Subject
- Agricultural pests -- Control -- Congresses18
- Fruit -- Diseases and pests -- Control -- Columbia River Valley7
- Pesticides -- Application -- Columbia River Valley7
- Spraying and dusting in agriculture -- Columbia River Valley7
- Apples -- Diseases and pests -- Control -- Columbia River Valley5
- Cherry -- Diseases and pests -- Control -- Columbia River Valley5
- Pear -- Diseases and pests -- Control -- Columbia River Valley5
- Winter wheat -- Fertilizers -- Oregon4
- Conifers -- West (U.S.) -- Ecology3
- Fertilizers -- Oregon3
- Forest ecology -- West (U.S.)3
- Hazelnuts -- Varieties3
- Lake ecology -- West (U.S.)3
- Rural poor -- Oregon3
- Stream ecology -- West (U.S.)3
- Vegetable gardening -- Oregon3
- Aerial photography2
- Alfalfa -- Fertilizers -- Oregon, Western2
- Ecological succession -- Idaho2
- Ecological succession -- Montana2