Skip to Content

In the garden: Safer Insecticides

Find, identify and discuss the plants of all the SANParks

Moderator: lion queen

User avatar
Krokodile
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 265
Joined: Tue Dec 21, 2004 12:13 am
Location: Wondering if I'll ever get back to SA!
Contact:

In the garden: Safer Insecticides

Unread postby Krokodile » Thu Jan 19, 2006 12:35 am

Soapy water also helps keep greenfly away (in England, at least. Do you get greenfly out there??). Probably other nasty plant-eating bugs too.

User avatar
SAHGCA-UCT
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 52
Joined: Thu May 26, 2005 1:16 pm
Location: UCT Zoology Dept. SA Hunters & Game Conservation Association

Unread postby SAHGCA-UCT » Sun Jan 22, 2006 1:54 am

ye we get greenfly here. I call them aphids

Soaps are made from fats and oils, or their fatty acids, by treating them chemically with a strong (corresponding) alkali. Without getting into too much boring chemistry when the alkali is potassium hydroxide, a potassium soap is formed. Potassium soaps are softer than sodium soaps.

So you see where this is going then. Potassium is used in fertilizers to optimise plant growth AND its in soap.
Which is why soapy water may prompt growth.

which brings me onto the next good point soap for aphid control. The soap actually breaks down the waxy part of the aphids epicuticle, which is essential for water retention. When this wax breaks down the aphid dehydrates and dies. Good news for roses. its a contact aphidicide so it only kills those it covers. Sprayings needto be done every other day to be effective as they are baby factories (with a very interesting reproductive cycle known as parthenogenesis and will recover quickly if some are missed.

User avatar
Krokodile
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 265
Joined: Tue Dec 21, 2004 12:13 am
Location: Wondering if I'll ever get back to SA!
Contact:

Unread postby Krokodile » Sun Jan 22, 2006 7:52 am

Very interesting!
Does this only work on aphids though?

User avatar
SAHGCA-UCT
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 52
Joined: Thu May 26, 2005 1:16 pm
Location: UCT Zoology Dept. SA Hunters & Game Conservation Association

Unread postby SAHGCA-UCT » Sun Jan 22, 2006 2:32 pm

Small soft bodied insects will all be prone to rapid dehydration when the waxy epicuticle is removed. Small insects have a large surface area to volume ratio which results in a large area for dessication to occur and most will die. For your roses it also kills some soft scale insects whitefly and thrips. So all in all a relatively 'friendly' insecticide (not to insects). It wont affect twig wilters or hoppers having a go at your plants but at least its a start :)

[edit: its good to be back]

User avatar
bucky
Senior Virtual Ranger
Senior Virtual Ranger
Posts: 1539
Joined: Thu Nov 10, 2005 11:41 pm
Location: Gauties .

Unread postby bucky » Mon Jan 23, 2006 8:22 am

Nice info , I have also read that to make up a good safe insecticide , you mix a teaspoon of washing up detergent , with a teaspoon of bicarbonate of soda , with a litre of water .
It seems to kill aphids , ants and other soft type bugs , but seems to be safe to ladybugs which is a good thing , im sure it will do nothing to birds that eat the dead bugs either.

User avatar
Krokodile
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 265
Joined: Tue Dec 21, 2004 12:13 am
Location: Wondering if I'll ever get back to SA!
Contact:

Unread postby Krokodile » Tue Jan 24, 2006 12:20 am

...probably do them no harm but they may start foaming at the mouth..... :lol:


Return to “Plants”