FIGHTING ENDLESS HOARDS - the author's battle with grain mites...and how he won

Admittedly there has been a bit of a gap between my first ambitious attempt to examine the subject of mites on a broad scope, even at an introductory level, and this follow-up article. Partly, that can be chalked up to my procrastination. The other, and more prevalent, reason for the delay was that I ended up having to deal with a mite outbreak myself. Speak of the devil, just the subject I had been assuring others I had answers to had come a plague on my own house... quite literally.

As the picture to this article shows, I had what is typically experienced with an outbreak of grain mites – by the time I noticed them, they were already everywhere....and I mean, dripping off surfaces. While I am thankful this outbreak occurred in my apartment rather than in my bug collection, housed elsewhere, the mites were exploding in numbers on a shelf which held several other tanks. Among them included one which had a newly established colony of cotton springtails. The springtails and other tank habitants ensured that no unduly harsh chemicals were to be used, lest I put their lives at risk. However, as I looked at the source of the mites my heart sank: the very tank they poured forth from contained a species I was attempting to expand numbers of and get established in my collection so I could offer it to others. It felt as though I were trying to deal with an angry cobra next to a basket of puppies...ugh, not ideal. Typically, when one encounters a mite outbreak the immediate solution is to go full scorched earth; give up on the infected space, throw out all contents, use boiling water/rubbing alcohol/soap/whatever means necessary to eliminate all traces of the mites from the tank, walls, and surrounding area to which they had wandered.  

The instinct to take this course of action was strong...I had done it in the past. When faced with such overwhelming legions what else is one to do? It felt hopeless when I saw mites in such numbers that they literally discolored the surface they were on - turning the appearance from a beautiful dark stained hardwood, to an unsightly, gross beige from their countless mite bodies. They poured forth from under the lid of that tank, a solid glass plate that thankfully somewhat held them back to some degree, through the tiny gaps present between the glass and lid frame. Up the shelf they clambered, pouring forth in their hundreds at the base, thinning out to only dozens as one went further up in elevation on the shelf. On each level there were tanks for them to invade, and I expected that if they came to establish in those new worlds as well that I would have to remove the inhabitants before setting the shelf ablaze on my balcony.  

However, I realized that to carry out the nuclear option would be beyond a Herculaneum task...I simply put, I was unable and unwilling to commit to making that my first option. Surely, there must be another way, I reasoned. It has been a long and multifaceted battle, but now....it appears over (I say that with caution and haven’t unfurled the MISSION ACCOMPLISHED banner just yet). However, I am moderately confident in saying...the war is won. I want to I give my account of the tactics which lead to the victory. 

I decided to take a multipronged approach. Having worked in agriculture and horticulture there is a method to pest control which is termed IPM, short for Intergrated Pest Management. It is approaching pest control through a multi-lens view rather than just a singular approach (historically just a “spray and kill” mentality). IPM considers biological and cultural methods of pest management, which are employed in combination with chemical methods providing an effective trident to yield against pests. By using this method there are several positives; it means that one is not solely dependent on just using harsh chemicals, which not only can pests become resistant to, but end up being the same chemicals can also kill off useful beneficial "allies" which help control the very pests plaguing the crops. Regardless, I won’t go into depth on the agricultural perspectives surrounding IPM, but suffice to say – IPM was how I decided to approach to my mite infestation.

First, I noted that while the grain mites were contacting other tanks, that they were not exploding in number upon reaching these new lands. The tanks they were coming to were those which held tarantula species, mostly arid species but there is a tropical species as well, so all habitat opinions were available to them. It is my general experience that pest mites, at least those which seem to be problems for those which keep herptiles and inverts, seem to prefer drier conditions. Before someone shouts out, “What about water mites?” I am aware that my statement there is a broad generalization...and am unsure of how problematic water mites are for captive animals. HOWEVER, from my time dealing with a variety of pest mites I would argue that if you are dealing with them in your springtail colonies that one of the simplest options is to flood the colony. From there, simply pour off or scope out as many springtails as possible and use them to start a fresh colony. Regardless, flooding my tanks was not a viable solution at this time anyways, and isn’t necessarily a practical one for many other people either. What I wanted to highlight is one of the things which causes the mites to reach plague proportions in some cases, but not in others – the over-abundance of food resources. The offending tank from which the mites were pouring forth contained a new species of beetle I'd been culturing. As such, the amount of dried food, dead insects, and other calorie dense items which could be fed upon far exceeded what the beetles/larvae could consume within a short period of time. With endless food for them to feed upon, it was easy for the new beetles to build in number...but this stood true for the mites as well. With endless resources to feed upon it simply meant that numbers could go up and up until the mites came to cover every surface in and on the tank. Not taking the nuclear option off the table, I removed as many beetles and mature larvae as possible to clear them of mites, start their culture anew if need be, and then returned to the infested tank... 

The tank in question had held the new species for long enough that surely there were eggs and newly hatched larvae which were too small to readily save. I was hesitant to toss out the babies with the bathwater, given how numbers were still so small in the colony. In a move which likely extended the infestation I was fighting, I decided to remove as many sources of food BUT to largely keep the substrate, filled with dog kibble/dead insects/fish food and young dermestids, in the tank. My gamble that these mites would fail to spread to my other tanks provided to ultimately be correct: with no food source for them to feed upon in the tarantula tanks, and thankfully they failed to establish at all in the other environs they encountered. The only one which brought me concern was the one which held the new cotton springtails, for I did provide them with a small amount of high calorie food which they could feed upon to encourage decent population growth. It was the tank which was the furthest from the infested one, which may have helped but did not shelter it completely, as I noted the grain mites managing to climb up to the very top of the shelf. What I personally believe contributed to the tank with the cottons being spared was two things- first, that the food sources were still very limited, far below what would have been required for a full-blown infestation. The second was the presence of the cotton springtails themselves. By that stage they had in fact come to have a robust number of them present in the vivarium. Cotton springtails are, for a springtail, quite solid, robust, and readily hold their own against other mesofauna. From my observations it appeared as though while there was food upon which grain mites may have used to establish, that the competition from the springtails kept them from exploiting that food source, and in turn from having another boom in numbers.  

So that was my first lesson in fighting the mite horde; attempt to limit their food resources if possible, and if there is to be food present ensure that there is sufficient competition for it. The small number of beetles/larvae present were clearly awash in excess food and thus this only meant that there was plenty leftover to be exploited by the grain mites.

If mites have endless food resources available to feed upon then it is hardly a surprise to experience a subsequent enormous explosion in their population. This is particularly true if they lack any serious competition for the food resources.

Due to my reluctance to remove all excess food entirely I was still left with an inordinate number of grain mites. This when I chose to employ simple methods in number reduction – I took a paper towel, sprayed it thoroughly with rubbing alcohol, and wiped surfaces down. I wiped down the shelf, the lid and walls of the tank, and the outside of neighboring tanks. I knew that my failure to significantly remove the inciting overabundant food source in the original tank meant that this would be something would end up becoming routine...and I was right. Surge after surge, the problem continued. It felt as though even when I would kill thousands of mites wiping down the surfaces, another wipe down would be required again only days later. The concentration of rubbing alcohol was high, about 70% even with dilution, so it evaporated quickly and was effective in killing the mites it contacted.

Lesson two: Physically reduce numbers whenever possible. Simple and straightforward. You won’t get them all, but any reduction in numbers is in your favour.

Despite what felt like Groundhog Day in dealing with these mites, they did not spread and it felt that after some time I had come to a bit of a stalemate. That’s when I deployed another weapon against the grain mites- the introduction of a predator. These days it goes by the name Stratiolaelaps scimitus, but formally was called Hypoaspis miles. Whatever name they go under these predatory mites boost an impressive resume. Traditionally used in the horticultural industry these mites go after a huge range of soil dwelling pests; thrips pupa, woolly root aphids, fungus gnat larvae, shore fly larvae, spider mites, and more. Their broad diet saw them gain notoriety in the herptile world as well; they readily go after snake mites and grain mites as well. These "soil lions" can eat as many as five prey items a day! In the absence of pests they will also feed upon springtails, or lacking suitable arthropod prey they will even eat pollen and algae. This mite is able reproduce both sexually and asexually, and females can lay as many as 3 eggs a day. Upon hatching in one to three days the young mites start out as gawky six-legged larvae but in the span of a couple weeks become an unstoppable soil predator.

Given their wide versatility these mites immediately attracted my attention (a while before this outbreak in fact) and I already was lucky to have multiple cultures being propagated under my care. I liberally applied them in the hundreds to the infested tank after a wipe down of the outside surfaces and let them get to work.

My third lesson in successful grain mite mitigation: use of a biological control agent allows for successful reduction in numbers in cases where direct physical eliminations simply aren’t possible.

The use of Integrated Pest Management appears to have been a success – the combination of reducing food resources for the grain mites, introducing competition to the limited food remaining, physically killing with rubbing alcohol wipe downs, and the introduction of an effective biological control, all came together to eventually end the outbreak.

Each method employed has its advantages, as well as its drawbacks, but it is safe to say that none would likely have been sufficient on their own to have resolved the issue while preserving the arthropods in the tanks which faced the infestation. I have started to deal with any pest management issues in my tanks and cultures using IPM and believe that this

holistic and systems-based approach to be one of the most effective approaches for dealing with terrarium pests.

Should anyone be interested in obtaining Stratiolaelaps scimitus mites to assist with the management of pests in their own terrariums and vivarium, I offer them on the website – they are sold under the product name SOIL GUARDIANS. I offer the scimitus mites in tandem with another highly effective biological control, for an unbeatable combo to effectively deal with many common pests of indoor potted plants and of terrariums. Check out the link above to view more information on these beneficial inverts and see how they can be used to protect and treat your own planted spaces through natural controls.

Thank you to those who read to the end of the article! I love hearing from others and know this is a subject to which many can relate; have you battled with a outbreak of grain mites? What tactics did you use to bring it under control? Do you have any experience using any biological controls in trying to control outbreaks, whether it be mites or undesirable arthropods, in your own collection?