Page 12 - Griffin Gazette Issue 1 - 2019

Make 2019
THE YEAR OF…

Greenhouse Herb Production:
Keeping It Clean

By Rick Yates, GGSPro Technical Services Manager
Greenhouse production of herbs continues to increase in all of its
manifestations. Cell packs and small pots for planting into the garden, or
for “windowsill farming," have been joined by herbs grown on to harvest
by both hydroponic and traditional production techniques. Consumers
understandably have little or no tolerance for insects, mites or diseases
in their fresh herbs. Growers are challenged to meet that objective by the
fact that some herbs are particularly prone to such problems, while the
number of pesticides labeled for greenhouse herbs is relatively small. Add
to that the fact that some growers seek to be certified organic, making
threading that needle a little more challenging. So what’s a grower to do?
Let’s start with disease management. Even the best fungicides can fail
if we haven't first done all we can to optimize the growing environment
to discourage disease development. Sometimes overlooked is variety
selection. A good example would be downy mildew of basil, where
important breeding work is underway to produce disease-tolerant
varieties, such as the new Amazel basil from Proven Winners.
Herbs are often grown at a high density, which can sometimes backfire
when it comes to disease prevention. Tightly spaced crop canopies can
create microclimates of high humidity air in the crop which favor disease
development. This can also make applying the microbial fungicides that
are primarily contact products difficult to deliver to where they are needed
the most. Evaluate your crop spacing, especially for notoriously disease
prone herbs.
The tried-and-true IPM technique of scheduling irrigations to minimize
the length of time that the foliage stays wet should be employed as well.
Herbs grown in NFT hydroponic systems or in small pots on troughs
benefit from dry foliage and the ability to get air movement to the base of
the plants.