So you have an avocado tree and you’re wondering what those circular, brownish-orange patches on the leaves are? Papayas from your tree have sunken spots on them?

The avocado tree could be suffering from algal leaf spots. The papaya tree could be suffering from anthracnose, a group of diseases caused by different fungi that afflict the foliage of many fruit species, including avocado, mango and banana, and are most severe in Hawaii’s high-rainfall locations.

With Landscape MD, a new app developed by the University of Hawaii at Manoa’s College of Tropical Agriculture and Human Resources, you can now diagnose what’s ailing your tree or plant and get some advice on what to do. Links to publications with more in-depth information are provided. The app is available for free on Apple iTunes.

Search by plant name, symptom or part afflicted, whether it’s a leaf, a stem, a flower, fruit or roots. If your avocados are suffering from algal leaf spots, for instance, you can help by removing the spotted leaves, pruning affected branches and keeping the tree well fertilized.

Scot Nelson, a plant disease specialist, is one of the creators of the app, along with Arnold Hara, a retired ornamental entomologist from the university, and Ruth Niino-Duponte, a researcher.

Nelson said the seeds for the idea were planted about five years ago and it evolved into an app that included information on both plant and insect diseases, accompanied by color photos.

“These are diseases people have probably seen before, but don’t know what they are,” said Nelson. “The beauty of having an app like this is one can create more materials and update it at iTunes at no cost.”

Nelson, also the author of two other UH-published apps, Pic-a-Papaya and Leaf Doctor, hopes to reach a larger audience with the Landscape MD app. The Leaf Doctor, launched in May 2014, is geared toward plant scientists looking for a quick, quantitative assessment of plant diseases on leaves while out in the field and submitting a photo. The Pic-a-Papaya app, which was also launched in May 2014, is designed for citizen scientists to help survey and map out the occurrence of the ring spot virus in Hawaii.

The Landscape MD app is designed for home gardeners and landscapers alike as a quick diagnostic tool for common plant diseases and insect pests, according to Nelson, who also provides training for the college’s master gardeners — volunteers who answer the public’s questions about horticulture.

The apps can help the public look up and answer some of these questions independently and reach more people, said Nelson.

“With the apps and Internet, we can really reach people who are looking for information,” he said.