The details (esp. route maps) provided here is mainly aimed at those of you planing to drive from Mysore to Wayanad. If you are looking for public transport, the bus connectivity options are explained at the end of this page.

Essentially, there are three popular routes from Mysore to Wayanad district. The first one (Route A) is via Hunsur and Nagarhole National Park ; the second (Route B) is via HD Kote and Nagarhole National Park ; the third is via Gundlupet and Bandipur National Park.
So select your route based on to where in Wayanad you are heading to. For example if your destination the northern part of Wayanad (like Kuruva Island, Tholpetty Wildlife Sanctuary, Thirunelly Temple, Mananthavadi etc ) take Route A or Route B. Both the routes cross Nagarhole forest (Rajiv Gandhi National Park) located on the Karnataka Kerala border ( Route A along the northern fringes, while Route B through the south ) and joins at small town called Kattikulam in Wayanad.

Route C altogether takes a different direction. It heads straight south from Mysore to Gundlupet , from there turn westward to Kerala border and finally hit Sulthan Bathery in Wayanad. Take this route to reach Edakkal Caves, Kalpetta, Vythiri, Pookot lake, Wayanad Wildlife Sanctuary and a host of trekking designations located on the southern and eastern region of Wayanad.

If you are on a round trip tour of Wayanad from Mysore, take one of the routes , say Route A/Route B, cover attractions in Wayanad from north to south; start the return journey from Sulthan Bathery to Mysore via Route C. Or you can do the itinerary in the reverse direction. The idea is you'll avoid a lot of crisscross travel in Wayanad (saves you time and fuel), and also will enjoy the suspense of a new route for the onward and return drive.

A quick snapshot of the distances from Mysore to Wayanad for the three routes:
Mysore to Mananthavady via Hunsur, Nagarhole, Kutta (Route A): 140km
Mysore to Mananthavady via HD Kote, Nagarhole, Bavali (Route B): 110km
Mysore to Sulthan Bathery via Gundlupet, Bandipur (Route C): 115km
Please explore more detailed description on each of the routes and photographs the links provided above.

One pint to keep in mind is about the night time travel restriction. This restriction apply to all the three routes. Basically restriction was imposed due to the disturbance and fatality to the wildlife caused by the speeding vehicles.
The Hunsur, Nagarhole, Kutta route is closed for inward traffic from 5pm to 6am. See the alternate route explained at Mysore to Mananthavady page. Also two wheeler traffic is not allowed in this route.

The Bavali route via the forest is closed between 6pm to 6am.
The Gundlupet, Bandipur route is closed from 9pm to 6am.
The Gundlupet, Bandipur route is a major commercial route between the states and there are compulsions to lift the ban on night traffic. As of Dec 2010 the restrictions are still on. Cross check with current sources about the status on this ban.

As promised in the beginning, here are the details of bus connectivity between Mysore and Wayanad. There are quite a few buses operate between Wayanad and Mysore via Gundlupet.
Most of then are heading to southern districts of kerala (Trichur, Ernakulam, Trivandrum etc) . A number of them originate from Bangalore and pass via the Mysore, Gundlupet, Sulthan Bathery, Kalpetta route. Both the KSRTCs (Karnataka and Kerala) operate it from the Mysore KSRTC bus stand. Look for Rajahamsa services (by Karnataka RTC) that is value for money as well more comfortable relative to the 'Super Fast' service by the Kerala RTC, though the later is a bit cheaper.

SH33 near HD Kote
Then there is the AC "Volvo" bus called Airavat service.
You will not find as many fancy services to Mananthavady via HD Kote, and hardly any direct bus via Hunsur. However both HD Kote and Hunsur are well connected by quite a few express services from Mysore.There are a few private buses too to Mananthavady via HD Kote route from the Mysore Private Bus Stand.

Try online booking or booking through one of the franchises for the Karnataka RTC. Generally the seats get over booked, during the weekends.