Spring Isn’t Just For Showers, It’s For Beneficial Nematodes Too

As spring finally arrives for those of us in need of a deep thaw, our attentions turn to the garden and how to best put it to use in the upcoming season. For the organically inclined, there is no better first step to a healthy spring garden than applying beneficial nematodes. They help control a vast range of insect and arachnid pests in the soil and help maintain a bioactive soil network essential for healthy plants. 

The question is: when is it best for them to be applied?

The truth is, there are probably native beneficial nematodes overwintering deep in your soil already. For raised bed or container gardeners this may not be the case. A general rule of thumb is to apply the nematodes after your last expected frost date (found here). Unfortunately, weather patterns and climates have become quite unpredictable in the past few years, so the listed date may not always apply. For those aberrant weather anomalies, it is helpful to know the temperatures at which nematodes remain active. 

These hardy creatures are effective parasites in soil temperatures down to 42 degrees Fahrenheit; below that they enter a period of dormancy. It is important to note that soil temperature, not air temperature is the main factor for nematodes’ continued viability in the soil. 

Soil temperatures may be radically different from air temperatures for a variety of reasons:

• Climate and season

• Orientation to the sun and topography in the area

• Plant cover

• Soil makeup and texture

• Rainfall and moisture content

• Organic matter content

Because soil temperatures are the critical factor, a soil thermometer is a handy tool to have lying around. Measuring soil temperatures periodically allows gardeners and growers to chart changes from year to year and adjust treatments accordingly.

Just like timing insecticide applications, timing your biorational control treatments properly is a vital part of successful integrated pest management. 

We welcome input from our readers and would love to hear any tips, tricks, questions or comments you have below!