Damage: Spotted Wing Drosophila in Ontario
Table of Contents
While it is not possible to distinguish SWD larvae from those of other common vinegar flies, the presence of larvae in intact fruit prior to harvest should be viewed as suspicious. Signs of infestation by SWD may be confused with normal aging of mature fruit. Most uninfested ripe fruit will show mild overall softening after several days.
When fruit has been attacked by SWD, early mould, wrinkling and softening can be seen at 2-3 days following egg-laying, and most fruit show obvious damage after 3-4 days (Figure 7, 8, 9).
Figure 7: Raspberries show damage quickly, with scarring and collapse appearing as soon as 1-2 days after egg-laying.
Figure 8:Strawberries deteriorate quickly following egg-laying. Fruit wrinkles and fruit softens, with mould appearing after only 3 days.
Figure 9:Blueberries start to soften
after about 3 days.
Pin-prick sized scars or holes (Figure 10) from which sap exudes may also be evident.
Figure 10: Infested cherry showing
pin-pricks and damage directly under the skin. In this shot, it
is possible to see larvae and pupae which have exited the fruit.
Small holes created by larvae for breathing may also been seen, sometimes with larval breathing tubes visible (Figure 11).
Figure 11: Larval breathing holes
Eventually, fruit softens in spots and the skin collapses, with a wrinkled appearance that becomes very obvious after about 5 days. Fruit left hanging following harvest may show signs of heavy infestation (Figure 12).
Figure 12: Fruit left on the tree
following harvest is often heavily infested. Note presence of pupae
on the cherry clusters.
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