The discovery of tiny insects crawling in the soil of your potted aloe plant is a common experience for houseplant owners. While finding unexpected life in the pot can be alarming, it is rarely a sign of imminent plant death. These small organisms are often attracted to the rich, damp conditions created by indoor growing environments. Resolving this issue requires correctly identifying the specific pests and then adjusting the plant’s environment to make it inhospitable to them. This approach focuses on eliminating the current population and preventing future infestations.
Identifying the Most Common Soil Pests
Accurately identifying the small creatures inhabiting the soil is necessary, as different insects require targeted treatments. One of the most common is the fungus gnat, which appears as a small, dark, mosquito-like fly often seen erratically buzzing near the plant. The adults are mostly a nuisance, but their larvae live in the top inch of the soil. These tiny, translucent white worms with black heads can feed on fine root hairs, especially in young or stressed aloe plants.
Another frequently observed type is the springtail, a minute, wingless insect typically white or gray, known for its distinctive jumping behavior when disturbed. Springtails primarily consume decaying organic matter and mold rather than healthy plant roots. Soil mites are even smaller and can appear as tiny red, white, or brown specks scurrying across the soil surface. Most soil mites are detritivores, feeding on debris, though a few species are pests.
A more concerning pest is the root mealybug. These are characterized by a white, cottony, or waxy mass found directly on the roots and hidden within the soil. Root mealybugs are sap-suckers that cause damage by feeding on the root system, leading to a decline in plant health that can be mistaken for a watering problem. Identification of this pest usually requires unpotting the aloe and examining the root ball for the fuzzy white clusters.
Addressing the Environmental Causes
The presence of soil-dwelling pests is almost always an indicator of environmental conditions that favor their survival, particularly excessive moisture. Aloe plants are succulents, naturally adapted to arid conditions, and their soil should be allowed to dry out completely between waterings. The larvae of pests like fungus gnats require consistently damp soil to survive and develop, laying their eggs in the perpetually moist top layer.
Overwatering or using a potting mix that retains too much moisture creates the perfect breeding ground for these insects. When the soil remains saturated for extended periods, it encourages the growth of fungus and algae, which provides a food source for gnat larvae and springtails. Poor drainage exacerbates this issue, preventing the soil from aerating and drying properly.
The solution involves adjusting watering practices specific to aloe care. Allowing the soil to dry out several inches deep, or even entirely, between waterings stresses the larvae and cuts off their food supply. This makes the growing medium far less appealing for pests to establish a population. For established plants, waiting until the soil is bone-dry for at least a week before rewatering can significantly reduce pest populations without harming the drought-tolerant aloe.
Effective Treatment and Eradication
Eradicating soil pests requires targeting both the adult insects and the larvae living in the soil. For a heavy infestation, repotting the aloe in fresh, well-draining succulent soil is recommended. This process involves gently removing the old, infested soil, thoroughly rinsing the roots to remove any clinging larvae or root mealybugs, and transplanting into a clean container.
To target remaining larvae in the soil of plants that are not repotted, a biological control agent called Bacillus thuringiensis israelensis (BTI) is used. BTI is a naturally occurring soil bacterium that is harmless to plants, pets, and humans. When ingested by fungus gnat larvae, it produces a toxin that kills them. The most common application involves soaking BTI granules in water for several hours to create a “tea,” which is then used to water the plant, delivering the larvicide directly to the infestation zone.
For a non-chemical physical barrier, a thin layer of food-grade diatomaceous earth (DE) sprinkled over the soil surface is effective. DE is a fine powder made of fossilized diatoms, whose microscopic sharp edges desiccate and kill soft-bodied insects like gnat larvae and adults upon contact. Yellow sticky traps should also be placed near the plant to capture the flying adult fungus gnats, preventing them from laying new eggs and helping to monitor the effectiveness of the larval treatments. Combining BTI waterings with a DE soil barrier and sticky traps addresses the entire life cycle of the most common soil pests.