Spider mites are considered more of a nuisance pest than anything else. They don't trouble us every year, but when they are a problem, it's often a major one.
Spider mites often develop damaging populations just as the crops can least tolerate them; under hot, dry almost drought-like conditions. They are like adding insult to injury.
Peanuts is a crop that suffers from spider mites on occasion. This plant is relatively susceptible to the feeding damage from the mites and the injury often takes place at a very critical time for pod development.
Hot weather problem
Mid to late summer is the time that spider mites generally are at their worst. A little heat, a little bit of dry weather, some insecticide use to kill some of the beneficials, fungicide use that prevents a fungal disease from decimating the mite population, and the next thing you know you are spraying for mites.
Almost as serious as the mites themselves is the cost of obtaining good control. Two sprays are often necessary.
While we talk about the hot, dry weather in the summer and its effect on the spider mites, events much earlier in the year may be the biggest factors. Our observations in North Carolina have indicated the weather in April is often a major factor in spider mite outbreaks later in the year.
A warm, dry April seems to give the spider mites a bit of a jump start. The mites often increase in numbers in areas adjacent to the field, along roadsides, headlands, ditches, etc, and move into some fields early in the year.
Most commonly, spider mites often move into corn early in the year and then as the populations increase and the corn matures they often blow in the wind to other adjacent fields including cotton and peanuts. This often coincides with more hot, dry weather and the use of pesticides that increase the likelihood of mite outbreaks.
The small size of the mites makes them difficult to detect until damage becomes quite obvious. When control strategies are initiated well after the mites have gained a strong foothold, control becomes very difficult. Often the only truly effective means of control is a prolonged period of cooler, wetter weather.
With this information at hand, we should be reminded to scout often and early when hot, dry conditions exist. Based on the fact that at the time I am writing this (just before Easter) we have already had 90 degree temperatures, it is becoming a good spring for spider mites.
In addition, above normal temperatures and below normal precipitation is forecast for the next 10 days. All of this points toward a greater than average likelihood of mites.
We also need to be reminded that unnecessary use of pesticides can cost us in many ways, including the added costs associated with increasing the chances of spider mites.
It is also important to remember to follow label directions specifically for gallons per acre and pressure when using products such as Danitol or Comite. Application procedures are critically important when using these products against mites.
Finally, it is important to note that our climate often goes through cycles. In the 1980s we experienced a number of hotter and drier years and as a result suffered through some serious mite outbreaks. Recently, meteorologists at North Carolina State University predicted that we are about to enter one of those hotter and drier periods.
Plan scouting program
This, of course, is not a good forecast as a whole and certainly doesn't bode well for the possibility of spider mites. We should keep this forecast in mind as we plan our scouting programs.
We have also determined that higher ozone layers also increase the likelihood of spider mites and ozone levels during hotter summers are often higher.
Overall, the potential for spider mites appears quite high this year as well as the next few years.
While we can't change the weather, we can be prepared for what weather brings us relative to pest problems. The key factor in the effective management of spider mites is timely application of the appropriate pesticide. Timely application comes from effective scouting.