Spider mites are a devastating pest that can destroy your crop within a few weeks if left unchecked. Thankfully, there are many choices of predators on the market that can help with a spider mite infestation, but some of them are specialized to work in certain situations, so it is critical that you make the correct choice to ensure proper spider mite control.
Before choosing the best biological control, it is important to ensure you are dealing with the most common spider mite species; Tetranychus urticae, which represents the majority of all spider mites found in Canadian crops. Other spider mite species found in Canada are the European Red Mite (Panonychus ulmi), Carmine Mite (Tetranychus cinnabarinus), etc. It is important to identify the spider mite species, as only certain biocontrol's will prey on these while all the ones noted below will prey on Tetranychus urticae (Two-Spotted Spider Mite).
The primary types of biological controls are: predator mites, gall midges and predatory beetles. In the majority of situations predatory mites (Phytoseiulus persimilis and Neoseiulus californicus) are all that is needed for an effective spider mite control program. Gall midges and predatory beetles when used, are typically supplementary only. Gall Midges (Spidend – Feltiella acarisuga) and Predatory Beetles (Stethorus punctillium) are primarily used in greenhouse vegetable (cucumber and pepper) crops for additional hot spot control in addition to predator mites which provide the back bone of the program.
Predator mites are small mite species that occur in nature. Depending on the species, predator mites live on the underside of leaves, inside flowers or buds, as well as soil surfaces. Predator mites are the best choice for the majority of situations as they’ll stay in your crop, have a quick numeric response based on pest life cycle, and will hunt prey by following volatiles emitted by plants in areas of spider mite damage. Predator mites have long been proven to be an effective and economical mite control; Koppert has been rearing and selling Phytoseiulus persimilis since 1967.
Predator Mites used for spider mite control fall into three primary classes:
- Type 1: Specialized Mite Predators – These are obligate predator mites of spider mite species.
- i.e. Phytoseiulus Persimilis, which are highly specific to Tetranychus sp.
- Type 2: Selective Predators of Tetranychus sp. – These are typically predator mites that are primarily focused on preying on web spinning mites such as Two-Spotted Spider Mite, but can also survive on other food sources such as thrips, pollen etc.
- i.e. Neoseiulus californicus & Neoseiulus fallacis
- Type 3: Generalist Predators - are predator mites that prey on and can reproduce on a host of pests. They will prey on spider mites, but don’t have a strong preference for them. This makes them a poor choice for bio-control. These types of predator mites are commonly used for thrips and whitefly control.
- i.e. Amblyseius swirskii, Neoseiulus cucumeris, Amblyseius andersoni, Amblyseius degenerans, and Amblydromalus limonicus
For almost all situations, Spidex (Phytoseiulus persimilis), Spical (Neoseiulus californicus) or a combination of the two will be the best for your situation. Phytoseiulus persimilis (Spidex Vital/ Spidex Red/Spidex Boost) is a type 1 specialized predator mite. It is better adapted to hunting in heavy webbing than other predator mites. It also has the highest numeric response to spider mites and does not require specialized plant hairs to oviposit (lay eggs) on like most predator mites, so it is better able to reproduce on plants lacking these hairs such as cannabis or many ornamentals. Instead, Spidex (Phytoseiulus persimilis) will oviposit directly onto the leaf surface or into spider mite webbing. The downside to this predator mite is that it declines in crops quickly during low levels of spider mites and only controls Tetranychus species of spider mite.
Neoseiulus californicus (Spical, Spical Ulti-Mite, and Spical Plus) is a type 2 selective predator mite. It is best used preventatively or in low pest density situations. It will disperse more than Phytoseiulus persimilis finding smaller spider mite populations and can survive longer without a food source. It is also known to predate on many less common mite species (European Red Mites, Carmine Mites, etc.). The downside to this predator mite is that it requires specialized plant hairs to oviposit. These are present in traditional vegetable crops like cucumber and peppers, but often lacking in crops such as cannabis and many ornamental plants.
Other mites that have been thrown into the spider mite biocontrol market are:
- Amblyseius andersoni (Anso-Mite) - this predator mite has been discussed to control spider mites, but it is actually a type 3 generalist predator mite, so it is not a great choice for spider mite control. It is better used as a generalist predator, similar to how Amblyseiulus swirskii or Neoseiulus cucumeris are used, except in cooler weather conditions.
- Neoseiulus fallacis - is a type 2 predator mite, so it will feed on spider mites. Neoseiulus fallacis works similar to the more commonly used Neoseiulus californicus, however mostly utilized in outdoor cool climate fruit crops where it is a common native predator.
Feltiella acarisuga (Spidend) is the only commercially available gall midge species for spider mites. It is sold in the pupa form. Once placed in the crop the pupa emerges into adult form. The adults actively search for spider mite colonies and deposit eggs next to them. Once the larva emerges, they feed exclusively on spider mites.
This product is best used in crops such as cucumber, eggplant or peppers that regularly have some hot spots for Feltiella acarisuga to establish and spread from. Feltiella acarisuga (Spidend) has a very high numeric response to spider mites and excellent searching capabilities, so once established they often find and clean up hot spots before growers even find them. The major downside to this bio-control is that it is sensitive to climate conditions and pesticide residue, due to this it’s efficacy can vary greatly between crops and geographies.
Stethorus punctillium (aka the Spider Mite Destroyer) is the only commercially available spider mite specific predatory beetle. It works best when there are large localized spots of spider mites and is most commonly used in cucumber and pepper greenhouse crops with traditionally heavy pest pressure. Once placed in the crop, Stethorus punctillium disperses through the crop by air, hunting by scent and multiplying in high mite density areas. Stethorus punctillium will also feed on some of the less common mites previously discussed, as well as diapausing mites. There are some limitations that come with this biological. It is slow to develop in low light and low temperatures and is more prone to disperse from the crop than other biologicals. Stethorus punctillium is typically not a stand alone product, but can be a useful addition to predator mites in some situations.
For the majority of users dealing with Two-Spotted Spider Mites (Tetranychus urticae), which represents the majority of mites found in Canada, either Spidex (Phytoseiulus persimilis), Spical (Neoseiulus californicus) or a combination of the two is usually the best choice for control. See our products for this below: