Holly Bud Moth (?) Treatment

I think I might have holly bud moth on my Ilex crenata (one cloud pruned, the other a topiary cone). Symptoms are brown leaves at the branch ends which are matted together. When teased apart the matted leaves contain tiny black frass and occasional small dark larvae about 8-10mm long.
I’m removing as much as I can by hand but can anyone suggest an organic spray treatment please?

 

Here's a suggestion from Google that includes an organic option -

AI Overview
To control the holly bud moth on your Ilex crenata, begin by removing and destroying any rolled or webbed leaves by hand, as the larvae are the damaging stage. For a more widespread problem, you can apply a Bacillus thuringiensis (Bt) product to the foliage when the larvae are feeding and before they spin their webs, ensuring it gets on the inside of the bushes. Alternatively, an application of a soil-applied systemic insecticide like dinotefuran or imidacloprid in early spring can provide season-long protection for the following year.

Identify the Pest

• Adult Moth: A mottled brown and silver insect with a wingspan of about 0.5 inch.
• Larvae: Greenish-brown caterpillars with dark heads, approximately 0.5 inch in length.

Recognize the Damage

• Webbing: Caterpillars tie leaves together with webbing.
• Rolled Leaves: They roll and distort the leaves.
• Bud Damage: The spring generation of larvae feeds on the plant's buds.

Cultural Controls

• Handpicking:
  For light infestations, handpick and crush the larvae found inside the rolled leaves.
• Pruning:
  Prune away and destroy any infested leaves or rolled leaf clusters to remove larvae and eggs.
• Hygiene:
  Collect and dispose of fallen leaves to eliminate overwintering pupae and eggs from the soil.

Biological Control

• Bt (Bacillus thuringiensis): This bacterial insecticide can be sprayed on foliage during the feeding stage. The larvae consume the bacteria and stop feeding, eventually dying. Apply to the inner surfaces of the foliage.

Chemical Control

• Systemic Insecticides:
  Apply a soil-applied systemic insecticide such as dinotefuran or imidacloprid in early spring for season-long protection. These products are taken up by the plant and kill the feeding larvae. Read and follow all label instructions.
• Foliar Sprays:
  In May, during the larval feeding period, you can use a foliar insecticide containing active ingredients like spinosad or acephate to control the larvae.

 

That is one of the problems with all these AI suggestions. They are US orientated.
Both dinotefuran or imidacloprid are banned in UK and, I believe, in EU.

 

Fair comment - I'd not mentioned the location was in the UK when asking.
If I do, then -

AI Overview
For organic control of holly bud moth on Japanese holly in the UK, use manual methods by hand-picking larvae and removing rolled, webbed leaves, and destroying all plant debris. Biological controls, such as Bacillus thuringiensis (Bt), are effective but not licensed for home use in the UK and are only available to professionals.
1. Monitor and Identify

• Inspect in Spring: Look for the first signs of tight, webbed areas within the plant where the larvae hide and feed, which is a tell-tale sign of the holly bud moth.
• Check for Larvae: Once eggs hatch in early spring, you'll find the small larvae.

2. Physical and Mechanical Control

• Hand-Pick Larvae:
  For small infestations, you can manually pick and destroy the caterpillars as you find them.
• Remove Infested Parts:
  Cut out and destroy the rolled leaves and webbing that the caterpillars create, ensuring you collect all the debris.
• Prune Infested Tips:
  If the infestation is well-established, you can shear the infested tips of the plant to remove larvae before they pupate.

3. Destroy Infested Material

• Remove All Debris: Collect any fallen leaves or plant material that has been affected by the pest and dispose of it by burning or taking it to landfill.

4. Prevention

• Monitor New Plants:
  Inspect new hollies carefully before planting them into your garden to avoid introducing the pest.
• Improve Plant Health:
  Provide good growing conditions by ensuring good drainage and adequate watering. Healthy plants are more resistant to pests.

5. What to Avoid

• Don't Buy Infected Plants:
  Take care to purchase plants from reputable nurseries that are aware of pest issues.
• Bacillus thuringiensis (Bt) for Professionals Only:
  While Bt is an effective biological control, it is not licensed for use by home gardeners in the UK and should only be used by professionals.

 

Thanks @Pete8 and @Fof. Yes, I am in the UK. The AI extract says Bacillus thuringiensis (Bt) is not available for home gardener use in the UK. However, a search on Amazon gave a product that contains Bt. Sorry, the forum won’t allow me to post a link yet.

PlantPro Box Tree BuxRevive Treatment - Caterpillar Spray For Plants - Safe For Bees And Birds - Treats Up To 150m²

 

I hope this is the link you are after.
https://www.amazon.co.uk/PlantPro-B...-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

 

Has anyone used this product with any success?

 

The reviews on Amazon seem to be good.

I asked Google why it's not available to gardeners in the uk -

AI Overview
Bacillus thuringiensis subsp. kurstaki (Btk) is not banned in the UK but is only licensed for professional, agricultural use, not for general consumers or the hobbyist gardening market, due to a lack of sufficient safety data for specific uses and potential environmental and health risks highlighted by regulatory bodies like the European Food Safety Authority (EFSA) and the UK's Office for Environmental Protection (OEP). Products sold for consumer use are therefore considered illegal.
Why Btk is restricted for consumer use:

• Lack of data for specific uses:
  While Btk is a well-known biopesticide for caterpillars, there is insufficient data to fully justify many claims of low toxicity and environmental safety for all intended uses, particularly in open fields or greenhouses.
• Concerns about non-target effects:
  Although Btk is considered highly specific to certain insects, there are concerns about its potential impact on non-target organisms, including its effect on beneficial insects and the long-term consequences for the food supply of insectivores, notes the National Institutes of Health (NIH).
• Potential foodborne illness risk:
  Although rare, there have been links between B. thuringiensis residues in food and diarrheal illnesses, with regulatory reviews finding a need for further data on foodborne safety, says ScienceDirect.com.
• Regulatory landscape:
  Regulatory reviews, including a 2012 review by the EU and subsequent reports from EFSA and the OEP, have identified gaps in the data and concerns about potential risks, leading to stricter regulations on its approval.

In summary:

• Btk is a natural bacterium used in professional pest control.
• It is not approved for use by hobby gardeners or for the general public.
• The restriction is due to ongoing concerns about insufficient safety data and potential risks to the environment and human health, according to the National Institutes of Health (NIH).
• Therefore, consumers should not purchase or use Btk products.

 

Not a great fan of AI summaries on Google. It can come up with some really odd ‘facts’
However, I’m not prepared to risk using Bt as perhaps simply removing the bugs by hand on my two affected plants would be effective.
On another tack - Looking for natural bug treatments, I came across Neem oil. Any thoughts on this alternative?

 

I've never used neem oil myself, but have heard good reports from friends for a product called SB Invigorator.
It's not toxic but works by 'glueing' the bugs in place so they can't move or respire so they die.

Pyrethrum is an organic insecticide and is toxic to some bugs. It's not systemic so any bugs need to be sprayed with it. Pyrethrum is derived from a type of chrysanthemum.

 

SB invigorator sounds interesting. The reason I’m wanting some natural product is that I live on a floating home on a lake and can’t risk anything contaminating the water. I garden in many containers/pots/troughs on the decking. I’ve contacted the manufacturer of SB invigorator for advice. Will keep you posted…

 

Update from the SB Invigorator people. I quote…

“SB Plant Invigorator is a surfactant-based product so, as with all soaps, they can be harmful to aquatic life.

However, this would only apply if significant amounts were mixed with the water. Spraying an application at the specified dilution rate near a large body of water such as a lake, would foreseeably have no impact on aquatic life.

Unfortunately SB Plant Invigorator won’t have an effect on Holly leaf miner moths for two reasons. Primarily, it only controls small delicate plant pests such as aphids by a physical, non-toxic mode of action, and secondly, it doesn’t have translaminar properties and so would not penetrate within a leaf to where the leaf miners are feeding.

Since the moth larvae will be feeding within the leaves, only a systemic pesticide or a translaminar one would have to be used. I don’t know of any that are registered for use on this insect.”

So it looks like my only option is to pick off the pesky little things by hand. Although Neem oil by be of use.