Giant foxtail, Setaria faberii

Life Cycle

Annual

Propagation

Reproducing only by seed.

Stems

Up to 2 m high, smooth.

Leaves

Leaf sheaths mostly smooth, except hairy along the margins; leaf blades 30 - 55 cm long, 3 - 17 mm wide, usually finely hairy throughout the entire upper surface (G, H) of all leaves and occasionally also on the undersurface (seen by rolling the leaf over a finger and viewing it against the light); ligule a dense band of hairs, about 1.0 mm long; no auricles.

Flowers and Fruit

Inflorescence dense, spike-like, erect or the larger ones usually somewhat curved or nodding, 4.5 - 17 cm long and 1.5 - 3 cm thick, surrounded by light yellowish-green awn-like bristles which give the inflorescence a bottle-brush appearance; spikelets 1.5 - 3 mm long; grains (“seeds”) light green and abundantly cross-wrinkled. Flowers from late July to October.

Roots and Underground Structures

Fibrous root system.

Habitat

Giant foxtail is native to China and was recently introduced from the USA where it is a very common weed; it is becoming abundant in fields and waste places in southern and eastern Ontario.

Competitiveness

Corn yield loss (%)*: 2 % at 1 plant/m2 10 % at 5 plant/m2 Soybean yield loss (%)*: 3 % at 1 plant/m2 12 % at 5 plant/m2 *assumes that the weed has emerged with the crop and has been left uncontrolled all season.

Distinguishing Features

It is distinguished from Green foxtail by its usually larger, nodding inflorescence, its distinctly cross-wrinkled grains and usually hairy upper surface of leaves, and from Yellow foxtail by its larger, greenish-yellow rather than orange-yellow inflorescence, and by the upper surfaces of its leaf blades being finely short-hairy throughout their length rather than bearing a few long, kinky hairs near the stem. The technical character that distinguishes Giant foxtail from Green foxtail is that its second or upper glume covers only about ¾ of the fertile floret, whereas in Green foxtail it covers nearly the entire floret.

Toxicity

Giant foxtail is not known to be toxic.

Human Health Issues

Giant foxtail is not a known allergen.

Forage Quality

No information exists at this time.

Species Benefits

No information available at this time.

Often Mistaken For

Green Foxtail (SETVI), Fall Panicum (PANDI)

Power Ranking Corn

Power Ranking

↑ 11

 

Power Ranking Soybeans

Power Ranking

↑ 12

 

Biological Control

Currently none available for this weed. For the latest research on biological weed control: http://res2.agr.ca/Lethbridge/weedbio/index_e.htm#toc

Biopesticide Control

Currently none available for this weed.

Herbicide Resistance

Populations resistant to sulphonylurea and imidazolinone (WSSA group 2)herbicides exist in Lambton county (ON). For more information on weed resistance: http://www.plant.uoguelph.ca/resistant-weeds/


Figure #1.

Giant foxtail: G. Yound plant showing finely hairy leaf surfaces. H. Leaf-base showing dense covering of very short hairs on upper surface of leaf-base, hairy ligule with longer hairs at margins of collar, and short hairs along edge of leaf sheath.


Figure #2.

Ligule: hairy.


Figure #3.

Leaf blade: Hairy upper leaf surface and hairless lower leaf surface.


Figure #4.

Leaf sheath: Hairy margins.


Figure #5.

Seed head.


Figure #6.

Entire plant.