Growers should not forget about Mediterranean fruit fly even though temperatures are dropping and its effects are less obvious, according to the Department of Agriculture and Food.
Department development officer Alec McCarthy said actions over the coming months would be critical in reducing the carryover populations of fruit fly which growers have to deal with next season.
“Getting in now and removing struck fruit and killing larvae before they mature will pay dividends down the track,” Mr McCarthy said.
“If you want fewer flies attacking your fruit next spring and summer, then knock them off now as much as you can.”
The breeding cycle of the Medfly depends largely on temperature and surviving flies can overwinter as adults, larvae (in suitable winter fruits) or pupae (in soil or leaf litter) in most of the South West. Their development slows when temperatures drop below 10°C, but they do not die and simply take longer to go through the stages.
The adult Medfly needs protection from the cold and rain, so will not hang around leafless trees but seek shelter in leafy trees and bushes, such as citrus or avocado.
However, day temperatures only need to reach 17°C for adult flies to mate and lay eggs in suitable fruit allowing new larvae to develop.
“If you have susceptible winter fruits, particularly citrus, you should continue to bait at least fortnightly during cooler months,” Mr McCarthy said.
“Also consider baiting evergreen trees near your orchard during warm spells. This will help reduce the number of adult flies surviving to spring. Adult Medflies can survive the entire winter if protection and food are available, ready to kick-start the next generation.”
If no suitable fruit is available for adults to lay eggs into, this helps break the cycle. So if you have winter fruits in or near your orchard that are not of commercial value, then you should consider removing them, he added.
When mature, Medfly larvae emerge from the fruit then burrow into soil or leaf litter to pupate. The pupal stage is the hardiest and most common stage to overwinter, resulting from flies striking late season fruit left on trees or the ground.
These overwintering pupae complete their life cycles when the soil warms up in spring and usually start to emerge in September as young adults looking to strike fruit and continue the cycle.
“Orchard hygiene is important throughout the year to remove fly breeding sites, but critical now,” Mr McCarthy added.
More details can be obtained from the department website at agric.wa.gov.au by searching under fruit flies.
Media contact: Jodie Thomson, media liaison +61 (0)8 9368 3937