The Kentucky Pest News, Weekly Newsletter had a great article about pest management in high tunnel situations, mostly biological control, as many chemical control products are not labeled for high tunnel use. Here is the link: https://kentuckypestnews.wordpress.com/2018/11/06/biological-pest-management-in-kentucky-high-tunnel-greenhouse-tomato-production-systems/ .
Addressing mostly arthropod pests, these are good guidelines for disease control too: 
- Sanitation and cultural controls in and around structures, which includes screening and weed control.
- Biweekly Monitoring – visual inspection of plants and sticky cards, keeping written records.
- Recognize pest problems early, before they are at critical levels. Properly identify pests; for some, identifying them to species. County Extension offices can help.
- Release beneficial species (natural enemies and pollinators) – monitor effects – consult with extension specialists. Beneficial species require management.
- Anticipate future problems based on previous crop history (refer to records).