| Life Cycle: | There is a lot of confusion between the cabbage maggot and the turnip maggot. Many universities and journals don't make a distinction. The two most prominent differences are that the cabbage maggot has two generations per season while the turnip maggot has one (usually falling between the two generations of the cabbage maggot). The turnip maggot tends to burrow directly into the root while the cabbage maggot generally feeds on the outside of the root. Labrador and northern parts of Newfoundland are more likely to have turnip maggots. In most other respects they behave the same. There is a black stripe along their predominantly gray bodies. Adult flies emerge in the spring from June to July. The female will begin laying eggs one week after emerging and will lay from 50 - 200 eggs over a five week period. The eggs are 1 mm in length and are white. They are usually deposited just beneath the soil surface at the base of a host plant. The larvae emerge in 3-10 days and immediately begin burrowing into the soil and feeding on the host plant's roots. The turnip maggot is white, legless and about 0.5 - 1.0 cm long. In preparation for pupation, the maggot will burrow down from 5 - 20 cm. The pupae resemble kernels of wheat in both colour and length. The pupae over winter in the soil. |
| Host: | The turnip maggot only attacks members of the cabbage or mustard families. |
| Bio Region: | Turnip maggots are a problem throughout North America where cole crops are grown. The warmer the climate the more generations. |
| Damage: | The damage is caused by the maggots burrowing into the root system of host plants. Symptoms of maggot damage include wilting and pale colour and so are often confused with other problems such as nutrient deficiencies. Crops affected by the turnip maggot are generally unmarketable. |
| Management: | Prevention is the best strategy as there are no commercial controls. Consider a late June planting of susceptible crops. The maggots do not like heat. If this is not possible, ensure that transplants are in the soil at least one week prior to adult emergence. Row covers are effective against the adults provided fields are rotated. Crop debris should be incorporated into the soil immediately after harvest. |
| Controls: | There are no chemical controls that are allowed in organic systems. A variety of beetles will eat turnip maggot eggs and there is some evidence that parasitic wasps will help keep the population of maggots down. It should be noted that intervention with such biological controls is unlikely to be helpful unless an infestation is detected prior to symptoms in the plants themselves. A generally biodiverse soil will help reduce the frequency of infestations. |
