This is one of a series of monthly articles for the OliveCare® Newsletter, authored by internationally renowned plant pathologist Vera Sergeeva.
The series is aimed at assisting olive producers to apply Integrated Pest and Disease Management (IPDM) principles to reduce their reliance on chemical use in olive groves:
Part 3 – Olive lace Bug Management:
By Vera Sergeeva, OliVera, http://olivediseases.com/
Olive Lace Bug (Frogattia olivinia)(Hemiptera: Tingidae), is a native species first described feeding on the Native Olive (Notelaea longifolia) in 1974. Itis now one of the most common pest of olives and is found in most olive growing areas in Australia.
Olive lace bug (OLB) is native to NSW and southern Queensland is known as a pest of European Olive (WA Agriculture 2004). It has established widely on feral European olives in South Australia causing small olive fruits on heavily infected trees to fall before ripening. Olive growers in the Hunter Valley identified the lace bug as a threat to their crops as early as 1990, and infestations were recorded on olive tree in NSW in 2002. Tasmania is free from the olive lace bug.
OLB has not yet been found in other olive growing regions of the world.
It is also observed that pests can be present on olives without causing economic damage. In any plant–insect and plant–pathogen interaction there is a continuum of possible outcomes, ranging from extreme susceptibility to complete resistance.
The author believes OLB lives on some Oleaceae plant species such asthe wild or African Olive1.(Olea europaea subsp. cuspidate). (Synonyms – Olea cuspidataand Olea Africana – now considered a single subspecies Olea europaea subsp. Cuspidate), but does not damage them as it does in commercial olive groves, (but created a reservoir of OLB). African Olive is a listed as a noxious weed in 11 local government areas of NSW and has been listed as a key threat under the NSW Threatened Species Conservation Act 1995, and is also a problem in some areas of South Australia and the ACT. When it invades native bushland it creates a dense canopy that restricts the growth of native plants in the understory, leaving a monoculture of olives that transforms the ecosystem if it is not controlled. African Olive has the ability to establish on dry exposed ridgelines, yet is also able to grow in conjunction with other woody weeds in the Oleaceae such as Privet (Ligustrum spp).
Feral olives: (Olea europaea) have thrived in many parts of the country particularly SA, where in some areas they have been declared weeds which the author believes could be hosts for OLB.
General Description: The parasitic sap-sucking insect- OLB (Frogattia olivinia) is the equal-first insect threat to Australia’s multi-million dollar olive industry, with the other being brown or black scale. Damage caused by OLB is significant and it a major problem in Qld and NSW, also recorded in Vic and SA; increasing problem in other states and rapidly becoming of concern in WA, where it now deemed as endemic, having spread into WA from NSW and across Australia by itinerant workers and / or harvesting machinery. In Australia’s olive industry, it’s not uncommon for machinery to go from grove to grove and state to state without washdown, which can help spread different pests and diseases including OLB. Olive lace bug can also infest groves on the wind from forests, or within a grove, from nearby groves, and from nurseries with plant movement. It’s a big problem.
Biology: OLB is a small, flat insect, adults are mottled dark brown and cream, about 3 mm long with see through lace like wings. Antennae are very large in proportion to the adult body. Eggs are deposited in or on the tissue of newly developing leaves, usually along the midribs. The adult secrete a brownish to black substance that hardens over the eggs, which secures them to the leaf. The nymphal stages are clustered on undersides of leaves. Adult bugs are less clustered and fly short distances. First generation is usually discrete, later can have overlapping generations. The nymphs with early instars varying in colour from light cream or greenish yellow to pinkish orange without spines; whereas later instars are green to greyish black and with spiny appearance. Nymphs are oval in shape and wingless at first, with wing buds progressively developing from 3rd instar onwards. OLB lives on the underside of leaves out of direct sunlight.Both adults and nymphs are sap-suckers.
Lifecycle: OLB appear throughout the year. Eggs that have overwintered on the tree usually begin to hatch out in spring or late winter. There are five nymphal instars. Depending on the weather, the life cycle requires four to seven weeks, and there are one to four generations a year that can be completed before the final generation adults lay overwintering eggs to complete the annual cycle. Some eggs may hatch during the winter months. Some adults may also survive the winter. OLB overwinter in protected places on the tree.
Damage: The first clue that OLB is present is a pin-head sized yellow spotting noticed on the top of the leaves. These spots are easy to see as they contrast clearly against the dark green leaf surface. The yellowing is associated with blackness and dirty smears of secretions and excrement on the underside of leaves. Although most OLB activity occurs on the underside of the leaf, the most common indications of an infestation of OLB are on the upper leaf surface where leaves become stippled with greenish stippled with yellow, brown dots and later blotches on the upper surface to rusty and even severe infestations cause leaves to become half or whole rusty, remind as a leaf disorder.
As OLB colonies grow, brown dead areas develop where there has been heavy feeding damage. All stages (nymphs and adults) attack leaves with piercing mouthparts, causing yellow spotting. Heavy feeding can cause striking leaf discoloration and early leaf drop and twig dieback may. Flowering and fruiting can be delayed for a year or more, thereby reducing the vigour and productivity of the trees. OLB can defoliate whole groves, resulting in no fruit the following season. In some cases dead areas look like tip-burn, but the necrotic areas are surrounded by living tissue. If the sap-sucking insect present in large enough numbers, pest will defoliate a young tree and kill it. OLB has led to the removal of thousand’s trees on some groves after the trees were found badly infested with the pest.
Lace bugs restrict their feeding to the undersides of leaves, inserting their needle-like mouthparts into leaf tissue cells to extract cell contents cause stress in the olive tree, reduce its photosynthsis through damaged leaves and loss of leaves resulting in lower growth potential.
Woody tissue photosynthesis was observed on olive trees after heavy infestation of OLB. The tree loses the leaves is that it takes a lot of energy to maintain the new leaves. Trees without leaves have photosynthetic bark so they actually capture sunlight on their trunk and branches and bark of olive tree turn in green colour. Trees also use their branches and twigs for photosynthesis. When the leaves go, the tree’s branches take over the job of photosynthesis. Stem photosynthesis resembles leaf photosynthesis. Corticular or bark photosynthesis occurs in stems of woody plants, in chlorenchyma layers located under a well-developed stomata-free periderm. Chlorophyllous tissue is present in the bark of olive stems up to several years old.
OLB is a serious olive tree pest, which can cause heavy defoliation and total crop failure if not managed effectively. Approved control options are currently limited. Some growers are finding it can be controlled for a number of years using a particular chemical, only to find the bug develops resistance to it soon after. Nutrition management is important – increasing nutrients to increase chlorophyll on leaves, can increase tree health and reduce lace bug.
Effective control depends just as much on ensuring your olive trees are in optimal healthy as it does on controlling the numbers of OLB by a well-timed spraying regime.
The three most important areas to focus on are:
- Tree Health
- Spotting OLB early in the Spring
- Early, Effective use of insecticide sprays
Tree Health:To reduce the problems over time make sure that the trees are kept in good health. Healthy trees – even alongside heavily infested unhealthy trees will repel attacks by OLB, stay healthy, and produce good fruit. Trees that are drought or nutrient stressed are more prone to attack. In the Hunter Valley OLB numbers have exploded, fed by a damp, cool summer. Hot and humid conditions major influence, contributed to the lace bug infestation as well. Lace bug caused by a combination of conditions.
Olive trees are able to resist an attack by OLB, however grove owners will need to work on:
- Provide proper cultural care so plants are vigorous: Control the size of trees by pruning– “right- sizing” the tree for the water supply it has access to. Trees high on a slope will probably get less water in a dry year. Adequate water supply in a dry year; this may involve irrigation, but also careful positioning of the trees, mulching, and building up the organic content of the soil.
- Before spraying badly infested trees, carry out pruning to reduce tree height and open the canopy to make the spraying more effective. Regular pruning will also open up the tree, improving airflow and the all-important access for insect predators such as birds. Pruning will help rejuvenate badly damaged trees by encouraging new shoot development.
- Good Soil Nutrition: Look carefully soil and leaf analyses and deal with any significant deficits. Start the plant biology working so the trees look healthy with a dense leaf colour. Chemically treated soils produce weaker plants that are more physiologically stressed and these plants become more susceptible to disease and insect damage as well. Sometimes spraying with approved chemicals fails because rain washed off the chemical into the soil.
- Magnesium and Leaf Chlorophyll: Chlorophyll is the stuff in the leaves, which makes photosynthesis possible. It is vital for tree health and a component, which is damaged by OLB attack, which causes the leaves to turn yellow. Magnesium builds chlorophyll and helps the tree resist OLB attack. So look hard at the soil analysis and work on the Ca:Mg balance. Growers may have to spread some dolomite to raise the Mg content.
Early, Effective, Use of Insecticide Sprays: Monitor the spread of OLB: OLB does not “just happen”; OLB hibernates in and around olive grove, as adults and eggs in protected places. For effective control of OLB in late winter start to inspect your grove often. Usually the OLB start to appear in the same places each spring – quite often spreading from south to north. In spring the eggs hatch, and go through several wingless stages (instars) before turning into the winged adults, which spread across the grove and lay more eggs. The full life cycle is short, only 12 to 23 days, so you have to move quickly to stop them. Early identification of an infestation will limit the number of threes you need to spray.
For effective control of OLB:
- In late winter start to inspect your grove often. Early identification of an infestation will limit the number of threes you need to spray. See where are eggs hatching, and spray them in their early stages without wings to stop wingless nymphs spread, and prevent the laying of eggs.
- Spray those trees very thoroughly,to get the good spray under the leaveswhen OLB adults or nymphs are observed on foliage in the spring; naturally it is much easier if only have to spray a few trees because you caught the infestation early.
- Go back and check again at weekly intervals; spray any new infestations as you find them. To achieve season-long control, it may be necessary to spray more than once. Take action when a population begins to increase and before damage becomes extensive.
Biological control:Around us an infinite battle is constantly waged, which we usually do not pay attention to. It occurs between insects that try to eat plants, and plants that protect themselves from attack. Each side constantly acts, develops and tests new methods of attack and defense, attracts allies on its side . Natural enemies of OLB include lacewing larvae, lady beetles, jumping spiders, pirate bugs, and predaceous mites. OLB are reported to have an egg parasite but this is unlikely to be present in many conventional olive groves, particularly if the ground is bare. Egg parasites are usually nectar feeders as adults and are more likely to be established in groves with flowering groundcovers. The Green Lacewing is an insect predator native to Australia. The native green lacewing is commercially available are to be encouraged but are unlikely to control heavy infestations. However, is an essential part of a long-term integrated pest management program.
Use chemicals wisely and where necessary:Many pesticides kill beneficial insects as well as pests. Since pests tend to breed very fast, they will often come back first. Killing a beneficial insects we inherit its job, we are attempting to take on the task of an expert. Whenever we fail, the environment suffers.
The author is in favour of avoiding the use of complex chemical insecticides because they tend to kill beneficial insects as well as the OLB. Whilst this advice may not be applicable to all growers, because those olive growers using chemicals already have stressed plants. Stressed and weak plants more susceptible to pests and diseases. The authors philosophy is to use chemicals wisely and only where necessary and to focus more on enhancing tree health and vigour. Healthy, productive plants can use their natural defense systems to resist environmental stresses. As a result, they need less chemical input for survival and productive long-term growth. Pests can be present without causing economic damage. Tolerate lace bug damage where possible; in most cases, it does not seriously harm trees. OLB has a threshold beyond which control is required.
Insecticides will not restore an undamaged appearance, but can reduce or prevent further damage. Good spray coverage is essential. The OLB is difficult to control as it feeds and breeds on the underside of the leaf, it also multiplies prolifically. OLB eggs are protected within plant tissue and it is difficult to achieve complete insecticide coverage of leaf undersides and throughout a dense canopy and also on suckers. The lace bug is difficult to control as it feeds and breeds on the underside of the leaf and it also multiplies prolifically. The timing of sprays is very important. At the same time a systemic pesticide is absorbed into a plant and distributed throughout its tissues, reaching the plant’s stem, leaves, roots, and flowers or fruits. Systemic pesticides are water-soluble, so they easily move throughout a plant as it absorbs water and transports it to its tissues. If phytotoxicity is severe, damaging trees, this also makes them unhealthy and may die.
Insecticides registered for control of OLB in accordance with Australian Pesticides and Veterinary Medicines Authority (APVMA) label registration and minor use permits (application rates should be according to label or permit recommendations):
- Potassium soap (Natrasoap®), PER14414 – Until 30 September 2023
2 applications/season 7-10 days apart – organically registered.
The potassium soap (Natrasoap) spray has questionable efficiency against the more mature stages of the bug. Natrasoap are not very effective against the eggs and work best against active populations (adult lace bug only), normally in springtime. Insecticidal soap solution will only kill pests on contact. Therefore for heavy populations two applications about two weeks apart should be made. it’s should spray thoroughly to give good coverage on the trunk, branches, leaves, suckers and shoots.
Follow and observe the directions and requirements on the permits: Natrasoap formulated using potassium salts combined with fatty acids in a vegetable oil base. Spray when insects are noticed. Spray insects directly and repeat as necessary. A complete coverage of the target is necessary. Apply to the point of run-off. Apply morning or evening when temperatures are cooler. Re-apply 5-7 days later or as necessary. Use high pressure with fine droplet. It is important that the spray makes direct contact with pests. Always add SPRAYTECH OIL (Canola oil 70-99%). Shake the container before opening. Pre-mix NATRASOAP with SPRAYTECH OIL before adding to the water.
- Dimethoate (Rogor®, various) PER13999 – Until 6 march 2019. Max 4 applications/season. 2 sprays 7-14 days apart. Not to be used for table olives WHP 42 days (6 weeks)
Dimethoate is organophosphorus used mainly to control sucking pests (fruit fly, ticks, aphids, thrips) on crops and ornamentals. Dimethoate is a systemic insecticide, which means it enters the sap stream of the plant through roots and foliage and is distributed throughout the plant. Unfortunately, when systemic insecticides are used on edible crops, residues cannot be washed from the produce because the chemical is not on the surface.
- Clothianidin (Samurai®) PER14897 – Until 31 March 2023 1 spray WHP 56 days (8 weeks)
For insecticide resistance management Sumitomo Samurai systemic Insecticide is a group 4A insecticide. Some naturally occurring insect biotypes resistant to Samurai.
- Deleted: Bifenthrin (Talsar ® ) This permit has expired and will notbe renewed .
Talsar is called bifenthrin, which is in a type of pesticides called the pyrethroids. They act directly upon the nervous system of insects. Synthetic pyrethroid insecticide – Pyrethroids are synthetic chemicals based on pyrethrins. Pyrethroids have a long residual period after spraying and are thus more lethal to a wider range of insects than pyrethrins.
- Esfenvalerate (Sumi-Alpha Flex Insecticide) PER81949 – Until 30 November 2021,Synthetic pyrethroid insecticide. Insecticide active constituent : 50g/L Esfenvalerate solvent, 744 g/L Liquid hydrocarbons( Liquid hydrocarbon extracted from petroleum or coal tar).
Group 3A .
- Permit Pending: Adama – Trivor (acetamiprid 186 g/L + pyriproxyfen 124 g/L). Currently under trial, with a permit expected by February 2020.
Apply post-flowering when crop monitoring indicates the onset of crawler release.
- Pyganic Organic Insecticide (Pyrethrum) PER81870 – Until 31 October 2019.
Note: Sumitomo is currently investing adding olive lace bug to the label registration and are looking for input from olive growers on their experience using this product.
In summary: Foster healthy trees, early spotting of hatching insects and thorough early spray treatment can help beat olive lace bug.
No treatment will restore stippled foliage, which remains until pruned off or replaced by new growth.
If damage has previously been intolerable, monitor plants early during subsequent seasons.
References:
- Cuneo P; Leishman MR, 2006. African olive (Olea europaea subsp. cuspidata) an environmental weed in eastern Australia: a review. Cunninghamia, 9(4):545-577.https://core.ac.uk/download/pdf/14530354.pdf
2.Sergeva V.(2015) Management of olive lace bug. Australian and New Zealand olive grower and processor 2015, p.26-27.
https://issuu.com/provincialpressgroup/docs/og_june_2015_issuu
3.Sergeva V.(2015) Olive lace bug. GROWER FACT SHEET.
4.Sergeeva V. (2014) Effective environmentally sensitive pest management in olive production. 2014Proceedings of the 5thInt. Conf. Olivebioteq pp.319-325
- Pancia A. (2016) Growers pull trees as olive lace bug infests Western Australian groves 2016 http://www.abc.net.au/news/rural/2016-11-08/olive-lace-bug-affects-wa-groves/8006556
6.Pesticides MATERIAL SAFETY DATA SHEET (MSDS)
- African olive (Oleaeuropaeasubsp. cuspidata)http://weeds.dpi.nsw.gov.au/Weeds/Details/4
- http://www.herbiguide.com.au/Descriptions/hg_Olive.htm
- https://keyserver.lucidcentral.org/weeds/data/media/Html/olea_europaea.htm
What is your experience of OLB?
Growers are invited to share their observations and personal experiences of OLB.
Is it a problem in your grove?
What grove practices impact on the incidence of OLB?
Do you use IPDM strategies such as promoting soil and tree health?
Do you have any experience using and encouraging beneficial insects (predators and parasites) in your grove?
If you use chemical control options – what works and what doesn’t work?
Please send your comments / suggestions to Dr Vera Sergeeva sergeeva@tpg.com.au
