open to getting feedback (comments now closed), but many people called. They wanted to know the facts behind the differences in commercially-produced nematodes. The fact there were differences was well received and many realize shopping for nematodes doesn’t have to be as confusing as it seems, but people are inquisitive and really wanted to know why.
It was decided an article describing some of the various methods of rearing, host-extraction, collection, packaging, and storage was called for. This would answer all those burning questions. So here it is:
Rearing Methods.
There are really two methods of rearing. One is cheap and easy, the other, however, is in our eyes vastly superior. They are the in-vitro and in-vivo methods. The former utilizes an artificial host diet. This method is scientifically engineered and has been perfected over the years. The latter methodology, on the other hand, uses a living host, the larva of the wax worm, Galleria mellonella, and although it happens in an environmentally-controlled laboratory — for culture optimization and control — the entire process is natural. We feel strongly the latter method produces a far superior product.
Extraction.
This concerns nematodes using the natural in-vivo method, but some of the adverse effects of one of the extraction methods described herein may also play a role in the well-being and overall quality of an in-vitro product as well. There are two basic ways to get the nematodes out of the host (or medium). One is to remove them manually, the other is to let the nematodes to do it on their own. Extracting them manually involves crushing and dissolving the host so it can be put through a sieve to separate the nematodes from their host residue. This is an ineffectual method in that the detritus or debris isn’t fully removed leaving bacterial residue and particulates with the ready-for-storage nematodes and this reduces the storability considerably unless additives are incorporated into the storage medium or device (sponge). Another drawback to removing the nematodes manually is that not all are ready, meaning they aren’t necessarily in the right stage, “J-3,” and those which are not will more than likely die outside the host. They are susceptible to various threats as they aren’t fully protected (encapsulated) in stages pre-J-3. We strongly prefer letting the nematodes come out on their own. For one thing they leave all the bad stuff behind. Our nematodes, specifically, are tasked with moving several centimeters uphill before being collected, which as a result leaves them very “clean” and this also confirms their vigor — those that don’t make it are left behind. Survival of the fittest. Another benefit to letting the nematodes be auto-extracting is that they are really ready, on their terms, not the lab tech’s.
Packing and Storage.
There are differences here as well which add to the overall effect. There are a few types of packaging, and this goes hand-in-hand with their storage and effective shelf-life. The methods are as follows: First we have the binding agent. In this case the nematodes are packed in clay or a similar material for the sole purpose of constricting their movement. The object here is to allow the nematodes to be stored warm (and active) while not allowing them to move effectively. The shelf-life in this case is very short, and it’s not a happy life. The nematodes aren’t in great shape. They are usually the cheapest but you get what you pay for. Second we have a medium such as vermiculite. This is a decent method as it is a refrigeration method, and keeping nematodes cold is the best way to store them. It has the least impact on their well-being. If done right, this is a very good product. Then there is the nematode-only cold storage method, no medium so to speak, whether it be nematodes in a mass group, supporting each other, or in an aerated liquid. These are fairly short-term methods and usually involve large, bulk-counts. Another method, the last we will offer here, is the sponge-packaging technique. We favor this one. Again, this packaging is designed for cold storage. We like that this method uses a synthetic sponge because it is close to sterile (more so than vermiculite due to vermiculite’s handling) and if the nematodes are extracted by the best method, this product can be stored for months. Do note that the sponge must be kept slightly moist with tiny monthly introductions of distilled water.
With nearly any combination of the practices being used in the industry you can now better see why there are huge differences in the cost, storability, dosing, and, of course, overall quality.
