Dalotia the Rove Beetle
What's lurking around the floors of the greenhouse? This area often goes unnoticed but could be harboring pests like thrips and spider mites. In addition to releasing biocontrols onto plants, adding predatory insects onto growing media, to floors and around the perimeter of the greenhouse is another way to combat pests. Stratiolaelaps scimitus, the predatory soil mite, is often used in these areas, along with Dalotia, the rove beetle. These two make a great team and are often used together for fungus gnat and thrips control. Dalotia has a longer life cycle and takes longer to establish than Stratiolaelaps, but they make a great foundation for biocontrol in the greenhouse.
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Dalotia are quick, aggressive predators and are always hungry. They are used to target fungus gnat larvae and thrips pupae, but the Dalotia diet also includes shorefly, root aphids, root mealybug, moth eggs, organic matter and mold. Once released they are difficult to scout, as they spend most of their time in the soil. You may see them flying in a wave type pattern as they search for new food throughout the greenhouse. Even though they are considered a soil predator, they have been observed feeding on leaves and foliage. An adaptable beetle.
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Dalotia beetles love to live in loose soil and course bark mulch. These are both good media for creating a Dalotia breeder box which ensures a constant supply of these fantastic little beasts in the greenhouse. They also adapt well to other media, including rock wool and coconut fiber. They do prefer moist areas, but can't survive freezing or flooding conditions. At the end of the crop cycle when the plants move out, Dalotia tend to stay within the greenhouse structure. Releasing a small amount preventatively every 3 to 4 months is recommended. The low rate is 100/1,000 sq. ft.
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A typical rove beetle lives for around 50 days and passes from egg, to larvae, to pupa to adult. The complete life cycle takes between 17 to 25 days depending on temperature. Adults are mobile and can fly in search of food, but spend most of their time in the soil. Both larvae and adults are predatory. Adults are 3-4 mm long, glossy black in color and covered in fine hairs with an abdomen that curves upwards like a scorpion.
An interesting side note on rove beetles is discussed in an article from the Museum of Natural History. It discusses how rove beetles have evolved to mimic ants to invade their colonies, steal food resources and even feed on ant larvae. Roving in costume!
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The advantages of using this tiny little beetle for biocontrol are many. They are generalist feeders, eating up all types of pests in the soil and elsewhere. They are easily reared in breeder boxes, making them quite cost effective. They are mobile, shifting through soil and then relocating as they take flight through the air. Dare to discover the excellent predator Dalotia.
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Pictured are 3 different developmental stages of mealybugs right next to each other. Smaller nymphs leading up to a full grown female adult mealybug.
