Overview

Brief Summary

New York Invasive Species Information

Introduction

The Swede midge, an invasive agricultural pest (also known as the cabbage crowngall fly and cabbage gall midge) was first detected in New York in 2004 in Niagara County. Although the insect is a native of Europe and southwestern Asia, it is believed the midge was introduced into NY from the Canadian province of Ontario where it was first found on broccoli in 1996. By the end of 2007, the Swede midge had been confirmed in 12 NY counties (Allegany, Chenango, Franklin, Herkimer, Jefferson, Livingston, Onondaga, Otsego, Rensselaer, Steuben, Suffolk, and Yates).

Biology

This species is a small (1.5 - 2 mm), light brown fly that is indistinguishable from many other midges except by an expert entomologist. Adult midges emerge in the spring from pupae that have over-wintered in the soil. Adult flies mate soon after and females search for suitable host plants. Each female can lay about 100 eggs during their one to five day lifespan. The females lay their eggs on the growing point of young plants. Larvae hatch from the eggs after a few days and begin to feed in groups on the growing plant tissue. Larvae complete their development in 7 - 21 days after which they drop to the ground and pupate in the soil. Adults can emerge within two weeks, restarting the cycle. Depending on temperature and length of growing season, there can be up to five overlapping generations of Swede midge per year.

Damage

As they feed, Swede midge larvae produce a secretion that breaks down the surface of the growing point of the plant and liquefies the cell contents, resulting the formation of leaf and flower galls and a misshapen growing point. Damage caused by Swede midge larvae feeding results in distorted growing tips and may produce multiple (or no) growing tips; young leaves may become swollen or crumpled and leaf petioles or stems may exhibit brown scarring. Swede midges feed only on cruciferous vegetable crops, such as cabbage, cauliflower, broccoli, and Brussels sprouts, frequently causing severe losses. The insect also damages canola, collard, horseradish, kale, mustard, rutabaga, turnip, and radish.

Management

Insecticides can be used to kill adults or prevent them from laying viable eggs. However, controlling larvae is much more difficult because insecticide would have to enter the plant tissue upon which the larvae are feeding. Currently, the best way to manage Swede midge damage is to limit the spread of the insect into new areas. Adults are very weak fliers, so the primary vector of introduction is believed to be the movement of transplants which may contain eggs or larvae, or movement of soil which may contain pupae. Repeated working of infested soil can reduce the number of viable pupae. Also, because adult Swede midges cannot travel far, crop rotation using noncruciferous plants can help to reduce the likelihood of spreading an infestation.

  • Based on information published by J.R. Kikkert and C.A. Hoepting (Cornell Vegetable Program) and A.M. Shelton (Department of Entomology, NYS Agricultural Experiment Station, Cornell University
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Distribution

National Distribution

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Contarinia nasturtii

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: NNA - Not Applicable

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NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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