{"id":2454,"date":"2020-03-07T03:38:17","date_gmt":"2020-03-07T03:38:17","guid":{"rendered":"http:\/\/blogs.oregonstate.edu\/mgmetro\/?p=2454"},"modified":"2020-03-07T03:38:23","modified_gmt":"2020-03-07T03:38:23","slug":"winter-damage-caterpillars-vs-slugs","status":"publish","type":"post","link":"https:\/\/blogs.oregonstate.edu\/mgmetro\/2020\/03\/07\/winter-damage-caterpillars-vs-slugs\/","title":{"rendered":"Winter Damage: Caterpillars vs Slugs"},"content":{"rendered":"\n
Natter’s Notes<\/h2>\n\n\n\n
By Jean R. Natter, OSU Master Gardener<\/h2>\n\n\n\n
The Winter\nCutworm, Noctua pronuba, w<\/em>as officially identified by Oregon Department\nof Agriculture (ODA) as an invasive pest in Oregon during 2012. Even so, the\nmetro Master Gardener offices had been receiving complaints about their\nactivity since 2001. <\/p>\n\n\n\n
Plants were nibbled and\/or destroyed from fall through the winter. At first, most folks assumed the damage was due to slugs and snails. However, the mutilation was different than the shredded tissue left behind by slugs and snails. Seedlings were toppled; emerging bulbs lost their heads and sometimes flower buds; and hostas lost leaf tips or had gaping holes. At my place, the pests would climb my 3- to 4-foot tall delphiniums to eat the flower bud at the tip of the stalk, sometimes settling down for a snooze. To accurately identify the culprits, MGs in the offices had to activate their Master Gardener CSI mode. <\/p>\n\n\n\n
The Winter Cutworm, Noctua pronuba<\/em><\/strong><\/h2>\n\n\n\n
As you likely recall, caterpillars (Order Lepidoptera) have\ncomplete metamorphosis, with 4 life stages. After the adults mate, the female lays several\nhundred eggs in a large tidy patch, most often covering, or nearly so, the\nsurface of a leaf. The larvae (youngsters) hatch in 2 to 4 weeks. These\ncaterpillars have different habits than most you are familiar with because they\nfeed at night, whenever the temperature exceeds 40F, from fall through winter. <\/p>\n\n\n\n
Perhaps the most effective treatment strategy is to go\noutdoors about 10 pm or so, with a cup of soapy water and tongs or a pair of\ngloves. As you trek through your plantings keep any eye out for caterpillars\nchomping at your expense. They may be anywhere from \u00be to 1.5 inches long, the\nsize depending on their age. They\u2019re often aligned with the edge of a leaf, or\nout-of-sight among the leaves. Hand pick and drop into the cup.<\/p>\n\n\n\n
During the day, the larvae hide just under the soil surface, typically quite close to the stem of the victimized plant. Disrupting a bit of soil often reveals their hiding place.<\/p>\n\n\n\n
The caterpillars of the Winter Cutworm (Noctua pronuba, aka the Large Yellow Underwing) appear bright green after they have molted; the color will gradually change to the various browns within hours. Source: http:\/\/www.wildlifeinsight.com\/british-moths\/large-yellow-underwing-moth-and-caterpillar-noctua-pronuba\/ <\/figcaption><\/figure><\/div>\n\n\n\n
Fun for gardeners <\/strong><\/h2>\n\n\n\n
This spring, as you prepare your garden, it\u2019s very likely\nyou\u2019ll find a number of Lepidoptera pupae in the soil. Rearing the pupa is the\nbest way to determine the parent moth\u2019s identity. <\/p>\n\n\n\n
To rear pupae, place in clear container with a porous lid, such as paper toweling secured with a rubber band. Set the container somewhere you\u2019ll see it, but not in the sun, then wait for the adults to emerge.<\/p>\n\n\n\n
The Gray Garden Slug<\/strong><\/h2>\n\n\n\n
Slugs, especially gray garden slugs (Deroceras reticulatum)<\/em> thrive throughout the northwest, feeding in gardens, greenhouses, roadsides and fields. They\u2019re omnivores which feed on live plant material and much more, including mushrooms, dead slugs, earthworms. They have the ability to detect predatory carabid beetles through the use of olfactory cues. And, because slugs are hermaphrodites, reproduction is by cross-fertilization which may occur year-round when conditions are favorable. Mating occurs mainly at night with each animal capable of laying approximately 60-75 eggs (4 mm each) in a clutch, totaling about 700 eggs per year per slug. Each slug may live a year or two. (https:\/\/idtools.org\/id\/mollusc\/factsheet.php?name=Deroceras reticulatum<\/a>) <\/p>\n\n\n\n
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