Mary's Veggie Garden

February 2, 2015

The New Pest in the Garden

Filed under: Gardening — marysveggiegarden @ 11:13 am

In autumn 2013 my kale suddenly developed huge holes in the leaves. I searched for caterpillars but found very few. I did not recognize the caterpillars and could not find them in my trusty “Rodale’s Color Handbook of Garden Insects” (1979).

I ignored the problem and unfortunately it did NOT go away. The kale was devastated and I ripped it out before frost.

Fast forward to October 2014. My garden held a lot of Brassicas (cabbage family crops), most transplanted into the garden 7/21. Napa cabbage, kohlrabi and cabbage plants were approaching harvestable size.

Cross-striped cabbage worms on kale, 10/2015

Cross-striped cabbageworms on kale, 10/2014

The Brassicas were not protected so I was doing my weekly check for Imported Cabbage Worms. That’s when I noticed the new caterpillar, with its blue-grey back and yellow racing strips down the side. This time I turned to Google with the search terms “blue-grey caterpillar yellow stripe cabbage”. Bingo! The first image was the caterpillar in my garden. The picture provided a name: ‘Cross-striped cabbageworm, Evergistis rimosalis (Lepidoptera) ‘ and Googling the name brought me to the Massachusetts Extension. Up close, in good light, wearing my reading glasses, the cross-stripes are obvious.

The adult form of the Cross-striped cabbageworm is a cryptic moth who lays her eggs in packets of 3-25. The packets are yellowish and flattened and attached to the underside of Brassica leaves. After hatching the larvae grow to 3/4” over 2-3 weeks. The masses of caterpillars feed on the underside of the leaves and may not be noticed until they break through the leaf surface and move to the top. By then it is too late. I was able to salvage only the hearts of my Napa cabbage and the kohlrabi bulbs. There are 2-3 generations per year so fall infestations are severe.

Apparently this pest has moved north with global warming and is now in southern New England and adjacent areas of NYS. It affects all Brassicas including broccoli, collards and Brussels sprouts in addition to cabbages, kale and kohlrabi. Control methods include hand-picking the egg packets and caterpillars, planting under a floating row cover, or spraying with Bt – Bacillus thuringiensis – a product allowed in organic gardens.

Luckily, these are the same techniques used to control our old friend the Imported cabbageworm.

Imported cabbage worm

Imported cabbage worm

With spring plantings I use floating row covers. Unfortunately, my fall plantings are often scattered around the garden, making them difficult to cover.

7/19/2014 Spring broccoli growing under an Agribon floating row cover

7/19/2014 Spring broccoli growing under an Agribon floating row cover

Assorted cabbages protected by tulle.

5/2014 Assorted cabbages protected by tulle.

2014 was my first time using tulle as a row cover. I worried the rough tulle would be abrasive to plant leaves so I used stakes (ski poles free from my neighbor) with several layers of rags tied to the top to hold the tulle above the plants. I liked the tulle because the plants were clearly visible and they let through plenty of light. Tulle may be locally available at fabric and craft store and the price may be right with a coupon.

Tulle, like my Agribon floating row cover, slowly degrades in the garden and is good only for a single season.

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10 Comments »

  1. I’m so glad you identified this new pest I didn’t find it when I tried searching for it. This was the first year I have seen them.

    Comment by Hella henny — February 2, 2015 @ 2:13 pm | Reply

  2. I like tulle too. It is also cheaper than Agribon. Which reminds me that I have to order more for next year.

    Comment by daphnegould — February 2, 2015 @ 2:16 pm | Reply

  3. I bought some tulle at the local fabric store for only $1/yard. I am so excited to try to keep those horrible SVB’s off my squashes this year. Here’ hoping it works!

    Comment by crafty_cristy — February 2, 2015 @ 2:18 pm | Reply

    • Squashes are bee pollinated. In my area (Poughkeepsie, NY) there is only one generation of SVBs and the row covers can be removed from squashes July 4.

      Comment by marysveggiegarden — February 2, 2015 @ 2:44 pm | Reply

  4. i have the SAME issue. I just bought some agribon & i’m going to use it this spring for my brassicas.

    Comment by newbiegardengirl — February 2, 2015 @ 4:04 pm | Reply

  5. Yep, those critters devastated quite a bit of my brassica last year also, I did not spray but will have to this year.with Bt. I too use tulle and get it from the fabric store with 40% off coupon, good value.

    Comment by Norma Chang — February 2, 2015 @ 7:12 pm | Reply

  6. Ugh…another brassica pest to watch out for. I use insect netting from a local seed house on all the brassica beds. I did try tulle, but it wasn’t on sale when I purchased it so it actually ended up costing about the same as the insect netting sold at a local seed house. $1/yard is an AWESOME price for the tulle….I think I paid 3x that amount & it was a bit of sticker shock when I got to the register, especially as it wasn’t as wide as the seed house netting so I would have to use 2 lengths to cover a bed instead of one.

    Comment by Margaret — February 3, 2015 @ 10:26 am | Reply

    • I lucked into a partial bolt of free tulle. It wasn’t wide enough for medium plants in a 4′ bed (bush beans, broccoli) and when I priced the wider widths online, the tulle was double the 110″ insect weight floating row cover. So shop carefully.

      Comment by marysveggiegarden — February 3, 2015 @ 10:49 am | Reply


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