Biology and Control of Blueberry Gall Midge

1
Biology and Control of Blueberry Gall
Midge Chemical Trials
Wei Q. Yang,1 Lynell Tanigoshi,2 Eduardo Chavez,1
and Jason Harpole1 1 Oregon State University,
North Willamette Research and Extension Center,
Aurora, OR 2 Washington State University,
Northwestern WA Research Extension, Mount
Vernon, WA
Abstract
Results
Since completing the initial blueberry gall midge
(Dasineura oxycoccana Johnson) life cycle and
finding no relationship between number of midges
and shoot tip damages from 2004-2005, we
concentrated our effort in determining the timing
and insecticide application for its control. In
2006, the insecticides used were Mustang Max
(0.025 lb(AI)acre), Admire (0.125 lb(AI)acre),
and Platinum (0.5 lb(AI)/acre). In 2007, the
same experiment was repeated, substituting
experimental Brigade (0.1 lb(AI)/acre) for newly
registered Mustang Max. The treatments with an
untreated control were applied as a soil drench
after fruit set and arranged in a randomized
complete block design with each experiment unit
consisting of a 40 row of mature blueberries.
Several soil traps were placed along the drip
line of treated plots and yellow cards were hung
on the trellis wire in each plot. Each week
after insecticide application, traps and yellow
card samples were collected to count number of
adult gall midge fliers. Preliminary data
analysis indicated all soil drench treatments
resulted in good suppression of the emergence of
midge adults in both years. In 2007, our
modified soil trap seems to work better than the
ones used in 2006. The new trap design will be
displayed during the poster session.
i
Yellow card samples were examined under a
disecting microscope and the number of adult
midge fliers was recorded with results shown in
the graphs below. In 2006, Mustang Max, Admire,
and Platinum all showed good control of midge
adult emergence with Admire being the most
effective. In 2007, Brigade, Admire, and
Platinum again showed good control of midge adult
emergence. All three insecticides seemed to have
equal effectiveness in suppressing midge fly
emergence from puparia in the soil. It was also
clear that there were two peak midge emergences
from the soil before harvest as shown by the
hanging cards graph. The long suppressing period
of all three insecticides was also noticed.
Overall, all soil drench treatments resulted in
good suppression of the emergence of midge adults
in both years. The newly designed soil trap
worked well for monitoring adult midge emergence
from the soil and made the removal and
replacement of the yellow cards very easy.
Introduction
Field surveys conducted in Oregon and SW
Washington from 2004-2005 found that blueberry
gall midge was present in all blueberry fields
sampled. The damage caused by blueberry gall
midge is primarily aborted and/or blackened young
shoot tips as well as distorted developing leaves
(h), which is often confused with boron
deficiency. In heavily infested blueberry
fields, a witches-broom like symptom may occur.
It generally takes about 7-10 days for mature
larvae to form puparia. The estimated time for
the 1st larval instar to develope into an adult
fly is about 2-3 weeks. There are multiple
generations in a growing season with two main
peaks of blueberry gall midge infestation. One
peak is prior to harvest and the other after
harvest. There is a dramatic decrease in
infestation during harvest due to the lack of
newly developed shoot tips during that time.
Because the last generation of puparia
overwinters in the soil, using an insecticide
drench in early spring seems to be an effective
way to reduce adult midge emergence.
Picture descriptions (a-c) Soil drench
application in a commercial blueberry field. (d)
Field traps and yellow cards were used for
monitoring blueberry gall midge flies in 2007
(e) soil trap (f) Yellow sticky cards hanging on
the trellis wire (g) Soil trap assembly (h)
Shoot tip damage by blueberry gall midge larvae
(i) Blueberry midge male fly.
Objectives

• Determine the effectiveness of insecticide
  application used as a soil drench for controlling
  blueberry gall midge

Future Direction
Method
We have noticed morphological differences of
adult midge fly from the soil traps between
spring and fall. It seems that the midge fly
from early spring samples shared the same
characteristic of blueberry gall midge. However
the midge adult fly from the fall sampling did
not appear to have the typical characteristics of
a blueberry gall midge. We suspect there maybe
differences in midge species in the northwest
during a growing season. We plan to closely
follow the morphological changes of adult midge
fly next growing season to determine if there are
more than midge species present.
Started in spring of 2006, a commercial blueberry
field with heavy blueberry gall midge infestation
was chosen to determine the effectiveness of soil
drench with Mustang Max (0.025 lb(AI)acre),
Admire (0.125 lb(AI)acre), and Platinum (0.5
lb(AI)/acre). Several soil traps were placed
along the drip line of treated plots (each 40
long). Treatments including an untreated check
were arranged in a randomized complete block
design. Sprays were applied using a commercial
tractor driving soil surface sprayer with a spray
width about 2 feet. In 2007, the same experiment
was repeated, substituting experimental Brigade
(0.1 lb(AI)/acre) for newly registered Mustang
Max, while using a modified soil trap. Yellow
cards were also hung in each treated plot. Cards
were collected every 3-7 days.
Potential Significance to the Industry
From this study, we feel its possible to
significantly reduce the number of adult midge
fliers emerged from soil with a soil drench
application. The timing could be early spring
before bud break. Controlling blueberry gall
midge could be beneficial to young blueberry
fields with heavy gall midge infestation, which
could reduce young plant growth because of the
repeated damage to growing shoot tips.