^6 Journal of Agriculture, Victoria. [lo Jan., 1912.. 



Peronospora tnfoliorurn is a common parasite on various legumes in. 

 America and Europe, and in the former country there is record of 

 damage to lucerne by this pest. Until the specimens under notice came to- 

 hand there was no record of it for Victoria. 



As this fungus belongs to a genus, many of which are destructive to 

 cultivated plants, it behoves the growers of lucerne, especially in irriga- 

 tion areas, to be on watch, lest their crops be invaded by this pest ; if 

 once established, it would be most difficult, if not impossible, to ex- 

 terminate. It is spread not only by conidia, which are blown from plant 

 to plant, but also by oospores or resting spores formed within the tissue- 

 of diseased leaves. The latter, falling into the crowns of the plants 

 and on to the soil, serve as fresh sources of infection, frorr. which the 

 disease spreads during the foliowing year. Even if the lucerne be eaten 

 down to the crowns by sheep or other stock, a certain number of fallen 

 leaves would be trodden into the soil and start the disease afresh in the 

 following spring. 



Although onlv a few specimens of this disease have been brought under- 

 notice, and probably but few lucerne growers have seen it up to the pre- 

 sent time, it does not follow that the disease is of no econonrx importance. 

 Until a few years ago, the Lucerne Rust had not been obser\ed in Vic- 

 toria ; the first specimens obtained were found by the writer on the rail- 

 way embankment at Garden Vale, near Melbourne. At the present time, 

 many parts of the State are infested by this disease, and tons of valuable 

 fodder are destroyed every year. Lucerne rust was, without doubt, 

 imported with consignments of seed from other countries, as in nearly 

 every shipment of lucerne seed spores ccmld be ol)tained in abundance. 

 Most probably, the resting spores of the downy mildew of lucerne have 

 reached Victoria in fragments of diseased leaves, niixed through ship- 

 ments of seed. 



General Appearance of Diseased Plants 

 The specimens under notice had a stunted and unthriliy look, the- 

 upper portions of the stem and leaves being covered by a thick greyish, 

 or violet-grey downy layer Many of the diseased leaves were coated 

 on both surfaces and had their edges curled downwards and inwards 

 towards the mid-rib. Others again, were of a yellowish grey, more- 

 especially those exhibiting the downy coating on the under side only. 

 Several of the stalks were almost bare of leaves on their lower portions 

 and clearly showed the disastrous effects of the disease. 



If a small portion of the grey felted coating be mounted for examina- 

 tion by the microscope, it will be found to consist of minute tree-like- 

 structures, bearing, at the tips of the many fo'-ked branches, oval egg- 

 shaped bodies known as conidia. These minute bodies are capable of 

 infecting any lucerne or clover plants on which they may fall, weather 

 conditions being favourable. 



If small patches only of the field be attacked, they .should be at once 

 covered with straw and burnt over to destroy all diseased plants and" 

 fallen leaves. By taking this precaution, it is possible that the disea.se 

 mav be arrested in its destructive course. 



As irrigation colonies become more numerous, so will the conditions 

 be more favourable to the spread of various diseases — warmth and mois- 

 ture constitute suitable conditions for the development of fungoid pests. 

 Settlers should therefore be continually on the lockout for the appearance- 

 of anv disease such as the one under review. 



