If you have been growing rosemary indoors in pots or outdoors (bush, hedges), your plant might become susceptible to pests and diseases for various reasons. In this post, you will learn about rosemary pests and diseases and problems, how to prevent them and treat them successfully indoors or outdoors.
Common rosemary pests and diseases that affect rosemary include aphids, spittlebug, thrips, mealybugs, scale, root rot. Other diseases affecting rosemary include botrytis blight, downy mildew and others.
What is rosemary?
Rosemary is an upright, hairy evergreen shrub cultivated for its herb-like leaves. The plant makes groups of 5–10 blue, purple, or pink flowers and thin band fruit on small lateral roots. Rosemary species can grow up to 2
meters (6.6 feet) tall and last for many years (up to 30 years if conditions are optimal).
The rosemary plant is typically upright, with branched woody stems and leaf tufts. Chard, rosemary, and tarragon are popular spices in kitchens, but they are aromatic leaves and therefore classify as herbs.
The leaves are alternate and bladelike, with a glossy shade of green. Since spices are produced from smashed portions of plants exceptionally high in natural products, they have a better taste than herbs.
Natural pest control for rosemary
- Organic insecticidal soap like this. Insecticidal soaps contain fatty acids that paralyze and kill pests with soft bodies. Those include spider mites, mealybugs, whiteflies, aphids, thrips, powdery mildew and more.
- Neem oil (preferably organic) like this. This oil’s main working component is azadirachtin, and is a natural repellent and pest control. With neem oil that doesn’t leave a harsh residue, you can get rid of many pests, including beetles, flies and more.
- Horticultural oils like this, mainly containing mineral oil and helping get rid of many adult pests and their eggs.
Avoid using toxic pesticides and insecticides to treat pests and diseases in rosemary, especially for pests that don’t affect plant health in a serious way. Steer clear of toxic pyrethrum, rotenone, ryania, pyrethrin, sabadilla.
What is more, copper based fungicides should only be used in extreme cases, on plants that you don’t plan to consume. The negatives are that these fungicides also kill good organisms and affect plant’s growth if used many times.
Common rosemary pests and diseases
Pests and diseases that lead to a rosemary plant’s death would often cause it by infesting an already weak or damaged plant. Sadly, despite our best attempts, most rosemary plants grown indoors are in a weaker position.
The firmer you are with yourself in making sure your rosemary plant is adequately watered and receives sufficient light, the less likely are pests to attack the plant.
Even though rosemary is a pest and disease-resistant plant, some insects can still land on it to survive and reproduce. However, the majority of these, on the other hand, would avoid rosemary.
You should always try to get rid of pests and diseases on your rosemary naturally. Using chemicals increases toxin levels in your garden, and should be avoided if you grow rosemary for consumption.
Aphids in rosemary
They are tiny insects that appear on plants as small black or pale spots. Also, aphids spread quickly and pose a severe threat to a weakened rosemary plant or bush. Aphids bugs are a concern because they suck the nutrients that rosemary produces for itself, depriving it of nutrition.
The easiest way to get rid of aphids on rosemary naturally is to spray it every other day with a dependable pressure washer. What is more, you can use organic insecticidal soap like this one to get rid of them naturally.
Thrips in rosemary
Thrips are also pests that can affect rosemary. They look like small black dots and cause leaf stippling. As a result of thrips, the tissues around certain feeding spots die after the plant cells are drained, leaving silvery patches on the leaves.
Scraping and rasping at tender leaf surfaces causes damage to the plant, which generally results in the plant’s death. That is why thrips are considered a pest.
Spittlebug in rosemary
On rosemary trees, spittlebugs leave small wads of saliva-like foam. These tiny brown insects feed on the sap from the roots and are surrounded by white, foamy excrement.
If you notice it, flush away the bubbly waste and any insects hiding inside with a quick stream of water.
Whiteflies in rosemary
Whiteflies are winged insects with a soft body that is similar to aphids and mealybugs. Despite their name, whiteflies are not flies, although they have wings and can fly. They also secrete sticky substance, which also leads to black mold to appear in no time on rosemary plants.
Wash whiteflies off crops with a quick stream of water and encourage predators to get rid of them naturally, just as you would with aphids.
You can also use insecticidal soap, neem or horticultural oil. Or, you can try hanging non-toxic flypaper like this near your plants to catch them.
Mealybugs in rosemary
Mealybugs are tiny insects that feed on the sap of rosemary plants. Males are thinner and lack wings, while females are larger and have wings.
Mealybugs can be a nuisance, especially if you’re cultivating rosemary indoors. Neem oil, which is also a powerful insecticide, can help to get rid of them.
Spider mites in rosemary
Spider mites are also pests because they suck chlorophyll, water, and nutrients from leaves. These bugs are about the length of a grain of pepper and look like tiny spiders.
They can be of various colors, including red, black, brown, and yellow. Spider mites suck on the plant juices, scraping chlorophyll and adding toxins, resulting in white spots on the leaves.
Webbing is often noticeable on the vine. They make vegetation yellow, making it dry and cause stippling. They reproduce quickly and thrive in arid environments. You can use insecticidal soap or horticultural oil to get rid of them. Mist your plant with cool water to remove spider mites as well.
Scale in rosemary
Scale insects have a waxy outer shell, and suck the juices from plant stems and leaves, similarly to mealybugs. They weaken plants, making them more vulnerable to pests, pathogens, and other environmental factors.
Scale insects are brown and bumpy and leave sticky sap residue. If they’re crawling (moving insects), you can use a cotton swab soaked in rubbing alcohol to control them, or you can scrape them off with your fingers.
Affected sections of the rosemary plant should be pruned. You can also treat affected parts with horticultural oil during the growth season
Root rot in rosemary
Root rot disease can ruin your rosemary plant unless treated. Overwatering or a fungal infection are the two most common causes of root rot in rosemary plants.
Affected and rotting roots spread the rot to healthy ones, potentially destroying the entire plant. Root rot is caused by a hibernating fungus in the soil that takes control when the plant receives too much water.
If your rosemary plant starts to wilt or turn yellow without a visible reason, you may have root rot. Examine the plant’s roots and base right away. Slow growth is also an indication of a fungal disease in rosemary.
Roots that have been infected turn black and are smooth to the touch. Water your rosemary plant only when the topsoil dries, and please ensure it’s in a well-draining place/pot to prevent standing water.
Rosemary leaves turning yellow and falling off
When the bottom leaves turn yellow in the rosemary and the plant’s growth is slowing, it’s a sign that it requires to be fertilized or that it’s rootbound.
If the roots are circled around inside the container (rootbound), clip them and repot the plant.
Botrytis blight (gray mold) in rosemary
Botrytis blight is a viral infection that starts with older leaves’ decaying around the rosemary plant’s middle part. It thrives in high humidity, cloudy weather, and lack of air exchange. Unfortunately, it can quickly spread to healthy parts of the rosemary plant. It is an airborne and waterborne disease.
The fungus can manifest in grayish mold, brown areas or water spots on the plant’s stems that are affected. Botrytis blight causes brown or grey fuzz to disperse over the rosemary plant’s rotting sections when the concentration is incredibly high.
When the fungus is spread, it releases spores that aid in the progression of the virus. Sadly, Botrytis blight will destroy a rosemary plant if left untreated.
Place plant containers further apart for better air circulation to avoid gray mold disease.
It can begin with unusual yellowish bald patches on the leaves or water-soaked dots on the stems. When touched, the fungus turns fuzzy grey and releases a cloud of spores.
To prevent the spread of the disease, keep any rubbish away from the plants. Pea gravel may be used as a mulch to help reduce humidity among plants. You will need to prune all the affected areas and disinfect shears to prevent spreading the disease.
Damping off in rosemary
When growing plants from seed, this is one of the most common problems. The seedlings seem stable at first but then wilt and die for no apparent reason.
Overwatering is caused by a fungus active when soils and average temperatures are above 68 degrees F, and with lots of moisture available.
It usually means the soil is too wet or has a lot of nitrogen fertilizer in it. To prevent overwatering seedlings, please follow the general guidelines:
- Keep seedlings moist but not overwatered. Stop over-fertilizing your seeds.
- Thin out seedlings to avoid crowding.
- Ensure proper air circulation.
- If planting in containers, wash containers with soapy water and rinse in a ten percent diluted bleach after usage, before re-using the again.
- Provide seedlings with bright light
Downy mildew in rosemary
Downy mildew is a serious disease and will ultimately kill a rosemary plant in just a few days or weeks. Water stimulates and spreads downy mildew, which only appears on the underside of the leaves. Mold can be purple, white or gray in color.
Downy mildew is most commonly connected with greenhouses, but it may also occur in outdoor and indoor plant pots. Many varieties of flowers,
including snapdragon, geranium, alyssum, pansy, rose, rosemary, viola, and other ornamentals, serve as hosts. It is an airborne disease of plants growing in wet soil.
Mix one gallon of water with one tablespoon of baking soda and one-half teaspoon liquid, non-detergent soap, and spray the mixture generously on the plants. Prevention aims to reduce the amount of moisture needed to spread this mildew. Make sure to provide proper air circulation (especially if growing rosemary indoors).
All fungal prevention begins with watering from the root, regulating moisture, and allowing room and aeration to avoid moisture accumulation.
Fungicides for prevention are also an option. Make sure that the soil has enough drainage.
Powdery Mildew in rosemary
Have you noticed white powder on your rosemary flowers? Powdery mildew on rosemary, a widespread plant ailment, is responsible for the white powder on the leaves. It is caused by a wide range of closely associated fungi. It is one of the most common issues with rosemary plants, as well as all indoor plants.
The rosemary plant will not be killed by powdery mildew, but it can weaken the plant slightly. However, avoid using stronger chemicals to kill powdery mildew, as it’s not worth it.
Powdery mildew can be removed in part by gently rubbing the leaves of your rosemary plant. If left untreated, it will trigger leaf drop in your rosemary. Powdery mildew on rosemary plants will deplete the nutrients required for growth.
A fungicide, such as neem oil, may be sprayed on the rosemary to destroy the fungus. Before using a fungicide, you can try spraying it with water every few days to get rid of the mildew.
Root rot and crown rot in rosemary
A variety of infections can cause root and stem rots in rosemary. Yellowing of the leaves, drying of the leaves and leaf tips, and browning and death of whole branches are all signs of rot. IF your plant is infected, unfortunately, you need to get rid of it to prevent spread to other plants.
To avoid rot, especially in the roots, make sure the plant is not sitting in water constantly. For potted plants, remove the soil and repot using fresh potting mix. Add organic material, for example compost to the soil to allow better air exchange.
What pests does rosemary repel?
Herbs like mint, sage, thyme, basil, parsley, and rosemary are excellent repellents because slugs and snails don’t like strong scents. Planting basil, rosemary or other aromatic herbs near every other plant in a garden will protect them from bug infestations.
Snails are pests that thrive in humid, temperate regions, with their strong calcium shell protects them. Snails, like slugs, hibernate in the soil during the winter and appear in the spring to lay thousands of eggs near the soil surface.
Young snails begin feeding right away, and they are most active at night and in rainy conditions. Plants with strong-smelling foliage, such as rosemary, marigolds, and lavender, seem to be avoided by them.
Snails can consume just about any plant, but they prefer the tender vegetation of young plants and leafy varieties like lettuce.
Lost seedlings or large, randomly oriented holes on leaves or fruits indicate their presence. Snails and slugs can even leave a trail of shiny slime on the surface of the plant. Snails avoid plants with glossy, waxy, or hairy leaves in particular.
How to protect your rosemary from snails and slugs?
Remove them by hand
Snails can be removed from your rosemary plant by hand, without the use of any chemicals or special techniques. However, it takes time, may not be a complete solution, and requires being comfortable handling snails.
If you have the practice and experience to use this approach, you will need to check your landscape for snails daily and, if necessary, remove them.
When you spot one or more, remove them from your plants and relocate them at least 20 feet away (around 6 meters) from the plants you don’t want them all to consume.
Water your garden in the morning
Snails find it increasingly difficult to move about in dry soil than in the wet ground. Snails like to ruin gardens at night, so water your plants’ first thing in the morning.
This way, you’ll give the top layer of the soil more time to dry out. And this, in turn, will be before the snails start making their way to your landscape buffet.
Thank you for reading this post on rosemary pests and diseases! If you would like to learn more about rosemary plant care, please see this page.