Scouting  

Scouting is key to Fraser fir IPM. There are many pests of Fraser fir Christmas trees in western North Carolina. Some, like the balsam twig aphid, can be a problem almost every year. Others, such as rust mites, are only occasionally a problem. Almost all Fraser fir pests are small, and can go undetected for months until they have already caused damage. Only through scouting can a grower learn what pests are present in sufficient numbers to cause economic loss and therefore require a pesticide application.
    What is scouting? Scouting involves regular, repeated inspections of plants in the field throughout the year. The objective is to catch pest problems as they begin to develop but before they cause much damage to plants. Scouting also involves keeping records so that trends in pest populations can be followed over time.

There are four goals to scouting:

1. Assessing what pests and natural predators are present and their stages of growth.
2. Detecting if pest numbers have reached a critical threshold and control is needed.
3. Determining if it is the proper timing to control a particular pest.
4. Deciding if pesticide treatments or other control practices worked well.

    Scouting blocks. A block is a scouting unit which can include as few as 100 trees or more than an acre. Different-aged trees are scouted separately, since they have different pest problems and the treatment threshold is often higher for younger plants that won't be marketed as soon. Very large fields of the same-aged trees can be broken into smaller blocks by farm roads to make scouting easier.
    Treatment threshold. No pesticide is free and the cost of the labor to apply a pesticide is usually higher than the cost of the pesticide itself. This total cost of application must be justified before it makes sense to treat for a particular pest. The decision to apply a pesticide should be based on an understanding of the level of damage a plant can tolerate without losing growth or market value. Christmas trees during the year of sale cannot tolerate much pest damage of any kind. However, younger trees can sustain damage from spider mites or twig aphids with minimal loss in growth or market value. Other pests, such as rust mites, have to be present in high numbers before any damage results.

    The treatment threshold is the point at which the cost of applying a pesticide is justified because of the damage the pest will cause if left uncontrolled. It is usually expressed as the number of pests found per number of plants, or as the percentage of plants found with the pest. Treatment thresholds are developed through research and observations over several growing seasons. The treatment threshold takes into account the rate at which a pest multiplies, so that pesticides are not applied too late. The increasing economic value of the trees as they mature is also reflected in many thresholds. For instance, it takes far fewer spider mites to reach treatment threshold on trees the year of sale than for three-foot trees.
    Since every grower has different costs and is growing trees for different markets, the treatment thresholds found in this manual are only a suggestion and should be tailored to the individual situation. By keeping accurate scouting and pest control records, each grower can fine tune these thresholds.
     Scouting to assess pesticide controls. After any pesticide is applied, it is important for the scout to return to the field to determine how well the pesticide worked. A second application may be needed, or perhaps a different application technique or pesticide should be used.
    Tools for scouting. Effective scouting can be done with very few tools, but all of them are important. Be sure to have the following supplies:

• Scouting forms. Sample forms are available from your county extension agent.
• Map of blocks. Even rough sketches can help record scouting results.
• Pocket knife for removing shoots and bark samples.
• Hand lens with 5X to 15X power.
• Counter to keep track of the number of shoots sampled.
• Flagging to mark problem trees.
• Plastic bags to keep samples of damaged shoots or insects that cannot be identified in the field.
• Beater tray when scouting for spider mites. (Optional)
• Soil probe for taking soil samples.
• Plastic bucket for mixing soil samples.  Pruners for taking plant tissue samples.

    The scouting calendar. Different pests are active at different times of the year. In order to catch problems early, it is important to be in the field as each pest becomes active. Some pests require multiple visits throughout the year to learn whether populations are increasing or decreasing.
    At the end of each scouting visit, the time of the next scouting visit should be noted on your calendar. For more information on planning a scouting calendar, see page 24.

IPM Management Record
IPM Management Calendar