Illinois Field Crop Applicators Practice Test

What is the economic threshold for bean leaf beetles feeding on cotyledons and first true leaves?

1. 10-20 beetles per foot of row

2. 30-40 beetles per foot of row

3. 50-60 beetles per foot of row

4. 20-30 beetles per foot of row

The correct answer is: 30-40 beetles per foot of row

The economic threshold for bean leaf beetles feeding on cotyledons and first true leaves is 30-40 beetles per foot of row. This threshold represents the point at which the damage caused by the beetles is sufficient enough to justify taking action, such as applying a pesticide. Bean leaf beetles, particularly in the early stages of plant development, can cause significant harm. Their feeding can lead to diminished plant vigor and reduced yield potential. The economic threshold is based on research that indicates this range (30-40 beetles per foot of row) is where the financial loss from the beetles exceeds the cost of potential control measures. This threshold alerts growers to monitor their fields carefully and take appropriate action to prevent economic damage before significant yield loss occurs. Understanding this threshold is critical for effective pest management, allowing for timely interventions when populations reach a level that could threaten crop health.