Factors Influencing Herbicide Performance

Question 1

What term is used to describe the binding of herbicide molecules to soil particles?

Answer 1

Adsorption

Question 2

Name four basic components of soil that determine texture.

Answer 2

Sand, Silt, Clay, Organic matter

Question 3

In which soil texture is leaching most likely to occur?

Answer 3

Sand or sandy soils

Question 4

How can humidity change the effectiveness of an herbicide application?

Answer 4

Low humidity can dry the herbicide droplets on the leaf surface before they have a chance to
penetrate the leaf. Also, plants that grow in dry climates typically have a thicker wax layer, which
can impede herbicide penetration.

Question 5

What growth stage of plants generally is the easiest to control?

Answer 5

seedling growth stage

Question 6

What is a rosette?

Answer 6

The rosette is the main vegetative stage of biennial plants. This stage grows low to the ground and
forms a circular pattern.

Question 7

Perennials can be controlled effectively at several growth stages. What are they?

Answer 7

Seedling, vegetative, early bud, and fall regrowth. Treating weeds at the flowering stage might
control the plant, but it usually does not prevent the plant from producing viable seed.

Question 8

When does the best control occur for woody plants?

Answer 8

In general, best woody plant control
occurs when the majority of the sap flow is not
moving up the tree. Check label directions or the
PNW Weed Management Handbook for recommendations
and timing.

Question 9

For effective control of woody plants, the herbicide

must be placed where _____.

Answer 9

the tree sap flows, the (cambium)—
the conductive tissue located near the
outside rings of the stump.