Chemicals – Good and Bad

Some thoughts on the benefits and pitfalls of using chemicals in the garden plot. Plus a bit of advice.

I was a bit worried about my tomato crop this year, particularly in the polytunnel. Despite the soil in the border being enriched with manure and compost they were looking peaky.

Nutrient Deficency Chart courtesy S-Chelate web site

It’s not easy to be sure what the problem is. Possibly a manganese deficiency or magnesium. Maybe iron. Possibly, although I doubt it, simple nitrogen due to the additions made to the soil at the start of the year. The problem is that all those deficiencies present in pretty much the same way.

Usually a compost made from varied materials will provide the micronutrients that are needed but in a situation like this where I need to do something quickly an artificial chemical fertiliser is the best answer. A vitamin pill for the plants.

My booster tomato feed that I made up myself with added s-chelate trace elements was applied about 10 days ago and they’ve responded well. They’re looking greener and healthier already. I’ve given them another feed this weekend just to reinforce the benefits.

Although I like to use natural, organic feeds where practical, that isn’t always the best answer. Sometimes chemicals – by which I mean artificial fertilisers – are the best way to ensure a decent crop.

It’s important to be thoughtful on fertiliser use. Over supply won’t give any additional benefits and is wasteful at best. At worst it is counter-productive causing sappy growth that pests love and even killing the plant by damaging the roots.

Pest Control

Moving on to pests, I’ve been getting a lot of correspondence about aphids, blackfly and whitefly. They seem particularly bad this year for some reason.

The first rule is simple, “Don’t Panic!”. Plants tend to cope with a certain amount of pest pressure. Given time the predators numbers will increase and naturally gobble up most of the problem for you.

If you do have to take action, do the minimum you can. For example, blackfly on the growing tip of broad beans is often a problem. A hosing with a jet of water to wash them off is often enough. The next step is to just snip the juicy, blackfly-attracting tips off.

There are sprays that are organic and safe like SB Plant Invigorator that you can use on crops without fear of residues in the food. They work by smothering the pests, blocking their breathing. SB Plant Invigorator also contains a plant stimulatingt foliar feed promoting strong healthy growth that resists the pests better.

Being truthful, organic sprays take longer to apply as you need to be more thorough. They’re often not as effective as an insecticide chemical based spray. But, and this is what you need to really think about, are you comfortable with ingesting a tiny amount of a bug spray when you eat your produce?

With insecticide sprays check they’re suitable for edible crops. Some bug killers may well be effective and environmentally friendly – not killing beneficial species – but if the powers that be have not approved them for use on crops you could be poisoning yourself after harvest.

Read the directions. Don’t ever think ‘I’ll use a bit extra in the mix’ These chemical sprays are effective and safe only when used as directed. That goes for things like slug pellets as well.

Posted in Allotment Garden Diary
10 comments on “Chemicals – Good and Bad
  1. Ian says:

    As an ex agronomist with a chemical company, my view is possibly slightly biased. I wholeheartedly object to not be able to chemicals in the garden that would 1. Boost production and 2 improve quality.
    A typical example of this is a blight spray for potatoes.
    Treatments for root fly, good slug control etc etc.

    We are encouraged to grow our own veg and fruit and yet they ban chemicals which would make it more productive. Some, but not all chemicals are allowed for agricultural use so where is the harm in making smaller packages for garden use?

    • John Harrison says:

      The theory is that the farmers are qualified to use these chemicals but us gardeners are too stupid to read the instructions. It annoys me too – I’m not a great lover of pesticides or herbicides but there are times when a spray can save the day.

  2. Martin Lawson says:

    Our local Parish Council are about to take the decision as to whether to use chemicals or not out of the tenants hands by banning their use completely.

    They intend to do this by changing the tenancy agreement for the next renewal.

    No consultation with the tenants has taken place.

    • Bruce Robinson says:

      I am on a self managed allotment committee. If I were you I would email the NSALG – the National Allotments Society for advice. As landlords they have a responsibility to their tenants Health, Safety and Welfare. How do you know they intend to change the tenancy agreement?

    • John Harrison says:

      Great to know that they know more than DEFRA who approve chemicals for use. We can get rid of their expensive scientists and get the Parish council in to handle things. Do they do brain surgery?

  3. Simon Newcombe says:

    Why are so many Parish Councils obsessed with banning chemicals. We are not able to use anything that will kill a weed as it is ” A weed killer” Has anyone got any reasonable answers/solutions so I am not on my hands and knees digging weeds out whilst I should be tending my crops.

    • John Harrison says:

      I’m looking at doing more planting through membrane as I’m having trouble coping with weeds. The action of hoeing hits my sciatica. It saves a lot of effort with the squashes and I’m intending to use the system for cabbages, corn, swedes and maybe onions.
      See Planting Pumpkins & Squash

    • Sandy says:

      Hi I have been using baking soda for a few years now with some very good results on spider mites and other insects also mildew, I use 1table spoon baking soda, 1 table spoon vegetable oil and a few drops dish washing liquid (organic) use 2 table spoons of oil for blight.

  4. Jannie says:

    I live in central France and for the last 2 years we’ve had almsot permanent hosepipe bans in our area (in spite of all the rain we’ve had this year). I’ve been using recycled bathwater to water the polytunnel and so far, since using this system, haven’t had any bad bug problems in there. It doesn’t seem to affect the good bugs as I have a “resident” carpenter bee and this year the ladybirds have moved back in. I use 4 waterings of bathwater then one of spring water. Last year the spring ran dry so I was forced to use tap water instead. I also grow Nasturtiums and Pot Marigolds in there but they haven’t been inundated with black fly although the outside ones have. Just wish that watering system worked on the weeds.

  5. Susan says:

    Although a retired horticulturist I’m not a fan of chemicals and don’t use any. I have a slug/snail problem, (who doesn’t) Tried many organic methods but still munching away. As I keep chickens and use diatomaceous powder food grade which I add to their dust baths and feed. On reading more about the product I found it had some success with slugs and earwigs (my dahlias grr) so gave it a go on my beds and borders and had good results even after the powder was rained on after sprinkling it on the leaves of my salvias no more slug damage and it does remain on the leaves after rain, I wait until the plant gets more established then wash any residue off. If you do try it try Multi-Mite on eBay they guarantee a pure safe food grade product reasonably priced and also send a info leaflet. Have to say the old fashioned method of the upturned plant pot on a stick with straw, hay or dried bracken in works for me,early evening just empty out the contents of the pot and dispose of the escaping earwigs.

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