New pest in the garlic patch

One of the critters that we're seeing in different garlic gardens is the garden springtail.

Globular springtails are tiny (1 mm/ 1/16th inch), primitive wingless insects (Fig. 1). Females lay their eggs in moist soil, with a preference for areas of high organic matter (Fig. 2 - life cycle). The young often only differ from the adults in colour. Both lifestages spring away when disturbed using a structure called a furcula, located on the underside of their abdomen (hence the name springtails). As an aside - these little critters can propel themselves a distance of up to 20 times their body length!

Fig. 1. Globular springtail.
© 2009 Lynette Schimming. www.bugguide.net/node/view/254638

Fig. 2. Springtail life cycle.
Source: http://www.pfc.cfs.nrcan.gc.ca/diseases/nursery/images/full_images/fig82.jpg

Most springtails are considered beneficial soil scavengers, feeding on decaying matter, fungi, moulds and other soil microbes; however, there are a couple of species, including the garden springtail (Fig. 3) which feed on plants. Young garden springtails are orange in colour, while adults are reddish-black.

Fig. 3. Adult garden springtail - actual size (left) and 15x magnification (right). Special thanks to Bryan Mailey for all garlic photos.

In general, springtails thrive in moist soil environments where there is an ample supple of decaying plant material (e.g. leaf litter, decaying wood, high levels of organic matter, soils amended with compost). Species that spend most of their time in the soil are very susceptible to desiccation. Based on what I've observed, this may not be true for the garden springtail. In garlic, both immature and adult springtails were happily feeding in the heat of the day under a clear blue sky with temperatures reaching 28?C. With that said, they could leave the plant at any time and take refuge under ground cover.

Damage caused by the garden springtail is shown in figures 4 and 5. In most cases, damage is only observed on the oldest leaves. Feeding sites are pale yellow in colour, and appear as though the springtails have 'sucked' out the chlorophyll. Lesions may be mistaken for botrytis leaf blight. Botrytis is often found throughout the field and affects young and old tissues alike. Also, botrytis lesions are often larger than those caused by the springtails. And finally, springtail feeding removes the chlorophyll but doesn't appear to change the leaf texture. Botrytis lesions cause death of tissue and have a different texture than healthy leaf tissue. In addition to the feeding damage, I also observed a lot of leaf yellowing of the oldest leaves. When these plants were pulled, we found that springtails weren't the only critter munching away - bulb and stem nematode was also present. The question now is - which came first? Are the springtails more attracted to the garlic due to activities of the nematode, or vice versa? Are the decaying garlic bulbs, attacked by the nematodes releasing chemicals that are attractive to the springtails? Are plants fed on by springtails more susceptible/attractive to the bulb and stem nematodes?
Many questions!

Fig. 4. Springtail feeding damage on garlic leaves (left and right).

Fig. 5. Springtail damage (leaf lesions) and leaf yellowing caused by bulb and stem nematode (top and bottom photos).