Plant Protection Research Institute

Uitenhage, South Africa

Plant Protection Research Institute

Uitenhage, South Africa

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News Article | May 16, 2017

Speaking Darwinistically, the planet should have no truck with the spodoptera genus, commonly known as armyworms. Fat, slow over the ground and unspeakably terrible looking, they should never have evolved into anything more than an entomological pilot project. In some variants, their heads resemble human brains that have been caramelized with a blowtorch. Mandibles, jammed into the bottom of the face part, glisten with alien goo. In their most gregarious morphological variation, black and dun stripes run down their bodies, mimicking something an avid golfer would wear to a funeral. They are speckled with sparse little hairs, like the budding moustache of a teenage Lothario, while their stubby legs appear to have been distributed randomly, and without consideration for balance and mobility. Unfortunately, as it happens, armyworms do not appear fat and ugly to each other – or not, following one of nature’s great acts of mercy, when they’ve hatched into the world’s most boring looking moth. They reproduce at a staggering rate, with each female laying about 1000 eggs in a 10-day lifetime. And though they may be slow crawlers, they are strong fliers. Every year spodoptera frugiperda, or the fall armyworm, travels from Mexico to Canada, a distance of at least 3000km. But if they have a dominant evolutionary superpower, it is rapacious communalism: in their larval stage, they advance in squadrons, platoons, battalions, armies – tens of millions storming the countryside, eating every crop or garden they can get their mandibles on. Most pests will consume only the good bits, but armyworms will strip even a fully-grown maize plant down to the last leaf. Spodoptera have proved to be a blight in North America, South America, the Middle East, the South Pacific islands, Australia – pretty much everywhere. There are five species of armyworms, but we’re concerned here with the aforementioned frugiperda which is headquartered in North and South America; and the exempta, usually based in Africa. Spodoptera exempta – the African armyworm – specialises in cereals, and has been causing havoc on the continent for decades now, spreading out slowly from the east and in 2009 sparking a state of emergency in Liberia. The new arrival, however, is spodoptera frugiperda, more commonly and chillingly known as ‘the fall’. This variant, which eats pretty much anything, has enjoyed a long, awful history in South America – managing it costs the Brazilian economy a staggering $600 million a year. In January 2016 it was detected for the very first time in Africa, in Nigeria. (As for how it it got there from the Americas, it either flew in on prevailing winds, or caught a plane. No one is yet sure). By April 2016, the pest had travelled to several other West African countries and to Central Africa. By December, it was detected in Zambia, Zimbabwe and Malawi, and was storming South Africa’s borders. Last week, Ghana’s parliament was asked by the minister of agriculture to declare a ‘state of emergency’, and take urgent action as the fall arrived en masse. But why this particular plague, and why now? Is it the newish mash-up between local and invasive species that has produced such unstoppable consumption machines? Or has modern farming – in particular, modern African farming, which depends increasingly on planting vast tracts of a single staple – made it easier for them to advance? In regions stricken by climate change, and which in some parts have recently suffered (or, in some cases, is still suffering through) a once-in-a-generation drought, are armyworms not just another manifestation, albeit the most revolting, of the colossal challenges facing Africans as the world warms? At this stage, no one is really sure certain how best to answer these questions. But there is one last, and far more pressing, problem: can the armyworms be stopped before they eat Africa bare? If there is a three-star general currently conducting the war against genus spodoptera, it must be a Lancaster University professor named Kenneth Wilson. According to his university profile, Wilson “ is fascinated by the interactions between parasites and their hosts, be they insects, birds, mammals or humans.” He first became interested in African armyworms after studying their migration through Kenya 25 years ago. The sweetener, as far as his particular discipline was concerned, was the armyworm’s achilles’ heel: when he tried to transport live specimens back to a lab in Nairobi, he found that they would succumb to a virus, and none of them would survive the journey. There was a devastating natural loop at work here: a voracious parasite was felled, and easily so, by a voracious infectious agent. His work began to echo almost exactly the plot of HG Wells’ War of the Worlds, in which invading Martians are eventually killed off by microbial infection to which they had no immunity – “slain, after all man’s devices had failed, by the humblest things that God, in his wisdom, has put upon this earth.” Wilson, who is currently in the field in Tanzania, remains in equal measures enthralled and terrified by these critters. “I got to wondering how armyworms could be such a devastating pest when they seemed so susceptible to this virus,” he explained over email, “and I have been studying the interaction between armyworms and their viruses ever since.” His research suggested that the obvious solution to any armyworm infestation was to replicate the virus, and employ it as a biological agent in order to eradicate the blight. But this was easier said than done, and his research was anyway focused exclusively on the African armyworm. The recent introduction of the fall into the African theatre served, according to Wilson, “as the latest twist.” And not a good twist. Given that the fall has only been in Africa since January 2016, no one is quite sure how severe the impact will be. “People are rightly scared about what’s going to happen,” Wilson told me. Making matters worse, armyworms tend to love maize, the local staple. The practice of monoculture farming – lots and lots of maize, as far as the eye can see – is a key component to any form of industrial agriculture. But it has provided the African armyworm, which specialises in cereals, with a continent-wide all-you-can-eat buffet. “For the many farmers who also grow small amounts of other crops such as beans, peas and other vegetables, their livelihoods were safeguarded to an extent by these other crops,” Wilson explained. “But the fall armyworm has a much broader host range”– translation: it’ll eat anything – “so potentially can also eat these other crops if maize is not available.” This attack on regional food security has been compounded by an X factor: climate change. “Drought followed by lots of rain is perfect for armyworms,” said Wilson, describing exactly the kind of weather conditions that are becoming the sub-Saharan norm. And so, in dry years, African crops suffer for the obvious reasons. In non-drought years, there are still the armyworms to contend with. Southern Africa’s recent drought, vicious by any estimation, was broken by the tropical cyclone Dineo, which touched down on the coast of Mozambique mid-February. Much of the region was swamped with massive, in some cases unprecedented, amounts of rainfall. Undaunted – nay, encouraged – onward marched the armyworm. When the infestation was detected in South Africa in January, it did not come as a surprise to the Department of Agriculture, Forestry and Fisheries (Daff), who had effectively posted wanted posters throughout the agricultural community in preparation for a first sighting. The fall armyworm was already listed as a quarantine pest for South Africa in terms of the Agricultural Pests Act 1983. After the first suspected specimens were collected on a farm in the northern province of Limpopo, Daff requested a diagnostic report from the Agricultural Research Council, Plant Protection Research Institute (Arc PPRI), which on February 3 confirmed the armyworm’s identity. Daff had already constructed a sort of historical narrative regarding the outbreak, which squared with Kenneth Wilson’s and other expert assessments. Relying on a worst case scenario, which had been realised in other countries as the worm made its way south, Daff thus informed commodity and research organisations of a possible threat, and encouraged farmers to report suspicious pest damage. Serendipitously, Daff had recently introduced the South African Emergency Plant Pest Response Plan, which was designed to diagnose and detect new pest infestations. Wisely, the government treated the outbreak as a crisis, and detection was just the first in what was necessarily a tiered attack. According to Makenosi Maroo, Daff’s chief director, stakeholder relations and communications, the department set up an internal joint operations centre, along with a steering committee that included “research, industry and provincial government role players”. But if African armyworms were the known known, the fall was the known unknown – there was no protocol in South African on how best to halt its progress. As ever, the fallback option was to nuke them with chemicals. But which chemicals? “As the fall armyworm is a new pest to South Africa, no pesticide was previously registered to be used against it,” said Daff minister Senzeni Zokwana, during a hastily called press conference on 6 February. “A process of emergency registration of agricultural chemicals is ongoing with two active ingredients already registered to be applied against this pest. As with all agricultural remedy applications the label instructions must be followed in accordance to the supplier’s recommendations.” Which was sound advice. But given that the effectiveness of the pesticide regime was still largely speculative, South Africa was due a lucky break. And the country got one due to a quirk in the harvesting schedule: the bulk of the season’s maize crop was unaffected and already drying for harvest, which meant that the armyworms were late for dinner. And there was more good news, at least as far as South Africa was concerned: the country produces most of its maize crop in areas where frost occurs, and armyworms can’t handle the cold. But in the warmer northern provinces of Limpopo and Mpumalanga, to say nothing of the rest of the continent, this was hardly an upside worth mentioning. Still, Hamlet Hlomendlini, a spokesperson at AgriSA, a local lobby group, seemed to feel that the crisis was not much of a crisis at all. “We don’t see it as a threat right now,” he told me. “We feel that the department of agriculture is on top of it, and it was restricted to a few isolated farms in Limpopo. It was a question of finding the right pesticides. It seems like things are under control.” This would likely sound like an excess of sanguinity to Wilson. When I asked him how seriously African policymakers should be taking the armyworm blight, he was unambiguous. “Very.” Nothing is certain at this point, but it’s clear that the infestation is spreading rapidly, without respite. A state of emergency has just been declared in Ghana. But the real kicker is that fall and African armyworms, as Wilson puts it, “have teamed up to provide a deadly double act.” This entomological suicide squad will cost a lot of money to control, and if they aren’t kept in check, the stakes get higher. From Africa, said, Wilson, “it’s possible that they will spread to Southern Europe, with seasonal migrations into northern Europe and possibly also into Asia.” There’s some hope of nailing down an effective pesticide regimen, but that comes with its own problems – poisoning the environment, pollinators, livestock and humans not minor among them. Besides, the fall is resistant to many of the chemicals currently being deployed across the continent. With this in mind, Wilson and his collaborators have been working on a biopesticide derived from the natural disease that was killing his specimens in Kenya all those years ago. By his own admission, this is a time-consuming and expensive pursuit. At the moment, Wilson is in Tanzania battle-testing the new weapon. “We are currently at the stage where we are asking some fundamental questions,” he told me. “Will the armyworms develop resistance to the biopesticide in the same way as insects often do against chemicals? Will the virus evolve to be less effective if we produce lots of it under field conditions? And can we make the biopesticide more effective by formulating it in a different way?” The armyworm is not waiting for Wilson and his team. And while the outbreak is apparently under control in South Africa, no other African country can match Daff’s sophistication. The Central African Republic is in the midst a long-simmering civil war; Zimbabwe is in perennial economic free-fall; and even boring Zambia is undergoing political instability. Next year, according to the experts, a drought beckons. The world’s ugliest worm thrives on exactly this kind of chaos. Join our community of development professionals and humanitarians. Follow @GuardianGDP on Twitter. Join the conversation with the hashtag #Dev2030.

This catalogue provides a comprehensive record of the 284 entities of organisms (insect, mite and pathogen species, or biotypes thereof) that have featured in biological control of invasive alien plants (weeds) in South Africa, since 1913. Fourteen of these entities are native species, or foreign species that have, by some unknown means, entered the country, while the remainder were intentionally imported specifically for biological control. The majority (237 of 284, i.e. 83 %) are phytophagous insects, the balance being made up of five species of mites (Acari) and 42 entities of plant-pathogens. The catalogue comprises the names of each of the target weeds, their origin, and an assessment of the degree of control that has been achieved with biological control, together with names and details (feeding guild, date released where applicable, current status and extent of damage inflicted) for each of the agents. Key references are provided. Of the 270 entities that were introduced into quarantine and tested for host specificity: 106 (39 %) were eventually released as biological control agents; 16 % are still under investigation; approximately 24 % were rejected by researchers because of doubts about their safety or efficacy; and 21 % have been shelved pending possible further study. Two of the pathogen species were developed as mycoherbicides. Seventy-five (71 %) of the 106 agents that were released in South Africa have become established on 48 invasive alien plant species, in 14 plant families. According to a rating system that has been widely adopted since 1999, and slightly amended in this account, approximately 21 % of the weed species on which biological control agents are established have been completely controlled, and another 38 % are under a substantial degree of control.

In South Africa, two imported insect species have been used in attempts to control invasive Australian myrtle trees, Leptospermum laevigatum (Gaertn.) F.Muell. (Myrtaceae): a bud-galling midge, Dasineura strobila Dorchin (Diptera: Cecidomyiidae), which was inadvertently introduced, possibly in the mid-1980s, and a leaf-mining moth, Aristaea (Parectopa) thalassias (Meyrick) (Lepidoptera: Gracillariidae), which was released in 1996. The latter agent attacks young leaves only and has no discernible impact on mature trees. The number of L. laevigatum buds on mature trees that are galled by D. strobila was monitored from 1994 until 2008. Initially the prognosis for biological control by D. strobila was extremely promising. However, the numbers of galls then declined sharply at most of the sites, on average to less than half of their previous peak levels. Gall-midge mortality, induced by native parasitoids, was very low initially, and, some years later, peaked at an average of only about 8 %. In 2004, predatory mites, mostly Pyemotes species (Trombidiformes: Pyemotidae), were discovered, killing an average of 27% (9.8-61.3%) of the D. strobila larvae and pupae in the galls, but their role in regulating populations of D. strobila has not been proven. A chemical exclusion experiment on seedlings showed that leaf damage by A. thalassias together with galling by D. strobila reduced the growth of young L. laevigatum plants by nearly 50%, but, again, the impact of the two agents in aggregate, on mature plants, is negligible. A gall-inducing scale insect is presently under consideration as a potential agent, and there are some other possible agents that might be useful, but, overall, the prospects for biological control of L. laevigatum do not appear to be good.

In 2008, a field survey was conducted in northern Argentina to collect natural enemies of Cestrum species (Solanaceae) for use as biological control agents in South Africa. The rust fungus Uromyces cestri Bertero ex Mont. (Pucciniales: Pucciniaceae) was found on Cestrum parqui L'Hr. and imported into quarantine facilities in South Africa. No damaging pathogens were found on Cestrum laevigatum Schltdl. Preliminary host-range studies showed that U. cestri was able to infect and cause disease on C. parqui and on Cestrum elegans (Brongn. ex Neumann) Schltdl. in South Africa, and could have potential for the biological control of these species. The rust did not infect any of the other Cestrum species tested, and neither did it infect C. laevigatum which is the most problematic Cestrum species in South Africa.

Van Der Westhuizen L.,Plant Protection Research Institute
African Entomology | Year: 2011

Madeira vine, Anredera cordifolia (Ten.) Steenis subsp. cordifolia (Basellaceae), is native to South America but has become invasive and problematic in many countries, including South Africa. Weedy vines are notoriously difficult to control through conventional mechanical and chemical means, so biological control of A. cordifolia in South Africa was initiated in 2003. No agents have yet been released against this plant in South Africa but exploratory observations on the life-history and host-specificity of two leaf-feeding beetles, Phenrica sp. (Coleoptera: Chrysomelidae) from Brazil and Plectonycha correntina Lacordaire (Coleoptera: Chrysomelidae: Chrysomelinae) from Argentina and Brazil, are reviewed here. Adults and larvae of both chrysomelids feed extensively on leaves and new growth of A. cordifolia, resulting in leaf and above-ground biomass reductions. The laboratory host-ranges of these potential agents seem acceptably narrow, with normal development restricted to the host plant. Adult feeding was recorded on other non-indigenous species within the Basellaceae, Portulacaceae and Talinaceae. The Phenrica sp. colony, being reared in quarantine, died out and re-collection has not been possible. Host-specificity studies are continuing on P. correntina.

Goszczynski D.E.,Plant Protection Research Institute
Archives of Virology | Year: 2010

The presence of rugose-wood-associated viruses of the genera Foveavirus and Vitivirus in the family Betaflexiviridae was investigated in various clones of own-rooted and grafted Vitis vinifera cv. Shiraz that were affected, or not, by Shiraz decline, and in rootstocks. RT nested-PCR amplification of double-stranded RNA using degenerate primers for the simultaneous detection of foveaviruses and vitiviruses (Dovas CI, Katis NI in J Virol Meth 170:99-106, 2003), cloning of DNA amplicons, SSCP analysis of clones, sequencing and computer-assisted analysis of sequences was used to characterize viral genetic variability. A total of 1,137 clones were analysed by SSCP, and, of those, 371 clones were sequenced. The results revealed that variants of five molecular groups belonging to the species Grapevine rupestris stem pitting-associated virus (GRSPaV), including highly divergent variants related to strain SY (Lima MF et al. in Arch Virol 151:1889-1894, 2006) were present in plants of various clones of Shiraz regardless of their Shiraz decline status, and in rootstocks. Grapevine virus A (GVA) and grapevine virus B (GVB) were detected in a relatively small number of plants. This study suggested no involvement of GRSPaV, GVA or GVB in Shiraz decline. © 2010 Springer-Verlag.

Analysis of two Grapevine virus B (GVB)-infected LN33 hybrid grapevines revealed that a plant exhibiting clear symptoms of corky bark (CB) disease was infected with two molecular variants of the virus, whereas a plant exhibiting no disease symptoms was infected with only one variant. Sequence results indicated that the single variant in the CB-negative grapevine was also one of the two present in the CB-affected hybrid. Plant extracts from these two grapevines were used to successfully transmit the virus to N. benthamiana. After further cloning and sequencing, two clearly divergent variants were identified. Comparative molecular analysis of the variants, named here GVB 953-1 and GVB-H1, respectively, transmitted from CB-affected and consistently CB-negative plants, revealed short genomic regions, most of them highly divergent, that encoded amino acid sequences, containing significant amino acid substitutions altering the net charges of their respective proteins. Interestingly, a comparison of these variants to genome sequence data of GVB variants GVB Italy and GVB 94/971 available from the GenBank, revealed that these significant amino acid substitutions were the same for, and unique to, the variant pairs GVB 953-1/GVB Italy and GVB-H1/GVB 94/971. This despite the variants of each pair being otherwise clearly different at nucleotide and amino acid levels. In addition, both sets of variants differed substantially in their respective 3'-non-translated (3'NTR) regions. The relevance of these findings is discussed. © 2010 Springer Science+Business Media, LLC.

Goszczynski D.E.,Plant Protection Research Institute
Journal of Phytopathology | Year: 2013

The alignment of the complete genomes of genetic variants of Grapevine leafroll-associated virus 3 (GLRaV-3) representing phylogenetic groups I, II, III and VI revealed numerous regions with exceptionally high divergence between group I to III and group VI variants. Oligonucleotide primers universal for all the above groups of the virus were designed in conserved short stretches of sequences flanking the divergent regions in the helicase (Hel) and RNA-dependent RNA polymerase (RdRP) domains of the replicase gene and the divergent copy of the capsid protein (dCP) gene. Cloning and sequencing of the 549-bp RT-PCR amplicon of the helicase domain from grapevine cv. Shiraz lead to the detection of a variant of GLRaV-3, which shared only 69.6-74.1% nt similarity with other variants, including the recently reported, new, highly divergent variant, isolate 139. This was confirmed by the results of the analysis of 517-bp amplicon of the HSP70 gene of GLRaV-3 generated in RT-nested PCR based on degenerate primers for the simultaneous amplification of members of the Closteroviridae family designed by Dovas and Katis (J Virol Methods, 109, 2003, 217). In this genomic region, the variant shares 72.3-78.7% nt similarity with other variants of GLRaV-3. This previously unreported, new, highly divergent variant was provisionally named GTG10. From the alignment of the HSP70 sequences primers for the specific RT-nested PCR amplification of the variant GTG10 and members of group VI, and specific simultaneous amplification of variants of groups I, II and III, were designed. The results obtained from brief testing of various grapevines using all these primers suggest a relatively limited presence of GTG10 variant in vineyards. © 2013 Blackwell Verlag GmbH.

Kilic T.,Plant Protection Research Institute
Phytoparasitica | Year: 2010

In August 2009, boring lepidopteran larvae were found on aerial parts of tomato (Lycopersicon esculentum Mill.) plants in the Urla District of Izmir Province within the Aegean Region of Turkey. Larvae created blotched leaf galleries and superficial mines on fruits. The pest was identified as Tuta absoluta (Meyrick 1917) (Lepidoptera: Gelechiidae). This is the first report of this pest in Turkey. © 2010 Springer Science+Business Media B.V.

The genus Astichus Förster (Eulophidae: Entiinae) is recorded for the first time from sub-Saharan Africa and four new species are described from South Africa: A. micans n. sp., A. silvani n. sp., A. gracilis n. sp. and A. naiadis n. sp..Astichus species are known as parasitoids of Ciidae (Coleoptera) tunnelling and living in bracket fungi. The South African species emerged together with Ciidae from a variety of bracket fungi from many localities in the region. They are easily separated from known Astichus species from other regions in the world by their distinctive colour and patterning. A key to the South African Astichus species, distribution maps, and notes on biology are included, as well as identifications of Ciidae and bracket fungus specimens encountered in the study. Copyright © 2012 Magnolia Press.

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