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Plantwise Technical Factsheet

cherry fruit fly (Rhagoletis cingulata)

Host plants / species affected
Prunus avium (sweet cherry)
Prunus cerasus (sour cherry)
Prunus mahaleb (mahaleb cherry)
Prunus serotina (black cherry)
Prunus virginiana (common chokecherrytree)
List of symptoms/signs
Fruit  -  discoloration
Fruit  -  extensive mould
Fruit  -  gummosis
Fruit  -  internal feeding
Fruit  -  lesions: black or brown
Fruit  -  lesions: scab or pitting
Fruit  -  obvious exit hole
Fruit  -  odour
Fruit  -  ooze
Symptoms

Attacked fruit will be pitted by oviposition punctures, around which some discoloration usually occurs. Infested fruits appear normal until the maggot is nearly full-grown, at which time sunken spots appear. Maggots and their frass inside the cherry render the fruit unsalable. Infested fruits are more susceptible to fungi. The third larval instar forms one to three holes (about 1 mm in diameter) through the skin of the cherry, before it leaves it for pupation in the soil (Frick et al., 1954).

Prevention and control

Control

Upon detection, fallen and infected fruit should be removed and destroyed. This aspect is very important, but normally rarely executed as it costs time and money.

Chemical control

Cherry fruit fly control has relied for many years on the use of broad-spectrum insecticides. Boller and Prokopy (1976) note already that systemic organophosphates, such as dimethoate, are highly effective against most species, killing eggs, larvae and adults. Belanger et al. (1985) discussed the use of pyrethroids, but these were only of use when pest activity was low. Use of soil insecticides to kill puparia has been considered by AliNiazee (1974) and Boller and Prokopy (1976) referred to experiments with juvenile hormone analogues applied to the soil. However, regarding ecotoxicological aspects soil applications should not be considered anymore. Advanced IPM systems have been implemented in some areas, for example, Michigan (Edson et al., 1998). Broad-spectrum insecticides are still in use (Rothwell et al., 2006), but due to the re-evaluation processes underway for pesticides in the USA, Canada and Europe these most probably will disappear. In Germany, dimethoate has no registration any more for cherry fruit fly control since 2005 and its use has only been allowed by special permit since then. Studies with newer insecticides, e.g. neonicotinids or acetamiprid (Fried, 2003; Galli, 2003), and others are ongoing. In the USA, particle film (Kaolin clay) is another option for cherry fruit fly control.

As a new and environmentally friendly measure, progress has been made with bait sprays (food bait mixed with low quantities of insecticides) containing spinosad as an insecticide (e.g. Yee and Chapmann, 2005; Pelz-Stelinski et al., 2006b; Yee and Alston, 2006; Köppler et al., 2008). Bait sprays can be applied as spot treatments on the trees. In comparison with cover sprays, the amount of insecticide used is drastically reduced with bait sprays. Constraints in their effectiveness are high population densities and rainfall, because bait sprays up to now are not rainfast. Furthermore, infestation sources, i.e. untreated host trees, should not be in the vicinity in order to avoid immigration of fertile females.

Biological control

Investigations in biocontrol using entomopathogenic nematodes (EPN) have shown that maggots of Rhagoletis species are highly susceptible (Yee and Lacey, 2003; Köppler et al., 2005). However, high efficacies could not be achieved under practical conditions with one to several applications of a commercially available product based on Steinernema feltiae (application rate 250.000 to 500.000 EPN/m²) (Herz et al., 2007a,b; 2008). The reasons are manyfold: pupation occurs too quickly (when larvae enter the soil; larval dropping to the soil occurs over a long period (2-4 weeks)); survival of nematodes in the soil is short (frequent and cost intensive applications of EPN would be necessary); and soil conditions are often unfavourable (too dry and too warm, for optimum nematode survival and infectivity). Even with repeated irrigation in field investigations carried out by Herz et al. (2007a,b, 2008), efficacies were far from sufficient.

Entomopathogenic fungi as biocontrol agents have been tested against Rhagoletis species in Europe and the USA (Yee and Lacey, 2005; Daniel and Wyss, 2008; Ladurner et al., 2008). A product based on Beauveria bassiana is registered in Italy for control of the European cherry fruit fly, R. cerasi. Field experiments have resulted in significant reductions of fruit infestation, but efficacies varied (Daniel and Wyss, 2008; Ladurner et al., 2008). This may be due to varying climatic conditions, which have a high impact on myco-pesticides.

Phytosanitary Measures

Consignments of cherries (Prunus avium, P. cerasus) and of P. salicina from countries where R. cingulata or R. indifferens occur should be inspected for symptoms of infestation and those suspected should be cut open in order to look for larvae. The European and Mediterranean Plant Protection Organization (EPPO) recommends that such fruits should come from an area where R. cingulata and R. indifferens do not occur, or from a place of production found free from these pests by regular inspection for 3 months before harvest. Fruits may also be treated, but specific treatment schedules have mostly not been developed for Rhagoletis species, since there is no need for them in North America. Irradiation has been successfully tested as a quarantine treatment against R. indifferens (Burditt and Hungate, 1988).

Plants of host species transported with roots from countries where R. cingulata or R. indifferens occur should be free from soil, or the soil should be treated against puparia, and should not carry fruits. Such plants may indeed be prohibited importation.


 

Impact

R. cingulata is an important pest of cherries in eastern North America. In Europe, where it is found in cherry growing regions, it attacks late cherry varities, often tart cherries.

Related treatment support
 
External factsheets
NYS IPM Factsheets, Cornell University, Cornell Cooperative Extension, 1988, English language
British Columbia Ministry of Agriculture Factsheets, Government of British Columbia, 2016, English language
Ontario CropIPM factsheets, Ontario Ministry of Agriculture, Food and Rural Affairs, Canada, 2015, English language
Ontario CropIPM factsheets, Ontario Ministry of Agriculture, Food and Rural Affairs, Canada, 2015, French language
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