Ticks are small insects that latch on to hosts such as People and other animals. In particular, Dogs are known for easily picking up ticks as they run through tall grasses. They can be battled using similar methods as to fighting Mosquitoes, such as wearing long Clothing and using insect repellant. Though the town proper shouldn't usually have ticks in it, many of the open Fields within, and especially outside of Davis, are home to ticks (e.g., along Putah Creek, Ditches, etc).
In California, all ticks should be assumed carriers of lyme disease. The California Lyme Disease Association has several brochures available to educate the public. Key: tick nymphs are most hazardous to your health due to their size and feeding patterns. Take all proper precautions when venturing into tick territory. For example, use tick repellant, tuck pant cuffs into your socks, wear light-colored clothes, keep your arms covered, and wear a hat. In heavily infested areas, applying permethrin is not a bad idea, but keep away from cats.