CCA Pest Diagnostics and Disease Management 2

Question 1

Fungicide application for managing gray leaf spot in corn is most economically justified at which growth stage?

Accepted Answer

VT to R1

Answer

Fungicide applications for gray leaf spot are most cost-effective at VT (tasseling) to R1 (silking) when disease is moving into the upper yield-determining canopy.

Question 2

Crop rotation is the most effective long-term management strategy for which soybean pest?

Accepted Answer

Soybean cyst nematode (SCN)

Answer

Rotating to non-host crops like corn starves SCN populations because the nematode cannot complete its life cycle without soybean roots.

Question 3

Seed treatments containing metalaxyl or mefenoxam are specifically effective against which class of plant pathogens?

Accepted Answer

Oomycetes (water molds)

Answer

Metalaxyl and mefenoxam are phenylamide fungicides that specifically inhibit oomycetes such as Pythium and Phytophthora, which cause damping-off and root rots.

Question 4

Which cultural practice best reduces white mold (Sclerotinia stem rot) pressure in soybeans?

Accepted Answer

Wide row spacing to improve canopy airflow

Answer

Wide row spacing improves air movement through the canopy, reducing humidity and slowing ascospore infection by Sclerotinia sclerotiorum.

Question 5

The economic threshold (ET) for applying a pest control measure is defined as the pest level at which:

Accepted Answer

The cost of treatment equals the economic value of damage prevented

Answer

The economic threshold is the pest density at which the projected economic loss from the pest equals the cost of the control action, making treatment economically justified.

(CCA) Certified Crop Advisor Practice Test

(CCA) Certified Crop Advisor Practice Test

CCA Pest Diagnostics and Disease Management 2