Issue 45: Greenhouse IPM – Around the World

Issue 45
March/April – 1999
Story Title: Greenhouse IPM – Around the World
Author: Roger Fox

A series of grower workshops held around Australia recently, focused on Integrated Pest Management practices in Europe, Canada and America, and looked at how we can implement them here.

Australia’s greenhouse industry needs to embrace Integrated Pest Management (IPM) practices much more broadly, if it is to meet World’s Best Practice standards. This was the underlying theme to come out of a recent visit to Australia by a group of international experts in the field of IPM, who spoke to growers in four States. The Grower Workshops on IPM were organised by NSW Agriculture, in association with NIAN and the HRDC, and held around Australia during January.

The speakers came from Europe and North America and included Dr Don Griffiths, IPM specialist and consultant to Novartis BCM in the UK; Professor Mike Parrella, Professor of Entomology at the University of California, Davis, USA; Les Wardlow, IPM consultant and formerly Senior Entomologist with the UK Agricultural Development and Advisory Board; Karel Bolckmans, IPM specialist with Koppert in Holland; and Graeme Murphy, greenhouse IPM specialist with the Ontario Ministry of Agriculture in Canada. The sessions were coordinated by Stephen Goodwin and Marilyn Steiner, senior pest research scientists with NSW Agriculture. The diverse backgrounds of the speakers made for a highly informative series of workshops, which were heard by around 500 – 600 attendees around Australia.

Greenhouse IPM in Europe
Dr Don Griffiths began by putting IPM practices into their historical context. Biological control, he explained, was actually started in the 1930s with the use of Encarsia wasps for countering greenhouse whitefly. However, after the Second World War, new chemicals gained new favour and the use of biological controls was essentially lost until the 1960s, when serious resistance problems developed in treatments for red spider mite. At this stage, the predatory mite Persimilis began to be used.

In the 1980s, the appearance of Western Flower Thrip and Leafminer renewed interest in developing new biological control agents, the primary motivation being the fact that existing chemicals were proving ineffective. As a result, Dr Griffiths said, the last 10 years have seen attitudes to chemicals change among growers, while Government pressure has often forced their hand. For example in Denmark, punitive taxes on chemicals have been introduced to force greenhouse growers into adopting IPM. In addition, many European supermarket chains now have “good practice guides” for growers, to explain preferred methods of growing particular crops.

Dr Griffiths explained that the first step towards true IPM was what he calls an ‘Integrated Crop Management’ approach. Integrated Crop Management (ICM) rejects the use of persistent hard chemicals, while allowing ‘soft’ chemicals to be used as a back-up when necessary. Converting a greenhouse enterprise to IPM has to be a sequential process, he said, which starts with an analysis of the pest/disease profile, then removes hard chemicals and replaces them with a combination of soft chemicals and introduced beneficial insects. Dr Griffiths observed that in Australia presently, too many hard chemicals are used in greenhouse horticulture, and only about 10% of our chemicals are compatible with Biological Control agents. Hard chemicals are those that are very harmful to beneficial insects and have a long persistence in the crop.

“Compatible insecticides are underused here,” he commented.

He believes Australian growers should approach conversion to IPM slowly, over 2 or 3 seasons. “You can’t change overnight by introducing a Northern European style approach,” he said.

Importantly, a significant change of attitude is essential for IPM to really become adopted. “It has happened in the Spanish industry,” he said, “and I believe you can do it here.”

According to Marilyn Steiner from NSW Agriculture, more soft chemical options are being introduced into Australia and chemical companies are being pressured to speed up this process. She pointed out that some soap-based sprays can be used with a program of beneficial insects, though it is critical that the timing of such spraying is very carefully managed.

IPM in Canadian Greenhouses
Graeme Murphy works primarily with flower growers in the province of Ontario, Canada, where until the late 1980s, regular chemical use was normal practice among greenhouse growers. However, a Government program introduced in 1987, established the target of reducing agricultural pesticide use by 50% by the year 2002. This led to the development of IPM programs for various commodity groups, the establishment of IPM demonstration trials in local greenhouses (which tracked pest populations over a period of years) and the gradual education of growers through workshops, to assist their conversion to IPM systems.

Mr Murphy explained that introducing IPM is presented to Ontario growers as a three-phase program:

– Phase 1 is monitoring of pests, using sticky cards, etc.
– Phase 2 is pesticide modification.
– Phase 3 is biological control – the use of living organisms to control pests.

According to Mr Murphy, successfully introducing biological control requires a total committment from the grower and the involvement of all staff. A high level of back-up support is also needed, so that growers know what pest they’re dealing with, which predator is most suitable, and what to do if things go wrong. Mr Murphy advised that growers should start small, if possible screening off a section of the greenhouse to prevent the entry of pests from outside. They must know how to monitor both the natural enemies and the pests, and they must know what pesticides can be used in conjunction with the biological controls (compatible pesticides).

Another more recent component of IPM in Ontario greenhouses has been the use of insect-exclusion netting which, although adopted by only a small percentage of the industry to date, has shown excellent results in reducing pest numbers. In hot climates, however, there are some concerns over the reduction in air flow from netting use, and this may require the introduction of positive air movement during the summer months, Mr Murphy observed.

IPM Strategies for US Rose Growers
Professor Mike Parella works primarily with growers of cut flowers and potted flowering plants in California, where much of the US flower industry is concentrated. For example, 90% of all roses in the US are grown around the San Francisco Bay region.

According to Professor Parella, US growers are being pressured into the adoption of IPM methods, through the steady loss of chemicals which are legally useable. At the same time, consumers are becoming more vocal in expressing their dislike of chemical use in agriculture/horticulture, and there are significant worker health and safety regulations which apply to greenhouse employees. For example, a “72-hour re-entry interval” after the use of strong chemicals, means that workers cannot go back into the greenhouse for 3 days!

Accordingly, US rose growers are supporting the development of IPM programs which make use of a combination of reduced risk pesticides (with short term re-entry intervals) and biological control. Control programs need to focus on the entire complex of rose pests, so that control of one pest does not interfere with biological controls for another. An important component of the program has been the control of Western Flower Thrip, for which an insect killing fungus (Beauveria bassiana) and beneficial nematodes are being used.

Research into the habits of the target pest also assists control. In the case of thrips, it was found that most of the thrips in a rose crop are located at the top of the plant, and much better results were achieved through targeting the sprays in this area, rather than spraying the whole crop to run-off. Similarly, yellow sticky traps, which are routinely used as greenhouse pest indicators, have been studied as predictive models of pest numbers throughout the crop. For example, growers can now count a 1-inch strip of the card and equate this with the number of thrips in the whole greenhouse, and therefore the treatment required. A count of 30 – 40 thrips per card, it was found, equated to only 1 thrip per flower, and this led to imperceptible damage to the bloom.

Regarding the issue of colours for attracting insects, Professor Parrella pointed out that blue sticky traps attracted more WFT than yellow cards, but yellow was better for attracting a general range of insects.

IPM in Greenhouse Vegetables
Biological pest control is well established in European greenhouse vegetable production, and has been the cornerstone of IPM for the last 30 years. Karel Bolckmans, from biological control company Kopperts in Holland, explained that as well as its environmental benefits, IPM adoption has given European growers significant savings in labour and costs.

Mr Bolckmans explained that biological control isn’t total control of pests, but rather effective management of the pests, a concept with which growers need to become familiar. There is, he said, an “acceptable level” of pests in certain crops – for instance a tomato plant can lose a third of its leaves to leaf miner, without the crop being effected.

It is essential, Mr Bolckmans said, for growers to keep records which show insect patterns over a year, and in which parts of the greenhouse pest outbreaks start. Critical to the successful use of biological control agents is the timing and method of release. In Holland, for example, growers may start releasing Encarsia as soon as they plant their tomatoes, to establish a population of beneficials. Later, when whitefly start to appear, Encarsia releases are increased.

According to Mr Bolckmans, biological control without some form of chemical control is almost impossible, but it is possible to use low toxicity sprays, such as spray oils, insecticidal soaps and garlic preparations. Spraying technique and timing are very important, and it’s useful to detect “trouble spots” in the house, since these can often be spot-treated with sprays.

Mr Bolckmans said that introducing IPM to a greenhouse enterprise is quite complex and cannot be done without technical support. Echoing the comments of the other speakers, he said that for growers converting from chemicals alone to IPM, it’s a case of “weening off, not going cold turkey”.

Practical IPM
Les Wardlow, an IPM Consultant in the UK, presented a series of practical steps that growers need to follow to introduce IPM to their enterprise. Firstly, he said, assess any potential limitations to implementation:

– If there has been intensive use of pesticides recently, beneficial insects may fail.
– Establish the availability of biological control agents. Reliable supplies and delivery are an essential.
– A greenhouse inundated with pests is not suitable for starting IPM – clean it up first.
– The grower must be committed to starting IPM and ensure all the staff are also.

There are also some basic requirements for growers starting an IPM program:

– A hand-held lens (10x)
– Some identification training. Growers need to be able to recognise pest damage symptoms, pests and predators. Regular monitoring must become a routine practice.
– Preparation of a program appropriate to the crop, with the assistance of a technical support person.
– Ordering of the appropriate chemicals, sticky traps and bio-controls.

Mr Wardlow urged growers to “get in the sticky trap mode”. He said that only 4 trapping sites are needed for every 1000 – 2000 square metres of a house, but that each site should have one yellow and one blue trap. The blue trap indicates how well thrips are breeding in the house, while the yellow will also catch whiteflies, aphids and leaf miners and give a good idea of what is migrating into the house.

Practical tips for distributing beneficials were also explained by Mr Wardlow. These included:

– Releasing beneficials as soon as they are received;
– Not putting out beneficials within a day of any pesticide use.
– In tall crops, releasing predatory mites from the top of the plant (since they are reluctant to travel up towards sunshine).
– Ensuring the greenhouse temperatures suit the beneficials you are releasing (minimum 18°C, but preferably 21-22°C). In cooler temperatures, the use of emergence boxes may be necessary for some beneficials, such as Encarsia.

Mr Wardlow told the assembled growers that IPM was “the only way to practice pest control in the future”. He said that in the UK, initial doubts on the part of growers about the complication of the technique, are soon dispersed as the programs become a routine. Dispensing with the need for expensive pesticides, which may not work, and the staff to apply them, soon wins favour with growers. At the same time, the greenhouse becomes a more pleasant environment for working, and the quality of the crops improves.

The First Step . . .
For growers wishing to set out down the path to IPM in Australia, Stephen Goodwin provided attendees with a list of relevant Departmental contacts for each State. For further information on this, contact Stephen or Marilyn at NSW Agriculture, Tel: (02) 4348 1900 Fax: (02) 4348 1910.