Page 24 - Simply Veg Issue 1 2016

I am going to update a series
of articles that I wrote on pests and diseases about twelve years ago in
the bulletin before Simply Vegetables was produced, but I thought it would be useful to put this article in rst as an introduction. The articles written are mainly intended
for the less experienced grower but even amongst experienced growers no one knows everything so I hope they will learn a bit as well.
Pesticides
Pesticides is a term that covers all chemicals that control the various pests, diseases, weeds, and other living animals that attack plants, see the table for the range of pesticides.
Fungicide Acaricides Nematacides
These can be
classi ed in several
ways; rstly they
can be concentrates
(powders or liquids)
these have to be
mixed with water to
dilute them before
use. Another type
which is commonly
sold in garden centres
are the ready –to –
use sprays which are applied directly to the plant or pest. Other types of pesticides are pellets or dusts. They can either be contact, stomach poison or systemic in action and they can be organic or inorganic.
Concentrates
These are sold in small bottles to be diluted and sprayed onto the plants. The dilution rate
Fungal diseases Spiders and mites Nematodes
is stated on the label and must be followed exactly. Adding a
bit more to be “on
the safe side” is not only wasteful but can harm the plants and is not good for the environment. They are relatively cheap but
of course you have to have a sprayer to
An Introduction to
Pesticides and Fungicides
By Derek Brooks F.N.V.S. Worsley Manchester
They can either be contact, stomach poison or systemic in action and they can be organic or inorganic.
apply them.
Ready to use sprays
Chemically these are similar to concentrates but are sold diluted ready to use in a spray bottle with a pump action. They work out more expensive than concentrates but are useful if you only have a small infestation on a few plants. If you only need a small quantity it is not worth diluting concentrate because you may have to mix more than you need and they can be used straight away.
Pellets
Principally used against slugs and snails. They are baited to attract the pests and contain a poison. Their effectiveness decreases after rain so they need replacing when this happens. There is an organic version if this is what you prefer.
Insecticides that are sprayed onto the plants can either be contact, stomach or systemic in action.
Contact insecticides
These can only kill the pests that they come into direct contact with. The plants therefore, need spraying thoroughly, paying particular attention to the undersides of the leaves where many pests congregate. If the pest is not hit it will not be killed.
Stomach insecticides
These kill the pests only if they have eaten part of a leaf which has been coated with the insecticide, it poisons the pest.
Systemic insecticides
These are actually absorbed into the plants and travel in the sap to all parts of the plant. They are particularly useful for sap sucking insects such as aphids, thrips and white y. In contrast to contact insecticides which are only effective for a short period, these remain in the plants and are effective for several days.
FUNGICIDES
Much of what I have said about insecticides applies to fungicides as well so I am not going to repeat the same things again.
There are concentrates and ready-to-use sprays and they can be contact or systemic in action, as for insecticides.
Type of pesticide
What it controls
Insecticide
Insects and some mites
Herbicide
Weeds and plants
Mollusicides
Slugs and snails
24 simplyvegetables