Fruit Piercing Moth on Citrus
a perspective including control
developments
Harry Fay, Department of Primary Industries and Fisheries.
Introduction
A fruit piercing moth possesses a strong, armoured proboscis with which it penetrates the skin or rind of fruit to feed on the juice. These large moths only feed at night and particularly the first few hours after sundown. While over 40 different fruit hosts have been recorded as being attacked, various citrus are amongst the most preferred.
In this DPI&F Note, the moth life history is discussed as well as means of managing this pest to moderate the damage. Although citrus is highlighted, the information is generally relevant to other susceptible crops.
Moth description
The main species active on citrus are Eudocima [Othreis] fullonia, Eudocima [Othreis] materna and Eudocima salaminia. They have 7-10 cm wingspans, with forewings of mottled brown, grey or green and silvery white. The forewings of males and females differ in the first two species. The hind wings are characterised by the orange-yellow colour, extensively bordered by a black and hatched area and a central black mark (kidney shaped or round). These are often exposed when the moth is feeding. An individual moth can spend several hours feeding from the one fruit but would generally attack a number on a single night. They are usually first spotted by their large red eyes reflecting torchlight.
Fruits are generally pierced as they mature and ripen, but green fruit is also susceptible if moth populations are high and ripe fruit is limited. Pierced fruit tends to ripen prematurely and frequently falls to the ground. The latter is an obvious sign of fruit piercing moth activity in citrus.
Damage is difficult to detect immediately after it occurs. Close inspection of a fruit will reveal a neat pin-sized hole and when pressed usually squirts out juice. A sizeable area beneath the skin is bruised and often honeycombed. Fruit rot organisms rapidly invade the wound causing fermentation and breakdown. In mature fruit a large, round, brown spot develops on the skin around the piercing site. Damaged fruit are completely unmarketable and must be removed at packing to avoid contamination of sound product.
Figure 2. Male Eudocima fullonia feeding on mandarin
Life cycle
The moth species mentioned above only breed on twining vines of the family Menispermaceae. While there are about 24 species of this family in Australia, with the majority occurring in rainforest, two species are more widespread and can be found in drier inland areas, Tinospora smilacina and Stephania japonica, and these contribute substantially to the pest problem.
Eggs are laid on or near the host plant. These hatch in 3-4 days in summer. From pale green caterpillars about 5 mm long they grow into large, attractively patterned, semi-loopers in around 2.5 weeks. Fully grown (6-7 cm long) the caterpillars are generally black or brownish coloured, with two distinct eye spots behind the first 3 pairs of legs and with fine spots and mottling all over (orange, white and yellow). Caterpillars web leaves together at the completion of feeding in which to pupate. The shiny dark brown puparium protects the developing moth for 2 weeks before it emerges. Moths commence feeding and mate within a few days of emergence. They can live and continue to feed for about 4 weeks in summer. Although orchards close to breeding areas are at greater risk of damage, moths have been known to transverse hundreds of kilometres.
Host range
Fruit piercing moths attack most tree and vine fruits with the exception of those with very hard skins eg. durians. Even capsicums, tomatoes and melons can suffer damage although reports of this in Queensland are not as common as in some other regions. In their pursuit of juice they are now known to attack more than 40 different types of fruit.
The main crops affected in Queensland include:
|
citrus |
guava |
mango |
papaw |
|
carambola |
kiwifruit |
lychee |
persimmon |
Moth population trends
Moth populations are driven by the condition and availability of host vines. Soft new growth is essential to the survival and development of newly hatched caterpillars.
Intense early summer rain after a long dry season seems to support vigorous growth in host plants. Such growth results in large moth numbers by January/February and breeding in north Queensland peaks in February, March and April. In areas south of Rockhampton damage occurs mainly in Washington navels between March and May, but here tends to occur infrequently (every 7-10 years).
Declining rainfall and temperatures into May/June result in reduced vine growth and a drop in moth breeding, although it continues throughout the year in coastal north Queensland. In the coastal tropics moths attack crops from November-August.
A number of native wasps (Telenomus sp., Ooencyrtus sp.) parasitise the eggs of fruit piercing moths and must play a role in determining the size of moth populations. They are particularly active in autumn but do not exert the necessary control in summer to impact sufficiently on moth numbers.
The large range of fruit crops now grown have increased the quantity and length of time fruit is available. This has contributed to an increased egg-laying potential.
Fruit piercing moth on citrus
In coastal and inland north Queensland, fruit piercing moths can be major pests of early maturing citrus, particularly navels, mandarins, Meyer lemons and pummelo. Grapefruit and other citrus are occasionally attacked. Eudocima fullonia, Eudocima materna and Eudocima salaminia are the most important pest species in that order, with Eudocima materna increasing in prominence the greater the distance from the east coast. These 3 species are also those which cause damage to citrus in central and southern growing areas, where the problem except in the Byfield area is more sporadic. Large influxes of moths in outbreak years have precipitated substantial losses of fruit and there have been few effective counter measures available.
Control on citrus
Immature stages cannot be controlled because fruit piercing moths breed in scrub and forest areas often remote from orchards. Growers are left to combat the adult moths as they arrive to feed. Insecticidal control has not been an option because insufficient contact of the moth with the fruit denies knockdown and, in any event, an adequate withholding period is not achievable as ripe fruit are normally attacked. Various traps have been explored but these have minimal impact when populations are high. Lights emitting yellow-green wavelengths suppress moth feeding by about 70% at moderate population levels but establishment costs are considerable and no other pests are controlled. Effective inhibition of fruit piercing moth damage is only possible by bagging fruit or netting trees or orchards. Netting has become increasingly popular and cost effective where crops, for example grapes and lychees, also suffer attacks from birds and flying foxes. However, there has been less compulsion on citrus growers to adopt this method.
Control developments
Feeding attractant studies have shown that species such as Eudocima fullonia are most responsive to the general fruity esters fruits produce. These esters are very volatile and contribute an increasing proportion to fruit odour as ripening occurs. However, other volatile compounds, particularly some aldehydes and alcohols, are important in the attraction process by contributing the 'greenness' which determines the level of ripeness. In fact, tests have shown that moths seek out fruits of a particular stage of maturity based solely on proportions of the volatile components produced.
Combinations of attractants have been developed and incorporated into sugared baits, which also contain a toxicant to kill the moths. Field trials with experimental baits in navel and navelina oranges over several years in Queensland orchards have shown that fruitpiercing moth damage can be substantially reduced, particulalrly when baits are deployed before most fruit are ripe. The baits are less competitive, but still very attractive, when nearly all fruit have reached the ripe stage. Negotitiations are currently underway to commercialise this technology.
Figure 3. Male Eudocima fullonia on an experimental bait
The repellency qualities of neem oil and some synthetic pyrethroids have also been evaluated. While neem products show some repellency to fruit piercing moths they do not appear to significantly reduce the damage caused by them, at least when applied to near-ripe fruit. Other products and application methods continue to be tested.
The citrus grower, particularly in southern areas, requires a control method for fruit piercing moth which can be set in place rapidly on those occasions populations are potentially extreme. In much the same way as male attractants and protein baits are effective against fruit flies, attractants may yet hold the key to cost-effective control of fruit piercing moths.
Further information
DPI&F Customer Service Centre on 13 25 23 - local call 8 am to 6 pm Monday to Friday (non-Queensland residents phone 07 3404 6999). E-mail: callweb@dpi.qld.gov.au
Information contained in this publication is provided as general advice only. For application to specific circumstances, professional advice should be sought. The Department of Primary Industries and Fisheries, Queensland has taken all reasonable steps to ensure the information in this publication is accurate at the time of publication. Readers should ensure that they make appropriate inquiries to determine whether new information is available on the particular subject matter.
Last updated 10 November 2005