The main pests and diseases affecting olives trees in Australia are: scale insects, lace bug and peacock spot
Scale insects
There are two types of scale insects that attack olive trees in Australia; soft scale and armoured scale.
Most soft scales often have only one or two generations per year, while most armoured scales can have several. Eggs of both types of scales are usually hidden under the mother’s cover and are not visible. Eggs hatch into tiny, usually yellow crawlers with legs. The female adult dies soon after the eggs have hatched.
Crawlers walk over the plant surface, are blown by wind to other trees, or can be inadvertently moved by people or birds.
Armoured scales settle down permanently after a day or two in the crawler stage, molt and begin to form their characteristic covers. Soft scales move around for a while longer but also eventually settle at permanent feeding sites.
Sooty mould is an unsightly fungus that is often associated with scale infestation. The mould grows on the excretions (honey dew) produced by the scale insects as they feed on the tree. The fungus does not cause any direct damage to the trees but can cause a significant reduction in photosynthesis by blocking sunlight from the leaves. Sooty mould can only be removed if the insects producing the honeydew are controlled. Once the scale insects are gone the honeydew supply stops and the sooty mould will slowly dry and flake off with exposure to sunlight and rain.
Scale : Biological Control
Beneficial insects that are natural enemies of scale can be used to help manage scale. These include: the scale eating lady beetles. The larvae of these predacious lady beetles can be found under the female soft scales feeding on scale eggs and crawlers. Many parasitic wasps are important natural enemies of scale.
Parasite activity can be monitored by checking scale covering for the round exit holes made by emerging adult parasites and by turning armoured scale over and looking for immature parasites.
Ants deter natural enemies, and if large numbers of ants are climbing up trunks to tend scales they should be controlled. Deny ants access to plant canopies by applying a sticky material (such as Stick’em) to the base of the tree trunk.
Scale : Cultural Control
Canopy structure and density will have a major influence on the development of scale.
Scale prefers moist, dark, environments with mild temperatures for optimal growth. Regular pruning opens the canopy and exposes scale to sunlight, higher temperatures and drier conditions. Pruning to provide open, airy trees will help discourage scale and favor the activity of beneficial insects.
Open canopies will also help improve the penetration of sprays through the trees making spray applications much more efficient.
Scale : Chemical control
White oil and botanical oils are safer organic inputs that can be used if chemical control is required.
These work by smothering the young insects when they are at the crawler stage. Applications of these chemicals must be carefully timed to reach immature scale in the crawler stage. At later stages the scale are very resistant to treatments.
The main crawler stages for scale are in spring and summer. A second crawler stage may also be present in autumn. At least two sprays during each crawler stage are necessary because treatments do not affect the eggs. The second spray targets crawlers developing from the eggs still unhatched at the time of the first spray.
Apply white oil treatments after a sharp increase in crawler production occurs or after crawler numbers have peaked and begin to decline.
Olive lace bug (Froggattia olivinia)
Olive lace bug is a common pest of olives. Heavy infestations can cause loss of vigor, severe defoliation and reduced fruit yield. The bugs are sap-sucking insects that feed on the underside of the causing a yellow mottling of the leaf surface which usually turns brown and eventually drops.
The olive lace bug can have numerous generations per year depending on the climate. New infestations can occur regularly throughout the growing season. Eggs that have over-wintered on the tree usually begin to hatch out in spring or late winter.
Olive Lace Bug : Chemical control
Monitor the trees in early spring for evidence of insect infestation. Apply natural insecticide treatments soon after lace bug activity is first noticed. Lace bug populations can build up rapidly if left unchecked. At least two sprays are necessary 10-14 days apart to control each infestation. Keep in mind that chemical treatments do not kill the eggs. The second spray (10- 14 days after the first) targets the nymphs emerging from the eggs that were unhatched at the time of the first spray.
Low toxicity Pyrethrum products are effective in controlling olive lace bug.
Natural pyrethrum (known as pyrethrin) is extracted from the flowers of Chrysanthemum spp. and has a low mammalian toxicity. Natural Pyrethrum is an approved organic input for growers.
Good coverage is essential when using natural pyrethrums as they are contact sprays that have a very low residual life and break down quickly in sunlight.
Synthetic pyrethrum ( known as pyrethroids) mimic natural pyrethrum compounds but have the advantage that they have a longer residual life and are cheaper to produce. They are very effective in controlling lace bug.
Synthetic pyrethrum’s are the active constituent in most household cans of fly spray. For commercial growers Sumi-Alpha Flex is registered with an off label permit for olive Lace Bug. Sumi-Alpha Flex is a synthetic pyrethrum.
Olive Lace Bug-Cultural control
Lace bug are not difficult to kill but it is essential to obtain good spray coverage when applying chemical treatments. Before spraying badly infested trees, it is recommended that severe pruning is undertaken to reduce tree height and to open the canopy.
As well as making the management of the trees much easier, pruning will improve airflow and facilitate the penetration of spray through the trees making control of pests and diseases much more efficient.
Pruning will also help rejuvenate badly damaged trees buy encouraging new shoot development.
Once the infestation is controlled, regular monitoring of the pest is required on a fortnightly basis throughout the growing season. Usually “hot spots” will occur along the edge of the grove and/or in the vicinity of prior infestations. Hot spots start with the adult lace bug infesting a few trees. If these “hot spots” are sprayed as soon as the lace bug develops then the whole grove will not need to be sprayed.
Peacock Spot (Spilocaea oleaginea)
Peacock spot is a widespread fungal disease of olive trees that affects the foliage and to a lesser extent the fruit. The disease requires moist warm conditions to develop and usually becomes prevalent in autumn and spring. Small sooty blotches develop on the leaves, which in time grow into greenish-black circular spots that measure 2 to 10mm in diameter.
A faint yellow halo is often evident in the tissue around the spots. As the disease develops the leaves become yellow and fall. Most of the infected leaves will fall prematurely by the start of summer. In severely infected trees complete defoliation can occur.
Peacock Spot : Chemical control
Peacock spot is best managed by applying a preventive copper spray in late autumn. A second application in late winter is also recommended in areas subject to warm winters and spring rainfall.
If you missed these sprays an application in spring is recommended to prevent inoculum slowly building up and causing a major disease problem down the track. Copper applications will last around 8 weeks on a tree but will be washed off if rainfall occurs.
The common fungicide Copper Oxychloride ( mix 4g copper with 1L of oil) is used to manage peacock spot in olive is an approved organic input.
Peacock Spot : Cultural control
As with other pest and diseases pruning to provide open, airy trees is an essential management practice. Open trees will discourage Peacock Spot infection and make spray applications much more efficient.
General Spray information
When both a fungicide and insecticide need to be applied at the same time, mixing the two together in the same spray tank can reduce spray operations.
The compatibility of various chemicals can be checked on the product label or by contacting the manufacturer.
It is not recommend that chemical treatments are applied to the trees during flowering as some chemicals can cause flower abscission and disrupt fertilisation and subsequent fruit set.
Comments 29
Brilliant information thank you!
Am going to spray olive tree in a pot with copper oxychloride – it looks like it has peacock spot.
Thank you so much for such an informative page!
Proberly wax scale…. put tree in shade if possible and spray with diluted neem oil…. or wipe off scale with diluted methylated spirit diluted to 75spirit to 25 water.. lightly wipe with cotton wool…hope this helps
Thank you so much for this article. I really needed photo evidence to help identify my pest problem, and this has helped substantially!
Thanks for all the good information. I have two Olivetree in my front yard. For about 7 years and this year they gave us the big juicy fruit but unfortunately full of Waite worm. Jus t wanted to confirm that Pyrethum and Dipel are recommended by you and where can I obtain them. My email address is fhosseiny1952@gmail.com. Much appreciate your input
My 30 year old olive tree suddenly started drying out severely on one side and I was worried about the who tree dying. The leaves would point along the branch and the branch would eventually die. Co-incidentally a neighbour built a new housing extension of which this tree was blocking their sunlight. After many months of desperately managing this tree’s health it’s beginning to recover but peacock spots are now rife as the olive tree is still weak. I’ve given it a few copper sprays and the branches and new growth started looking better but the peacock spot is still very persistent on the leaves of the lower branches. I’ve just resorted to a canola spray on the tree’s lower growth. The leaves on the whole tree are still not back to their deep olive green lustre. Is there anything more I can do to save this beautiful tree.
Have a olive tree in a pot, South East Queensland.
The leaves and stem is covered in little white spots. They are very sticky and looks like candle wax.
Can’t identify it. How should I treat it? Thank you
Author
Hi Jacqueline,
It seems like the trees is infested with a type of scale insect. I suggest you use a combination of white oil and pyrethrum sprays to manage the pest.
Proberly wax scale…. put tree in shade if possible and spray with diluted neem oil…. or wipe off scale with diluted methylated spirit diluted to 75spirit to 25 water.. lightly wipe with cotton wool…hope this helps
Hi,
Hope someone still reads these as I am planting a grove in our school and was wondering if there are any particular plants/trees/shrubs/etc. I should plant around the outside in order to deter pests/bugs etc.
A bit like the companion planting in the veggie garden.
Thanks
How often do you recommend spraying with Copper fungicide for Peacock spot and quantity per litre of water as I can’t find that sort of information? We were overseas for 3 months in winter 2022 and came back in October to discover the peacock spot ( had a very wet winter & spring in Tassie). My 3 trees are in the ground, about 3 years old and about 2.5- 3 m tall? Can I spray in our summer ?I have been removing the leaves and picking off the ground and not putting in our compost . Whilst it’s not too bad at this stage, I don’t want it to get out of control and defoliate the trees! Thanks .
Author
Hi,
The rate for copper oxychloride is 4gl per litre of water.. Typically you apply a preventative spray in Autumn before the winter rains. No problem spraying in ummer every 8 weeks.. this will help reduce the inoculum spore load coming into Autumn/Winter.
Thank you but what does 4gl mean ?
Author
4 grams ( approx 1 tea spoon) per litre of water
Hi I have a few Guava trees and have a problem with fruit fly. Could you please suggest a solution to control or eradicate them
Lyndon
Author
Fruit Fly Control
Nets
Netting trees with very fine UV stable mesh is effective to control fruit Fly as long as complete coverage to ground level is obtained. Alternatively you can build a simple hoop frame around the tree, using poly pipe or PVC pipe and 4 star Pickets. The frame is then cover it with the netting. You may need to install nets when fruit begins to develop so insects can pollinate flowers early in the season.
If you have had a fruit fly infestation previously, fruit fly pupae may be in the ground under your fruit trees. In this situation, secure the bottom of the net to the trunk base to stop any adult fruit flies emerging from the ground to inside the net.
Baits
Baits are an insecticide that is mixed with a Queensland fruit fly food attractant. They are usually spot-sprayed onto the trunk and branches of tree.
The spray is NOT applied to the fruit, but on the trunk or foliage of the tree. These sprays contain a fruit fly specific protein attractant, and an insecticide which will kill the fruit fly when it eats the protein.
Baits can be purchased from nurseries and home garden retailers.
Thank you for a brilliant rundown on the problems we are have. I wondered why we were experiencing a small re-flush of aphids after the first two treatments. I guess we just need a third (3 weeks since #2 and Eco Oil seemed to do the trick). Also helped me identify the scale eggs – as we have plenty of ladybugs and wasps I’ll just keep an eye on them for the time being.
Author
Hi Stuart,
I assume we are talking about Olive lace bug rather than Aphids. They are similar in size but aphids generally don’t affect olive trees. Lace bug will re-infest throughout the growing season and although eco oil may help to control the insects i suggest will have much better success if you use a Pyrethrum based product.
Hi I have olive trees in pots about 2 mtrs,
It seems like they are losing there leaves , cannot see any bugs,shall I spray with insecticides or I have a mavrik gun designed for pests.
Will that be okay Many Thanks.
Author
HI Robert,
Olive trees usually only have two pest problems lace bug and scale insects…if no bugs are present it is no point spraying with insecticide. Leaf drop in olives is usually caused by lack of water or a fungus caused olive leaf spot. This is controlled by spraying the trees with copper oxychloride see link for more info http://fruittreelane.com.au/olives/pest-and-disease-tips-for-the-home-olive-growers/. Lack of fertilizer can also cause the trees to look unthrifty and to drop leaves. In pots we recommend fertilizing with a slow release fertilizer like osmocote or nutricote etc
Hi, We have one olive tree in our garden about 8yrs old. It looks like it has Peacock spot. I’ve read above about using fungicide and insecticide spray. I was hoping for some advice, does the whole tree need to be sprayed (It is pretty tall) if we do not treat it, will it just keep coming back each year and will it kill the tree?
Author
Hi Cath,
The treatment for peacock spot is Copper Oxychloride. If you don’t treat the tree the fungal spores will slowly spread and it can get a lot worse especially if you have a wet Autumn Winter season. It generally won’t kill the tree but it will cause a lot of the foliage to drop and the tree will look very un-thrifty. The whole tree will need to be sprayed. Any leaves on the ground should be raked up and removed.
Can any Olive Grower comment on using ‘Good’ bug control successfully, please?
We are in contact with bugsforbugs, but we would like to have field knowledge from a Grower as to the best way they have found to ‘spread’ the Good Bug Lacewing Larvae with most effect.
Shaking boxes of larvae over the Olive Tree, as recommended by bugsforbugs, seems a bit casual.
Also, we are trying to establish pollen gardens close to our Olive Groves.
Any comments would be appreciated.
Looking to identify small grass like fungi attached to olive branches in south eastern Qld
Author
The grass-like fungi are likely to be a form of stringy type Lichen. These are not harmful to the tree but may be an indication that the tree is in a poor condition. I would fertilize and prune the tree if it has not been done in a while
Hi I have an olive tree that is a late variety. I have found that I have many little bunches of olives that have a brown saw dust, web like matter attached to the internals of the bunch and when pulled apart there is little entry holes. on further inspection if you pick into olive flesh you find a track. at the end is a little worm. Do you know what it is and how to stop infestation for next years crop. I have been manually pulling all affected olives and drowning them in a closed bucket of water.
thanks for your help!!
Author
Hi Jennifer
The fruit damage described is caused by a type of fruit boring caterpillar. Eggs are laid by a moth on the leaves or the surface of the fruit. On hatching, the larvae tunnel into the fruit and feed on the flesh. The entry hole in the fruit usually has sawdust-like excrement and webbing protruding from it. The caterpillars sometimes web a few leaves together to form a shelter. Fungi usually infect the fruit through the entry hole causing fruit rot and premature drop.
Sprays applied for other insect pests such as lace bug should keep the pest in check. However, if sprays are not being applied for other pests then a specific spray, targeting the caterpillar is required. As it is difficult to control the larvae once they have entered the fruit it is essential that regular monitoring is undertaken so that the problem can be treated before it gets out of hand. Spraying may not be warranted if only a small percentage of trees are affected. Economic damage, however, can be significant if the insect population is high. Organically acceptable sprays include Pyrethrum and Dipel
thanks for your reply, much appreciated.
jennie
Im looking for an APPROVED (Omri approved) application fir fungus control on Olive trees. Any advice?
Author
Copper oxychloride is Omri approved with the following restrictions…..may be used for plant disease control if the requirements of 205.206(e) are met, which requires the use of preventative, mechanical, physical, and other pest, weed, and disease management practices. Must be used in a manner that minimizes copper accumulation in the soil and shall not be used as herbicides.
Copper oxychloride is useful in managing Peacock Spot and fruit rot in olive trees.