The Plantsman Nursery has extensive experience of both chemical and biological pest control. We are keen to encourage all gardeners to learn about and try the modern generation of biological pest control which under the correct circumstances are extremely effective. However for a small commercial nursery such as ours where hundreds of different species of different plants, all at different stages of growth and all with different habits are in very close proximity and with enormous quantities of growth we have found biological control unsuitable and not cost effective. Our Plants must be dispatched in a pest free and undamaged condition; we have found that the collateral damage that accompanies biological control is unacceptable to our customers and damaging for our reputation. We spent a lot of time and finance trialling Encarsia formosa  and Phytoseiulus persimilis for the control of two major glasshouse pests, White Fly and Red Spider mite respectively. With different microclimates in different greenhouses, polytunnels and net tunnels we found that the results were often very variable and the pest population was controlled only after peaking at some point by which time damage had occurred and we found that a low level infestation was present all the time with rising and falling pest and predator populations. By contrast we found that by extremely careful integrated chemical pest and disease control we could eradicate the problematic pest or disease and prevent any damage to the stock. The main pests in commercial tropical horticultural production being Red Spider Mite and Two Spotted Mite and Mealybug and Whitefly and last but by no means least Western Flower Thrip. In the production of hardy containerised stock the worst problem is Vine Weevil. Products now exist that are from a new generation of chemicals and Vine Weevil can be controlled by the use of Imicloroprid under the band name of Intercept for commercial growers and Vinil containing Fiprinil for public & commercial usage albeit in different formulations. These products can be used not only to control Vine Weevil but all pests that feed on the sap, roots and leaves of the plant. They are systemic and are absorbed into the plant via the roots after the soil has been treated with a liquid drench or as granules incorporated into the compost prior to potting up. The granular protection seems to last in our stock for several years and is infinitely more effective than Suscon Green which was an organophosphate based granular product that at one point about 5 years ago was the only commercial control available to the commercial grower. Fiprinil in the UK & Europe is also the active ingredient in the veterinary products FrontLine used for protecting pets from fleas & ticks. In addition to Imicloroprid being used for vine weevil it also has ‘off label’ use to control other pests and has good knock down effect when used in a spray formulation. Great care must be taken to avoid pest tolerance developing and we are informed that one treatment each season is the maximum dosage and three consecutive treatment per full year. We have observed that overdosing has no benefit in terms of having a proportionally stronger effect and in fact can cause plants to reduce growth and fail to flower that year.
In addition to using these new ‘smart’ chemicals we still rely on good old fashioned poisons such as Malathion, Nicotine as a pure liquid or as impregnated shreds which are ignited for glasshouse fumigation. It is relatively easy for the amateur gardener to make his own Nicotine mixture by soaking either a pouch of fresh tobacco or 100 plus cigarette ends in one litre of water and leaving it for several days. The resulting mixture should be strained and then used as a 10% mixture to 90% water to be then sprayed in a hand sprayer. Because the strength of this brew is variable it should be tested at the low doses and the results observed in order to find the correct dose. The concentrate can be kept for later use in the coming months I am advised by friends that one drop of washing up liquid added to the nicotine mixture is particularly effective if you have a woolly aphid or mealy bug problem and acts as a wetting agent by enabling the contact of the nicotine spray to the body of the pest. The concentrate is strong & smells so great care should be taken when handling the mixture as you would with any chemical.
Sadly the pesticide debate seems to me to characterise modern Britain whereby the issues have become political and the dreaded Health & Safety Regulations have caused the withdrawal of all retail products that contain any chemical that are not ‘safe’ and a startling quantity of commercial formulations now leave commercial UK growers with no effective product and at a positive disadvantage to other EU countries and growers where legislation is far less draconian. It has always seemed absurd to me that any effective chemical pesticide could be safe, after all they must be poisonous enough to fell the pest and would if swallowed by humans cause injury to health. It seems however that like many products within the retail sector anything strong enough to work is reformulated to such a benign strength that they are ineffective. Even organic chemicals such as Nicotine and Derris and Pyrethrum and Sulphur are no longer available in the UK. I am almost sure that Soft Soap is still available & is sold under the trade name of Savona which is a good general purpose insecticide and also has some preventative action. It can also be used as a carrier for other chemicals like nicotine and I believe NicoSoap is still available to commercial growers.
Petroleum spraying oil is also a very effective and especially against scale insect and mealy bug. Old recipes from the post war era advised 3 pints of petroleum oil or emulsion to 5 gallons of water for a winter and early spring wash/spray and 6-8 fluid oz of Petroleum emulsion to 5 gallons for late spring & summer use. I have used the emulsion and found it very effective. Care should be taken with all of these products to avoid spraying in strong sunlight which can cause some discolouration especially of soft tissue.
My advice is to use whatever products are still available in the UK garden centre and to stock up on what used to be available in the UK in mainland Europe next time you visit. Sadly the idea of a ‘flat playing field’ is not a reality in Europe as I have discovered in my recent relocation to France and though I am sure that other EU countries have a schedule for withdrawing many pesticides; my local French garden centre has a formidable arsenal of products available that are no longer available in the UK but which the French, Italian, Belgium and Spanish & Portuguese gardener has at his disposal.

Disclaimer
The views expressed in this website are not intended for any other purpose other than as a personal opinion. The Plantsman Nursery and author of this article accept no responsibility for any damage or personal injury arising from of the interpretation of the views expressed herein and in no way encourage the contravention of any legal requirements or laws pertaining to COSHH(Care Of Substances Hazardous to Health) or other Health & Safety rules & regulations pertaining to the use of pesticides or any other harmful substances contained in this article.
The Nursery advises all products referred to above to be used strictly in accordance with the manufacturer’s instructions.