In SE Queensland, two species of Fruit Piercing Moth (FPM's) cause the majority of FPM damage. These are Othreis fullonia and Eudocima salaminia. A third species, O. materna, is usually only a local problem. All have an armoured proboscis which they use to pierce even firm ripening fruit and this distinguishes them from the numerous Fruit Sucking Moths, which can only feed on damaged, over-ripe or soft fruit. The main species are migratory and the larvae develop in Australia only on vines of the family Menispermaceae.
E. salaminia larvae feed exclusively on the forest vine Stephania japonica. This is widespread in moist woodlands and along creeks. Moths can fly up to 30 km per night, so local eradication of larval food plants will have little effect on FPM in the orchard. However in dry summers when S. japonica growth is poor, there are fewer moths and damage is lower. This was probably the case in North Queensland this year.
O. fullonia prefers the vine Tinospora smilacina as a larval food-plant, but in SE Queensland other menisperm vines are more abundant and more often utilised.
Adult E. salaminia can live up to 70 days, but have no diapause (resting state) in the larval stages to assist over-wintering in SE Queensland.
For adult moths, temperatures below 16°C during the activity period (the 4 hours after dusk) prevent feeding, mating and egg-laying. Egg, larval and pupal survival are all adversely affected by cold, and in SE Queensland there are generally more than 50 nights each winter with temperatures below 10°C when pupae fail to develop. Mortality due to natural enemies is less than 15% in Australia and in coastal SE Queensland food for adults is not a limiting factor.
In 'normal' years, with a cold winter, E. salaminia adults do not over-winter in SE Queensland. Migrants move down from North Queensland in late November, attack lychees and carambolas and set up breeding colonies. Over summer they may complete 5 generations and these attack mangoes, citrus and later, persimmons.
In years with 'unusually mild' winters, adults over-winter in the South East and produce breeding populations in early spring. These can cause damage to stone fruit and may complete 7 generations in the year. O. fullonia is not known to over-winter in SE Queensland and usually migrates south 2-3 weeks after E. salaminia.
Last summer, the levels of FPM in January and early February, were the highest on record. Dr Don Sands, leading the CSIRO FPM research, believes the reason for the population explosion of O. fullonia was apparently the non-arrival of E. salaminia this year.
E. salaminia was so badly hit by the drought it did not migrate south in significant numbers. This left the door open for O. fullonia alone, which bred on the unusually lush and plentifully larval food plants. By the second generation, they were in plague proportion.
Late lychees, mangoes, green persimmons and longans were all hit with damage up to 50% in unprotected situations in less than 2 weeks. A final generation was predicted in early May. The migratory behaviours, widespread larval food sources, and longevity and feeding habits of adult moths make FPM's extremely difficult to control.
PRESENT CONTROL STRATEGIES
The current control strategies are:
1. Netting trees or bagging fruit. One persimmon grower bagged all fruit in February with 3 types of bags. Special Japanese paper bags appear the best with about 10-20% stung fruit, some flying fox, but no bird damage. Clear polythene bags were 100% stung or hit by birds. Brown polythene bags were about 50% effective. Costs were 50.01 each for paper bags and 1000 fruit bagged/day was a good work rate. Picking is slower because it is harder to assess maturity in the bag.
2. Trapping with Gamgee traps (see below on attractants).
3. Night-time squash!
4. Spraying with any chemicals is likely to be ineffective and possibly illegal.
PROMISING CONTROL STRATEGIES
The control strategies being researched are:
Biocontrol - Introduced Parasites
ACIAR has funded two CSIRO projects in Fiji and Samoa using two parasites from Papua New Guinea. In both cases a single parasite was introduced and this has achieved significant increases in FPM egg mortality.
The parasite in Fiji is now apparently reducing the FPM population only 18 months after introduction. The aim is now to introduce both parasites (Ooencyrtus sp. and Telenomus sp.) to Tonga and hopefully achieve a high level of biocontrol. However these island states are isolated and have a smaller number of non-target species than Australia.
To introduce these parasites to Australia and test them against native non-target species requires funding for a 2-3 year period. There is little chance of them eradicating any native species, but hopefully the FPM problem could be greatly reduced. There is, however, the small risk that after testing, the parasites could prove effective in controlling FPM's but unacceptable to non-grower groups. If egg parasites were ineffective, larval parasites would be investigated. Dr Sands has submitted a proposal for 3-year funding to RIRDC which is still under consideration, but grower support is essential.
TRAPPING USING ATTRACTANTS
There is work in progress by CSIRO attempting to identify and manufacture the chemicals attracting FPM's to fruit. This work has funding but may take a long time to complete. Interestingly, some fruit (ripe bananas) attract more females and others (pawpaw and mango) attract equal numbers of males and females. Females have a higher feeding requirement.
There are many opinions on the best ripe fruit for Gamgee traps, ranging from peeled lychees and bananas to carambola cv. Wheeler but no firm favourite. At present it is believed that fruit traps only catch a small percentage of active moths. They are, however, a very useful indication of FPM levels.
DATE: May 1993
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