n8 



IRISH GARDENING 



Gooseberry Cluster-cup Disease. 



Whether it is because this disease is becoming 

 more common or because, as is perhaps more 

 probable, growers since the advent of the dreaded 



Fig. I. (gooseberries showing areas affected with 

 the dust er-cup fungus. 



American gooseberry mildew are more on the 

 alert for signs of disease of any kind in their 

 gooseberry bushes, it certainly is a fact thai 

 enquiries concerning this trouble have been 

 becoming more and more numerous during the 

 past leu years. Hence a brief accounl of it may 

 perhaps be acceptable to the readers of ibis 

 pa per. 



lu the lirsl place it may be slated thai the 

 disease has been known for a very long time, 

 and that its ravages are as a rule not verj serious. 

 Nevertheless. 1 lie diseases due to the " lllst 



fungi" and this is one of them are in man\ 

 cases of such supreme economic importance thai 

 it would be unwise to suppose thai the gooseberry 



cluster-CUp disease may not at some future time 



assume serious epidemic proportions. 



The disease appears both on the Leaves and on 

 the berries, at lirst in the form of reddish-yellow 

 or orange-coloured t hickened areas wit h a. smool h 



surface. Later on this smooth surface becomes 

 broken up by tie- bursting forth from beneath 

 it of numerous cup-like bodies, each of which 

 has a more or less jaggedly-fringed margin ami 

 contains numerous yellow spores. These spores 

 are discharged from the cups, an I at this stage 

 the diseased areas are of a Lighter yellow colour 

 i linn previously. 



The accompanying figure 1 shows a, few berries 



affected with the cluster-cup disease, while in 



figure _ is shown, considerably enlarged, a small 



portion of the diseased area of one of these 



berries. The clusters of partially emptied cups, 

 with their rellexed fringed margins, are clearly 

 defined, but the magnification is nol sufficiently 

 great to show the spores themselves. 



As indicated above, the fungus which produces 

 the disease is one of the group of rusts all of 

 which are strict parasites, and have Eorthe most 

 part more or less complicated life histories. 



ineut many rusts (including tin 1 present one 

 require two host plants. On the one they 

 produce spores which differ completely from 

 those which are developed on the other, and it 

 is not surprising that before the Life-histories of 

 these rusts were understood mycologists regarded 

 the different stages on the separate hosts as 

 distinct fungi, and named them accordingly. 

 Thus, in the case of the gooseberry cluster-cup 

 fungus, the stage on the gooseberry was formerly 

 known as .1 it-id i n m Grossularice l'ers.. while its 

 more correct name is now Puccinia Prings- 

 hti miana Kleb. 



Now. the spores which are produced in these 

 cluster-cups will not themselves cause the infec- 

 tion of gooseberry leaves or fruits, consequently 

 they are not the direct cause of the spread of 

 the disease in the summer. < >n i he other hand, it 

 has been shown 1 hat they will germinate on and 

 produce pustules of other kinds of spores on 

 certain species of sedge -namely, Carex ticnttt 1.. 

 and ('. Goodenovii Gay. Further, it has been 

 shown that these other spores, produced on the 

 sedges, will, if they reach gooseberry bushes in 

 the spring, produce on the foliage and fruit the 

 clusl er-cup disease. 



From a knowledge of the life-history of this 

 fungus, therefore, it is possible to suggest means 

 for the prevention of the disease. First, all 

 affected berries and leaves should be gathered 

 and burned, thus cutting off the source of infec- 

 tion of the sedges. Secondly, ditches and other 

 damp places in the neighbourhood of gooseberry 

 plantations where sedges are Likely to grow 



should be kept well trimmed and free from rank 

 growth. It is on the sedges that the fungus 

 passes the winter, and it is from them that t hi' 

 gooseberry bushes are infected in the spring. 



It is here tacitly assumed that the second host 

 is absolutely necessary for the continuance of the 

 life of the fungus. It is. however, only fair to 

 add that it is now well known that in the case of 

 some rusts, at any rate, the presence of the 

 second host is not necessary. Thus in the case 

 of one of the wheal rusts the second host plant 

 is the barberry, but this wheat rust occurs and 

 recurs in places where barberries are conspicuous 

 by their absence. Hence, the fungus must have 

 some other means at its disposal enabling it to 



appear every year in its role as a disease-producer. 



It would be going too far to discuss this matter 

 here, suffice it to say t Ei.it it is possible that the 



Fig. 2. — A small portion of the diseased area 

 Showing the clustered clips (considerably 



