Diagnostic Horticultural Resources

Abotic - Non-living agents such as weather extremes, poor soil conditions, and drought.

Abiotic Problems – U of MN;

Hortsense - Washington State U., choose Common Cultural Problems in top left column.
Drought
Drought Information Center - PA Dep. of Environmental Protection.
How to garden in drought conditions - Franklin County Extension, PSU.

Insects

Entomology Fact Sheets – PSU
Purdue Plant and Pest Diagnostic Laboratory
Plant and Pest Digital Library - Purdue

Lichen

Lichens - UMD HGIC Plant Diagnostic Website.

Ten things you should know about lichens - OSU Fact Sheet.

Plants

Home and Garden Information Center's Plant Diagnostic Website (HGIC) -
U. of MD, photographic keys, photos of beneficial insects.

Hortsense – Washington State Universtiy, Search Engine

Needlecasts – PSU Plant Disease Fact Sheet

Plant and Pest Digital Library - Purdue

Plant Disease Diagnostics – U of MN

Plant Disease Fact Sheets - OSU; photo ID, ornamentals, insects/diseases, turf, fruit/veg.

Plant Disease Fact Sheets - U. of IL Horticulture; trees, turf, vegetables.

Plant Pathology Fact Sheets - PSU; common diseases of plants frequently grown in greenhouses, interiorscapes, and in outdoor landscapes and nurseries in the northeastern U.S.

Purdue Plant and Pest Diagnostic Laboratory

Solution Source - PSU Colege of Ag.; Compost; Flowers, groundcovers, vines; Holiday plants/gifts; Horticultural basics; House plants; Lawns; Pesticide Safety; Specialty Gardens; Trees/shrubs.

Vegetable and Herb Disease Info Notes - NCSU

Weed ID 

Web resources - Texas A&M; Grass Weed ID Guide - VA Tech. 

Horticultural Categories Link