As home gardeners, we all know that our fruits and veggies are susceptible to a variety of pests. Citrus trees are no exception and, in fact, have a plethora of damaging pests which may infest the fruit. Among these are citrus fruit flies.
There are a number of fruit flies in citrus. These are some of the most common marauders:
One of the most disastrous pests, the Mediterranean fruit fly, or Ceratiitis capitata (Medfly), has afflicted areas from the Mediterranean, southern Europe, the Middle East, Western Australia, South and Central America and Hawaii. Medfly was first recognized in Florida in 1929 and damages not only citrus fruits but the following:
One of the more common citrus fruit flies to plague citrus groves is called the Caribbbean fruit fly or Anastrepha suspensa. Caribbean fruit flies found in citrus are native to the islands of the same name but have migrated over time to afflict groves worldwide. Caribbean fruit flies have been found in citrus groves of California and Florida in the United States, Puerto Rico, Cuba, the Bahamas, the Dominican Republic, Haiti, Hispaniola, and Jamaica.
Also known as the Antillean fruit fly, or the guava fruit fly, this genus includes other species such as Anastrepha ludens, or Mexican fruit fly, known to affect fruit production and marketability of ripened citrus. A. supensa is about ½ to 2 times larger than the average house fly and has a wing band of dark brown whereas its counterpart A. ludens is yellower in hue. The dorsal or top of the thorax between the rear two plates is marked with a black dot.
Eggs are not usually visible, as the fruit flies of citrus trees lay their eggs singly under the peel of the fruit, and generally not more than one or two eggs per fruit. The insect transforms through three larval instars prior to pupation. The larvae tunnel through the fruit and then once completing their three instar stages, drop from the fruit to pupate in the ground. The pupa is long, oval, shiny brown and hard to the touch.
There are two strains of A. suspensa. The Key West strain afflicts overripe citrus fruit as well as guava, Surinam cherry, and loquat. There is also a strain referred to as the Puerto Rican strain which is the more problematic of the two. The Puerto Rican strain affects the following citrus and other fruits:
While the damage has been relatively minor with regards to production, protecting citrus from fruit fly pests has been a major concern among commercial growers.
Methods for protecting citrus from fruit fly pests range from chemical to biological controls. Limited spraying of groves has been shown to reduce fruit fly populations; however, more often integrated pest management has been brought into play using biological control techniques.
The introduction of endoparasitic braconid wasps, which parasitize the larvae of the fruit fly, have shown excellent reductions in the population. Commercial citrus growers also release many sterile flies which interrupts the population since mating will not result in offspring.
SERIES 26 Episode 26
Jerry visits an insect specialist to learn all about how to deal with fruit fly
Fruit Fly costs Australian orchardists millions of dollars every year and they're a bane of home gardeners too. Most of the damage to fruit is done by just two species - the exotic Mediterranean Fruit Fly on the western side of the continent and the native Queensland Fruit Fly in the east.
Commercial growers once relied on blanket chemical spraying, but nowadays more targeted strategies are often favoured. I'm going to show you some of those strategies that work really well in home gardens with assistance from entomologist Gurion Ang, here at the Bethania Street Community Garden in eastern Brisbane.
Like many insects, fruit flies have four life stages - egg, larvae, pupae and adult. Gurion says that understanding this life cycle is the best way to target home garden pest management strategies. "You can see here some Queensland Fruit Fly eggs. You're very unlikely to see these eggs at home because these eggs are laid within the fruit. The female will use her ovipositor - she uses that to puncture the fruit and occasionally the puncture sites will get infected by bacteria and as soon as you see that, it might be a good idea to set out these traps to capture the adults."
"You might also be able to spot the second stage of this insects' life cycle. This is the larval stage and we have some maggots here that are feeding on cherry tomatoes. Again, they feed inside the plant but on the odd occasion, you'll see them jumping off the plant and that's when you know you've got some maggots. You can occasionally also just slice the fruit and check if you think you've got an infection and if you want to get rid of these things, solarising your fruit is probably a good option." Put damaged fruit into a plastic bag, seal it, put it in the sun and allow the whole lot to cook before binning them.
"The third stage is the pupal stage," Gurion continues. "These guys actually pupate in the soil, so the best way to take care of that is to let your chooks out to do the work for you!"
"And the final stage of the fruit fly's lifecycle, which most people are familiar with, is the adult, flying phase. It's the adult stage where some of the most effective control mechanisms can occur - like the use of pheromone traps."
WHAT TO WATCH FOR IN YOUR GARDEN IN A FRUIT FLY ZONE
"The idea behind these traps, Jerry, is to lure, trap and kill. The one I'm going to put up here is pheromone-based. It releases a sex pheromone that only the male flies are attracted to. The beauty of pheromones is that they travel over long distances, so you really only need one of these traps in your backyard."
The more common traps, however, use a very different type of bait. "Protein-based baits attract both male and female fruit flies, as both male and female flies require protein to sustain themselves."
If you opt for the protein-based bait pots, they need to be every two metres apart. Soapy water in the bottom of the pots means that once the flies have been lured in, they fall into the water and drown. Some of these pots come with an insecticide built-in as well.
However, some of the work Gurion's been involved in indicates that while you can attract a fruit fly to the trap, it doesn't necessarily kill them. "That's right. They don't necessarily go in the trap, so we always recommend that in conjunction with traps, you should use other forms of control - for example exclusion methods. But you must still remember that the ovipositor of the female can still go through fruit fly mesh and attack the fruit, so you want some distance between mesh and fruit."
Other exclusion techniques involve enclosing individual fruits, like mangoes and passionfruit, inside paper bags.
So there's a lot to consider when trying to control fruit flies.
Better than controlling fruit fly just in your own garden is getting your neighbours involved at the same time. By synchronising fruit fly control, you can expand your kill. It's really amazing how much fruit you can save by doing it and all it involves is being a good neighbour!
Rotting, fermenting foods are serious attractants for fruit flies.
Fruit flies are attracted to moist environments with fermenting food waste. They like garbage disposals, kitchen waste baskets, and of potentially, worm bins.
Of the various wastes you might find in a worm bin, fruit flies are especially attracted to the very same sugar-rich foods that your worms will find the most attractive: pumpkins, honeydew, canteloupe, banana, watermelon, etc.
Fermentation is the anaerobic processing of sugar into alcohol or acid, so sweet, carbohydrate-rich foods like the ones mentioned above are prime candidates for attracting fruit flies.
The adult fly is 3–5mm long. Its body is light brown and the abdomen is encircled by two light-coloured rings. The thorax (middle) has irregular patches of black and silver, giving it a mosaic appearance. The wings are mottled with distinct brown bands extending to the wing tips.
Don't confuse Medfly for Queensland fruit fly (Qfly), which is larger and reddish brown and has clear wings. Refer to the Qfly web pages for more identifying information.
The Medfly female has an ovipositor or egg-laying organ but the male does not. Adult Medflies may live for two to three months and are often found in fruit tree foliage, especially citrus trees. As long as fruit is present most Medflies do not move more than 50 metres. However, they will travel further if no hosts are present.
Medflies prefer to lay eggs in soft-fleshed fruit such as apricots, peaches, plums and nectarines. When Medfly numbers are high and competition is greater, females become less choosy and will infest less preferred hosts such as olives.
They will also infest such fruits or vegetables if preferred hosts are not available, even when their populations are low.
Once a suitable host is found, the ovipositor is used to pierce the fruit skin. Batches of up to 300 white banana-shaped eggs are laid into this hole. Eggs are just visible to the naked eye and take 2–4 days to hatch in summer and 19–20 days in winter.
The eggs and larvae of Qfly and Medfly are almost identical, and larval identification needs to be carried out by an expert.
But what you're dealing with can be most easily determined by where the insects are congregating. If they're in your kitchen eyeing up the ripening produce, they're fruit flies. If they're flying around and burrowing into the soil of your lemon tree, they're fungus gnats.
Also, what's wrong with my citrus tree? Overwatering: Citrus may become stressed and more susceptible to pests and diseases as a result of poor drainage or standing water. Trees may also become chlorotic as a result of wet or waterlogged soils, anaerobic soils, root rot diseases, or damaged roots.
Hereof, are fruit flies attracted to citrus?
Answer: Fruit flies are not attracted to citrus oils (or fresh citrus fruit) they are attracted to the vinegary fermentation products of rotting fruit. And you can actually set fruit fly traps filled with apple cider vinegar.
What do you spray on citrus trees?
If present, apply horticultural oil or insecticidal soap. Control on bearing trees is generally not needed as damage is not usually significant enough to warrant spray. For citrus leafminers (on new growth) little control is available. Either leave it alone or spray with horticultural oil twice, spaced two weeks apart.
Fruit fly are an incredibly annoying pest - they can destroy a range of fruit and vegetable crops in a very short space of time. It is heartbreaking to be nurturing a fruit tree for years, sustained by the anticipation of your first juicy fruit only to have your dream shattered by a tiny, flying bug and its larvae.
If you grow fruit, it is actually your responsibility to actively control fruit fly in your back yard. The Ag Department can enforce this, particularly if you are located near commercial growers.
Unfortunately Fruit Fly are very difficult to control using purely organic methods however you CAN help keep numbers down, and we will try and give you a few ideas which should help you enjoy the fruits of your labour (excuse the pun).
Queensland Fruit Fly were eradicated from Perth in the 1990's, and we need to be vigilant to ensure we remain free of them. The common Fruit Fly we get here in the west is the Mediterranean Fruit Fly (Medfly - see picture), thought to originate from tropical Africa, and was first detected in WA in Claremont in 1895.
The activity of Medfly depends on the temperature. In late spring, summer and autumn they are most active around Perth. Over winter, the fly may become inactive in the cold, however they can survive through this season in all stages of their life cycle, and when temperatures begin to warm up, new adults begin to emerge from their pupae in the ground, and surviving adults become active. Adult Medfly typically live for 2 - 3 months and are often found in foliage of fruit trees. As long as fruit is available, they tend not to spread further than 20 - 50 metres from their place of origin.
After mating, females will search for a suitable host in which to deposit her eggs. Soft fruit (such as apricots) are more preferable than harder fruits like apples and pears, but where populations are higher or there is a lack of preferred fruit, a much wider range of fruits can be infested.
The Larvae (maggots) will hatch within 2 - 4 days. These little white grubs start out 1mm long but grow to about 8mm long, and are what most people recognise as fruit fly. Their activity causes fruit to rot and spoil. Once fully grown, the larvae leave the fruit, and burrow into the soil to pupate. The pupae resemble a small brown capsule about 6mm long. The pupation stage varies with temperature - it lasts around 2 weeks in summer, and can be about 7 weeks over winter. Eventually the adult emerges from the pupal case and burrows up through the soil.
Here are the main methods to control Medfly:-
These are non-organic and I believe there are only three commercial insecticides registered for use in Western Australia. Cover sprays are non-selective pesticides so for this reason their use is declining and alternative methods being increased - however for highly susceptible crops to be commercially viable, they are still used.
While we always recommend organic gardening methods, in extreme cases we recognise it may be necessary to use pesticides. Hopefully once you have a severe outbreak under control, in future years you can practise less drastic control methods.
ALWAYS read labels, follow instructions concerning withholding periods and NEVER use more than the recommended application rates.
The spray is NOT applied to the fruit, but on the trunk or foliage of the tree. It is claimed that spraying on 1m2 area of foliage, or on a board which is then hung in the trees will control fruit fly for a 50m2 area. These sprays contain a fruit fly specific protein attractant, and an insecticide which will kill the fruit fly when it eats the protein.
We stock Eco-Naturalure which is Certified Organic by BFA.
Another product on the market is Yates Nature's Way Fruit Fly Control. Although not organic, it is claimed to be low toxic and also has no withholding period.
A number of different types of traps and baits are available for Medfly. Some are pheromone based and will attract either males or females, depending on the product. Other baits or traps are based on a food source, and will attract both sexes, and possibly a number of other insects (both 'good' and 'bad') which will also die once captured.
Traps can contain a bait and an insecticide, or they can be a simple 'wet' trap, where insects enter but then cannot find their way out, and will eventually drown in the solution.
Traps are not considered to be hugely successful in controlling large numbers of Medfly, but they will certainly HELP, and can also help show the numbers of Medfly around, so if you DO choose to spray, you can do so at the most effective time.
Commercial traps and baits are available to purchase (we have both available in stock) or you can very simply make your own as per the diagram below. (The diagram shows a 2L bottle with handle - but any plastic bottle will do!)
What you choose to use for bait is up to you. If you look on-line, there are a huge number of suggested recipes, many of which can be made from things you will already find in your cupboard. Here is one to try:
1L hot water
1/2 tblspn Cloudy Ammonia (available at supermarkets in the cleaning section)
1/2 tspn Vanilla Essence
1 tspn Dishwashing Liquid
1 tspn Vegemite
Dissolve the sugar and Vegemite in the hot water. Allow to cool before adding in remaining ingredients and mixing. Makes enough for approx. 3 - 5 traps.
Use between 3 - 6 traps in and around each tree (hang amongst the foliage), and replace the baits every two weeks at least, or if they become full of flies, or the liquid evaporates too quickly. Baits which are too low or diluted with rain will be less effective. If you are using a non-toxic bait, you can dispose the trap contents into the chookpen - fowls are quite appreciative of the protein!
Traps can also be placed in non-fruiting trees, and this can be an effective way to keep the flies away from your precious fruit too!
Exclusion Bags and Netting
Exclusion bags are available in a wide range of types and sizes locally from Guildford Town Garden Centre (9279 8645), and also on-line from Greenharvest. Completely organic, they prevent the adult fruitfly from getting to the fruit to lay her eggs - if used at the right time (again, you may find traps helpful as an indicator). Exclusion bags also prevent sunburn of fruit, and are re-useable.
Netting trees with insect netting or by using old net curtains is also effective, providing you can cover the tree to ground level. This method has the added benefit of keeping birds away from fruit, but is only practical where you have a small to medium tree that you can easily cover. At GLSC, we carry insect netting packs in varying sizes.
The other way to use netting, or soft flywire, is to simply cover selected branches - think Christmas bon bons! Ensure you join all edges together well - you only need a tiny gap to allow the flies access.
Simple, cheap - but why is it common to see fallen fruit left to rot at the base of a tree? This soft fruit is easily available for adults to lay eggs, and will allow numbers to explode. When picking up fruit that has been struck with Medfly, don't bury it or put it straight into the compost. The eggs and larvae can survive. Freezing, cooking or pureeing the fruit will destroy the Medfly (and the fruit can then be fed to chooks). Soaking in water too will work, however the larvae can survive for weeks. It is recommended to add a thin layer of kerosene to the water, to seal the water and prevent the oxygen exchange.
Alternatively put the fruit into a plastic bag (with no holes), tying it up securely, and leave it in the sun for a couple of weeks. The fruit will continue to break down, but it will also reach high temperatures which kill off the larvae. Check, and if no signs of life, the fruit can then be composted or disposed of. We have been shocked to find larvae still alive after 8 weeks.
Finally, select varieties of fruit which are less susceptible to fruit fly - either through type of actual fruit or by when in the season it ripens. Often, early ripening varieties are less affected simply because Medfly numbers tend to build up as summer goes on. Alternatively if you move to a property that has a fruit tree you don't want, either arrange to give the fruit away or have someone harvest it for you (there are often people who will be happy to exchange a load of fruit for a supply of jam!) or perhaps remove the tree and replace it with something else (preferably also green and alive). That way you won't be contributing to fruit fly numbers in your area and you won't have the worry anymore.
Using a combination of these methods will certainly help keep numbers of Medfly down, and you should be able to enjoy your own home grown fruit! Encourage your neighbours to do the right thing and control numbers too otherwise all your hard work can be to no avail if your yard is continually being populated from over the fence! If they aren't keen gardeners, why not offer to make and check baits in their trees too - whilst being neighbourly it can also make a huge difference to your own harvest size!
Visit our online shop for Ceratrap baits, Eco-naturalure and other pest control products.