Monthly Fruit Fly Trends Report

Towns that are trapped currently are:

1. SUMMARY FOR HOME GARDENERS – 17 October 2017

Numbers of male Queensland fruit fly (Qff) trapped over the first two weeks of November 2017, in the Goulburn Murray Valley (GMV), decreased significantly compared with September and early October capture rates.

The decrease in numbers is likely to be due to the overwintering population of adults dying out. The weather, during this time has been very good for fruit flies to survive, mature and mate.

The observed decrease in flies trapped may also be due to successful active Qff control in the form of hygiene (e.g. harvesting and picking up and disposal of unwanted fruit), host plant removal plus an increase in the number of male-targeting Qff traps being deployed in the region.

Gardeners are warned that any drop-off in fly numbers in early November does not mean that fruit flies have disappeared. Some of the overwintering adults, which are now dying out, have matured their eggs, found mates, mated and laid eggs into any available fruit that is around during September, October and early November. So, vigilance should be maintained.

Qff does exist at this time – but it will be as eggs and larvae in fruit and pupae in the soil. If not monitored carefully and, if necessary, controlled, these immature flies will emerge some time in November/ December 2017 and will be the cause of large Qff outbreaks throughout urban and peri-urban areas of the GMV around Christmas/ New Year.

However, if anti-fruit fly activities have been carried out successfully then the volume of infestable fruit that are present in the region at this time may be limiting. If this is the case then the Qff population build-up may be delayed or even quashed.

IMPORTANT: Vigilance from now on is essential as there may be a hidden Qff population present as immature life stages in infested fruit. If these fruit, or their parent plants, can be found and disposed of adequately then these immature stages will not result in an upsurge of Qff populations from late November 2017 on.

It is recommended that householders deploy male- and female-targeting fruit fly traps. They should take advantage of unwanted tree removal offers and consider future fruit fly control methods such as home garden hygiene, fruit bagging, tree netting and fruit fly baiting. They should also consult with local friends and neighbours to see if fruit flies are nearby. Your local Fruit Fly Co-ordinator can help with suggestions on possible options.

2. SUMMARY FOR FARMERS – 17 November 2017

Trapped fly numbers increased during September and October 2017 compared with those trapped in winter 2017. However, trapped numbers decreased during the latter part of October and the first two weeks of November 2017.

Temperatures during late October/ early November were suitable in all parts of the GMV for Qff maturation, mating and egg-laying. It is likely that the drop-off in numbers of adult flies caught in traps seen in early November is due to overwintering adults dying out due to old age. However, it must be remembered that before dying many female adults will have laid eggs into whatever ripening or ripe fruit present.

The observed decrease in flies trapped may also be due to successful active Qff control in the form of hygiene (e.g. harvesting and picking up and disposal of unwanted fruit), host plant removal plus an increase in the number of male-targeting Qff traps being deployed in the region.

Qff does exist at this time – but it will be as eggs and larvae in fruit and pupae in the soil unless anti-fruit fly activities mentioned above have been enacted. If not monitored carefully and controlled, these immature flies will emerge some time in November/ December 2017 and will be the cause of large Qff outbreaks throughout urban and peri-urban areas of the GMV around Christmas/ New Year.

Due to the small overall surge in fruit fly numbers seen in the past couple of months, compared with winter trappings, it would be wise for farmers with fruit trees to plan future fruit fly control programs. Keep in mind that fruit trees planted in house paddocks are also very susceptible to fruit fly infestations which often go unnoticed and, therefore, untreated).

Farmers on the peri-urban fringe of large urban areas which have a history of fruit fly problems should deploy fruit fly traps and keep an eye on ripening fruit for fruit fly sting marks.

IMPORTANT: Vigilance from now on is essential as there may be a hidden Qff population present as immature life stages in infested fruit. If these fruit, or their parent plants, can be found and disposed of adequately then these immature stages will not result in an upsurge of Qff populations from late November 2017 on.

Farmers should remove unwanted fruit fly host plants, in their house paddock, along creek banks, on roadsides near their farm and other areas. If their farm had fruit fly problems last season they should consider future fruit fly control methods such as orchard hygiene and fruit fly baiting, placement of more traps for more accurate detection of fruit fly population incursions and purchase of approved pesticides and fruit fly baits. They should also consult with neighbours to see if fruit flies are nearby. Your local Fruit Fly Co-ordinator can help with suggestions on possible options.

3. SUMMARY FOR GROWERS – 17 November 2017

Fruit infestation, in rural areas of the GMV is likely during the last two weeks of October and the first two weeks of November because a) dusk temperatures at this time can be suitable for Qff mating (at least 15˚C to 16˚C) and b) there are a few ripe or ripening fruit around which can be infested. Some parts of the GMV will experience these dusk temperatures. In these cases, it is wise for growers whose crops experienced significant fruit fly problems in the preceding season, to set up fruit fly management strategies. Keep in mind that fruit trees planted in house paddocks are also very susceptible to fruit fly infestations which often go unnoticed and, therefore, untreated.

Trapping rates of Qff adults decreased significantly during the last 2 weeks of October and the first 2 weeks of November 2017. This is due to overwintering adult flies dying out due to old age. However, it should be remembered that Qff does exist at this time – as eggs and larvae in fruit and pupae in the soil, rather than adults flying around the orchard or home garden. If not monitored carefully and controlled, these immature flies will emerge some time in November/ December 2017 and will be the cause of large Qff outbreaks throughout urban and peri-urban areas of the GMV around Christmas/ New Year.

Because urban trappings showed positive trap captures, it would be wise for owners/ operators of farms on the peri-urban fringes of Shepparton, Mooroopna, Kyabram, Tatura, Cobram and Barooga to increase the number of traps deployed on town-orchard boundaries and consider commencing baiting of those boundaries.

Zero flies were trapped in the first two weeks of November 2017 in Ardmona, Barooga rural, Barooga urban, Bunbartha, Grahamvale, Invergordon, Kyabram rural, Shepparton rural and Tatura rural.

The Cobram urban area remains the highest flies per trap per week (with 11 flies from 33 traps) for the first two weeks of November. Undera and Mooroopna registered 2 flies trapped from a total of 8 traps and 11 traps, respectively. Growers in these areas should increase their Qff vigilance programs. All other areas registered 1 fly only or zero flies.

IMPORTANT: Vigilance from now on is essential as there may be a hidden Qff population present as immature life stages in infested fruit. If these fruit, or their parent plants, can be found and disposed of adequately then these immature stages will not result in an upsurge of Qff populations from late November 2017 on.

Farmers should remove unwanted fruit fly host plants, in their house paddock, along creek banks, on roadsides near their farm and other areas. If their farm, or next door’s, had fruit fly problems last season they should consider future fruit fly control methods such as orchard hygiene and fruit fly baiting, placement of more traps for more accurate detection of fruit fly population incursions and purchase of approved pesticides and fruit fly baits. They should also consult with neighbours to see if fruit flies are nearby. Your local Fruit Fly Co-ordinator can help with suggestions on possible options.

4. TECHNICAL SUMMARY – 17 November 2017

Trapping rates of Qff adults decreased significantly during the last 2 weeks of October and the first 2 weeks of November 2017. This is due to overwintering adult flies dying out due to old age. Or, it could be due to successful active Qff control in the form of hygiene (e.g. harvesting and picking up and disposal of unwanted fruit), host plant removal plus an increase in the number of male-targeting Qff traps being deployed in the region.

However, it should be remembered that, unless anti-fruit fly activities have been carried out diligently, Qff does exist at this time – as eggs and larvae in fruit and pupae in the soil, rather than adults flying around the orchard or home garden. If not monitored carefully and controlled, these immature flies will emerge some time in November/ December 2017 and will be the cause of large Qff outbreaks throughout urban and peri-urban areas of the GMV around Christmas/ New Year.

This suggests that householders in urban areas and farmers/ growers on the peri-urban fringe of affected urban areas should commence preparing strategies to reduce fruit fly populations over the next 4 weeks.

It is suggested that owners/ operators of orchards that are close to the peri-urban areas of large towns (where fruit fly numbers have increased) should prepare strategies for boundary protection against fruit flies entering their crops from the town within the next 4 weeks.

Undera (with two flies) registered its first trapped flies of 2017 (Table 2). Several other sites, but with only one fly each, registered their first trapped flies for the season – one site each in Cobram urban, Cobram rural and Shepparton East (Table 2). The data seen in Table 1 for Undera are exaggerated, proportionally, due to 2 flies being found in 8 traps over a two-week period. It could be worth investigating the sources of these flies, here, just in case of a potential hot spot.

Rates shown in Table 1 for flies/trap/week (x 100) suggest very, very low numbers of adults being present all over the region – rural, urban and small town areas.

IMPORTANT: Vigilance from now on is essential as there may be a hidden Qff population present as immature life stages in infested fruit. If these fruit, or their parent plants, can be found and disposed of adequately then these immature stages will not result in an upsurge of Qff populations from late November 2017 on.

Table 1. Comparison of IK Caldwell between trap capture numbers and trap capture rates through September 2017 (4 weeks), October (4 weeks) and the first 2 weeks of November 2017. NOTE: Rates in red are actual rates X 100 to facilitate interpretation. 

*  NOTE: Strathbogie traps have not been read since 10 October 2017 

Table 2. IK Caldwell traps registering fruit flies for the first time in 2017