New mobile app diagnoses crop diseases in the field and alerts rural farmers

Penn State News  online

2017-09-29

Researchers who developed a new mobile application that uses artificial intelligence to accurately diagnose crop diseases in the field have won a $100,000 award to help expand their project to help millions of small-scale farmers across Africa.

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What is the role of scientists in community activism?

Centre Daily Times  online

2017-09-15

Three Penn State scientists discussed their roles in community activism and the challenges that go along with that.

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In Fossilized Leaf, Clues on Zombie Ant

The New York Times  online

2010-08-23

The fossilized leaf may not look like much, especially with a chunk missing. But to scientists who examined it closely, it told the story of a 48-million-year-old ant infected by a parasite, and then driven to its own death in zombielike fashion.

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Mind-controlling parasites date back millions of years

NBC News  online

2010-08-17

Mind control by parasite sounds like the stuff of science fiction, but not only have scientists revealed that it is real across a range of animals including perhaps humans they now even have fossil evidence suggesting it has taken place for millions of years.

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Parasite manipulation of host behavior

Parasites can control hosts turning them into vehicles for parasite genes. To achieve transmission the behavior of the host can become an extended phenotype of the parasite[1]. Research into extended phenotypes can provide novel insights into parasite-host interactions because it integrates across a number of biological levels of the antagonism: expression of parasite genes leading to parasite phenotypes (e.g. secreted metabolites) that affect host process (CNS and motor-physiology) leading to altered behavior that affects con- and heterospecific responses (e.g. defense and predation respectively). If the altered behavior is non-transient then effects at the ecological level can occur as well. My work explores the integrative nature of parasite manipulation to address general issues in disease dynamics and virulence evolution. I recently developed as a model system one of the most dramatic examples of adaptive parasite manipulation of host behavior, the ‘death grip’ of ants infected by a fungus. Ants are the dominant fauna of all terrestrial ecosystems and in tropical forests almost 70% of individual insects are ants (yet ants account for

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Current and future directions

Currently my focus is progressing this system along a number of lines: The genomics and transcriptomics of behavioral manipulation. How does the finely detailed manipulation we observed in Southern Thailand vary geographically both in Thailand and in other areas where this host-parasite system occurs? What is the plant response to biting ants? How do natural enemies of O. unilateralis (and there are lots of them) impact disease dynamics? How do ants within the colony react to chimeras in the nest (ants + fungi) given that conflicts exist? How does a fungal disease spread in a tropical forest and how can individual and colony (superorganism) level behavior respond? I will shortly develop these ideas further on lab website. I will also detail my previous work on Strepsiptera-manipulating wasp and ant behavior and the collaborative work on hairworm manipulation of crickets (with the excellent Fred Thomas and his team at Montpellier, France).

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Applied research at Penn State

Ants pose a significant threat to agriculture because of their mutualism with phloem feeding insects such as hemipterans. Much of the disease incidence and spread of diseases on plants is due to the hundreds of thousands of ants that protect plant-feeding insects that vector disease. Ants farm these sucking insects and ‘milk’ them for the by-product sugar they excrete. This is a strong mutualism and ant protection increases the populations of plant feeding insects, and in turn, this greatly increases the rate of disease spread between plants as the bugs transmit viral and bacterial infections and the hundreds of thousands of ant legs and mandibles introduce fungi and psuedo-fungi (oomycetes) into leaf tissue. Reflecting the successful integration found at Penn State I am interested in bringing diverse approaches to study agricultural diseases. We are working now on ants on small holder Cassava and Cocoa farms in Ghana. You see further details on my approach to plant pathology in my recent lecture.

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Gene expression during zombie ant biting behavior reflects the complexity underlying fungal parasitic behavioral manipulation

Charissa de Bekker, Robin A Ohm, Raquel G Loreto, Aswathy Sebastian, Istvan Albert, Martha Merrow, Andreas Brachmann, David P Hughes

2015 Adaptive manipulation of animal behavior by parasites functions to increase parasite transmission through changes in host behavior. These changes can range from slight alterations in existing behaviors of the host to the establishment of wholly novel behaviors. The biting behavior observed in Carpenter ants infected by the specialized fungus Ophiocordyceps unilateralis s.l. is an example of the latter. Though parasitic manipulation of host behavior is generally assumed to be due to the parasite’s gene expression, few studies have set out to test this.

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Social, spatial, and temporal organization in a complex insect society

Lauren E Quevillon, Ephraim M Hanks, Shweta Bansal, David P Hughes

2015 High-density living is often associated with high disease risk due to density-dependent epidemic spread. Despite being paragons of high-density living, the social insects have largely decoupled the association with density-dependent epidemics. It is hypothesized that this is accomplished through prophylactic and inducible defenses termed ‘collective immunity’. Here we characterise segregation of carpenter ants that would be most likely to encounter infectious agents (i.e. foragers) using integrated social, spatial, and temporal analyses. Importantly, we do this in the absence of disease to establish baseline colony organization. Behavioural and social network analyses show that active foragers engage in more trophallaxis interactions than their nest worker and queen counterparts and occupy greater area within the nest. When the temporal ordering of social interactions is taken into account, active foragers and inactive foragers are not observed to interact with the queen in ways that could lead to the meaningful transfer of disease. Furthermore, theoretical resource spread analyses show that such temporal segregation does not appear to impact the colony-wide flow of food. This study provides an understanding of a complex society’s organization in the absence of disease that will serve as a null model for future studies in which disease is explicitly introduced.

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Behavioral Ecology: Manipulative Mutualism

David P.Hughes

2015 A new study reveals that an apparent mutualism between lycaenid caterpillars and their attendant ants may not be all it seems, as the caterpillars produce secretions that modify the brains and behavior of their attendant ants.

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Diversity of entomopathogens Fungi: Which groups conquered the insect body?

João P.M. Araújo, David P Hughes

2014 The entomopathogenic Fungi comprise a wide range of ecologically diverse species. This group of parasites can be found distributed among all fungal phyla and as well as among the ecologically similar but phylogenetically distinct Oomycetes or water molds, that belong to a different kingdom (Stramenopila). As a group, the entomopathogenic fungi and water molds parasitize a wide range of insect hosts from aquatic larvae in streams to adult insects of high canopy tropical forests. Their hosts are spread among 18 orders of insects, in all developmental stages such as: eggs, larvae, pupae, nymphs and adults exhibiting completely different ecologies. Such assortment of niches has resulted in these parasites evolving a considerable morphological diversity, resulting in enormous biodiversity, much of which remains unknown. Here we gather together a huge amount of records of these entomopathogens to comparing and describe both their morphologies and ecological traits. These findings highlight a wide range of adaptations that evolved following the evolutionary transition to infecting the most diverse and widespread animals on Earth, the insects.

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From Behavior to Mechanisms: An Integrative Approach to the Manipulation by a Parasitic Fungus (Ophiocordyceps unilateralis s.l.) of Its Host Ants (Camponotus spp.)

Charissa de Bekker, Martha Merrow, David P Hughes

2014 Co-evolution of parasites and their hosts has led to certain parasites adaptively manipulating the behavior of their hosts. Although the number of examples from different taxa for this phenomenon is growing, the mechanisms underlying parasite-induced manipulation of hosts’ behavior are still poorly understood. The development of laboratory infections integrating various disciplines within the life sciences is an important step in that direction. Here, we advocate for such an integrative approach using the parasitic fungi of the genus Ophiocordyceps that induce an adaptive biting behavior in Camponotus ants as an example. We emphasize the use of behavioral assays under controlled laboratory conditions, the importance of temporal aspects of the behavior (possibly involving the circadian clock), and the need to approach colonizing parasites as organizations with a division of labor.

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