Fungus Gnat (and Sciarid Fly)

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, following on from the fantastic article supplied by Lincoln University I want to highlight the work Paddy has carried out studying Fungus Gnat and Sciarid Fly.

 “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.

Fungus Gnat (& Sciarid Fly)

The Fungus Gnat (Mushroom Fly, Shore flies or Sciarid Fly) is endemic to all but new greenhouses and are found in damp areas near the soil/ root medium surface. At 23-34°C the life cycle can be as little as ± 10 days (egg-larva-pupa-adult) where approximately 100 new flies from each female can be the result.  It is an extremely serious problem in all greenhouse situations in that the larvae damage roots, allowing for easy pathogen infection. The flies sit on infected areas and are mechanical vectors for diseases such as Pythium, Fusarium, Phytophthora spp., GSB, Pseudomonas spp. etc.  The importance of controlling this pest is often overlooked in that the symptoms of other diseases, spread by the gnat, are treated, while re-infection continues unabated due to the presence of Fungus Gnat.

Identification

Small mosquito or fly-like black or grey insects (3 dark smudgy dots on the wings of some spp.) that “aimlessly” fly around the greenhouse near the medium surface, especially right after you water or disturb the soil. The adult midges are drawn to wet swampy areas where decaying plant material, algae and fungi proliferate.   Eggs are laid in these damp areas.  Other than most other insects, the adults are drawn to odours of plant decay (as is found on the damp medium surface and standing water in our structures) rather than colour (e.g. yellow chroma’s seen in commercial sticky traps).   The larvae appear as tiny semi-transparent worms with a dark coloured head that move around in the top layer of soil, mainly feeding on decaying plant material, fungi and algae, but also feed on and damage roots.

Examples of Gnat Larva on Fruit and plant material.  Above and below.

Adult Phase Identification: Small black or grey gnats (mosquito-like) with dark smudgy dots on wings. 

Gnat pupae on growth-medium, in a highly infected greenhouse.  Look closely and you can see a lot more than the two highlighted.

Fungus Gnat Pupae

Prevention

1. Avoid over irrigation and identify areas in the greenhouse that have standing water with moss or algae growing there.Typical problem areas are: Run-off furrows, uneven floors where water pools, on top of nutrient irrigated growing medium.The most inexpensive first step in control is to treat these breading areas by spreading agricultural lime (NOT on growing medium), which will:
2. “Dry out” the algal growth, and disguise the smell of the algae and moss, and
3. Change the pH of the wet areas, which will make it less favourable for the fungus gnats to breed in.
4. By breaking the life cycle at the larval stage, you will increase your chances of getting rid of the gnats.
5. Ensure that all areas inside and within 20m of the structure is free of any weeds and freestanding water, as gnats may breed in these areas, entering the structures at the doors, windows and with personnel.

Treatment

1. Large areas of yellow sticky traps are effective in reducing the number of fungus gnat adults if placed near the medium surface.
2. By placing of a layer of e.g. Vermiculite on top of the medium, wet patches can be prevented since it dries out quickly after irrigation:  Fungus gnats require moisture in the top few cm of medium in order to complete their life cycle.
3. Few “hard chemicals” are really effective, and some can even have a suppressive effect on plant growth.
4. A number of Biological control agents (“Beneficial’s”) for treatment against larvae are available that can be extremely effective in breaking the life cycle.

Potential Bio-Controls:

1. Fungus: Beauvaria bassiana                             
2. Bacteria: Bacillus thuringiensis isrealensis         
3. Predatory mite: Macrocheles robustulus                      
4. Entomopathogenic nematode: Steinernema feltiae                             

Macrocheles robustulus.  Against Eggs, larvae, pupae.

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: into@intensagri.co.za or telephone +2783 420 1392

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

https://www.facebook.com/StefanGrower2grower/

THE MOST EFFICIENT PLANT TYING SYSTEM IN THE WORLD!

TomSystem is an innovative plant staking system for greenhouse crops – it ties the plants onto the twine using galvanised metallic staples. This new tool allows a variety of crops to be tied swiftly and simply making it the most efficient machine available in the market.

The TomSystem was designed by Spanish company Agrifast, a subsidiary of Grupodesa which is one of Europe’s leading industrial groups in the fastenings sector. Following extensive trials in Holland the original Version.1 model was launched commercially in late 2012. Following further development, and reacting to great feedback from end users, the new Tomsystem V 2.0 was released in 2017. The new V 2.0 model is 350 gm lighter and more ergonomic then it’s predecessor making it much easier to use.

Tomsystem V 2.0

A MULTITUDE OF USES

The TomSystem was originally developed for use with tomato plants. However, it was quickly identified that the system was equally effective when used with cucumbers, peppers and aubergines.

KEY ADVANTAGES

The Tomsystem provides a variety of benefits to increase productivity and profitability. Key advantages include:

1. No specialized labour is required – users can be proficient in the greenhouse within 1 – 2 weeks

2. Clipping is faster (up to 60% more efficient than other traditional methods once proficient)

3.  The V46 clip used in the Tomsystem is biodegradable

4.  Clips are healthier on the plant – Tomsystem prevents stem breakage and damage to plants

Silex Tools Ltd (www.silextools.co.nz)  based in Nelson, are the New Zealand agents for the Agrifast Tomsystem. They can assist with the implementation of this product into your Greenhouse. For more information please contact Rod Sharp on Mob (021) 799 992 or email rod@silextools.co.nz.

New Zealand Horticulture Conference, 23rd to 25th July Christchurch, Preview-

What’s in it for covered crops?

From the 23rd to 25th of July it is the Horticulture NZ Conference, being held in Christchurch at the Wigram Airforce Museum.  I will be attending on Tuesday 24th and hope to write a few articles on the presentations.

This year’s horticulture conference is a partnership between Horticulture New Zealand, New Zealand Apples and Pears, Vegetables New Zealand Inc, Tomatoes New Zealand Inc and Process Vegetables New Zealand. 

The Australian HFF and PCA conference’s, which has a large focus on hydroponic greenhouse production (that I highly recommend you attend), the NZ Horticulture conference has a broader audience to cater for.  Therefore, the topics and speakers don’t always interest or attract greenhouse growers.  This year the speakers, on the Tuesday, caught my attention and I feel the information from these speakers should be relevant and interesting for a large proportion of Grower2Grower readers.

I will be attending the following presentations;

10.15am -11am Constraints on Growing and Overcoming them

Andrew Barber & Jon Manhire, Agrilink
Sharon Forbes, Lincoln University
James Ryan, Ballance Farm Awards

Jon and Andrew are from the Sustainability Dashboard and will be talking about the project, the goal of which is to significantly enhance sustainability assessment and reporting in NZ's agricultural sector in response to increasing market, business improvement/resource use and regulatory drivers and requirements. They have case studies from NZ wines and NZ apples.

Sharon co-authored a paper on reporting on environmental impacts and how it can be used to prove the claims. James from the Ballance Farm Environment Awards is going to talk about social responsibility.

11.45 -13.00 The Post-Pesticide Age

Dr Alison Stewart, Foundation for Arable Research
Dr Charles ‘Merf’ Merfield, BHU Future Farming Centre
Dr Steve Wratten, Lincoln University
Robbie McCormick, Mr Apple

The Post Pesticide Age session is about looking at the alternatives to agrichemicals and how they are being developed for commercial horticulture. There is a wide variety of work going on within NZ science and industry to develop commercially applicable physical, biological and ecological pest management techniques. During the panel session delegates will hear about some of these from four experts and practitioners, including real-life examples of the techniques being successfully used, and have an opportunity to ask them questions.

1400- 1430 Keynote Speaker

Kok Hwee Ng , Zespri

Kok Hwee from Zespri will be talking about marketing and how it’s consumer-centric. Including examples from their marketing into Asia as an increasingly important market

14.30 – 15.00 Keynote Speaker

Dr Steve Wratten, Lincoln University

Next-generation bioprotection in a volatile horticultural era:

Agricultural and horticultural practices are increasingly being challenged for their lack of true sustainability, including high use of damaging inputs and misuse of oil-derived products and water. Frequent pest, weed, and disease invasions compound these problems, often mitigated mainly by prophylactic pesticides.

Recent findings published in Science magazine confirmed the presence of neonicotinoids in global honey samples (including those from New Zealand).

The Bio-Protection Research Centre is addressing these challenges by moving towards sustainable intensification – understanding and enhancing the ecosystem services that appropriate biodiversity provides.

In this presentation Prof Steve Wratten will outline this ‘future-farming’ system, driven by next-generation bio-protection. He will also give examples of current research in this highly topical approach to system redesign.

15.00 – 1600 Production Issues/Robots

Jamie Lunam, Jenkins Freshpac
 

Jamie will be discussing “People and Automation, the optimised kiwi pack house.” I.e.: machines in pack houses, and how they are not replacing people but that different skills will be needed in the pack house – e.g. people to operate the machines/technology.

Please let me know if you are not able to attend the conference yet would like a detailed report on any of the presentations I will be attending.   e-mail stefan@grower2grower.co.nz

Is there potential for increased yield? 

It is that time of year again when most capsicum growers have planted for the new season.  Growers will already be seeing the first flowers and fruits forming.

I have always found capsicums to be a fascinating crop, they grow at a much slower rate than tomatoes but I have always felt they are less forgiving to mistakes.  If the wrong decisions, with temperature and plant loading, occur at the beginning of the season (of which light levels play a role) it will always be difficult to balance your crop and can be very hard to change a growth pattern for the entire season. If you need to alter the direction of a crop of tomatoes it is much easier to visually see the plants reaction to either a change in fruit loading or temperature in a relatively short period of time.

Whilst working for a nursery for nine years, many trials were carried out growing advanced plants for capsicum growers.   I firmly believe a strong generative flowering capsicum plant, at delivery, should be the goal.  Like many other greenhouse vegetable plants grown by a nursery an advanced plant, close to or flowering at delivery, has proven to be optimum.   One reason grower’s buy advanced plants is to reduce down time between the last harvest of the previous crop and the first harvest of the new crop, therefore an increase in production per annum.  Once I started growing advanced plants I realised another benefit, that balancing the crop was far easier at the beginning, I needed less temperature and my substrate dried down faster lessening the plants ability to go vegetative. A big advantage was the reduction in heating required (night time temperature) to ‘burn’ the excess energy off the plant to keep it balanced.

In my opinion for capsicum plants it is possibly even more important than tomatoes to get a strong generative flowering plant at delivery.  An observation, with some capsicum varieties, is that during a one-year cycle they grow too fast and reach the wire too quickly, the perception is if you plant an advanced plant that you will get to the wire even faster, but I am not so sure.  The fact the nursery has control of the plant in a relatively small block (volume) means they have the ability to manipulate the EC and WC in the growing media especially after day 30.  At this stage it is much easier to steer the plant.  Spacing plants in the nursery at the correct time will also lessen the competition for light, reducing stretching and help dry the block down faster.  The physical change this has on young capsicums is where the largest benefit for growers occurs receiving advanced plants.  It helps create a close internodal space between the leaves.  Using all of the tools available, the nursery from this point has total control over the plant. Another rather significant advantage for greenhouse growers in NZ is the two major nurseries now have supplementary lighting which will further allow stronger, balanced plants at delivery. 

With every solution there are always questions and observations made that ultimately convince the grower about the benefits of receiving advanced plants.   Capsicums, especially the older varieties, may not have root systems as vigorous as others.  Many years ago, I was advised that capsicum plants should be planted out in the greenhouse as soon as roots are visible at bottom of the propagation block to reduce the risk of damaging roots and preventing root disease from developing.  However, I don’t believe this should be a major factor for choosing advanced plants or not.  One company, that produces propagation material, has come up with a unique block which alters the pattern (or spread) of the root systems.  It has a substantial reduction in the number of roots forming at the bottom of the block during the propagation phase but once they are placed on top of the grower’s substrate, normal root establishment should occur. 

Limiting factors.

One limitation in NZ, is generally capsicum crops are re-planted from May to July.  Capsicum grower’s plant at large stem densities, which means a nursery would require a lot of ‘free space’ to grow advanced plants at a time of the year they are historically busy.   For larger growing areas of capsicum’s there will probably not be enough nursery space.  Unfortunately, as there is a need for extra space for only a short period of time it is probably not feasible for any nursery to expand to potentially accommodate for the share numbers of advanced capsicum plants needed.  Filling up the extra specially constructed nursery space with other crops during the following 9 months is not easy to do.  A nursery is like a hotel, it sells space and if the space is not filled there is still a cost and a return on investment that needs to be paid for, unlike produce growers whose space is filled 100% all year around, except when pulling out and cleaning in preparation for the arrival of a new crop.

If a nursery could accommodate you with advanced capsicum plants, I would purchase them. Ultimately these plants will give you an increase in yield and profit, especially if you consider picking your first set three weeks earlier than normal.  A faster return on energy should be accounted for as well.

Grafted Capsicum Plants (food for thought)

The potential of grafted capsicum plants is worth considering. Grafted plants will not only give you a stronger, more resilient root system but potentially allow either 3 or 4 stems to be on grown per plant without compromising production.  Initially this means you would need fewer plants at delivery, which in turn means less space a nursery needs to grow the quantity of plants you need to fill your greenhouse.   I believe that several seed companies, and their respective breeders, are working hard to develop new capsicum rootstocks.  There are several already in the market.  I will cover this in more detail, for capsicum growers, in a future article.

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

https://www.facebook.com/StefanGrower2grower/

Article Written by Stefan Vogrincic, Consultant, Grower2Grower