Earth mites - IPM Guidelines For Grains

Characteristics of earth mite species

Red legged earth mite Halotydeus destructor (view lifecycle)
Blue oat mite Penthaleus major (view lifecycle)
Balaustium mite Balaustium medicagoense (view lifecycle)
Bryobia mite Bryobia spp. (view lifecycle)

Mite species	Characteristic damage	Seasonal occurrence	Other characteristics
Red legged earth mite (RLEM) Image: cesar Adult mites 1 mm in length Body velvety black with red legs	Will damage all field crops and pastures. Reduces production and quality of older plants during the growing season Reduces seed yield of legumes in spring Silvering of leaves, distortion of leaf shape in broadleaf crops. Affected seedlings can die. Seedlings can be killed below ground before they emerge. In pastures, majority of damage occurs to clover and medics.	Active during cool, wet months (May to November). Hatch in autumn from over-summering eggs. Hatching triggered by a significant rainfall event in combination with 7-10 days of mean temperatures below 21ºC.	Over-summering eggs – produced in late spring. RLEM survive in diapause until autumn conditions trigger hatching.
Blue oat mite (BOM) Image: cesar Adults similar in size to RLEM Black body with red legs and small oval red area on back distinguishes it from RLEM.	Silvering of leaves (cereals, pasture, canola) High infestations in winter cereals can cause leaf tips to wither and seedling death Reduces growth of older plants and can impact on yield of legumes in spring. In winter pastures, most damage and loss is to grass component Penthaleus spp. have specific host preferences: P. major – pasture, oats, wheat P. falcatus – canola, broadleaf weeds P. tectus – oats, wheat, barley	Winter/spring. Hatch in autumn from over-summering eggs	At the end of spring the mites produce thick-walled over-summering eggs that are resistant to dry conditions. Mites are most easily seen in the late afternoon when they begin feeding on leaves.
Balaustium mite Image: cesar Up to 3 mm in length, adult almost twice the size of RLEM. Nymphs bright red. Body brown/greyish-red with red legs Short stout hairs covering body (microscope) Feed on plants and predatory on other mites	Canola: distorted and cupped cotyledons Pulses & cereals: bleaching of leaves especially leaftips	More likely to cause damage in warm, dry seasons. Lower risk of damage in cool, wet seasons. Can overwinter as eggs, but will survive all year round providing there is green plant material and protection from extreme temperatures. Hatching of overwintering eggs occurs when conditions warm and dry spring conditions prevail.	More easily found in warmest part of the day. Often found in southern coastal areas. Less abundant than other mites
Bryobia mite or clover mite Image: cesar Adult mites 0.75 mm in length, oval, rusty brown/orange – olive in colour Legs pale red/orange with long front legs held out in front of the body (may be mistaken for antennae) Nymphs bright red with pale legs Bryobia less active on the plant than RLEM.	Damages canola, wheat, lupins, clover Feed upper surfaces of leaves, leaving long trails of whitish grey spots. On succulent growth, early damage may look like leaf miner damage. In grasses and winter cereals, feeding damage results in silvering, but economic damage is uncommon In broadleaf crops, Bryobia causes similar damage to RLEM	Survive all year round providing there is green plant material. May not survive cold or very dry conditions unless protected. Overwintering eggs laid in early–mid winter and hatch as conditions warm up	Most active in warm conditions in spring, summer and autumn. Summer rains followed by warm mild autumns give bryobia mites the best conditions for survival and increase.