Gum leaf skeletoniser update
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Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.
From Forest Health News No. 66, August 1997.
Uraba lugens remains confined to the two golf courses and one park in Mt Maunganui and MoF Forest Health Staff are in the process of carrying out eradication action recommended by FRI (see FHNews 65: 2-3, July 1997). Many of the infested trees have been removed, mulched and buried and all remaining trees will be sprayed with the synthetic pyrethroid Decis (2.5g/litre deltamethrin). The early instar larval damage is very difficult to separate from leaf-roller damage unless the larvae are present or egg and larval remains can be found. It is proposed not to fell several large eucalypts until a further full survey is carried out in September when larval damage is expected to be much more obvious. If the infestation is still strongly confined it is likely large residual infested trees will be felled. Given the poor mobility of the larvae and comprehensive spraying of infested crowns the risk of spread in the next two months is considered low. Rumours that MoF Forest Health officers will spend the spring on Australian golf courses inspecting golf bags as part of a risk assessment initiative could not be confirmed.
Gordon Hosking, FRI
The Gum Leaf Skeletoniser, Uraba lugens, at Mt Maunganui.
From Forest Health News No. 65, July 1997.
Ministry of Forestry Forest Health Officer Les Renney found suspicious damage on a Eucalyptus tree on Mt Maunganui Golf Course during a Port Environs Survey on 13 June, and this was subsequently identified at the Forest Research Institute as Uraba lugens Walker (Lepidoptera: Noctuidae; Nolinae)*.
Uraba lugens is found throughout Australia except the far north and extremely dry areas. In the right circumstances it can cause serious defoliation to plantation and managed Eucalyptus forests, as well as to natural stands. There are several forms, having one or two generations per year, and laying their eggs in compact clusters or in parallel rows. The form found in New Zealand lays its eggs in parallel rows, and will probably be of two generations per year judging from the time of hatching. The young larvae are gregarious and eat the soft tissue of the leaf, leaving it skeletonised. Larger larvae can eat the entire leaf except the midrib, and feed as individuals. The larvae are hairy, and have two rows of pale spots down the back.
The hairs are reported to be irritant. There are up to 11 instars, and after about the first five the head capsules are not shed, building up on the head in the form of a hom. Pupae are found in the lower bark and in leaf litter on the ground. Adults are poor fliers. Factors which help populations build up include fresh, low foliage, close crowns and plenty of leaf litter. On the golf course, with its widely spaced trees and absence of litter, the population is low and gives the appearance of only just surviving, but in a plantation it may be a different story. A worst case in Tasmania had severe defoliation of Eucalyptus nitens and 17% mortality. The host range is a very wide variety of Eucalyptus species and Lophostemon (Tristania) conferta. To the best of my knowledge at this date it has only been found on about half a dozen trees on a small area of one golf course, and one tree about 2km away (on another golf course). It is in the young larval stage at this time of year, so there is time to consider the options for control.
* Some authorities consider the Nolinae to be a sub-family of the Noctuidae, others give it full family status as the Nolidae.
Roger Crabtree, FRI
With the discovery of three new eucalypt pests and diseases on golf courses it might be time that the level of quarantine inspection of used golf shoes and equipment (including bags and motorised golf carts) be reviewed and tightened.
(Geoff Ridley, Editor)
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