White invertebrates in cereal root systems

Reports of small, white invertebrates have been reported closely associated with the damaged root systems of seedling cereals in NSW

 

Where have they been reported?

Reports of small, white to cream invertebrates have been reported closely associated with the damaged root systems of seedling cereals in NSW. At Cootamundra in the South West Slopes district, small clusters of symphilids (possibly Scutigerella spp.) have been found at the base of stunted, unhealthy wheat seedlings. The rootlets and root hairs had been removed. Symphilids were also found attacking isolated cereal crops around Young, in the South West Slopes district of NSW. These issues occurred much earlier in the season.

At Boree Creek in the NSW Riverina, very small (3-5 mm) white worms were congregating in the soil around weakened wheat (yellowing) seedlings. In this case, the invertebrates were identified as juvenile earthworms, and were presumably feeding around the decaying root systems of diseased or otherwise unhealthy plants.

Symphilid habits and behaviour

These are the first reports of symphilids (that we are aware of) attacking cereal crops in Australia. Other reports from Australian horticulture, and those from the USA, suggest that symphilids are found mainly in moist open structured soils often associated with crop debris. They are sensitive to light and become very active when exposed. Importantly, symphilids feed on the root hairs of plants and can also tunnel into the roots and stems leading to stunting and plant loss.

Garden Symphilids feed on sprouting seeds and underground stems of seedlings. Depending upon the extent of feeding, plants are weakened or killed. On lucerne and corn, they chew off the hair roots and prevent development of a healthy root system. Infested corn plants often will produce a mass of numerous, fine roots in areas that have been chewed. More information can be found at the Vegetables Victoria website and Massey University - Guide to New Zealand Soil Invertebrates.

Control options

There is very little known about control options for symphilids, particularly in broadacre crops. To check for symphilids, turn over at least 10 shovels of soil. Sift the soil while looking for active symphilids. Some research suggests that an average of 1 symphilid per shovel of soil may warrant chemical treatment of the infested area before planting the next crop. Mark off the infested area; the entire paddock need not be treated. Numerous naturally occurring organisms prey on symphilids in the field including true centipedes, predatory mites, predacious ground beetles, and various fungi; however, nothing is known about their ability to control symphilid populations.

Description

Symphylans are not insects. They are more closely related to centipedes and millipedes. The Garden Symphilid, (also known as Symphylan in the USA), are small, white, soft-bodied "centipede-like" invertebrates, 3-7 mm long with 12 pairs of legs and a pair of antennae. The notable antennae are long and many-jointed. The soft, white body is divided into 14 segments, 12 of which bear pairs of hooklike legs. All of the legs on one side move simultaneously, alternating with those on the opposite side, thus producing a twisting and turning motion.

 

* Sources of field reports of symphilids

Mark Golder – Agronomist, Landmark (NSW South West Slopes)

Paul Parker – Agronomist (NSW South West Slopes)

Tom Robertson - Agronomist, AGnVet (NSW Riverina)