Evaluating Crop Loss


Solutions should be based on the correct identification of the slug species. IPM users must first set an action threshold—a point at which slug population numbers will become an economic threat and crop losses will occur, if an action is not taken. Finding a single slug does not mean control is needed—setting a personal threshold is critical to guiding slug control decisions.

Establishing stand:

  • Count the number of seedling plants found in a linear foot (or a meter, ~3 foot) during the establishment phase of plant growth.

  • Count plants in at least 5 random areas and take the average number of plants per linear row foot or a meter long.

  • Measure reduction in plant stand on 3 growth seedling occasions, for example: 1) at the cotyledon stage; 2) at 2-true leaf; and 3) at 4-true leaf depending on the crop. 

Established grass stage:

  • Record percentage of plants or grass crowns with signs of slug damage per linear row foot. Evaluate at least 5 areas in the field.

  • Suggested slug damage rating scale: Rate plants along a 5-point scale (0 to 4) based on number of plants gone or damage present to existing plant. Evaluate plant damage presence per linear row foot. Severity of damage can also be rated.

0:   0 —5%; Little to no slug damage

1:   6 — 25%

2:  26 — 50%

3:  51 — 75%

4: greater than 75% of plants with damage