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Garden Pests and Diseases – How to Save Your Vegetables, Herbs, and Flowers

Gardening can be such an enjoyable, relaxing hobby. Numerous studies have explored how fresh air, soil, plants, and physical activity in the garden benefit both physical and mental health – not to mention the healthy bounty of homegrown vegetables and herbs. But when garden pests and diseases threaten your precious plants, gardening quickly becomes a disheartening and stress-filled activity. Learn how to treat and prevent common pests and diseases in the garden so you can enjoy, not dread, walking among your plants again.

The following guide is divided by vegetables, herbs, and flowers, and includes links to helpful articles on the pests and diseases of individual plants.

harlequin bugs in my garden

Pests and Diseases in the Vegetable Garden

From beets to zucchini, learn about the pests and diseases that plague each vegetable, as well as how to treat and prevent these problems.

Beet pests and diseases

cercospora leaf spot

A wonderfully versatile vegetable, beets can be grown for their greens as well as their roots, and they’re rich in nutrients.

Pests:

  • beet cyst nematode
  • root knot nematode
  • darkling beetle
  • leafminers

Diseases:

  • bacterial blight
  • scab
  • beet curly top disease
  • beet western yellow virus
  • cercospora leaf spot
  • damping off
  • downy mildew
  • fusarium wilt and root rot
  • powdery mildew

Brassica pests and diseases

green cabbage worm

Pests:

  • cabbage worms
  • diamondback moth caterpillar
  • cabbage looper
  • harlequin bug
  • imported cabbageworm
  • armyworms
  • aphids
  • silverleaf whitefly

Diseases:

  • black rot
  • clubroot
  • downy mildew
  • leaf spot
  • powdery mildew
  • white blister
  • flea beetles
  • aphids

Carrot pests and diseases

diseased carrots with holes made by pests

Pulling this classic root vegetable out of the soil is immensely satisfying, so make sure your carrot crop remains healthy!

Pests:

  • aphids
  • carrot rust fly
  • carrot weevil
  • flea beetle
  • root-knot nematodes
  • wire worms

Diseases:

  • Alternaria blight
  • black rot
  • cercospora blight
  • cottony rot
  • downy mildew
  • powdery mildew
  • bacterial leaf blight
  • soft rot
  • cavity spot
  • damping-off

Cucumber pests and diseases

yellow with black spots cucumber beetle

Eaten fresh from the garden (maybe with a little salt!) or as pickles year-round, cucumbers have a wonderfully refreshing crunch.

Pests:

Diseases:

  • Alternaria leaf blight
  • anthracnose 
  • belly rot
  • cercospora leaf spot
  • downy mildew
  • fusarium wilt
  • gummy stem blight
  • powdery mildew
  • septoria leaf spot
  • target leaf spot
  • verticillium wilt
  • angular leaf spot
  • bacterial leaf spot
  • bacterial wilt
  • aster yellows
  • cucumber green mottle mosaic
  • cucumber mosaic
  • squash mosaic
  • watermelon mosaic
  • phytophthora blight
  • Pythium fruit rot
  • scab

Leek pests and diseases

Something like a giant green onion, leeks add excellent flavor to soups and many other dishes.

Pests:

  • leafminers
  • onion maggot
  • thrips

Diseases:

  • botrytis leaf blight
  • damping-off
  • downy mildew
  • pink root
  • purple blotch
  • white rot

Lettuce pests and diseases

a slug on a lettuce leaf

This leafy green is a must-have for salads and sandwiches.

Pests:

Diseases:

  • anthracnose
  • leaf drop
  • powdery mildew
  • septoria leaf spot
  • big vein
  • bottom rot
  • downy mildew

Onion pests and diseases

onion black mold

Onions are used to flavor many savory dishes and come in a wide variety of types to suit the need, from green onions to storage onions.

Pests:

  • bulb mites
  • leafminers
  • onion maggot
  • thrips

Diseases:

  • black mold
  • botrytis leaf blight
  • downy mildew
  • fusarium basal plate rot
  • fusarium damping-off
  • purple blotch
  • rust
  • smut
  • white rot
  • leaf streak and bulb rot
  • onion yellow dwarf
  • Pythium seed rot

Potato pests and diseases

colorado beetle larva

This starchy, crowd-pleasing root vegetable fits in at every meal, making it a great choice for the vegetable garden, too.

Pests:

  • aphids
  • Colorado potato beetle
  • cutworms
  • flea beetles
  • wireworms

Diseases:

  • bacterial ring rot
  • blackleg
  • common scab
  • black dot
  • black scurf and rhizoctonia canker
  • gray mold
  • pink rot
  • potato early blight
  • powdery scab
  • verticillium wilt
  • potato late blight
  • potato leaf roll
  • potato virus

Pumpkin pests and diseases

squash bug babies on a pumpkin

Whether for decorations or pies, pumpkins deserve a place in every fall vegetable garden.

Pests:

Diseases:

  • Alternaria leaf blight
  • Alternaria leaf spot
  • cercospora leaf spot
  • downy mildew
  • fusarium crown and foot rot
  • gummy stem blight
  • powdery mildew
  • septoria leaf spot
  • southern blight
  • verticillium wilt
  • angular leaf spot
  • bacterial leaf spot
  • bacterial wilt
  • aster yellows
  • cucumber mosaic
  • squash mosaic
  • watermelon mosaic
  • zucchini yellow mosaic
  • phytophthora blight

Sweet potato pests and diseases

white grub

This versatile root vegetable can be used in everything from soups to desserts and is surprisingly easy to grow.

Pests:

  • sweet potato stem borer
  • white grub

Diseases:

  • Alternaria leaf spot and leaf and stem blight
  • black rot
  • fusarium root and stem rot
  • bacterial soft rot
  • bacterial wilt
  • leaf and stem scab
  • pox
  • sweet potato virus disease

Tomato pests and diseases

diseased orange tomatoes

What’s a vegetable garden without tomatoes? Sweet cherry tomatoes, giant beefsteaks, fleshy pastes … there’s a variety (or three) for every garden. Check out my post about common tomato plant problems and how to fix them.

Pests:

  • aphids
  • beet armyworm
  • Colorado potato beetle
  • cutworms
  • flea beetles
  • hornworms
  • leafminers
  • loopers
  • stinkbugs
  • thrips
  • tomato fruit worm
  • root knot nematode
  • spider mites

Diseases:

  • anthracnose
  • black mold
  • early blight
  •  fusarium wilt
  • gray mold
  • leaf mold
  • septoria leaf spot
  • target spot
  • verticillium wilt
  • bacterial canker
  • bacterial speck
  • bacterial spot
  • bacterial wilt
  • blossom-end rot
  • catface
  • edema
  • fertilizer burn
  • little leaf
  • nutrient deficiency
  • sunscald
  • water stress
  • zippering
  • buckeye rot
  • late blight
  • tomato mosaic virus
  • tomato spotted wilt
  • tomato yellow leaf curl disease
  • curly top

Zucchini pests and diseases

squash borer damage

You may end up pawning off your bumper crop later in the summer, but you want to make sure you get some zucchini for stir-fries, soups, and zucchini bread in the first place!

Pests:

  • aphids
  • armyworms
  • cabbage looper
  • cucumber beetles
  • cutworms
  • flea beetles
  • leaf miners
  • squash bug
  • squash vine borer
  • stinkbugs
  • thrips

Diseases:

  • Alternaria leaf blight
  • Alternaria leaf spot
  • cercospora leaf spot
  • downy mildew
  • fusarium crown and foot rot
  • gummy stem blight
  • powdery mildew
  • septoria leaf spot
  • verticillium wilt
  • angular leaf spot
  • bacterial leaf spot
  • bacterial wilt
  • aster yellows
  • blossom-end rot
  • cucumber mosaic
  • cucurbit yellow stunting disorder virus
  • squash mosaic
  • watermelon mosaic
  • zucchini yellow mosaic
  • phytophthora crown and root rot

Pests and Diseases in the Herb Garden

aphids on herb flowers

Although herbs, most of which have a pungent aroma, typically repel pests, they still suffer from a few pests and diseases of their own.

Basil pests and diseases

Italian basil pairs perfectly with tomatoes for sauce, while Thai basil adds flavor to curries and tea.

Pests:

Diseases:

  • cercospora leaf spot
  • downy mildew
  • fusarium wilt
  • gray mold
  • leaf spot
  • root rot

Mint pests and diseases

Mint grows happily anywhere, providing you with plenty of leaves for refreshing iced tea (and potentially taking over), and it suffers from very few problems.

Pests:

  • aphids
  • cutworms
  • spider mites
  • thrips

Diseases:

  • mint rust

Parsley pests and diseases

Whether flat or curly, the leaves of this biennial herb have a wide range of uses in the kitchen.

Pests:

  • aphids
  • armyworm
  • cutworms
  • root knot nematode

Diseases:

  • Alternaria leaf blight
  • cercospora leaf blight
  • crater spot
  • damping-off
  • powdery mildew
  • rust
  • septoria leaf spot
  • carrot motley dwarf

Rosemary pests and diseases

A shrubby herb, rosemary can even be grown as a hedge in mild climates or protected locations.

Pests:

  • aphids
  • leafhoppers
  • spider mites
  • spittlebugs
  • thrips
  • whiteflies

Diseases:

  • cottony soft rot
  • downy mildew
  • crown gall

Pests and Diseases in the Flower Garden

Keep your flower garden healthy and beautiful by protecting your plants from — and, if necessary, treating them for — the pests and diseases that can damage them.

Rose pests and diseases

These classic, elegant blossoms come in a range of soft and vibrant colors, many with a sweet scent, and can find a home in almost any garden.

Pests:

  • aphids
  • Japanese beetles
  • mites
  • thrips
  • rose scale
  • rose leafhopper
  • rose slugs
  • leafcutting bees

Diseases:

  • black spot
  • powdery mildew
  • stem canker and dieback
  • rust
  • Botrytis blight
  • rose rosette disease
  • rose mosaic
  • crown gall

Peony pests and diseases

The large, ruffled blossoms of peonies brighten up the spring garden year after year, and these plants suffer few problems.

Pests:

  • Japanese beetles
  • scales

Diseases:

  • Botrytis blight
  • leaf blotch

Lavender pests and diseases

The soft green foliage and fragrant purple flower spikes of lavender fit in equally well in flower beds and herb gardens.

Pests:

  • spittlebugs
  • whiteflies
  • aphids
  • four-lined plant bug

Diseases:

  • root rot
  • crown rot
  • alfalfa mosaic virus
  • xylella
  • shab
  • Botrytis blight
  • septoria leaf spot

Clematis pests and diseases

Beautiful flowering clematis vines rarely have problems with pests and diseases once well established.

Pests:

  • aphids
  • slugs

Diseases:

  • clematis wilt
  • clematis leaf spot
  • powdery mildew

Sunflower pests and diseases

Large, cheery sunflowers brighten up vegetable garden borders, flower beds, and fence lines.

Pests:

  • cutworms
  • grasshoppers
  • loopers
  • painted lady caterpillar
  • seed weevils
  • silvery checkerspot caterpillar
  • stem borers
  • stem and root weevils
  • sunflower beetle
  • sunflower headclipping weevil
  • sunflower moth
  • sunflower bud moth
  • sunflower root moth
  • tumbling flower beetle
  • wireworms
  • woollybear caterpillars

Diseases:

  • Alternaria leaf blight
  • downy mildew
  • Phoma blight
  • powdery mildew
  • septoria leaf spot
  • verticillium wilt

When we learn to manage garden pests and diseases, our plants grow healthy, beautiful, and lush, and we can enjoy our gardens without worry.

Garden Pests and Diseases

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Adriana Copaceanu is a passionate nature lover living in the country on her dream property where she grows vegetables, lavender, and wildflowers that she shares with the wildlife they attract. When she's not in the garden, she loves spending time with her chickens and planning her next nature project. Check your her books below:

How to Grow Lavender for Fun and Profit: Lessons Learned from Planting Three Hundred Lavender Plants

How to Raise Chickens for Eggs: A Guide to Raising Happy, Healthy Chickens for Nutritious, Organic Eggs at Home

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