Yes I get this problem just about every gardening year. If your problem (and very well maybe) is the same as mine you probably have hornworms visiting your garden patch.
They can do a lot of damage in a short period of time if not controlled. One of the best web sites I discovered that helped me with this problem is garden-planting-tips.com they have lots of information on gardening. One of my fav sites to visit.

Here is the link if your interested to take a look.

Oh yes! If you go to their web site I believe they have a link called garden pest to read about hornworms.

Hope this helps.

Here is a link that might be useful: garden planting tips

You may have 'tobacco hornworms' (Manduca quinquemaculata - a sphingid moth) or 'tomato loopers' (Chrysodeixis chalcites - a noctuid moth). To the amateur, both are green, but have different sizes, markings and body features. Bacillus thuringeiensis sprays are safe and effective. New Spinosad treatments (e.g. 'Conserve SC', 'Entrust', ' Naturalyte', 'Monterey Garden Insect Spray' and 'Borer, Bagworm, Tent Caterpillar & Leafminer Spray') are probably effective and very safe, but you'd need to check the label. There are also registered chemical treatments, such as elemental sulphur (400 g/kg) + Cu as oxychloride (40 g/kg) + carbaryl (20 g/kg), or sprays of cyfluthrin, or pyrethrins, or fenthion. Just follow the label instructions for your Country, State or area. Then there are some generalist fungal control agents (e.g. Metarhizium spp. and Beauveria bassiana), but I'm not sure if they are commercially available to gardeners. Baculovirus agents against loopers are under experimental investigation. Good luck!