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Hands off my tomatoes!

A damaged tomato leaf as a result of Tomato Moth invasion

Holey Crap!

Having spent much of the week here, there and everywhere, the past couple of days I’ve taken some time to harvest some veg which was well overdue for a picking. Last night it was peas, which have been most excellent this year, while this morning I tended to my tomatoes in the greenhouse.

For a couple of weeks I’ve been noticing holes appearing in my tomato leaves with the associated spoil that gives away a sneaky caterpillar or two. I didn’t take much notice to be honest, as at this time of year I always get a few caterpillars chewing away at the leaves and never tend to get more than a half dozen altogether.

A damaged tomato as a result of Tomato Moth invasion

Not very appetising!

However, every morning I’ve visited the greenhouse this week I’ve been noticing a lot of bird poo on the floor and then I started to notice holes in my tomatoes too, not just the leaves. I assumed that the birds were having a go, as the blackbirds have been a real pest with a lot of my fruit this year, but when I started picking the tomatoes I noticed I had rather more caterpillars than I’d assumed and had to take action.

I don’t spray my tomatoes as I try to be as organic as I can for many reasons: 1) as a small-scale gardener I have the ability to look over my crops more thoroughly and can usually catch minor issues as they arise, 2) I don’t grow stuff commercially, it’s for my own benefit and every year is different, so if some years a crop is a bit poor it’s not the end of the world and I chalk it up to experience, 3) I don’t like putting chemicals on plants and the soil as you just never know how persistent they are and where they end up, 4) it costs money to buy chemicals!

A collection of Tomato Moth caterpillars

Tomato Moth caterpillars

Instead, I looked over my tomato plants and collected a number of green and brown specimens in a pot. I didn’t squish them, as my chickens are quite partial to this particular type of caterpillar and I wouldn’t want to deny them a tasty protein snack, not to mention that there’s a kind of rough justice in turning a pest into what will ultimately go from chicken poo to compost and therefore a life-giver to next year’s crop.

They were the same old caterpillars I always get and although they differ in colour, they all have the same distinctive double go-faster yellow and black stripes down their sides and tiny little black dots all over the rest of their bodies. I’d never given them much thought before, but as they seemed to be so much of a pest this year, I decided to take a few pictures and identify them.

Fresh Tomato Moth poo on a tomato leaf

Look out from above!

WARNING! SCIENCE! It appears that they are the caterpillar of the rather too-well named Tomato Moth, or Bright-line_Brown-eyeW to their friends and Lacanobia oleracea to their Latin-speaking cousins. This type of moth usually feeds on a wide range of plants, but has gained a bad reputation for occasionally becoming a pest of cultivated tomatoes.

Fortunately, I’m not short of tomatoes this year and so the worst of the moth-eaten fruit also ended up in the chicken’s direction (much to their delight). I’m sure I haven’t got all of them, but I’ve knocked back the invasion somewhat, and hopefully the visiting birds will keep paying a visit to pick off a few of the stragglers (I can only think that’s why I’ve had so much poo in the greenhouse this year).

Obviously it’s been a popular year for this moth in my greenhouse, but is it just a local phenomenon or is it more widespread? Has the exceptionally cold winter we had killed off a few of the moth’s predators/parasites this year? Let me know if you’ve had any of these little beasties on your tomatoes this year and whether you have them inside or outside of a greenhouse…

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4 Comments

  1. Sonia
    Posted 28 August 2011 at 11:09pm | Permalink

    I have had quite a bad tomato caterpiller infestation in my greenhouse this year. At first I noticed the poo then a couple of caterpillars and before I knew it the bugs had taken over one plant. When I tried to remove the plant from the growbag I couldn’t believe the amount of caterpillars that fell to the ground!!!!
    Do you think that horticultural soap might kill them or is vigilance the only answer?

    Sonia

    • Posted 29 August 2011 at 8:25am | Permalink

      Hi Sonia
      Thanks for your comment.

      It’s been a really bad year for tomato moth this year. I personally just pick them off, as I only have about 10 plants, but if you have a lot more, then I can imagine you being at your wits end.

      As far as I’m aware, insecticidal/horticultural soap (a totally safe and natural product approved for organic use, and made from naturally occurring plant oils and animal fats) is only effective against insects such as: Aphids, Mealy bugs, Spider mites, Soft brown scale, Psyllids, Rose or pear slugs (sawfly larvae), Earwigs, Whiteflies and Thrips. Basically, lots of small irritating insects that really do move in en masse, which would be difficult to remove manually.

      I have looked around for an alternative to picking off caterpillars and there do seem to be some references to the use of fungi (Beauveria bassiana – kills by taking nutrients from the insect’s body and also releasing toxins that assist in killing the pest) and bacteria (Bacillus thuringienis – paralyses the digestive system), but nothing specific to tomato moth. Also, these applications don’t seem to be widely available for home use at the moment.

      I can’t help thinking it might be more effective to hang up a ‘lure’ in the greenhouse which is more attractive to the moth than the plants, thus killing the moth and preventing a caterpillar infestation in the first place. However, the only lures available are pheromone traps which would alert you to their arrival, but not to their destruction.

      It seems we are not alone in the war against tomato moths, as they are a serious agricultural pest. Unfortunately, for the small-scale gardener, manual removal appears to be the only and most effective solution for now. Let’s hope that 2012 sees less of these pests in the greenhouse!

  2. Miriam
    Posted 1 September 2011 at 11:50pm | Permalink

    I’m so relieved to read this and find out that it’s not just me being a newbie! I thought I’d done something horribly wrong to have so many of these caterpillars on my tomatoes. I go over my plants every 3/4 days and pick off what I find, but there are still more. Apparently they’re night-feeders so perhaps going out with a torch one night and picking them off then would be more successful.

    Great blog by the way, thanks 🙂

    • Posted 3 September 2011 at 12:08am | Permalink

      Hi Miriam
      Never blame yourself unless you ‘know’ you’re to blame. The wonderful thing about growing things is that there are so many variables, that it’s actually quite difficult to predict what’s going to happen – weather, nature, kids with footballs… 😉

      I never thought about when the caterpillars are most active, but it makes sense for them to be night feeders as the moths certainly are (that’s how the pesky blighters manage to sneak in and lay their eggs in the first place). To be honest, I’ve found the majority of mine in the hour before sunset. The caterpillars seem to find a vertical object (e.g. stem of tomato plant, supporting wires and stings) and line up with it. The yellow ‘go-faster’ stripe makes them stand out a mile, regardless of colour (green or brown). So maybe you won’t need that torch after all…

      Interestingly, I’ve found a few of these caterpillars lurking around my carrots lately. No idea what’s in there for them to eat, as they’re certainly not attacking the carrots themselves.

      Glad you like the blog, it’s great to know it’s being helpful to other keen garden experimenters…

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