The excitement of a new summer vegetable garden can be quickly squelched if pests move in. Fear not, pests don’t need to be a reason to panic. A healthy garden can afford to have pests – in fact it is necessary to sustain beneficial insects. The key is to know when and what to act with.
Here’s a rundown of the most common pests I get asked about – or deal with myself – and ways to combat them.
Snails/Slugs
Young plants and seedlings can be wiped out overnight by these mollusks. As such, it is a good idea to preemptively act in a garden with such plants.
Iron phosphate is my go-to remedy if I see slugs/snails, their trails, or if I have emerging seedlings. Simply sprinkle the small pellets on the soil. The slugs/snails will consume the pellets, stop eating and die. Iron phosphate is labeled “safe to use” on edibles and around kids and pets. Reapply frequently since it breaks down with water.
Beer? Yes, this does actually work. No, it is not the alcohol the snails are attracted to – it’s the yeast. Place shallow containers on the soil so the snails fall in and drown. Make sure to clean out and refill traps on a daily basis.
Diatomaceous Earth is broken down diatoms and silica. When insects crawl over it, they receive severe damage, inducing death. This is safe to use on the soil around edibles, pets/people. Be careful because if placed on flowers or leaves it will harm pollinators/beneficial insects that come in contact with it. Reapply often as it loses effectiveness with moisture.
Aphids, Thrips, Whiteflies
These pests are “phloem suckers,” meaning they pierce into the sugar transport system of the plant and remove sugars. This results in a sticky coating over the plant and a secondary infestation of ants who “farm” the pests for that sugary excrement.
First, control the ants to allow natural predators to swoop in and remove the pests. Ants are very good at warding off beneficial pests. Use Tanglefoot (a sticky substance ants can’t crawl over) or any ant bait of your choice. Generally, if the infestation is mild or within the first few weeks of spring, then I tend to ignore them, as the pests will often dissipate. If pest numbers are increasing or the plant is being harmed (yellowing, losing leaves), then a simple blast of water from the garden hose works wonders. If temperatures are below 85, I may reach for neem oil. This oil is derived from the Neem tree, Azadirachta indica, and works to smother pests (and even has some antifeeding properties).
Companion planting is another (theoretical) strategy – the idea being that having two certain plant varieties by each other will result in one warding off pests from the other. For the most part, studies have not been able to scientifically confirm this. The example which seems to have the most verifiable data is garlic. Garlic is a cool season crop, but there is a bit of overlap with a summer garden. Best of all, garlic seems to be a generalist companion, in that it may help ward off pests from most other nearby plants.
Brad Gates, of Wild Boar Farms which specializes in creating new varieties of exotic heirloom tomatoes, swears by planting milk weed by his tomatoes to help with aphid reduction. Finally, at the UCD Conservatory we grow rue both inside and outside the greenhouses to use as a banker (sacrificial) plant for whiteflies. These pests love this plant and therefore ensure that our whitefly parasite, Encarsia formosa, will always have a primary host.
Foliage-eating larvae
If you notice large holes, chunks or entire leaves chewed off your plant, there is a good chance a larvae is the culprit. Cabbage white, tomato hornworms or cabbage loopers are generally the most common larvae. Another sign of infestation is their fecal matter, which looks like black pepper.
You can hand pick them off. Think of it as a gardener’s Easter egg hunt. Alternatively, you can use BT (bacillus thuringiensis), which is a soil-dwelling bacterium. Sprinkle or spray BT on the foliage of plants. When the larvae ingest the leaves they will also ingest the BT, ultimately causing them to stop eating. It is safe to use around edibles, people and pets. Reapply often as it breaks down in the sun.
Birds
Birds can quickly decimate a young garden. The go-to bird netting can be incredibly frustrating to use and not always effective. My frustration with netting and birds ended when I discovered that if I turned plastic nursery flats upside down they acted as a perfect defense against birds. They allow sunlight in, shade a bit, and when the seedlings are large enough – simply pick up and stack the flats.
Cats
As a cat lover I do understand the annoyance of felines doing their business in your nice, fluffed-up garden soil. A sensor sprinkler will work, but ideally making the area less desirable to dig is key. Place any objects over the soil that will deter the cats – I find large river rocks work. If worried about heat buildup, then try large pieces of wood.
There are of course many other pests that make their home in your garden, but these tend to be the most common. And as far as solutions – these are my go-to remedies when it is necessary to take action.