How LED Light Spectrum Can Contribute To Biological Control

Spider mites, yet tiny, are a huge problem for growers. A mite infestation can potentially become a long term problem of untreatable viruses and bacterial infections when not handled correctly and in time. This article will give you some insights and tips as to what you can do to prevent and handle a spider mite infestation.

The Two Spotted Spider Mite initially is not easily noticed and quick to infest. While mites live on the undersides of the foliage, early visual symptoms include flecking* of the leaves and a dusty feel on the upper and lower surface of the leaves. This “dust” is the exoskeletons of the mites. Later, a more obvious webbing appears, usually near the new, tender growth. Once the mites diminish the plants quality, the females catch a ride in the wind and move onward to juicier plants.

Mites come to maturity two weeks after hatching. At maturity the female mite can lay thousands of eggs which takes only 3 days to hatch. This is how the mites go from being almost unnoticeable, to a full-blown infestation. Not only do the mites cause stress for the plant, but the quality of final product is impacted. This insect moves from plant to plant, spreading pathogens along the way. If the mite infestation is in a room with stock/mother plants, then this can potentially be a serious long term problem of untreatable viruses and bacterial infections.

Light matters

The Two Spotted Spider Mite is attracted to plants under stress; for example, those with poor fertilization and improper watering as examples of stressors. Mites prefer warm, dry conditions. Growers using LEDs have noted that plants being grown under LED grow lights have reduced insect infestation. In the case of spider mites, this may be because of a lower temperature on the plant surface. The reduction may also be due to the insects attraction to certain light wavelengths.

Recent scholarly studies demonstrate blue light decreases egg production and insect survivorship. There is mounting evidence to suggest blue LED light may inhibit spider mite growth. Light that radiates intense infrared (IR) heat and dries out the environment, such as that from HPS lamps, acts as a catalyst for an infestation in production. LED grow lights, such as the Heliospectra LX60, do not radiate IR heat, and as such, do not dry out the plants. The combination of wavelength control and low heat production gives rise to LED grow lights becoming a part of a growers Integrated Pest Management program.

Be careful when using insecticides

A common mistake for treating plants against mites would be to apply a broad spectrum insecticide instead of using a miticide. Mites have eight legs and are a variant of a spider - they are not insects, but arachnids. Broadly speaking, insecticides are specific to soft bodied insects, larvae or arachnids and often target a specific phase of development to a specific type of pest. A broad spectrum insecticide could potentially kill any existing natural predators to the mite, thus increasing the population of spider mites.

Develop a predatory insect program

Build a relationship with an insectary and develop a predatory insect program. Ladybugs fly away and mantids eat everything, including each other. For spider mites, the predatory mite species, Phytoseiulus, released on a planned schedule, will greatly reduce or even eliminate a mite outbreak. These voracious mites scout out their food source. If there are no mites to be eaten, they will die away. Lacewing larvae are another great addition to a predatory insect control program. The lacewing larvae are not particularly picky and will also eat aphids and whitefly.

It doesn’t have to be complicated

The first line of defense against spider mites would be a cold water spray. Spider mites do not like to be cold or wet, so be sure to spray the undersides of the foliage since that is where the mites reside. A teaspoon of Dr. Bronner’s peppermint soap (or any non lotion dish soap) to 1 gallon of water works great as a curative and as a preventative. The peppermint leaves an undesirable smell and taste to almost all insects and arachnids. Neem oil is also known to work well as a preventative measure.

With all this said. We hope these insights and tips help you in your spider mite battle, or even better, helps prevent any new infestations in your greenhouse.