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Fruitcheque Useful Articles (Season 2006/2007)
Links to documents on this page:
Western Flower Thrips in Swan Hill
Cathy Mansfield (DPI Tatura) and Steven Lorimer (DPI, Swan Hill)
Western flower thrips (WFT) are being found in orchards around Swan Hill. To make sure WFT are controlled in your orchard it is very important that you identify their presence as soon as possible. WFT can cause significant damage, such as, silvering of the fruit particularly in the two weeks prior to harvest.
Below is some information to help you identify if you have western flower thrips in your orchard.
What symptoms might you see if Western Flower Thrips (WFT) are in your orchard?
WFT are good breeders so a common sign to look for is a dramatic jump in the number of thrips. Another sign is the presence of thrips after you've sprayed for thrips. This is because WFT are resistant to many of the insecticides commonly used for thrip control.
Signs of WFT on Stone Fruit
WFT damage young developing stone fruit as well as at final fruit swell through to harvest. Early season injury occurs when thrips feed under the shuck and cause russet before shuck fall. Silvering occurs when thrips feed on the surface of mature fruit. Damage is often found on fruit where thrips may have cover, where fruit touch, for example.
"Why should I treat WFT differently to other thrips?"
WFT arrived in Australia with resistance to a number of insecticides. It also has the capability to develop resistance very quickly. For this reason it’s important to apply insecticides only when needed and only insecticides known to be effective.
Western flower thrips lifecycle | Typical Signs of damage caused by Western Flower Thrips |
There are four stages to the lifecycle of WFT. Eggs are laid under the surface of plant tissue (fruit, petals, leaves or stems) by adult females. These eggs hatch into a wingless larval stage which feeds on the plant before forming a pupa. The pupal stage is usually found in the soil under the plant although on occasion, WFT may sometimes stay on the plant for the entire cycle. The adults hatch out of the pupal stage and proceed to feed on fruit, leaves, flowers or stems. The entire lifecycle of WFT can take as little as 8 days to complete.
Lifecycle of Western Flower Thrips
How do I check if WFT is in my orchard?
WFT over winter on a range of hosts including grasses and weeds on the orchard floor, they then move onto fruit trees as they begin to flower. Because WFT looks almost identical to other thrips commonly found in orchards it's important to identify WFT before spraying. WFT should be monitored in weed species around your orchard before the trees begin flowering. Collecting flowering weeds or tapping weed flowers over sticky traps could help you find WFT in your orchard. Later in the season, check fruit blossom for thrip numbers to determine if controls are needed.
Sticky traps should be wrapped in a single layer of clear plastic wrap and fresh samples should be placed in a sealed plastic bag to prevent escapees. Samples can be dropped off to Steven Lorimer at the Swan Hill DPI, 324 Campbell st, (Ph 0350331290) to be sent for identification.
What can I do to minimise the effect of WFT?
Controlling WFT is essentially an exercise in controlling the rate of resistance occurring in the population.
A small percentage of WFT at Bundaberg (QLD) were found to be resistant to spinosad, which is of concern considering its widespread use on WFT. While the percentage of WFT resistance to spinosad is currently low, other comparative results for a NSW site (only 12% susceptible) clearly shows the potential for WFT to develop resistance to newer, popular insecticides. The 3-spray strategy is an essential part of managing WFT effectively. | Sticky traps used to capture insects in orchards crops. |
Sprays do not affect eggs, which are laid inside the leaf nor do they affect pupae, which live in soil and debris. Three sprays of the same chemical are applied consecutively to target all the individuals within a generation:
- the first spray is targeted against existing larvae and adults
- the second spray targets adults hatched from pupae and larvae hatched from eggs
- the third spray is applied to “clean up” any remaining larvae and adults
This approach gives the best chance of killing all the individuals in one generation that are susceptible to the chemical before alternating to another chemical group. (Heisswolf & Right, 2006, p2)
Once WFT have been positively identified on your property speak to your chemical reseller or DPI FruitCheque officer for further advice.
References
Sue Heisswolf and Ross Wright. February 2006, Western Flower Thrips - Queensland Update. Department of Primary Industries and Fisheries, Bowen Crop Monitoring Services Pty. Ltd. and Crop Tech Ltd.Pty, Queensland.
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Swan Hill DPI Weather Station readings - Now Daily
The Swan Hill Department of Primary Industries (DPI) Weather Station has now been upgraded to automatically update everyday at 9.45 am.
If you had used this site in the past for:
- Irrigation scheduling
- Chill calculations
- Checking rainfall totals
- Soil temperature, or
- Wind
You may have found the format was slow to use and the updates were irregular.
Thanks to special drought funding from the DPI you can now use the data with confidence:
- That it has no human errors
- That it will be updated daily
- It is fast to view, even with dial up connections
Short history of the Swan Hill, DPI Weather Station.
- The station has been supplying data since 1969, when the readings were collected manually. The Swan Hill Weather station was installed on a research farm in Tyntynder, now a commercial dairy.
- The weather station was converted to automation using a CR10X data logger in the 1990's and since then has been downloaded over the phone.
- Since September 2003 "Chill hours" has been more accurately expressed as "(Utah) Chill Units ".
- Through a special 2007 Department of Primary Industries drought fund, the weather station is now updating the data on the web everyday giving growers more accurate and timely information.
You can learn more by following the link to the Swan Hill Weather site.
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