Because of the continuing above average heat in Tucson this year, insects have been very active. Although the higher temperatures lead to warmer pool temperatures that many of us enjoy, they also lead to increased populations of many insects, including the aforementioned pests. Insects are cold-blooded. This means that their body temperatures are regulated by their surrounding environment. In cold weather the internal temperature of insects drop which causes them to be less active. But in hotter temperatures, they become more active. Not only that, but larvae grow at faster rates and reproduction cycles also increase in speed. The hot conditions also drive many insects indoors to seek cooler temperatures, so they become more noticeable in general.
This is why during the summer months in Tucson, your tenant may be noticing more insects and contacting you, the landlord, about exterminating them. In our lease, unless it is an infestation of some sort (bees, termites, etc.), the tenant is responsible for any spraying for insects, as opposed to the landlord. That being said, some landlords choose to pay for an extermination service for the tenant. Whichever way you decide to handle it, you simply need to make sure that you have communicated it to the tenant. The best way to do that is at the beginning of the landlord/tenant relationship through the lease.