The Occurrence of Hypsipyla Shoot Borer on Species of Exotic Meliaceae Planted in the Northern Territory
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“where to from here with R&D to underpin plantations of high-value timber species in the ‘seasonally-dry’ topics of northern Australia?” Townsville 9th-11th May 2006. _____________________________________________________________________ DEPARTMENT OF PRIMARY INDUSTRY, FISHERIES AND MINES Private Forestry North Queensland Association Inc & Queensland Department of Primary Industries and Fisheries Workshop Townsville 9-11 May 2006 “Where to from here with R&D to underpin plantations of high-value timber species in the ‘seasonally-dry’ tropics of northern Australia?” The occurrence of Hypsipyla shoot borer on species of exotic Meliaceae planted in the Northern Territory D.F. Reilly, R.M. Robertson & H. Brown Agroforestry and Entomology – DPIFM Berrimah, Northern Territory. SUMMARY African mahogany Khaya senegalensis is the favoured species for high-value plantations in the Top End of the Northern Territory because it has outperformed others in extensive trials over 40 years. Despite its vigour, Khaya is characterised by poor form that may be related to its genetics, nutrition or chronic low level pest attack. However few pests and diseases have been recorded locally for Khaya or the other species tested. The Meliaceous shoot borer or tip moth Hypsipyla robusta Pyralidae (Phycitinae) was first observed attacking Khaya in March 2004; this was was recorded on recently grafted plants at Berrimah. Subsequent attack has been observed in the field on both Khaya (Howard Springs) and Chukrasia (Berry Springs). Identification has been confirmed by ANIC and DPIFM. Source of attack may be from the indigenous mangrove species Xylocarpus granatum (Meliaceae) known to be susceptible to shoot borer. Keywords: African mahogany, shoot borer, Khaya, Chukrasia, Xylocarpus, Hypsipyla, Northern Territory _________________________________________________________________________ The occurrence of Hypsipyla shoot borer on species of exotic Meliaceae planted in the Northern Territory – D.F. Reilly, R.M. Robertson & H. Brown 1 “where to from here with R&D to underpin plantations of high-value timber species in the ‘seasonally-dry’ topics of northern Australia?” Townsville 9th-11th May 2006. _____________________________________________________________________ DEPARTMENT OF PRIMARY INDUSTRY, FISHERIES AND MINES PERFORMANCE RELATIVE TO K SENEGALENSIS (KS) OF EIGHT SPECIES FOR SEVERAL TRAITS ACROSS A VARIABLE NUMBER OF SITES. For Ks the actual trait values are shown. Species Survival Relativity to K.senegalensis (%) Overall (no. of sites) (%) Height Dbhob (MAI Bole (MAI Straight- no. of traits > (MAI m) cm) m) ness Ks1 score K.senegalensis (6) 95.5 1.5 2.3 0.8 2.96 T. grandis (6) 89 111 88.4 137.5 111.5 3 S. humilis (6) 81.6 96.7 78.3 101.8 109.1 2 C. odorata (4) 52.3 81.7 73.9 100 98.8 0 T. belerica (3) 89.7 97.3 81.2 129.2 118.2 2 S. macrophylla (3) 61.3 93.3 72.5 120.8 108.1 2 C. tabularis (2) 71 110 100 168.8 120 3 P.macrocarpus (2)2 98 NA3 96 NA NA 1 P. indicus (1) 91 113.3 95.7 412.5 111.4 3 1 Counts in this column derive from the highlighting that indicates those species – trait values clearly exceeding the inferred ‘100%’ value for Ks. Note that ‘Survival’ has been included in the counts, giving a total of 5 comparison traits. 2 Species represented by a single plot at each site. 3 NA – not assessed. African mahogany has been grown in the Top End of the NT for more than 40 years on a range of sites and soil types with little or no recorded pest or pathological problems. This was a major reason for its selection in the series of NHT funded trials established in the Top End by NT DPIF, Greening Australia NT and the Commonwealth Government National Heritage Trust Farm Forestry Program. The species chosen for planting in the NHT trials were based on those successful in previous forestry evaluations by CSIRO and the NT Forestry Bureau. In this early work, African mahogany was the best survivor and performer among a few other notable species including: Pterocarpus (Rosewood), Chukrasia tabularis (Indian mahogany), Terminalia belerica, Eucalyptus pellita (red mahogany) and Callitris intratropica (northern cypress). Cypress was the only native species in the trials; although slow growing it is not affected by pests to the point that reduces productivity. African mahogany was also the best performer in the NHT trials for the productivity characteristics of survival, height growth and diameter growth and demonstrated its ability to grow well on a wide range of sites. These results were presented previously at the Mareeba Workshop (Reilly, Robertson & Hearnden 2004). The slide shows the superiority of Khaya for survival, height and diameter growth in all cases except where P. macrocarpus was slightly better for survival (very few sites) and where heights of Tectona grandis, Chukrasia tabularis and Pterocarpus indicus were slightly better. However the performance of Khaya senegalensis compared with other species in the stem form characteristics of bole length and straightness is much poorer and indicates improvement is required in these traits if Khaya is to be commercialized. The underlying causes of this poor form must be determined; in this regard assessing the impacts of present and potential pests and diseases is critical. _________________________________________________________________________ The occurrence of Hypsipyla shoot borer on species of exotic Meliaceae planted in the Northern Territory – D.F. Reilly, R.M. Robertson & H. Brown 2 “where to from here with R&D to underpin plantations of high-value timber species in the ‘seasonally-dry’ topics of northern Australia?” Townsville 9th-11th May 2006. _____________________________________________________________________ DEPARTMENT OF PRIMARY INDUSTRY, FISHERIES AND MINES THE CHALLENGE OR PROBLEM FACING THE USE OF AFRICAN MAHOGANY AS A PLANTATION SPECIES IS FAILURE OF MOST TREES TO MAINTAIN APICAL DOMINANCE AND DEVELOP A STRAIGHT BOLE! Possible causes of this problem have been suggested by many workers including at this workshop (with anecdotal and/or documented evidence) : • Chewing, sucking insects (Hypsipyla, crickets etc) • Herbivorous mammals (possums, tree rats etc) • Nutrient deficiencies (Ca, B, Zn, Cu etc) • Wind damage (firmness, nature of recovery etc) • Fires • Genetics Poor tree form of African mahogany is evident in trees of all ages up to 30 plus years old in Darwin and elsewhere ie short boles, lots of large branches – not a very millable tree in that form. The question that remains unanswered is: is the poor form of African mahogany due environmental influences, nutrition (or lack of ), influence of pests and diseases, or genetics that pre-disposes trees to a large open crowned habit ? Resolution of this critical issue, clarifying the relative contributions of underlying genetics, possible nutrient deficiencies and pests and diseases to the poor form of Khaya is essential to its successful domestication and genetic improvement. Current emphasis on tree improvement through recurrent phenotypic selection among trees generally of poor form needs to be balanced by higher priority being given to ensuring adequate nutrition at critical times, or the elimination of pests and diseases attacking growing tips and negatively affecting apical dominance, if these selection strategies are to be fully effective. _________________________________________________________________________ The occurrence of Hypsipyla shoot borer on species of exotic Meliaceae planted in the Northern Territory – D.F. Reilly, R.M. Robertson & H. Brown 3 “where to from here with R&D to underpin plantations of high-value timber species in the ‘seasonally-dry’ topics of northern Australia?” Townsville 9th-11th May 2006. _____________________________________________________________________ DEPARTMENT OF PRIMARY INDUSTRY, FISHERIES AND MINES AFRICAN MAHOGANY AND HYPSIPYLA Khaya (African mahogany) is a member of the Meliaceae a commercially very important family for high value timbers. Others are Swietenia, Cedrela, Toona and Chukrasia. Hypsipyla spp. are pests of trees in these genera; attack is most severe where indigenous tree hosts and insects co-habit. K. senegalensis as an exotic species in northern Australia, is susceptible to attack by the indigenous H. robusta. Attack was first recorded in March 2004 near Darwin but attack is restricted and damage minimal. The native mangrove Xylocarpus granatum is also a host to H.robusta and may be the source of infestation. The insects with greatest possibility to impact a plantation industry based on African mahogany are species of the phycitinid moth Hypsipyla (Pyralidae), a shoot borer that damages the soft actively growing tips in which the adult moth lays its eggs. Resulting loss of apical dominance causes the tree to form more branches below the damaged area. Hypsipyla robusta is the species native to Australia and SE Asia; it attacks native species of the Meliaceae including the commercially important red cedar (Toona ciliata) and the mangrove Xylocarpus granatum, which occurs in the Darwin area. At the Mareeba Workshop 2004, Roger Leakey indicated that endemic species of Hypsipyla were very aggressive and damaging to African mahogany in its native habitat in west Africa; a recent taxonomic revision has found that there are two species in this area distinct from H. robusta (Griffiths and Wylie 2006); neither are known to occur in Australia. Hypsipyla robusta was first observed attacking Khaya senegalensis in March 2004; this was was recorded on recently grafted plants at CCB-Berrimah