Category: CTP News

CTP news and student blog posts


Part of my fieldwork this season involves trying to catch live aphids on lettuce from various parts of the UK. I would provide you with ~30 lettuces to grow in your garden and I would ask if you see any aphids on the lettuce for them to be sent to me at Rothamsted Research. Costs for postage etc. would be paid for and you will also get a summer’s-worth of free lettuce to eat! This will not require anything other than keeping the lettuce alive and checking them for aphids when you pick one 😊.

If you are not interested but may know someone who could be, please send this on to them.

Thank you in advance.

Dion Garrett

Please email me for further details:

Project Progress Update from Dion Garrett: Where am I?

Written by CTP Student, Dion Garrett

Where am I?

It’s that time of year again where many are recovering from over indulgent festivities and making new year’s resolutions; to run 10km, eat healthier, learn a new skill, save more money, publish a paper in a journal, procrastinating less and being more focused – to name a few. If you have a new year’s resolution or not, most of us have had a moment of reflection and deliberation; fleeting or enjoyably reminiscent. I have used some of my time away from work to contemplate and reflect on both the positives and negatives of what has come to pass during 2018.

Personally, I am not someone who readily makes these types of resolutions or goals as I feel these generally fall by the wayside, usually due to busy schedules! I prefer long goals moreover the short ones, perhaps this is one of the reasons why I am doing a 4-year PhD; it’s not so much about the brief unsustainable gains but the long-term ones. Moderation and mind-set are big players and having retrospective helps keep me on track to achieve these long-term goals.

I thought it a fitting point in my PhD project to reflect on my own progress and how I am set for what 2019 has in store.

My project

Firstly, if I haven’t met you or managed to pull your ear off about my project before, I am a second year PhD student at Rothamsted Research researching into methods to control a serious insect pest of lettuce crop. The currant-lettuce aphid (Nasonovia ribisnigri) is the most damaging species to lettuce in the UK and parts of Europe (Diaz et al. 2012). Currently there is little control for this pest due to its preference to infest the centre of the lettuce, rendering foliar sprays ineffective (Fig. 1B) (Natwick & Lopez, 2016). This pest is caught in very low numbers with existing trapping methods, which make predicting when they are likely to move from their primary host (currants (Ribes spp.)) to their secondary host (lettuce). Resistant lettuce varieties were introduced in the late 1980’s and provided close to full resistance against the aphid. However, resistance breakdown was first reported in 2007, with resistant cultivars now having little effect against the currant-lettuce aphid (Broeke et al. 2013).


Figure 1: A) A lettuce field at my industry partner, G’s, where an outbreak of currant-lettuce was detected. B) The centre of a little gem lettuce with many nymph and adult currant-lettuce aphids.

I aim to create a more accurate and robust forecasting model to predict migration from the primary host to secondary lettuce host; where this species becomes an agricultural problem. This will be achieved through insect trap optimisation, field margin surveys, phenological data analysis and overwintering studies.

By using molecular tools, I want to obtain whole genome sequences of both resistant and susceptible biotypes (against the resistant lettuce cultivars) and identify where the resistance is located within the genome. Providing this is attainable, I hope to geographically map these resistant biotypes which will inform me on the spread and evolution of resistance over time using the currant-lettuce aphids caught in the Rothamsted Insect Survey (RIS) archive from 2003-present.


I have been working with my CASE Project Partner, G’s, on their Cambridgeshire site. This year I set out to identify the best method for capturing this elusive aphid. I incorporated a variety of insect traps throughout March-September and sampled twice a week, with all aphids identified to species level and other insects to order. This was quite an intensive schedule and I don’t think I really understood the amount of work involved to successfully complete it. Travelling and sample collection took a big chunk of my time but this was overshadowed by the time needed to count and identify all the insects in my traps. I did manage to find that one of my traps (pop-up suction trap (Fig. 2A)) by far was the most robust at catching high numbers of aphids; and I even caught a few of my species of interest too!

Figure 2: A) Me demonstrating the size of 6m mobile pop-up suction trap. B) Identifying aphids and other insects caught this year from the samples collected from my industry partner.

I’ve got previous taxonomic skills, primarily developed from my MSc Entomology course at Harper Adams University, but I additionally gained a pretty good grasp from spending tireless hours in the countryside hunting bugs and identifying them as a child. It was a steep learning curve to be able to be competent enough to identify aphids however. In the UK there are over 600 species of aphids, with over 400 being caught in the Rothamsted Suction Trap Network (Fig. 2B). Aphids are on another level of confusing but I persevered and I can happily say that I feel confident at identifying the main aphid pest species now.

Laboratory work

With access to the Rothamsted Insect archive of the suction trap network, I have gone through all the aphid samples from 2003-present and collected all the currant-lettuce aphids that were caught during this time. To put it in perspective, some of the samples was like looking for an aphid in a stack-full of aphids, which to the untrained aphid-spotting eye, all look incredibly similar… (Fig. 3). I now have ~500 samples now readily waiting in the freezer to be analysed!


Figure 3: A) A currant-lettuce aphid (N. ribisnigri) under the microscope. B) A typical sample of aphids collected from the pop-up suction trap. C) Once the aphids are identified and counted, they are put into a glass vial for long-term storage.

On the molecular biology side, I have been provided some currant-lettuce aphid colonies from Warwick University Insectary at their Wellesbourne site of both resistant and susceptible biotypes. I have reared my own colonies out of these and generated isogenic (clone) lines. It took some time to identify the best method for DNA extraction for whole-genome sequencing (WGS) but this is now complete and extraction/sequencing is underway.

Good things and the not so good things

My first year of the PhD has completely flown by (similar to most I’m sure!) with both field and laboratory work taking the largest chuck of my time. The remainder has been filled with reports, conferences and a plethora of training courses such as statistics (introduction to advanced courses), bioinformatics to presentation skills and courses in personality types/traits (very helpful!). I can now satisfactorily say, I have done my fair share. Although extremely valuable, these training courses, conferences, meetings did take a lot of time and took me away from my actual project. If I had my time again, I would schedule more effectively and prioritise the more pressing skills workshops etc. to the relevance of my project.

Doing a project such as this as been eye-opening in more ways than I thought. Working at Rothamsted Research is a great experience, with a strong PhD student community and working alongside like-minded people; I don’t think I could be in a better place. On reflection since starting this PhD, I have laid a good foundation for my project and feel like I am making some positive progression. This year is going to be difficult but I feel that I now know the direction I want to take the project and approaching this year with an optimistic mind-set.

Side note

If you would like to contact me to discuss anything mentioned in this blog, entomology-related or otherwise please feel free to drop me an email too (as above).


Broeke, C.J., Dicke, M. and van Loon, J.J., 2013. Performance and feeding behaviour of two biotypes of the black currant-lettuce aphid, Nasonovia ribisnigri, on resistant and susceptible Lactuca sativa near-isogenic lines. Bulletin of entomological research, 103(5), pp.511-521.

Diaz, B.M., Barrios, L. and Fereres, A., 2012. Interplant movement and spatial distribution of alate and apterous morphs of Nasonovia ribisnigri (Homoptera: Aphididae) on lettuce. Bulletin of entomological research, 102(4), pp.406-414.

Natwick, E.T. and Lopez, M.I., 2016. Insecticide Efficacy Against Aphids in Leaf Lettuce, 2015. Arthropod Management Tests, 41(1).

Enhancing Nature with a Little Nurture: A History of Avocado Breeding

Written by CTP Student Jessica Fostvedt

An ancient civilisation located in the south of what is now Mexico, the early Mesoamericans cultivated one of the most nutritious foods found on Earth.  The substantial value of this natural gift was not lost on them either.  In fact, avocados were a highly revered source of nourishment, thought to bestow strength and vitality.  It was only a small miracle that these early tribes were able to have such a wholesome fruit, since the giant ground sloths responsible for seed distribution went extinct thousands of years earlier.3

So, the early American tribes saved them from extinction, but how did avocados escape the New World and become a familiar addition to the modern diet worldwide?  For its introduction to Europe, the fruit was first described in a 1526 book by Martin Fernandez De Encisco.3  This was an important step in turning a tropical novelty into the modern commercial crop we recognise today, but the full process would take years of careful breeding…and some luck.

Tree breeding in general is a time consuming process, given the nature of the organism, but avocados in particular add an extra layer of challenge into the mix with their unique sexuality.  Like many plants, the avocado tree prevents self-pollination of its own flowers.  However, instead of simply separating male and female flowers, the avocado flowers have both sets of sexual organs, and expose them separately depending on the time of day.  For a ‘Type A’ tree, the female sexual organs open in the morning, while the male parts stay retracted and do not shed pollen.  The female parts then shrivel and die, while the male parts emerge the next afternoon and shed pollen.2  A ‘Type B’ tree opens its female parts in the afternoon and its male parts the next morning.  Performing cross pollinations by hand is naturally very difficult for this tree.  Breeders often just plant suitable trees within close proximity and hope for the best.

By sheer fortune, the best did come in the year 1926.  Rudolph Hass, a surname with which all avocado fans should be familiar, stumbled upon a chance product of the pollination lottery in a seed he purchased from an avocado nursery.  He intended to use the resulting tree to graft a Fuerte variety, but the new tree rejected his grafts and instead produced a strange new avocado.  In a few short decades the rich, nutty flavour of the Hass avocado outcompeted the once popular green-skinned Fuerte, and became the number one cultivar worldwide.1

The consistent flavour produced by grafting is great for consumers, but poses a challenge for the fate of avocados.  All commercial cultivars are genetically identical, and grafted onto disease-resistant rootstock when creating a new commercial tree.  To bring about real genetic change in the avocado industry, it will take more trials, many years, and some luck to take the next step forward.  Also, breeding must focus on more than just superior flavour and marketability.  A sustainable industry requires trees which use less water, hearty and disease resistant rootstock, and varieties that can face the more demanding climate challenges of our changing world.  The trend toward better environmental stewardship will ensure the most economical and highest quality fruit can be grown all over the world.  The expectations are high, but for a tree that emerged as a result of so many little miracles, it only needs a chance.

  1. “” Avocados From Mexico,
  2. “Growing Avocados: Flowering, Pollination and Fruit Set.” Agriculture and Food, Government of Western Australia,
  3. “The Origin Of Avocado: A Brief And Interesting History.” CureJoy, 13 Apr. 2018,

CTP Second Cohort Welcome Event

Written by Roz Wareing

Waitrose CTP welcomed its second cohort of students last month. The students travelled from their home institutes to Lancaster Environment Centre at Lancaster University for the 2 day welcome Event.

During the event the students and supervisors participated in a series of activities including introductions from CTP academic director and Alan Wilson from Waitrose, plus cohort team building activity in Grizedale Forest.

Dr Carly Stevens, the Waitrose CTP academic director, introduced the programme before handing over to the students. The students impressed the CTP board with their knowledge and enthusiasm of their projects with only two weeks work into their PhD programme.

Alan Wilson delivered an inspirational presentation and workshop for the students. Alan discussed leadership and management skills, good behaviours and attitudes in business and emotional awareness. In the afternoon our cohort joined a session with Centre of Global Eco Innovation learning research skills and creating posters about their projects

The agenda for day two involved the students getting to know each other.  The students conquered their fears and had fun climbing and swinging high from the tree top adventure at Go Ape in Grizedale Forest.

Thank you to everybody who attended


The Great British Weather Off

Written by Nick Kuht (CTP Student)

The weather seems to have been the main topic of conversation over recent weeks. For most of us, our biggest concerns have revolved around avoiding getting sunburnt and keeping ourselves cool in the heat. However, farmers across the UK have been facing much greater problems. During my field trial work and interactions with Sandfields Farms Ltd (G’s Growers) in this first year of the project it has become quite evident how much of a headache the weather can pose to growers.

Currently the UK is experiencing one of the warmest and driest summers in years. Extreme heat can have a negative effect on the growth of some crops. This was seen earlier this summer when it was reported that lettuces could be in short supply due in part to their inability to grow successfully in temperatures exceeding 30°C. Furthermore, the prolonged dry weather is now reaching a point where growers are suffering from water shortages, with river levels dropping and reservoirs drying up, leaving some with little option but to let their crops go thirsty. This could to lead to reductions in yields and may translate into price increases for consumers.

In stark contrast to the current heatwave it was not that long ago that we were suffering weeks of very wet and cold weather. I can recall earlier this year standing in an extremely wet field discussing with a grower the troubles they’d had simply trying to find a couple of dry days to sow their crops, after seemingly weeks of rain.

Furthermore, we only have to look back to 2017 when the supply of some produce was also interrupted due to severe rain and flooding in Spain. Again, unseasonal weather events having major consequences for growers and consistent supply of produce that we now take for granted.

These extremes of weather that we’ve seen this year cannot necessarily be attributed to climate change at the moment. However, the difficulties raised by the recent weather events have made me think more about how UK crop production will look in the future if current climate models become a reality. Temperature rises, changes in precipitation patterns and increases in the occurrences of extreme weather events are all predicted for the future, and are bound to have a significant impact on food production.

Farmers have always had to contend with the uncontrollable and largely unpredictable nature of the weather. Nevertheless, the predicted shifts in our climate are likely to make this challenge even greater and will require growers to start to considering how they may adapt to overcome these changes.

Irrigation has been required almost constantly throughout this summer due to the long periods of no rain and hight temperatures

Cracks in soil developing due to persistent hot and dry conditions