Dr. Phyto

alfalfa / lucerne

Medicago sativa

Diseases & pests on this plant

• Redlegged earth miteHalotydeus destructor

  Silvered, whitened or bleached patches on leaves and cotyledons where mites have fed; distorted, shrivelled seedlings; worst on cool, overcast autumn days on emerging canola, lucerne and pulse crops. Tiny 1 mm black mites with red-orange legs feed in dense groups.

• Verticillium wilt of alfalfaVerticillium albo-atrum

  V-shaped yellow wedges on individual leaflets, progressive yellowing + wilting from base of plant upward, vascular tissue browning visible when stem is sliced lengthwise, plants stunted + die within 2-3 years, gradual stand decline in established fields.

• Phytophthora root rot of alfalfaPhytophthora medicaginis

  Yellow stunted plants in wet low areas of field, root system blackened + rotted away to thin taproot only, plants pull easily from soil, gradual stand thinning over 2-3 seasons, regrowth after cutting reduced + uneven.

• Australian plague locustChortoicetes terminifera

  Marching bands of wingless nymphs and later flying swarms that strip pastures and crop leaves; rapid, patchy defoliation spreading from egg-bed areas; heaviest after warm, wet springs that trigger high densities.

• sclerotinia stem rotSclerotinia sclerotiorum

  White cottony growth on stems at flowering height, stems split open to show black sclerotia (1–5 mm) embedded in pith, premature ripening of affected plants.

• pea-and-bean weevilSitona lineatus

  Distinctive U-shaped notches around leaf margins from adult feeding (looks like someone took bites with a hole punch), larvae visible inside Rhizobium root nodules when pulled up, stunted + yellowed plants from compromised nitrogen fixation, severe attack in cold wet springs delays flowering.