Pesticides on Blackberry in Fruiting Season

Recently, one of our neighbors was walking on Mt Davidson. It’s the time of the year when the blackberry bushes bear fruit, to the delight of children and the public in general (and not a few animals and birds). She was unpleasantly surprised to find that the bushes were to be sprayed with herbicide.

“It’s the fruiting season!” she noted, wondering if this was legal.

Unfortunately, it is.  In 2016, SF Environment imposed restrictions on spraying blackberry bushes during the fruiting season. But the way the restrictions are written, they apply only to Tier I (“Most Hazardous”) pesticides and not to the Tier II (“More hazardous”) pesticides that the Natural Resources Division (NRD – formerly Natural Areas Program) also uses quite frequently. The NRD commonly uses “the fearsome four” pesticides: Garlon, Roundup, Milestone VM and Polaris (also called Habitat). All of them are toxic in some degree.

The herbicides used in this case are Milestone VM (aminopyralid) and Polaris (Imazapyr). Both are toxic and are classified as “More Hazardous” (Tier II). Imazapyr can damage eyes, and its breakdown product is a neurotoxin, which means it causes nerve damage. Aminopyralid is a newer chemical, but is known to be astonishingly persistent. It’s banned in some places because of that.



In 2016, the SF Department of the Environment engaged in a lengthy process of trying to improve its restrictions on  some of the most problematic use of pesticides in our parks.

(You can read the entire compliance guidelines here as a PDF. It’s from the SF Environment website. sfe_th_ipm_compliance_checklist – Copy )

Among them, they developed these restrictions:

 Pesticide use

✓ A written recommendation from a licensed Agricultural Pest Control Advisor (PCA) is required for any pesticide use. Departments that do not have PCAs on staff should contact the SF Environment IPM Manager.

✓ Only pesticides on the current SF Reduced Risk Pesticide List may be used. Usage must fall within the “limitations” listed for each product, along with label requirements.

✓ ‘Most hazardous’ (Tier I) herbicides have special limitations:

  • Use is prohibited for purely cosmetic purposes.
  • Use is prohibited within 15 feet of designated paths. If a park map exists, designated paths are those found on the maps. Otherwise, designated paths are those actively maintained by staff.
  • Use is prohibited within 15 feet of schools, preschools, playgrounds, or other areas frequented by children.
  • Use on blackberry bushes is prohibited when fruit are present 
  • If within the City limits, use requires onsite supervision by a licensed person (PCA, QAL/QAC) o No broadcast spraying with a boom is permitted except for golf courses (targeted spraying only)
  • Certain pesticide use is restricted in designated Red-Legged Frog habitat, which includes Golden Gate Park, Lake Merced, and several other areas in San Mateo and Alameda County.


Posting for pesticide use must be done 3 days before treatment, and remain up for 4 days after treatment, except for least-hazardous (Tier III) products, which require posting only on the day of treatment.

✓ Postings must clearly identify the area to be treated. Signs should be placed at locations most likely to be seen by members of the public using the treated area.

✓ Posting is not required for median strips or rights-of-way when these areas are not intended for public use.

✓ Posting is not required for areas inaccessible to the public. [See our recent article on this: San Francisco Pesticides and Inaccessible Areas]

✓ ‘Most hazardous’ (Tier I) herbicides have special notification requirements:

  • Blue dye must be used, and this must be noted on the posting sign. Blue dye is not required in areas where 1) posting is not required, and 2) staining may occur, such as ornamental stone median strips.
  • When treatment sites that cannot be readily identified by the posting sign alone, a map showing the general location of expected treatment area(s) must be attached to the posting sign.


Though the added restrictions in 2016 were a step forward, much more is needed. NRD seems willing to go by the letter of the rules, not the spirit of it. Blackberry should not be treated with persistent herbicides at all, especially not in the fruiting season. It’s going to affect children, wildlife, and anyone who loves picking the berries in season… most parkgoers.

San Francisco Forest Alliance stands for Pesticide-Free Parks – including natural areas.

Blackberry and Pesticides

It’s blackberry season!

All over the city, people are picking the delicious berries off the Himalayan Blackberry bushes. At Twin Peaks, we saw someone intently gathering fruit in a small bowl from bushes below Twin Peaks Boulevard. In Glen Canyon yesterday, children were having a great old time snacking on blackberries along the trails.  The Bernalwood blog announced that Blackberry Season Underway in Bernal Heights. (It has some luscious photographs.) Even the Presidio’s Facebook page had a pictures of a berry bush and said, “It’s blackberry season. Did you know that park visitors are allowed to harvest very small quantities of the five-leaved Himalayan blackberry fruits?”

And we found this delightful video of four generations of San Franciscans making blackberry jam with blackberries picked right here in San Francisco. It’s  the little girl’s first year picking blackberries.

[CLICK on the jam-jar graphic to go to Making Jam with Grandma Kathy.]

It’s not just children who eat blackberries off the bushes. Birds and other wildlife do it too. [CLICK HERE for a link to an article with a great picture of a bird on a blackberry bush.]

So we were dismayed when people reported that pesticides are being used on Mt Davidson (again!) and this time, one of the targets is blackberry – right during the fruiting season. The pesticides being used are Aquamaster (glyphosate) and Polaris (imazapyr). [CLICK HERE for information on these herbicides.]

The notice says “The manufacturer’s notice says it is safe to enter area when the spray has dried. Staff will stay on site until spray has dried.”

We’re not sure that leaves the berries safe to eat.

And as for the area being safe once the spray has dried… we’re not sure about that either.

“Is it even possible for the spray to dry on Mt Davidson?” someone asked. Mt D lies within the fog belt, and it doesn’t dry out in the summer. “It is very, very wet in the green zone of Mt. D right now because of the fog. The paths are very muddy and the water is streaming down the road.” The photograph seems to prove the point. It was sopping wet.

How wet is Mt Davidson in summer?

Like this. This is all water from the cloud forest effect, the moisture precipitated from the fog.