Garden Q&A: Don’t get rusty — inspecting plants for fungus now will help prevent spread later

Q: I heard rust fungus can infect junipers but that they aren’t worth spraying to treat. Is there anything else I can do to reduce the fungal spread from them to my other trees?

A: If you see and can reach fungal galls on the branches, clip them off. Some rust fungi, though not all, create a gall on their juniper hosts. Plant galls are tumor-like in that they’re clusters of malformed tissue, often in response to a pest or an infection. When the weather starts to be consistently mild in spring and we receive enough rainfall, the galls where the fungus is spending the winter will begin to exude their spores.

A rust gall on juniper with spore “horns” just starting to emerge. As soon as it rains, the “horns” turn gelatinous and bright orange, which will be too late to prevent spread.

These rust spores blow on the wind or wind-driven rain to vulnerable host plants like various members of the rose family. In our gardens, this includes apples, pears, hawthorn, serviceberry, quince and crabapple. Fungus spores are extremely tiny, so how will you know what to look for? If the gall is producing orange goo, you’re missing the window since spores are already being dispersed. Ideally, remove all visible galls before this point, while they’re still hard and dry. Now is an excellent time to inspect junipers on your property for galls. Trim them off with hand pruners and toss them in the trash, but don’t compost.

This is not a foolproof method for eliminating the risk of rust infection on other plants this year, but it certainly could help reduce the disease pressure. Fortunately, infections like cedar-apple rust, while an aesthetic nuisance from time to time, generally don’t cause serious damage to all hosts, though they can be more serious for some, like apple.


Q: Is this warming trend and the earlier emergence of bugs going to doom my vegetable gardening efforts?

A: Not necessarily. While some insects might respond to warming temperatures and emerge from winter dormancy earlier, others might be more ruled by the length of the day. Remember, it’s not just the pest insects that climate change may impact; beneficial insects that prey on them might also emerge early and remain in sync with their hosts. Plus, non-insect predators like birds, which are less reliant on weather to be active, can also help us manage garden pests, especially if we support them with high quality habitat.

Even when early pest emergence poses a problem, there can be workarounds. For one, if the window for planting a certain crop is long enough (for summer vegetables, they usually are), put in certain vegetables a bit later. This allows more of a pest population which emerged early to disperse or be eaten by predators by the time the crop goes in the ground. For example, cucurbits (cucumber, squash/zucchini) may evade most of the squash bug and cucumber beetle invasions if planted a couple or so weeks late. Sure, the trade-off might be a slightly reduced harvest overall, but if a gardener is less overrun with zucchini, that’s not too bad, right?

Zucchini may evade most of the squash bug and cucumber beetle invasions if planted a couple or so weeks late.

Another tactic to avoid insect outbreaks is to physically exclude as many pests as you can by sheltering veggies under floating row cover or insect mesh netting. In most cases you’ll need to lift it for pollinator access during bloom, but before that point you can prevent most insects from accessing the crop. Row covers can help prevent cold injury and promote more rapid growth in spring. Bear in mind that planting too early means the soil is still cold and the risk of a hard freeze is even greater, so don’t be too eager to plant with just any passing warm spell.

University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at Click “Ask Extension” to send questions and photos.