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Biological control of bellyache bush: Native range surveys in South America
A trip to South America was undertaken to conduct surveys in Peru, Bolivia and Paraguay for potential biological control agents for bellyache bush (Jatropha gossypiifolia) a serious weed of Queensland and a Weed of National Significance in Australia. In Peru, surveys were conducted across 42 sites in Tarapoto and Iquitos regions. All J. gossypiifolia populations surveyed were of purple-leaf form with purple flowers. Except for the probably naturalized populations along roadside between Picota and Bellavista, and on the river bank between Juan Guerra and Shapaja, all J. gossypiifolia sampled were in towns or in home gardens.
In Tarapoto region, the Jatropha leaf-miner Stomphastis thraustica and the Jatropha leaf-rust Phakospora arthuriana were widespread, and caused severe leaf loss. When identified, applications seeking permits to import the leaf-miner into a quarantine facility in Brisbane for host-specificity tests will be lodged. In Bolivia, surveys were conducted across 15 sites in Santa Cruz-Cochabamba region. In addition to the purple leaf J. gossypiifolia in a home garden, natural/native Jatropha populations (Jatropha excisa and Jatropha clavuligera) with deeply-lobed green leaves were seen along roadsides and in dry arid forests between Mairana and Comarapa in Santa Cruz Department and between La Villa and Arani in Cochabamba Department.
There appears to be distinct variations in the morphological traits (e.g. flower colour, fruit colour, depth of lobbing in leaves, number of leaf lobes, width of leaf-lobes, etc) between various Jatropha populations in Bolivia. In both the purple (J. gossypiifolia) and green-leaf (J. excisa and J. clavuligera) forms, severe damage by the Jatropha leaf-miner Stomphastis thraustica and the Jatropha leaf-rust Phakospora arthuriana were seen.
The leaf-miner was not seen on Jatropha curcas and the castor oil (Ricinus communis) plants that co-occurred with J. gossypiifolia. The green-leaf J. clavuligera in dry forests showed evidence of widespread shoot-tip dieback due to galling of shoot-tips, emerging leaves and stems. Only three fresh leaf-galls were collected, as most of the J. clavuligera plants had started dropping leaves due to the onset of dry season. From the three fresh galls, several immature cecidomyiid larvae were recovered.
A survey during the wet season (January-February 2014) is needed to collect fresh galls to identify the cecidomyiid. A fruit-feeding scutellerid (Chelycoris lethierryi) was also collected on J. clavuligera. In Paraguay, surveys were conducted across 16 sites. All J. gossypiifolia plants sampled were in towns and home gardens and were the purple-leaf form. It is likely that J. gossypiifolia in Paraguay is an introduced population, and not a native. In most sites, J. gossypiifolia showed evidence of old shoot-tip dieback, caused by the cecidomyiid Prodiplosis sp. near longifila (a species that was previously collected on J. gossypiifolia from Paraguay in 2012).
Leaf-feeding lepidopteron larvae (family Notodontidae) were consistently collected on J. gossypiifolia from most of the survey sites. The larvae were not found on closely related castor oil (R. communis) plants. The larvae were sent to a quarantine facility in South Africa, for rearing and identification. No leaf-rust was seen in Paraguay. Samples of the leaf-rust collected from Peru and Bolivia (including purple-leaved plants) were exported to CABI (UK) and DAFF (Queensland) for identification. The insects collected were sent to relevant taxonomy experts for identification.
This page was last updated on 24/07/2017
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