White pine weevil management

• Weevil management 
• Sampling to assess weevil attack
• Hazard rating
• Silvicultural methods of control
• Better site selection
• Resistance to attack
• Fertilization and weevil attack

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Sampling to assess weevil attack

Several sampling systems have been developed to assess weevil attack intensity. A sampling technique was described by Archambault, et al. (1993) for Norway spruce in Quebec. 

For quick assessments, a sequential sampling system is recommended. This system, described by Alfaro (1995), is designed to quickly assess if weevil attack levels in a stand are low (=20%). The system requires that a maximum of 60 randomly selected trees be examined in the sequential order in which they were selected.

Field application of sequential sampling 

One of the major drawbacks of sequential sampling in forestry is the requirement that trees be sampled at random and in the sequential order in which they were selected. This would result in an inefficient criss-crossing of the stand in order to maintain the sequence. It is suggested that, in the office, the area of the stand be divided into a grid of X, Y coordinates (e.g. a 10 m x 10 m grid). Then using a random number table or a packaged software program, select 60 random X, Y coordinates in the stand, keeping track of the sequential order of selection, i.e. 1 to 60. Divide the coordinate point list into two groups numbered 1-30 and 31-60. Examine for weevil damage the tree closest to each of the identified X,Y coordinates in the first group as you move through the stand in the most efficient manner. After sampling the first group, plot the cumulative number of attacked trees onto the attack assessment chart, maintaining the order in which the coordinates were originally selected.

If either of the decision lines has been crossed, stop sampling and record the stand as lightly or severely infested. If, after 30 samples, the cumulative attack line is still in the intermediate zone, sample the entire second 30-tree group in the most efficient manner. Add to the cumulative plot drawn on the chart. Again, while plotting, it is essential that the sequential order of selection be maintained. 

It is expected that this method will result in significant time and cost savings when classifying stands for treatment.

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