I'm with Jacalope.........My secret is to plant and use Marigolds. 'Calendula'
They are usually planted as a companion border plant to my veg beds....Their pungent smell helps to keep some crawlies away, but not all ! The tea will keep the other lot away......again- not all, but it certainly helps. The smell usually masks the smell of all those good things you have grown.
First try a bit to see if this does not chase the turtles away.....or they might even enjoy the flavor, who knows?

Making Natural Marigold Insecticide Spray

Take the whole plant.....leaves, stalks, flowers and roots. Shake off the soil in the roots...... Crush, pound or mash the plant.
Put in a pot and add 2 liters boiling water. Stir. Leave to soak for a day or longer. Strain to clean.
Dilute with 50% water.
This you use in a spray bottle and mist spray your effectd plants often till you notice that your problem has been eleviated.
I normally take the spray bottle with me every time I do a garden walk about.
You could add a half teaspoon of dish washing liquid to the spray bottle.... this helps to 'stick' the marigold 'tea' to the plants longer and is great for aphid control.

Target insects: Repels some beetles, tomato horn worm, some leaf cutting and chewing insects, aphids, ants, nematodes......
I have not had a problem with whitefly-yet! so I don't know if it's the tea or the neighbors garden is tastier than mine.
And for those folk you have chickens...........they say that marigold petals mixed with your chicken feed adds intensity to the color of the egg yolks.
Hope this helps a bit.
Heres a great link
http://www.kari.org/fileadmin/Publicati ... 020506.pdf