51 



WATERPRIMROSES 



BOTANICAL 



The Southeast, the region in which waterprimroses are fre- 

 quently nuisances in waterfowl habitat, has nine species of this 

 genus (Jussiaea). Some of the nine are too limited in distribu- 

 tion or too sparse to be serious weeds. Two of the most abundant 

 and troublesome ones are J. diffusa and /. grandiflora. Though 

 some species grow erect in moist soils, others root on muddy- 

 margins of ponds or ditches and produce dense beds over water 

 surfaces. 



IMPORTANCE 



Waterprimroses often do harm by competing with desirable 

 plants; their seeds have limited local value as duck food. 



CONTROL 



The most vulnerable period for waterprimroses is during maxi- 

 mum flowering. /. diffusa can be controlled fairly easily by vari- 

 ous 2,4-D formulations when applied at the rate of 4 pounds acid 

 equivalent to 100 gallons of water, sometimes by a single treat- 

 ment if the beds are not too dense. /. grandiflora is somewhat 

 more resistant and generally requires several treatments with 

 2,4-D. In Maryland, good results were obtained from spraying 

 with 2,4-D ester at 8 pounds acid equivalent in 100 gallons of oil, 

 applied during the vulnerable stage. Water-carried sprays re- 

 quired wetting agents, and results were not as good as with oil. 



