REPORT OF THE ENTOMOLOGIST AND BOTANIST 201 



SESSIONAL PAPER No. 16 



DIVISION OF BOTANY. 



CLOVER OR ALFALFA DODDER. 



From time to time inquiries are raade by farmers concerning curious leafless, 

 thread-like, fleshy parasitic plants which they find climbing over clover and alfalfa 

 in their fields. The Hlter plant is also know.n as lucern. The parasite injures the host 

 plants very much. As a rule only a few patches will be found in a field; but occasion- 

 ally, as in an instance referred to below, the dodder parasite increased to such an 

 extent that the crop of alfalfa was practically ruined. Specimens of the parasites 

 having been procured through the kindness of Mr. H. H. Miller, of Guelph, Ont. , upon 

 examination they proved to be the Clover Dodder, which in this country is more gen- 

 erally known under the name of Alfalfa Dodder. Formerly this species was known as 

 Cuscuta trifolii, Bab., from the frequency with which it occurred upon clover {Tri- 

 folium) in Europe, but it seems to be now generally conceded that it is the same 

 species as was described from plants growing parasitically upon the wild thyme, and 

 for which reason it had been named Cuscuta epithymum. There are several kinds of 

 dodders growing in North Araerica; but in Canada it is a small genus consisting of 

 only a few species. Of these there are only one or two which cause injury to crops; 

 and by far the larger number of cases reported are by the Clover or Alfalfa Dodder; 

 this is a European species which has doubtless been brought into this country with the 

 seeds of alfalfa or clover. It does not confine itself to the different kinds of clover, or 

 even to plants of that natural order, but has been found upon a great many different 

 kinds of plants. It is an annual coming up from the seed every year, and in the past 

 the injuries from this parasite have been so small that it would appear as if in many 

 seasons the seed did not ripen sufiiciently to allow the plant to increase and become 

 very destructive. It must be remembered, however, that very little alfalfa, which is a 

 long-lived perennial, has up to the present time been grown in Canada, and con- 

 sequently the only chance which the dodder had to establish itself, was upon Red Clover, 

 which is a much shorter-lived plant and, as a rule, at any rate, is ploughed down after 

 the second year's crop has been taken. 



The seeds of dodder would hardly be ripe before the first crop of clover was cut, 

 and its only chance for ripening seed and perpetuating itself would be in those pods 

 which formed low enough to be left on the stubble, or such as were ripe before the 

 second crop of clover was cut in the autumn. The fleshy pods seem to take a long 

 time to ripen; and among those I have examined, there were very few which seemed 

 dry enough to withstand the September frosts without injury. This, however, is only 

 conjecture, and doubtless in some places further west than Ottawa seed may have 

 ripened this year as it has in previous years to some extent. That this is the case, is 

 shown by the persistence of the plant for two or even three years in a field after it had 

 first been observed. However, such plants may come from seed sown with the clover, of 

 which the germination was delayed; for Mr. H. H. Miller, in a good article upon this 

 subject which was published in the Farmer's Advocate for Nov. 23 last, states that 

 ' the seeds will retain their vitality in the soil for five years or longer under favourable 

 conditions. Tests as to vitality have shown that the half-ripe seed of this species will 

 retain sufficient vitality to germinate almost as readily as the fully ripe seed. In 

 some cases, they germinate more quickly ; and, when the seeds have been found in their 

 capsules, the percentage of germination was but little inferior to that of well ripened 

 seed.' 



