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In this season of dormant spraying, consider adding biology to fix pest problems permanently.

Updated: Jan 14, 2020

It’s winter again, when the thoughts of orchardists turn to dormant-season pest control. In this reflective time of year, one should always keep in mind an important truth: it’s a great time to switch to biological management.

Any change to a farmer’s packed workload may seem daunting, so keep in mind another important fact: the switch doesn’t need to be abrupt. In order to work well, biological management must be an all-in endeavor – but that’s not to say it must be all-in right off the bat, necessarily.

Often orchards harbor known issues, like fungal pathogens that have reappeared in recent seasons. Producers may feel most comfortable applying something they know, like copper or sulfur, which makes perfect sense – doing so should reduce pathogens in a predictable fashion. At the same time, we need to remember that these substances, in the concentrations in which we apply them, kill not only pests but also the soil and foliar microbes we’re trying to nurture. So for a successful biological conversion, the trick lies in how quickly and thoroughly we switch to microbial inoculations after applying them.

Of the diverse microbes we apply, some among them will digest the residue from those inputs. Bacteria will gradually reduce toxic concentrations of sulfur and copper, while the oils used for control of overwintering insects feed aerobic fungi. We have implemented exactly this pattern on multiple occasions among different crops, always achieving success – high plant health and absence of infestation or infection, with no further pesticide use – well in advance of harvest.

At this stage, therefore, we have accomplished not just treatment of the symptom, but also correction of the underlying cause. Any sign of diminished plant health – outbreaks of disease, infestations of pests or pathogens – can be traced back to unhealthy microbial communities. With proper soil biology, it is impossible for any single organism to overpopulate.

The dead of winter can be a good time to start applying microbes, but it depends on climate. Here in California’s Central Valley and Foothill farm country, big chunks of winter can be decidedly spring-like, and therefore of temperatures hospitable to microbial activity.

In such conditions, we might also employ a bio-control product to target an acute pest issue. Commercially produced nematodes are proven effective at reducing overwintering insect populations, while commercial bacterial strains can control fungal pathogens.

In higher-elevation and colder climates, inoculation is best started in the fall. But if that didn’t happen, no worries. If all goes according to plan, anticipate that this season’s dormant sprays will be your last. If, that is, microbial applications are forthcoming when conditions warm a bit.

The bottom line: when you have stocks of dense, diverse microbes – which is to say, a full Soil Food Web – there is always a way to make dramatic improvements to your growing system quickly.

Give it some thought. A new year of healthy plant production beckons.

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