Pest: Garden Springtails (Collembolla)
Pest/disease identification and lifecycle, most common symptoms and crops affected:
Springtails are a very diverse group of soil dwelling arthropods, that largely feed on decaying organic matter. As such, most springtail species are playing a beneficial role in a healthy soil’s food web. That knowledge may be of little relief, however, if your young crop is one of the rare victims beset upon by large numbers of the garden springtail, Bourltiella hortensis.
At a glance, garden springtails and their damage resemble very much that of flea beetles, but springtails lack wings and are not true insects. They can be pale yellow to dark brown or gray. One defining feature of springtails is a tail-like appendage at the tip of their abdomen that they can use to launch themselves into the air, which is also the source of their name. Because they can’t actually fly, and because they favor tender young leaves, damage is typically restricted to cotyledons, and the first few true leaves, low to the ground. Garden springtails are generalists and have been found feeding on squash, cucumber, beets, chard, beans, and even onions. However, the only reports of significant damage in New England that I’ve been made aware of are on young cucurbit transplants such as squash and cucumbers.
Though severe damage is very rare, large populations could set back young seedlings or even result in crop failure in extreme cases. Springtail life-cycles are short (less than 3 weeks from egg to sexual maturity), and females can lay up to 400 eggs in their lifetime, so populations could build up fairly quickly under favorable conditions. Conditions favorable to springtails are high in decaying organic matter and with protection from drying out, as they require fairly humid surroundings.
Management begins with common best practices; good sanitation to limit habitat, improved airflow to facilitate drying out between waterings, keeping greenhouse trays elevated on benches, and planting out vigorous seedlings that will grow past susceptible stages quickly. Spraying garlic on lower leaves has been suggested to deter garden springtails, though I cannot vouch for its efficacy.
Organic pesticides (as a last resort):
PyGanic is labeled for springtails.