Hemp Update #16

Borers, Powdery Mildew, Males, Labs and More!

European Corn Borer in Stems

Borers in Stems

European Corn Borer has been seen damaging as much as 1-2% of the crop in the past couple of weeks.  Other borers are also possible culprits for the damage we have been seeing and we are identifying the insect of samples we have received.  In general, regardless of the specific insect, the female lays eggs on the stem and the tiny larvae bores in the stem and proceeds to eat and grow in the stem – protected from predators and pesticides (no, not permitted for hemp but possible for other crops).  During its feeding, damage results in  yellowing and possible flagging (snapping/bending of top part of the plant).  Then, when the larvae has had its fill, it proceeds to the next life cycle phase and pupates and then develops into an adult, where it exits the plant to repeat the cycle of reproduction.  Most of the Hudson Valley is in the early stages of the second flight of ECBII where the tiny larvae are just starting to appear on the crop.  The photo is of the damage and what appears to be larvae that died before it could pupate in the stem.  If these are ECB, even when pesticides are permitted, it will be a complicated pest to manage, as it is on sweet corn, because there is a very narrow window of time to control the larvae before they enter the stem.  Adults are too active/unpredictable to control with sprays and eggs are impervious.  Sweet corn producers rely heavily on trapping of adult flights to predict/manage spray programs.

More info on ECB here:

Forages page: https://fieldcrops.cals.cornell.edu/corn/insects-corn/european-corn-borer/

Vegetable Page: https://nysipm.cornell.edu/agriculture/vegetables/vegetable-ipm-practices/chapter-26/section-26-6-8/

Also this Week: Powdery Mildew

Powdery Mildew became a much more common occurrence these past couple of weeks.  Infections are still light to moderate in field-grown CBD.  Air movement is key to keeping this disease in check.  If you have weedy field edges or between the beds, consider reducing the vegetation that is keeping air from your plants as well as trapping moisture in the canopy.  Cornell researcher/Plant Pathologist, Dr. Chris Smart is always looking for Powdery Mildew samples to tests in her lab to see what/how many strains are living/thriving on what varieties.

Powdery Mildew: Do You Grow Hops Too?

See the attached PDF for an update on the association between hops PM and hemp PM.

Yellow Leaves – No Apparent Reason?

This week as flowers started to expand on many varieties, the “big” or fan leaf just below a flowering branch has begun to yellow.  You will see several of these yellow leaves throughout the plant and in all cases it will be where a flowering stem is growing.  This is the plant reducing nutrients to that fan leaf in favor of the flowers.  It is normal.  Although, at a distance it can make your field look quite sick.  As long as there are no spots on those fan leaves, you can disregard what appears to be a problem.  In marijuana culture, it is common to do what is called “big-leafing” which is to remove the leaves (sometimes suggested even before flower initiation as a pruning/suckering method).  In many cases this leaf will fall off before harvest but if you have the labor and the initiative, you may want to remove the leaves so they are not fodder for pathogens as several prefer dead/dying tissue, like Botrytis.  You also may want to remove them to decrease non-flower dry matter come harvest.

Keep Looking For Males:  Several CBD fields continue to show ~1.0% males in most cases and much more in a select few.  Keep an eye out for pollen sacks.  See picture.

Keep an Eye Out for Pollen Sacks

It’s Almost That Time…. Harvest Reports

NYSDAM requires you to inform them 21 days before you plan to harvest so they can send an inspector to sample the crop for THC analysis.  To request a sampling; a harvest report is required.  The report is available here:


However, you may want to test THC and other components before harvest and NYS is only testing the samples they collect for their regulatory role.  If you need additional testing, you need to arrange for it privately. 

Testing Labs…

These labs provide analysis for THC, other contaminants, and measure the preferred chemicals as well.  Each lab is a bit different in what is offered so be sure to obtain a sample result (COA-Certificate of Analysis) and compare them to obtain the analysis you are looking for.  Due to the increase in hemp acreage be sure to discuss with the lab you select what they expect the “turn-around” time to be on your results.