Weed Control News

Fungi to Control Purple Loosestrife

Are mycoherbicides a possible weapon in the war against purple loosestrife? Researchers in Minnesota examined fifteen genera of fungi frequently isolated from purple loosestrife for their potential as biological control agents. The objective was to develop a mycoherbicide that would be applied alone or in combination with other agents, such as insects, to reduce purple loosestrife populations.

They tested the different fungi for pathogenicity against 6-week-old purple loosestrife seedlings. Six of the fungi tested were classified as potential biological control agents, with each producing disease ratings above 3 on a scale of 0-5. The most virulent fungus tested was Septoria lythrina, followed by Alternaria alternata, Botrytis cinerea, Colletotrichum truncatum, Phoma sorghina, and Coniothryium olivaceum. Since these fungi were tested only against seedlings (to make it possible to test a large number of fungal cultures in a relatively short period of time and in limited space), future studies will concentrate on testing pathogenicity to plants that sprout from the crown. Size and age of the plant may affect susceptibility of the plant to some fungi.

Inoculation was most effective when spores were applied in a carrier called DIGS (a combination of dextrose, Intac, gelatin, and Silwet L-77). A. alternata, B. cinerea, and P. sorghina applied in DIGS showed the most promise for biocontrol of purple loosestrife in the laboratory. The DIGS carrier was developed because it worked well in laboratory research procedures, but it needs to be determined if this is the best carrier for applying fungi to plants in the field.


Nyvall, R. F. and A. Hu. 1997. Laboratory evaluation of indigenous North American fungi for biological control of purple loosestrife. Biological Control 8: 37-42.

Return to Commodity Menu Vol. V No. 1
Return to 
Contents Menu Vol. V No. 1
Go To Index