Springtails

Springtails are minute, primitive, insectlike organisms. Their bodies are less than 0.1 inch (2.5 mm) long and wingless. Most springtails are harmless scavengers, and are considered beneficial organisms because they aid in the decomposition of decaying plant material. However, P. fimata has been found to cause problems in cole crops in the Salinas Valley.

Most springtails have a forked appendage (furcula) at the tip of the abdomen, which they use to spring into the air when disturbed. P. fimata lacks a furcula and curls up when disturbed instead of jumping. It also lacks pigmentation and eyes.

Springtails lay their round eggs in small groups in moist soil, especially where organic matter is abundant. The immature stage is usually whitish, and adults tend to be whitish, bluish, or lack pigmentation. The immature stage differs from the adult stage only in size and color.

Springtail damage to cole crops is currently a problem in various parts of the Salinas Valley and the Central Coast. They are often a problem in fields that contain a high amount of organic matter and fields that have a recent history of their presence, though their infestations do not always occur under these conditions. Damage more often occurs in the spring than during other seasons. Springtails will stunt seedling growth by damaging germinating seeds, roots and seedling leaves when present in large numbers. The seedlings may appear wilted and may die if damaged when young. Damage occurs as minute, rounded pits on young, developing leaves or roots, or as irregular holes in thin leaves. Mature plants are typically not significantly injured.

Recent additions of organic matter (such as adding compost or incorporating a cover crop as green manure) as well as intensive irrigation (high soil moisture level for seed germination) can temporarily and dramatically increase springtail numbers.

P. fimata can be mostly suppressed with early applications of synthetic insecticides directed at the seed line. An at-plant application of a pyrethroid, neonicotinoid, or spinosyn insecticide is often effective for both direct-seeded and transplanted cole crops. Seeds coated with a neonicotinoid insecticide targeted to manage other soilborne arthropod pests can also reduce springtail numbers.

Monitoring is the key to determining the presence of springtails. There is currently no action threshold for springtails, but potato or beet slices can be used to monitor P. fimata presence or absence in the field. Determining whether or not springtails are present reduces unnecessary insecticide applications.

1. Cut thin slices (about 0.5 inch) of beet root or potato (preferably of a darker color).
2. Place the slices in the subsurface of the soil about 2 inches deep, and cover them with a plastic cover, such as white plastic bowls that are 3.5 inches in diameter and at least 1.5 inch deep.
3. Assess the slices about 24 hours after deployment. (Slices tend to dry out when left in the field for longer periods of time, and thus become less attractive to P. fimata.)