Weed management: a need for ecological approaches - Ecological Management of Agricultural Weeds - page 7

Table 1.1. Estimated applications of pesticides a used in greatest quantities for crop
production in the USAin 1987 and 1997

Active ingredients (millions ofkg)

Pesticide Use Applied in 1987 Applied in 1997

Atrazine herbicide 32-35 34-37

Metolachlor herbicide 20-23 29-31

Metam sodium fumigant (broad-spectrum biocide) 2-4 24-26

Methyl bromide fumigant (broad-spectrum biocide) no data 17-20

Glyphosate herbicide 3-4 15-17

Dichloropropene fumigant (broad-spectrum biocide) 14-16 15-17

Acetochlor herbicide 0 14-16

2,4-D herbicide 13-15 13-15

Pendimethalin herbicide 5-6 11-13

Trifluralin herbicide 11-14 10-11

Cyanazine herbicide 10-11 8-10

Alachlor herbicide 25-27 6-7

Copper hydroxide fungicide 0.4-0.9 4-6

Chlorpyrifos insecticide 3-4 4-6

Chlorothanil fungicide 2-3 3-4

Dicamba herbicide 2-3 3-5

Mancozeb fungicide 2-3 3-5

EPTC herbicide 8-10 3-5

Terbufos insecticide 4-5 3-4

Dimethenamid herbicide no data 3-4

Bentazon herbicide 3-4 3-4

Propanil herbicide 3-5 3-4

Simazine herbicide 1-2 2-3

MCPA herbicide 2-3 2-3

Chloropicrin fumigant (broad-spectrum biocide) no data 2-3

Note:
a Excluded from this list are pesticidal uses ofsulfur (22-34 million kg in 1997) and petroleum
oils and distillates (30-34 million kg in 1997).
Source: Aspelin & Grube (1999).

are commonly used or becoming more widespread in regions where rising
agricultural wages have reduced the cost-effectiveness of hand-weeding
(Naylor, 1994; Pingali & Gerpacio, 1997) or mechanical cultivation
(Miranowski & Carlson, 1993). Tractor-powered cultivation equipment
greatly reduces manual labor requirements for weeding, but may be less con-
sistently successful than herbicides in reducing weed density and protecting
crop yield (Hartzler et al .,1993).The cost-effectiveness and timeliness of culti-
vation can be particularly problematic on large farms with low crop diversity
(Gunsolus & Buhler, 1999).Additionally, herbicide use is favored by the adop-
tion of reduced and zero tillage practices (Johnson, 1994) and by the use of