Biological control

Question 1

What, according to the Weed Science Society of America, is the right application of biological control agents in weed management?

Answer 1

As a component of integrated weed management with judicious use of other BCA and chemical, physical, and cultural methods.

Question 2

BCAs useful for -

a. weed eradication
b. weed management
c. replacing other weed management practices

Answer 2

b. Management - reduction of weed population to a level where it has a low economic impact. The BCA needs a small number of the weed (host) for its survival.

Question 3

Three classed of BCAs.

Answer 3

1. Grazing herbivorous animals
2. Pest organisms (of the weed; insects, nematodes, bacteria, fungi)
3. Allelopathy (Organism which produces allelopathic substances or applying allelopathic or microbial compounds for their herbicidal activity).

Question 4

Selective grazing for weed management is NOT suitable for what kind of agricultural systems?

a. Vineyards
b. groves and orchards
c. vegetable intercrops
d. cereals
e. grasslands and pastures

Answer 4

d. cereals

NOTE: grazing is the most suitable method for grasslands and pastures

Question 5

Forage quality of weeds is best during-

a. Fruiting stage
b. late vegetative stage
c. early vegetative stage
d. flowering stage

Answer 5

c. early vegetative stage

Question 6

Which of the following statements is FALSE?
Selective grazing by animals
a. is helpful in eradicating specific target weed species
b. can cause less palatable species to become more prominent
c. can be reduced by increasing grazing pressure

Answer 6

a.

Question 7

What is Flash grazing?

Answer 7

Several animals in a small area for a short period of time.
Animals need to be rotated off to allow desirable plants to recover
Drawback: can reduce stand density.

Question 8

True or False:

Ducks, geese, and fishes can be used for the biological control of weeds.

Answer 8

True

Question 9

The majority of BCA used for weeds are:

a. fungi
b. mites
c. insects
d. viruses

Answer 9

c. insects

Question 10

Which of these is NOT a desirable trait when introducing a natural enemy as a BCA?

a. They are prolific
b. colonize all the habitats where the weed is present
c. have a wide range of host species- Broad-spectrum control
d. good plant colonizers

Answer 10

c. is False

Host specificity is desirable

Question 11

Biological control of weeds with introduced organisms is mainly used in-

a. agricultural crops
b. greenhouses
c. natural areas
d. all of the above

Answer 11

c. natural areas

Question 12

A fungal species used as a Mycoherbicide must-

a. be genetically stable
b. target specific host species
c. be able to grow and sporulate in the natural environment
d. all of the above

Answer 12

d. all of the above

Question 13

True or False:
Allelopathy is the negative interaction between plants, including microorganisms, through the release of chemical compounds (allelochemicals) into the environment.

Answer 13

False.

The interactions can be positive or negative.

Question 14

The herbicidal allelochemical derived from Parthenium hysterophorus (Asteraceae) is

a. Hysterophorin
b. Parthenin
c. Asteracin
d. All of the above

Answer 14

b. Parthenin

Question 15

True or False:
Ailanthone obtained from Ailanthus altissima, sorgolenone from Sorghum, and the essential oil from Eucalyptus species have herbicidal properties.

Answer 15

True

Question 16

List four crops that can suppress weeds.

Answer 16

Rye, sunflower, sorghum, wheat, oats, alfa alfa, rye.

Question 17

Which of the following management practices can help manage agricultural weeds?

a. burying crop residues (rye, sunflower, wheat, barley, rice),
b. using the crop as a cover (oats, alfalfa, rye)
c. making appropriate crop rotations.
d. all of the above

Answer 17

d. all of the above

Question 18

Arrange the following events pertaining to the release of a classical BCA in the correct sequence.

a. Approval, shipping, and quarantine of the natural enemy at the destination.
b. Testing on plots and mass rearing of the BCA for release.
c. Surveys for natural enemies
d. Identification and confirmation of the target pest/weed species.
e. Once released, monitoring the impact of the agent on target and non-target species.

Answer 18

1. (d) Identification and confirmation of the target pest/weed species.
2. (c) Surveys for natural enemies
3. Determining the host-specificity, impact on non-targets, and environmental impact of natural enemies of interest
4. (a) Approval, shipping, and quarantine of the natural enemy at the destination.
5. (b)Testing on plots and mass rearing of the BCA for release.
6. (e) Once released, monitoring the impact of the agent on target and non-target species.

Question 19

In what areas of weed management does biotechnology find its uses:

a. Creating herbicide-tolerant crops
b. Development of bio-herbicides
c. Weed diagnostics (identifying weeds that are hard to identify morphologically)
d. All of the above

Answer 19

d. all of the above

It is also useful for studying herbicide tolerance