Spring outlook

Higher than usual rainfall across the Goulburn Murray Valley combined with current higher than average daily minimum temperatures have resulted in ideal conditions for fruit fly. Weather conditions are optimal for fruit fly and will see an increase in fruit fly activity.

Stop the spread

Fruit fly management strategies in place in home gardens, urban properties and orchards in spring 2022 will help keep fruit fly activity under control through the upcoming season. A whole of community effort is required to help stop the spread of fruit fly.

Impact of floods on fruit fly

Floods have little impact on reducing fruit fly activity. In fact, fruit fly may benefit in some ways as very wet weather will cause significant increases in relative humidity and, as a result encourage, bacterial, fungal and yeast growth. These organisms provide a food source for adult fruit flies. Warm daily minimum temperatures associated with wet weather also favour the survival of adult fruit flies, eggs, larvae and pupae.

Flooding for fewer than 5 days will not impact egg and larval survival adversely as pupae (maggots become inactive and change into a brown hard pupae) are tolerant of flooding. They will float to the surface and then move to the edge of the water mass and survive. If forcibly immersed in water pupae can survive for many hours. Laboratory experiments with pupae stored 10cm under water at 26˚C showed that 48 per cent survived 3 days submersion and 7 per cent survived 7 days under water. It was estimated that to achieve 100 per cent mortality pupae would need to be held under water for more than 8 days.

Potential hot spots

A number of locations have been identified as sites of concern in October and November through the regional trapping grid. If you live in or near these locations, place monitoring traps out and check nearby ripening, ripe or overripe fruit for the presence of fruit fly.

Locations requiring extra vigilance include:

• Cobram *
• Shepparton
• Mooroopna
• Tatura
• Kyabram

*It should be noted that some flies trapped in Cobram urban may be previously released sterile fruit fly that have survived winter.

Mating potential

Queensland fruit fly will only mate at sunset and if the temperature is above 16˚C. Mating conditions were met with daily sunset temperatures at or above the mating threshold on several days during the first half of October, and daily from mid October. This will result in the first post-winter new generation of fruit fly emerging in about 6 to 8 weeks.