UMass Extension Vegetable Program

Pest Alert: Emergence of spring maggot flies is approaching

Weather data from stations deployed on-farm and at airports around Massachusetts indicate that Growing Degree Day accumulations have reached the threshold for emergence of seedcorn, onion and cabbage maggot flies.  Emergence of adults occurs over a period of time, and there is a lag between emergence and egg laying (in seedcorn maggot this is 65 Celsius GDD).  Growers transplanting spring brassica crops should be on the lookout for eggs, and take protective measures.

The following accumulative GDD were recorded on April 3, 2012.  See the attached articles for more information.

DATE: 4/03/2012

 

GDD (in Celsius)

 

Location

Base 39.2F (4C)

Base 40F (4.44C)

Base 50F (10C)

Belchertown

171.8

154.33

57.00

S. Deerfield

149.2

136.94

48.61

Stow

162.3

148.89

58.06

Bolton

159.5

146.39

59.17

Dracut

140.6

128.61

50.83

Tyngsboro

130.6

118.61

43.61

East Bridgewater

153.6

139.17

45.00

Boston

175.5

161.89

61.06

Pitsfield

127.1

116.17

36.39

To check for ongoing GDD updates, visit the Northeast Network for Environment and Weather Applications (NEWA)
http://newa.cornell.edu/, search for the weather station nearest your farm, and select the cabbage maggot pest forecasts.

 

Growing Degree Day Cabbage Maggot Stages

(Model by: J.L. Jyoiti and A.M. Shelton)

Stage                               

Accumulated Degree Days (Celsius)

1st Emergence

161    +/- 8.1

25 percent

204    +/- 2.8

50 percent

251    +/- 7.9

75 percent

304    +/- 36.6

95 percent

387    +/- 7.7

 

Comparison of first generation peak flight of key maggot fly pests using seasonal degree day accumulation.

Peak flight is when 50% of the population has emerged. Base Temperature is 4 degrees C.  (GDD in Celsius)

Generation

Seedcorn

Onion

Cabbage

1st Peak

200

250-300

250