Fruit Piercing Moth and Fruit Spotting Bug Research

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Harry Fay  –   Centre for Tropical Agriculture Mareeba – Nth Qld.

I’ve been researching Fruit Piercing Moth for almost 20 years. We’ve recently developed baits for the moth which while not providing total control do relieve a lot of the damage they cause.

Sheryl : Have you done any studies planting carambola nearby to see if they prefer to go there?
Harry:  No, but we have studied carambolas in orchards and there are some varietal preferences by moths, but fruit ripeness is the most critical factor. The moths seem to prefer the sweeter types like the Fwang Tung. In crops like papaws ripe fruit are much preferred.

Sheryl:   Is it the sugar they go for ie if you put out sugar water, would they go for that?
Harry:  They are after the sugar but fruit odours are critical to the attraction. Our baits contain  synthetic fruit odours which act to decoy the moths from the fruit. However, they tend to work better when the crop isn’t quite ripe as they don’t have to compete with lots of natural fruit odour.

Sheryl:   So after they take the bait, do they die?
Harry:   They’re suppose to, as there is insecticide in the baits!

Sheryl:   So what’s the success rate?
Harry:    That’s been really hard to determine because it’s not simply a matter of counting dead moths or comparing treated with untreated trees. In a couple of cases, in citrus and mangoes, we believe that we have  reduced the damage rate down from 20% to 4 or 5.

Sheryl:   Are you doing field trials in a commercial situation? 
Harry:     We’ve finished them now but we did 3 years of trials in commercial crops.

Sheryl:   What type of orchards? 
Harry:     Mainly citrus, because this industry funded most of the research. A few trials were also conducted in lychees, mangoes and carambolas. The baits appeared least effective in lychees and carambolas, because when they’re ripe they’re producing huge amounts of odour. If you can get the bait into carambolas before they’re fully ripe, you would expect a better job. In citrus, the baits seem to work reasonably well and it’s only when you get large influxes of moths at the end of the crop that the baits find it difficult to compete with the fruit. Citrus and mangoes are rarely protected by netting, so if the fruit is left on the tree to get fully coloured and ripe it’s particularly vulnerable to attack. Combining the baits with getting the fruit off at the right stage will reduce the damage considerably.

Sheryl:  Using the brix test, what percentage do they take the mango off at?
Harry:    I don’t know what it is with mango, but it’s usually around 8 in citrus.  Up here you don’t hear of Kensingtons being attacked by the moth – mainly R2E2, Keitt, Palmer and Brooks. The early mango types in Nth Qld tend to avoid the peak moth populations which occur from early January to early April.

Sheryl:  How many different varieties are there in the moth? 
Harry:    There are dozens of different species that can cause damage to soft fruits  but only 4 or 5 species from the genus Eudocima are considered economically important and capable of piercing harder fruits like lychees.

Sheryl:  Do they all have the orange spot? 
Harry:    No, the main species all have orange hindwings but the patterns vary.

Sheryl:  Do you have any coloured photos I could take back? 
Harry:    No, not of all the species.

Sheryl:   Do you have a CD perhaps?
Harry:     No, but I’ve got one colour page with photos of the 3 most important species. One of our trial sites in south-east Queensland where these 3 species occur was on the Burnett River. This site was adjacent to the Goodnight Scrub where there is believed to be a lot of moth breeding, and the orchard has significant problems each year.

Sheryl:  Do you have a list of what they breed on so we can address this issue?
Harry:   We do have some papers on the host plants but I’m not sure if they list all species (there are 24 or more in Australia). The Eudocima only breed on the Menispermaceae, which is a family of vines, but only a few of the species are really significant. The species mix varies somewhat as you move from north to south, but they do go right down as far as East Gippsland in Victoria and they’re right across northern Australia and into very dry country north of Alice Springs. So the moths can breed over vast areas and are supposed to migrate from these breeding areas into orchards hundreds of kilometres away.  One of the main menisperm species, Tinospora smilacina, is called Snake Vine as it tends to curl up trees – it’s well known in Aboriginal medicinal culture for uses such as snake bite.

Sheryl:  Who makes up the baits?
Harry:    We’ve done it ourselves here through the project. There is now someone interested in the commercial production.

Sheryl:  Who funded your project? 
Harry:    Horticulture Australia, the national citrus levy, GrowCom (formerly QFVG) and Bundaberg and Gin Gin grower groups.

Fruit Spotting Bug

Sheryl:  You’ve now finished the Fruit Piercing Moth project so you’re now on Fruit Spotting Bug? Harry: We do have a new RIRDC project looking at the potential of pyrethrum in organic situations for control of fruit spotting bug, so we’re looking at formulations/rates on various crops but using it very discretely. Because it’s broad spectrum you can’t spray it willy nilly as it knocks out all the beneficial species as well so we’ll also try some of the other potential organic treatments, like kaolin clays. There has been some work with these in Mareeba on mangoes, mainly looking at their sunscreen utility. In these trials kaolin did increase the mango scale populations but I believe the manufacturer has been tackling this problem.

Sheryl:  Any successful outcome from your studies? 
Harry:    We’ve only just started the pyrethrum trials which will run over 3 years. However, we’ve just finished a study of spotting bugs in papaws which indicated that small plants in the ground between  January and May are very prone to damage.

Sheryl:  What part do they attack?
Harry:    The growing tip is where they do the main damage in papaws but they also feed on the petioles. The growing tip gets very distorted due to the damage and a plant can actually die if it’s still small.

Sheryl:  Have you ever done any work with Guinea Fowl as they really get into leeches etc.
Harry:    I don’t think they would impact on spotting bugs. I worked in Africa for 4 years and where there are large concentrations of insects such as in rhino middens guinea fowl feed prolifically. Bugs tend to be distasteful because of defensive secretions, so birds don’t tend to go for them as much as some other insects. I suspect for spotting bugs it would have to be an arboreal type of bird in any case.