Ambrosia in Botany

Ambrosia in Botany

 

(1) White or pinkish blooms of the mycelium of the most primitive ascomycetes which line the passages in wood in which the larvae of bark beetles live; these larvae feed on the mycelium. The relations of the ambrosia and the larvae are an example of symbiosis since the mycelium, in turn, feeds not only on the wood, but also on the excrement of the larvae. Ambrosia does not have typical sporogenesis. The mycelium is transmitted to new wood in the form of special cells which remain in the intestine of the female bark beetles which fly to new trees. The ambrosia formed by the fungus Macrophoma is encountered in galls, the development of which is caused by Diptera from the genus Asphondylia on the legume, umbellifer, and borage families.

(2) Ambrosia is a genus of annual and perennial herbaceous plants from the Compositae family. There are 30 species which grow wild in America. Certain species have been carried to the islands of the Pacific and Atlantic, to northern Australia, southern Asia, Europe, and Africa. There are three species in the USSR which are considered pernicious quarantine weeds and infest the plantings of all crops.

Common ragweed (A. artemisiifolia) is an annual spring weed. The stem is up to 2.5 m high; the leaves are pinnately divided. Common ragweed is found in the area of Alma-Ata, in the northern Caucasus, in the Volgograd and Trans-carpathian oblasts, in the southern Ukraine, and in the Maritime Krai. In forming a large aboveground mass it greatly desiccates and depletes the soil and suffocates the crops.

Great ragweed (A. trifida) differs from common ragweed in its larger three- and five-lobed leaves. It is encountered in breeding grounds in the southeastern areas of the RSFSR and in Georgia.

Gymnopaniculate ragweed (A. psilostachya) is a perennial soboliferous weed which is externally similar to common ragweed. Its breeding grounds are in areas in the southern and southeastern regions of the RSFSR.

Preventive measures include scuffling of the stubble, periodic deep plowing of the soil, presowing cultivation, harrowing before and after the sprouting of the crops, the use of herbicides, and other measures. Ragweed pollen in large amounts causes an illness known as hay fever.