Winter
annual weeds are common pests of alfalfa Medicago sativa. These
weeds germinate in the fall and grow rapidly while alfalfa is dormant
or semi-dormant. These weeds compete well with newly growing alfalfa,
become readily visible in alfalfa stands in the spring, contaminate
the first-cutting hay, and reduce the quality and economic value of
the hay. Common winter annual weeds of alfalfa include downy brome, Bromus tectorum, tansy mustard, Descurainia pinnata, flixweed, Descurainia sophia, blue mustard, Chorispora tenella,
shepherdspurse, Capsella bursa-pastoris, and field pennycress, Thlaspi arvense. Expensive herbicides (over $20 per acre) like
Velpar and Pursuit are commonly used to control these weeds. Insects
commonly found in alfalfa in the spring include alfalfa weevil, Hypera
postica, pea aphid, Therioapis maculata, and alfalfa caterpillar, Colias eurytheme Boisduval. The alfalfa weevil typically is the
most frequently encountered insect pest in northeastern Colorado and
can significantly reduce the quality and quantity of first and second
cutting alfalfa. Insecticides such as Baythroid 2 and Warrior are commonly
used for management of this pest.
A trend
towards sustainable agriculture and organic products has encouraged
efforts towards identifying effective, economical alternatives to herbicides.
In addition, many alfalfa fields along the Front Range are becoming
closer in proximity to encroaching home developments, making herbicide
and insecticide applications more difficult and less desirable.
Flaming
treatments of alfalfa offer many benefits over chemical herbicide and
insecticide applications. When using flaming as a pest-controlling method,
there is no risk of contaminating water or soil and eliminates the potential
of human or wildlife exposure to pesticide residues.
Recent
trends in consumer buying habits suggest a real need for organic alfalfa
feed for livestock along the Front Range of Colorado. Flaming alfalfa
using propane could address weed and insect concerns of growers and
produce forage that could be marketed as a synthetic, chemical free,
high value forage.
The purpose
of this study was to examine whether propane flaming treatments of alfalfa
fields in the early spring could reduce winter annual weeds and/or insect
pests and produce quality alfalfa.
