Contents:
Survey of Auckland and the Surrounding Region for the Fruit Driller Coscinoptycha improbana
John R Clearwater
Clearwater Research and Consulting
Executive Summary
The Fruit Driller Coscinoptycha improbana was found in samples of Feijoa collected during April, May and June 2008 from home orchards in all suburbs of Auckland. The highest infestation was 78.5% of windfall fruit. Approximately half of the samples collected from the surrounding rural areas were free of this pest. This distribution is best explained as the result of the transport of infested fruit from Northland into Auckland city. No inference can be drawn that these infested fruit were Feijoas. This pest species has a very large host list. The study failed to identify a clear southern limit to the infestation.
Introduction
The Fruit Driller has been restricted to Northland until recently. Lees (2002) expressed concern about the potential of this insect to cause serious harm to NZ fruit growing. The pest infests Citrus, Nashi, Peaches, Plums, Feijoa, Guavas, Loquat and Macadamias. As the moth has not been reported south of Whangarei, concern has been rather muted recently. The complaint by a member of the Tree Crop Association that fruit from her Birkdale orchard were infested by small caterpillars initiated this survey.
Methods
The original report from Birkdale concerned an infestation of Feijoa fruit. Previous work (Clearwater unpublished) had found that this fruit was susceptible to attack and that damage was concentrated in the windfall fruit. The earliest attack results in fine burrows drilled in the outer cortex of the fruit. The fruit begins to rot as the attack develops but the caterpillar appears equally able to continue development in rotting and fresh fruit.
New Zealand Tree Crop Association Members were e-mailed a request for 50 windfall Feijoas. Samples were mailed or collected (April 22nd to the 6th June 2008), the location of the source recorded and the fruit sectioned finely (3-5 mm slices). The number of distinct burrows was recorded together with number and size of the caterpillars.
Results
Samples were obtained from 43 gardens from Warkworth and the South Kaipara heads in the North to Tuakau and Pukekohe in the south. Sample sized ranged from 3 to 105. Most were around the 50 fruit requested. One thousand nine hundred and thirty fruit were sectioned, 357 excavations found and 142 caterpillars caught (Table 1).
Table 1 - Collection sites and damage recorded
| Sample | Street | Suburb | N | Excav | % Dam. Fruit | Caterpillars |
|---|---|---|---|---|---|---|
| 1 | Warkworth | 50 | 0 | 0 | 0 | |
| 2 | Whangaparoa Pen. | 50 | 4 | 8 | 0 | |
| 3 | Red Beach | 35 | 1 | 3 | 0 | |
| 4 | Red Beach | 21 | 3 | 14 | 1 | |
| 5 | Red Beach | 54 | 3 | 5.5 | 2 | |
| 6 | Takapuna | 55 | 6 | 11 | 2 | |
| 7 | Grey Lynn | 42 | 86 | 78.5 | 60 | |
| 8 | Bombay | 35 | 0 | 0 | 0 | |
| 9 | Grey Lynn | 50 | 6 | 12 | 0 | |
| 10 | Glen Eden | 58 | 11 | 19 | 4 | |
| 11 | St. Heliers | 59 | 8 | 13.5 | 3 | |
| 12 | Glendowie | 74 | 32 | 43 | 17 | |
| 13 | Three Kings | 50 | 14 | 28 | 4 | |
| 14 | Leigh | 52 | 5 | 9.5 | 0 | |
| 15 | Pakuranga | 50 | 6 | 12 | 2 | |
| 16 | Whitford | 55 | 0 | 0 | 0 | |
| 17 | New Windsor Hts. | 50 | 13 | 26 | 5 | |
| 18 | Kaukapakapa | 27 | 0 | 0 | 0 | |
| 19 | Mt. Albert | 10 | 5 | 50 | 1 | |
| 20 | Mt. Albert | 105 | 49 | 47 | 9 | |
| 21 | Remuera | 54 | 7 | 13 | 0 | |
| 22 | Whangaparoa Pen. | 49 | 18 | 37 | 11 | |
| 23 | Henderson | 3 | 0 | 0 | 0 | |
| 24 | Ranui | 7 | 0 | 0 | 0 | |
| 25 | Henderson | 4 | 0 | 0 | 0 | |
| 26 | Orewa | 23 | 0 | 0 | 0 | |
| 27 | Helensville | 50 | 0 | 0 | 0 | |
| 28 | New Lynn | 50 | 5 | 10 | 4 | |
| 29 | Manurewa | 104 | 2 | 2 | 0 | |
| 30 | Mt.Albert | 50 | 13 | 26 | 3 | |
| 31 | Ranui | 58 | 1 | 2 | 0 | |
| 32 | Waimauku | 50 | 3 | 6 | 1 | |
| 33 | Arkles Bay | 24 | 5 | 21 | 0 | |
| 34 | Helensville | 49 | 12 | 24.5 | 5 | |
| 35 | South Kaipara Head | 79 | 14 | 18 | 3 | |
| 36 | South Kaipara Head | 55 | 1 | 2 | 0 | |
| 37 | Warkworth | 55 | 0 | 0 | 0 | |
| 38 | Tuakau | 47 | 4 | 8.5 | 0 | |
| 39 | Bucklands Beach | 64 | 11 | 17 | 3 | |
| 40 | Torbay | 6 | 3 | 50 | 0 | |
| 41 | Pukekohe | 50 | 6 | 12 | 2 | |
| 42 | Patumahoe | 5 | 0 | 0 | 0 | |
| 43 | Papakura | 12 | 0 | 0 | 0 | |
| Totals | 1930 | 357 | 142 |
Fig 1 - Map of collection sites.
Red spots indicate a wind-fall Feijoa sample containing the Fruit Driller.
Yellow spots indicate a sample free of this species.
Number indicates the percentage of fruit damaged.
Terrainmap Auckland scale [was 1:250,000] Infomap 262-3 Dept of Survey and Land Information
Thirteen caterpillars were near full grown, most were small (2 - 4 mm long.) Four native leaf-rollers were also collected.
Samples from Auckland city were mostly infested. The only city samples free of the pest were small samples from Ranui and Henderson. Larger samples may have found the pest present (Fig. 1 and table 1 ).
Table 2 - Structure of Fruit Driller Infestation 2008
| (A) Grey Lynn | (B) Glendowie | (C) Mt. Albert | (D) Whangaparoa | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Undam | 9 | Undam | 42 | Undam | 56 | Undam | 31 | |||
| 1 ex, 0 cat | 2 | 1 ex, 0 cat | 18 | 1 ex, 0 cat | 41 | 1 ex, 0 cat | 9 | |||
| 1 ex, 1 cat | 6 | 1 ex, 1 cat | 13 | 1 ex, 1 cat | 5 | 1 ex, 1 cat | 6 | |||
| 2 ex, 0 cat | 3 | 2 ex, 0 cat | 0 | 2 ex, 0 cat | 0 | 2 ex, 0 cat | 1 | |||
| 2 ex, 1 cat | 1 | 2 ex, 1 cat | 0 | 2 ex, 1 cat | 1 | 2 ex, 1 cat | 0 | |||
| 2 ex, 2 cat | 4 | 2 ex, 2 cat | 2 | 2 ex, 2 cat | 1 | 2 ex, 2 cat | 1 | |||
| 3 ex, 1 cat | 3 | 3 ex, 1 cat | 0 | 3 ex, 1 cat | 0 | 3 ex, 1 cat | 0 | |||
| 3 ex, 2 cat | 4 | 3 ex, 2 cat | 0 | 3 ex, 2 cat | 0 | 3 ex, 2 cat | 0 | |||
| 3 ex, 3 cat | 2 | 3 ex, 3 cat | 0 | 3 ex, 3 cat | 0 | 3 ex, 3 cat | 0 | |||
| 4 ex, 1 cat | 1 | 4 ex, 1 cat | 0 | 4 ex, 1 cat | 0 | 4 ex, 1 cat | 0 | |||
| 4 ex, 4 cat | 3 | 4 ex, 4 cat | 0 | 4 ex, 4 cat | 0 | 4 ex, 3 cat | 1 | |||
| 5 ex, 3 cat | 2 | 5 ex, 3 cat | 0 | 5 ex, 3 cat | 0 | 4 ex, 4 cat | 0 | |||
| 5 ex, 4 cat | 1 | 5 ex, 4 cat | 0 | 5 ex, 4 cat | 0 | 5 ex, 3 cat | 0 | |||
| 5 ex, 5 cat | 1 | 5 ex, 5 cat | 0 | 5 ex, 5 cat | 0 | 5 ex, 4 cat | 0 | |||
| 5 ex, 5 cat | 0 | |||||||||
Most detections were of a single excavation, half of which contained a caterpillar (table 2 and fig.2) .
Fig 2 Most commonly observed structure of damage Most fruit are undamaged. Damage is most frequently encountered as a single excavation, fewer than half with a resident small caterpillar. Feijoa sample from the Whangaparoa peninsula
The most heavily infested sample was collected from Grey Lynn (fig.3). Most (78.5%) of the fruit were infested and this was the only sample where more than one insect per fruit was frequently found. The most insects were found in a fruit with five separate excavations each with a small caterpillar.
Fig 3 - A heavily infested sample. Feijoa fruit from Grey Lynn. A fruit with five excavations each with a small caterpillar was the most heavily infested.
Small caterpillars would burrow close to the surface of the fruit but not penetrate the skin. (fig.4) A small caterpillar was found living in an excavation much larger that it could have excavated alone. It was thought that the small caterpillar was occupying an burrow of an earlier larger caterpillar that had completed development and had moved on. The caterpillars were the same size and similar speed of movement as Drosophila maggots but were easily distinguished by the pointed head of the maggot.
Some of the samples from rural areas were infested. Areas as remote as the South Kaipara Heads were infested. The southern most sample from Tuakau contained a few (8.5%) excavations.
A visit to the Otara fruit market on the 26th April found heavily infested trays of Feijoas offered for sale. The small size (and low price…….99c/kg) suggested local (city?) origin.
Fig 4 - A small Coscinoptycha improbana caterpillar. Body length 2 mm. Photograph with a Fujifilm Finepix S5500 and a Yu Lung SZ-3003 stereo microscope.
Conclusions
Homeowners in Auckland city will now find their fruit infested when harvested next season.. Though the survey sampled Feijoas exclusively, most the species of fruit grown and enjoyed by homeowners will be attacked. Almost a quarter of the fruit consumed by a previous generation of New Zealanders were homegrown. With escalating food prices, this activity would have been expected to increase. The presence of the Fruit Driller will be a serious disincentive. Few homeowners currently spray their fruit and few will be willing to start spraying (even if an effective spray was known!!) The development of a “people-friendly” means of control will be necessary to control this pest in the midst of our biggest city.
People living in un-infested rural areas have the possibility of remaining free of the pest provided that they are vigilant and promptly destroy (deep burial or freeze) any pack of purchased fruit that is infested. As the southernmost sample from Tuakau was infested, it is possible that the pest has moved further south. Aucklanders should refrain sending gifts of homegrown fruits to southern friends and relatives. Further work is needed to provide a clear southern limit to this infestation. A pheromone-based program will be needed.
The concentration of the infestation in heavily populated areas suggest that the pest has arrived in infested fruit from Northland. No inference should be drawn that these fruit were Feijoas……it could have been any of several types of fruit. The probability is high that the pest has been in Auckland for more than one year.
The cryptic nature of the pest aids its dispersal. The homeowner from Tuakau was sure that their fruit was clean of this pest. Small numbers of small caterpillars living under the unbroken skin of fruit easily escape detection.
References
Lees G. (2002) Urgent Action Needed on Guava Moth “The Tree Cropper” 30 pp.27-30
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