Nutrient Challenges and Gummy Stem Blight

The third in this series of technical articles supplied by Paddy de Vries.  Timely reminder for GummyStem Blight as I have seen it in the past week.  Perfect conditions for it at the moment.  Spring is here and we are in transition from Winter but the nutrient advice below still applies.  

Nutrient Challenges

During the cooler months, where the ambient air and foliar temperature as well as root-zone temperature is cooler and light (quality and quantity) may be deficient, nutrient problems (visually “pre-symptomal”) often occur. 

During cooler root conditions, many nutrients are taken up less efficiently than during optimal root temperatures.  While e.g. Potassium uptake is reduced, Nitrogen uptake is hardly affected.  The net result is that the N:K ratio is skewed towards a less than optimal K value.

N:K ratio should be adapted for cooler weather, increasing Potassium (1st check analysis).  However, root K levels should be monitored carefully since this mineral can, if allowed to increase too high, depress the uptake of other critical nutrients

Potassium plays a major role in taste of fruit such as tomatoes.  Some cultivars, especially vegetative types may require a substantial increase of K.

If symptoms are already visible or the fruit taste has already been affected by the cooler climate and poor light & shorter days, increase K in the fertigation mixture along with an increased EC. (photo above with K deficiency)

Phosphate uptake is drastically reduced by cold roots.  P is involved in critical processes including energy transfer, photosynthesis, nutrient movement and transformation of sugars and starches.  At <13°C root temperature, P uptake may be inhibited by as much as 30%.  The application of extra P in the nutrition will help, but the roots remain cold and uptake is still slow.

If acids Sulphuric or Nitric acid is used for pH control, replace a portion (must be calculated on N, P and bicarbonate levels) with Phosphoric Acid

Foliar application of a P containing product can be extremely beneficial in cold weather.  Using products that contain both P and K (no or insignificant N) along with trans-cuticle transport additives and organic chelates will be a distinct advantage.

Cucurbits:  Gummy Stem Blight (GSB) – Didymella bryoniae

Following on from my article in April, Paddy’s article gives added technical advice:  news/post/gummy-stem-blight–didymella–is-currently-affecting-some-growers/

Identification:

Leaves, stems and fruit can be affected.  Leaf margins normally first show signs of infection: displayed as v-shaped zones of chlorosis.  Leaf symptoms can be exhibited within the lamina of the leaf, sometimes incorrectly identified as Downy Mildew (Pseudoperonospera cubensis). While Downy Mildew exhibited as angular areas mostly within leaf veins, the GSB spreads over veins and is less angular.   The GSB symptoms progress to become necrotic areas of dead tissue that turn brown and have a yellow halo around the necrotic parts.  Close to the ground/medium level, the stems exhibit areas appearing dry and cracked with tan coloured corky lesions.  Within these lesions black fruiting bodies and beads of an amber exudate can be seen.  Fruit may also exhibit corky lesions with concentric rings and fruiting bodies (e.g. squashes). Cucumber fruit will exhibit thinning of the flower end, often with black fruiting bodies on a larger than normal calyx scar.  The fungus can completely decimate the stems and the plant withers and dies.  Symptoms normally appear at or after first harvest when the plants may be weaker due to metabolites being sent to the main metabolic sink(s), the developing fruit, and plants are more susceptible to attack

Above and below are picutes of GSB in the early and more advanced stages in the base of the stem.

Photo above of the GSB further up the stem.  This was probably infected from an open wound.  Below a good illustration of GSB on the leaf.

Prevention

Gummy Stem Blight infections occur when fungal spores are present on susceptible areas or lesions on the plant, due to optimal conditions for the infection process to occur.  During periods of high humidity, free water present on plant parts (e.g. plant temperature below dewpoint temperature), wet conditions and temperatures averaging 16-21 °C (typical in the early morning autumn, winter and spring greenhouse), the fungal spores bloom.

I have definitely seen this in the past week (NZ).  With the wild weather, as it is at the moment, I expect to see more of this if you don't take precautions.  Didymella is not totally avoidable.  I like how this shows the spores on the flower, this is how it starts and transfers into the fruits causing the rot.  

A sequence of management plans must be initiated to control Gummy Stem Blight (GSB):

1. Seed: One source of GSB inoculum could be seed.  Purchase seeds from reputable companies with a good history of GSB-free seed production.  Genetic GSB-resistant varieties are not currently available in any cucurbits to my knowledge.  Some varieties however will be less susceptible to infection, and companies will refer to them as “strong against….”, but will not claim resistance.
2. Transplants: GSB is common at the seedling stage and displays one or more of the characteristic symptoms (chlorotic and necrotic areas on the margin of the leaves, water-soaked regions on the stem, gummy ooze from the stem).  Growers should regularly inspect transplant seedlings in the greenhouses.  Whenever possible, avoid using healthy-looking seedlings from trays with infected plants. This is true for all diseases.
3. Organic debris: Another source of primary inoculum is organic debris from previous cucurbit crops.  As soon as a cucurbit crop is harvested (especially crops with GSB inoculum), the decaying debris from that crop should be destroyed.  Botrytis has the same danger of being re-infected from plant debris.
4. Volunteer plants: Many weed species and wild or volunteer cucurbits are other sources of inoculum and should be eradicated before planting the crop.
5. Crop rotation: Even though not practical in greenhouse / nursery situations, a two- to three-year rotation with non-cucurbits is an effective way to reduce incidence of GSB.  Utmost care should therefore be taken in removal and destruction of all the infected material and post-harvest or pruning material.  Where soil is the root medium, ensure that the soil is inoculated with suppressive beneficial organisms or apply chemicals within the relevant legal framework of your country or export destination market
6. Scouting: Routine scouting of the fields helps in timely application of fungicides or beneficial organisms that can prevent major crop losses.
7. Biological control and bio-pesticides:  The effectiveness of bio-control agents currently available in the market is heavily dependent upon environmental conditions at the time of application and therefore often show varied results in the prevention & control of GSB.  Time, type & mode of application is critical.
8. Fungicide application: When conditions favor the disease, preventative fungicides should be applied within legal constraints.
9. Storage: GSB infection & spread can also occur on the fruit post-harvest.  Avoid wounding fruits during harvest, and store fruits at 10°-12°C to prevent postharvest infection and growth. (Confirm specific optimal conditions for different spp.).

Treatment

Chemical & Other Control

1. Fungicidal treatment, both preventative and curative should be done within the legal framework of the local and destination market. 
2. Plants can be sanitized with “QAC’s” where legally permissible.
3. Remove infected material as per Botrytis and treat soil if legally permissable.

Paddy de Vries a hydroponic specialist in South Africa will be visiting New Zealand in October.  Paddy has been in the South African covered crop industry since graduating from The University of Stellenbosch in 1987 with a BSc Agric and  2 BSc Hons. degrees.  He has vast experience and has supplied me with insights into the South African greenhouse industry.  Paddy wrote an excellent newsletter regarding 'production pitfalls'.  Paddy has allowed Grower2Grower to publish this newsletter in a series of articles.  The technical nature of the articles is relevant and applicable for NZ growers.  In this edition, Paddy will focus on Gummy Stem blight and nutrient problems.

 “The best approach to preventing a problem from taking hold, and painstaking process of ridding the crop of the malady is a three-pronged approach: Identification, prevention and, unfortunately for those infected, treatment” Paddy de Vries.

Article content “Brought to you by Intens Agri Hydro” For more information, feel free to contact Paddy de Vries or Liandra von Below de Vries at:  Liandra.vonbelow@gmail.com or telephone +2783 420 1392

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Article formatted by Stefan Vogrincic, Consultant, Grower2Grower

What you need to know.

Peter Holwerda, Sales Manager, Apex Greenhouses, sent me an excellent e-mail last week in response to a classified in Grower2Grower, from a person wanting to purchase a second-hand greenhouse.  The email highlighted the unforeseen issues importing a second-hand greenhouse from overseas might cause you.

Apex Greenhouses will import second hand greenhouses from Holland. They are able to have them prepared to any client specification.  If it is a fairly straight forward glasshouse they generally work out costing around 15-20% less than a new build but they are usually already 10-15 years old.  Apex will take care of all shipping, customs clearance and delivery to site.  Most of the greenhouses imported are only four meters high but Apex will add longer posts (probably new) if the client wants a higher height.  The imported greenhouse will need new tempered roof glass and new wall glass.

What you need to be aware of:

1. There are NO guarantees on the running gear and NO warranty.
2. If there is any indication of dirt or contamination detected by MAF, there might be a rather large cleaning cost to the client.  While the suppliers say they clean the materials, something could sneak through which Apex would not be responsible or liable for.
3. Engineering code:  New Zealand Building Codes, are quite a bit higher graded than the Dutch.  Apex have found that some designs from Holland do not comply with New Zealand standards.  New Zealand wind zone calculations are quite a bit higher and earthquakes now also has an effect.
4. It is advised that before ordering a second-hand overseas greenhouse, that an engineer from Apex check out if the greenhouse you want to purchase would comply with the New Zealand building code. You should source as much information as possible regarding engineering calculations from the overseas supplier of the second-hand greenhouse.
5. Non-Compliance:  If the structure does not comply then the greenhouses can be strengthened or rectified before shipping.  Some truss designs from Holland, that are 10-15 years old, are 50% weaker than the Apex designed trusses.
6. Even second-hand New Zealand greenhouse structures might not be up to the most recent building codes.  Again, you should make sure that this is checked by an engineer before you proceed.

These are just some of the issues that could occur when importing second hand greenhouses as Peter explains: “It can be a bit tricky and there are some hurdles but even if you can find a second hand one in NZ, the building code updates in the last 10 years, might even require replacing posts or other parts.  Please check with me for advice if it will pass the code without major consequences.”

Initially you might save 15-20% buying a second-hand greenhouse, compared to a new greenhouse, but that is if everything goes well.  Is it worth the risk?  If you have a budget then building a greenhouse brand new, that was 15-20% smaller, but was within the budget would be something I carefully consider. 

For more information please contact Peter at Apex Greenhouses:

Peter Holwerda

Sales Manager | Apex Greenhouses (NZ) Ltd

6 Hosking Place, Waiuku,2123, Auckland

peter@apexgreenhouses.co.nz  | P +64 9 235 8618  | M +64 21 725 430 | apexgreenhouses.co.nz

Cover image is a second hand Dutch greenhouse re-built by Apex Greenhouses in the Pukekohe district.

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower, with the help of Peter Holwerda from Apex Greenhouses. 

Update! So far Sharma has reached $ 25,000+.  Well done Sharma, and lets hope you get some more money raised before you 'Brave the Shave'. Congratulations.

Help Sharma raise money for Cancer research

Last week Raj Sharma emailed me, along with other growers and suppliers, to ask if we would support him in his efforts to raise money for the Cancer Foundation.  Raj is going to shave his hair for the fundraiser.  Cancer is a terrible disease and has touched so many in our industry.

“The reason I've wanted to fundraise is simple. Over the course of 5 years, many of my relatives such as my brothers, mother-in-law, various relatives and close friends in New Zealand and abroad have been lost due to cancer. During the struggle with cancer, I saw some of the strongest people lose their confidence, courage and willpower. Truth is, I don’t want to see anyone else go through such an ordeal like that. That is why with the help of my community I want to raise money to help end cancer once and for all!” Raj Sharma.

So far, in total Raj has raised over $19,500 and hopefully with the help of Grower2Grower readers we can help Sharma in his goal to raise over $25,000.

Raj Sharma, is a well-respected and liked grower, this is reflected by the generous donations received so far.  A special mention needs to go to WPC (Waste Petroleum Combustion) and Vigour Seeds who have both made substantial contributions. Donations go towards vital scientific research into the causes and treatment of all types of cancer. 

Cancer affects 1 in 3 people, during their lifetime. It touches each and every one of us in some way.  Next February is the tenth anniversary of my dear Dad’s extremely sad death attributed to asbestos.  My family and I had to watch my Dad (Joe) endure eleven months of suffering.  My wife’s Aunty passed two years ago, after a nine-year battle with ovarian cancer. It is so sad to watch someone you love fight so hard but to still lose the battle.

Congratulations Raj and thank you.  Raj you reflect the following saying: “It’s nice to be important, but it’s more important to be nice” my dance teacher, Colleen Stuart, who passed from brain cancer, used to say this to me when I was young. This has become the Grower2grower moto.

If you would like to donate and follow Raj’s fundraising progress click on the link below;

https://bravetheshave.everydayhero.com/nz/raj-kumar

I appreciate your comments.  Please feel free to comment below or on the grower2grower Facebook page:

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower

Louise Millar, National Greenhouse Sales & Product Management, SPS

Louise Millar has worked for South Pacific Seeds for the past 12 years but has been involved in the horticulture industry her entire working career, she has seen many changes in the greenhouse industry in that time.  Her role as National Greenhouse Sales & Product Management involves working closely with growers, this has given her a unique insight into the different grower’s and their operations.  The relationship Louise has built with her customers has formed the solid foundation for her continued success and respect amongst the greenhouse growing community.

Louise’s work covers Capsicum, Chilli, Cucumber, Eggplant and Tomato greenhouse crops and she is also involved with supporting the South Pacific Seeds greenhouse team in Australia.

Louise was born and raised in Dannevirke in Hawkes Bay, she grew up in the town. Two of her Uncles were involved in the horticulture industry, one was an orchardist, growing apples and citrus, and the other working with process crops specialising in peas.  Louise has fond memories sitting in the pea harvester during hot summer days helping her Uncle.  After completing secondary school Louise decided to enrol at Massey University, and after two years study successfully gained a Diploma of Horticulture.  Louise wanted to compliment her first diploma so she studied for a further two years and completed a Diploma of Business Studies, endorsed in Human Resources, also at Massey University.

Soon after graduating, Louise was offered a position at Fruitfed Supplies in Tauranga.  For the next three years she worked as a sales representative servicing the kiwifruit industry.  In 1990, Louise asked for a one-year career break so she could embark on the great Kiwi OE.  On her return to NZ, a role as Branch Manager was offered at Fruitfed.  The job was situated in Kumeu.   Louise worked at the branch for 3 years before being promoted to the position of Sales Manager for the Northern Region.  During that time Louise met her future husband (Derek) at a triathlon event, they were married in 1997.  In the year 2000, with her first son Joshua on the way, Louise decided she would become a stay at home mum.  Her second son William was born in 2001.

In 2004 Louise received a phone call from a recruitment agency asking her if she would be interested in a position at Webling and Stewart Seeds.    This presented the perfect opportunity to re-enter the work force.    Louise was employed as National Manager; the company had just been purchased by South Pacific Seeds along with Yates Vegetable Seeds.  Over the next two years with two others, Louise was tasked with selling the remaining seed inventory.  After two years the company was then dissolved and merged with South Pacific Seed Sales (NZ) Limited.   Louise was then asked to transfer and was offered a role at SPS, and the rest as they say is history.  Since 2007 she has been focused on the greenhouse industry.

Louise has seen a huge amount of change in the industry and believes growers have become a lot more professional, she believes compliance, technology and new varieties have improved grower output. One thing she would like to see is more grower discussion groups and sharing of information.  Annual trips are made to Holland, and she believes it is extremely important to gain first hand knowledge of any new varieties that could be suited to New Zealand.  Louise said the Enza Zaden breeders (who supply their greenhouse genetics to SPS) thoroughly understand New Zealand growing conditions and will only introduce new varieties they believe will potentially thrive in New Zealand.  When she visits Europe, the trials are half way through the season, Louise believes this is an advantage as it already identifies new material which could be trialled in New Zealand.

Louise has spent a great deal of time focusing on capsicums and after her recent visit to Europe believes that grafted capsicum plants will offer growers the real potential of higher returns.   Seven percent increases in production have been achieved in Europe.  Improved fruit size and root health are the main reasons behind the increase in production.  The other ‘huge’ positive is the reduction of root treatments.

It is these advances in technology, cultivation and genetics that keeps Louise challenged in her role with South Pacific Seeds and continues her interest in building partnerships with the greenhouse growers of New Zealand.

Louise and Sashi Cassidy, Manager from Gourmet Waiuku. 

Louise and Sashi checking on the progress of a new trial variety

Louise amongst a crop of Campari tomatoes (supplied by SPS) illuminated with LED lighting at Gourmet Mokai.

For any information on greenhouse vegetable varieties please contact Louise.

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower

The urban sprawl and the effect on outdoor Pukekohe growers.  What are the alternatives?

Last week, I read a report prepared for Horticulture New Zealand presenting current and potential future effects on the growing hub of Pukekohe.  There is concern, because of the urban sprawl, we will lose some of the best fresh vegetable growing areas in NZ.  I quote” For an area accounting for only 3.8% of New Zealand’s total hectares of fruit and vegetable production, the Pukekohe hub punches far above its weight.  The revenue generated by the hub’s horticulture businesses of $327 million equates to 26% of New Zealand’s total domestic value of vegetable production, and to a lesser extent of fruit.”

After reading this very interesting report, I could not help but think of the opportunities and possibilities, which were only briefly covered, as potential alternatives to providing the fresh fruit and vegetables we rely on for both local and export markets. What role will new technology play and in particular, how will greenhouse production potentially be a solution to producing the types of food that is mainly been grown in the market gardens of Pukekohe?

In the 63-page document I found a point, on page 44, that mentioned glasshouses, ‘Growers change farming practices in response to land use constraints.  For example, they might change their operations to intensive production methods, like glasshouses or vertical farming, or may increase machinery or labour to crop more efficiently on their existing land.  The greenhouse industry worldwide, the opportunities and growth it is experiencing is what I would suggest be considered. 

After 23 years in the greenhouse industry, travelling and working in the UK, visiting Holland and contracting to a Dutch substrate company, I am convinced a large amount of the food, still grown outdoors, could in the future be grown in greenhouses using current methods we use today and differing types of vertical farming systems.  Recently I have written articles about technology and its rapid advancement, it is moving so fast that keeping up with it is almost impossible.   Intensification, producing every gram possible per m2 of area, is and will only be a consequence of the ideal growing conditions a greenhouse offers.  There are of course constraints, the biggest being the margins and return on capital investment when building a greenhouse, but if we are serious about maintaining and growing our food production then greenhouses should be a huge part of this discussion and seen as a positive solution.  We are lucky to have on our doorstep, world leading greenhouse construction companies and all the required support businesses in South Auckland already. Possibly some sort of regional development fund from government could help investigate converting current market garden crops to greenhouse production?

If you read part's the following article you will understand I am not alone in the way I view how greenhouses should be considered as a genuine addition to help protect our growing food industry.

https://singularityhub.com/2018/05/18/these-4-tech-trends-are-driving-us-toward-food-abundance/#sm.0000sflzkgap1edrtxg14q3o2mm7m

I think the report I read last week, is a good and fair representation of what will happen as the urban sprawl of Pukekohe grows.  I hope the Pukekohe outdoor growers are able to protect their lands for sustainable cropping but I hope they take a look at the pathway that tomato, cucumber, capsicum and eggplant growers have potentially laid for them.  

With change comes opportunity.

Greenhouses are already a major part of the Pukekohe and South Auckland landscape.  These photos illustrate that.  The cover photo and these photos are taken in Pukekohe West only a few Klm from the Pukekohe township.

This photo was taken directly from the dividing line between cropping land in Pukekohe West and the current urban sprawl.  Only a few years ago, the land where the new buildings are was producing vegetable crops.

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Article Written by Stefan Vogrincic, Consultant, Grower2Grower

Article based on the reoport prepeared for Horticulture New Zealand: New Zealand's Food Story: The Pukekohe hub August 2018