[Information based on DipWSET D1 material]
Six common pests growers encounter in the vineyard, discussing management options for each.
A dingo ate my grapevine…
What it is: An aphid-like buggy that feeds on AND lays eggs on the roots of grapevines. This weakens the roots, causes swellings and cracks, ultimately leading to rot. Gross. Symptoms include: vines dying of drought in increasingly large patches vintage to vintage; vine roots covered with insects and yellow eggs (ew); swelling on older roots; pale green leaf galls on the under-side of the leaves. Additionally, slow, stunted shoot growth and leaf yellowing happens around 3 years after infestation. Vine death happens around 5 years after infestation.
How it spreads: The insects do crawl and fly, but Phylloxera is more commonly spread via humans: on the young roots of vines, in the soil, on equipment, and even by irrigation water. The pest was first “discovered,” if you will, back in the mid 1800s in Europe and was “accidentally” introduced in the U.S. from imported vines. Oops.
- American vine species (including V. berlandieri, V. riparia, and V. rupestris) are less susceptible to Phylloxera infestation. These lot can form hard, corky layers that surround the eggs, seal the wounds, and prevent infections from bacteria, fungus, etc.
- Sadly, Americans smell. I mean…”planting these American vines led to different and undesirable aromas in the resulting wine.” Solution: graft European varieties onto American rootstocks.
- Double sadly, the rootstocks of single American varieties are incompatible with European soils, specifically the calcareous soils that contain high lime content. Solution: rootstock hybrids derived from American species.
- Bonus points: creating these hybrids lead to the development of several kinds of hybrids that can deal with other vineyard issues: nematodes (see below), extreme soil pH, water stress, salinity, vine vigour, etc. So, today, growers can pick and choose which rootstocks are most suitable to their needs.
- PS: vineyards on sandy soils are immune to Phylloxera.
What it is: Tiny worms that are actually quite common in soils but are super super small, so you can’t actually see them with the naked eye. They can cause damage to the vine by feeding off the roots which will cause slow, gradual decline. They can also transmit viral diseases—like Fanleaf Virus.
How it spreads: These buggers are either in the soil already or get into the soil via unclean nursery stock (don’t shop there), irrigation water, or even your vineyard equipment. Bad news: Once they’ve infested your vineyard, they can only be managed, not eliminated. So, then, let’s look at…
Get soil samples tested by a lab to determine how much and what type of nematodes are present. Once that’s determined options include…
- Leave the soil fallow
- Fumigate. Unfortunately—or fortunately—most effective chemicals are now banned in most regions.
- Plough mustard plant cover crop. Mustard contains compounds that work as biofumigants, which can actually kill nematodes.
- Buy nematode-resistant rootstock. (Ramsey and Dog Ridge—both Vitis champini—are resistant to root-knot nematodes.)
3. Grape Moths
What it is: There are several different kinds of moths, but each do damage by eating the flowers and the grapes. What’s super sucky is that most species have several generations per season—so they can attack the flowers AND the grapes within the same year. Then, those wounds they create make the plant more susceptible to bacteria and fungus.
How they spread: Well, clearly they fly and stuff. But apparently, many species have been “inadvertently” imported—for example, the European grapevine moth infiltrated Napa Valley in 2009. Oops again.
- Biological control such as
- bacteria (namely Bacillus thurgingiensis if you’re curious) that produces a substance that’s toxic to the moths;
- pheromone capsules can cause “sexual confusion;”
- and of course natural predators (parasitic wasps, some spiders)
4. Spider Mites
What it is: It’s noted that there are several different kinds of mites that can damage grapevines, but it’s the Spider Mite who does the most damage. These guys feed on the surface cells of vine leaves which leads to discoloration, which then affects the photosynthesis process, thus delaying ripening and reducing yields.
How they spread: Spidey mites like dusty conditions. Your vines are most susceptible if they’re already water stressed.
- Reduce dust: use sprinklers, cover crops, mulches, etc, to make the environment less friendly to Spidey.
- Predatory mites
- General pesticides can be used, but they may kill off the predatory mites. It’s mentioned there are Spidey mite-specific insecticides, but these can be a bit pricey.
5. The Birds
What it is: Um. Birds.
What they do: Besides eating the grapes, birds can also spread fungus and bacteria to the grapevines.
How it spreads: Well, they usually fly I suppose. But I will add that there’s a note that vineyards where grapevines may be the only source of easily available food are more susceptible to The Birds.
- Bird scarers (like noise boxes, scarecrows, those kite thingies, etc.)
- Predatory birds (falcons, owls)
What it is: Warm blooded animals. Which warm blooded animal attacks your vineyard depends on where you are in the world. They can eat shoots, grapes, and leaves. They can break vine material, including grapes, making them more susceptible to rot. They can even damage your trellising.
How it spreads: I guess that depends on the animal—rabbits and kangaroos tend to hop; bears tend to saunter.
- Fences are the most common option, but you have to make sure it’s high enough or submerged into the soil enough (to keep out burrowing animals) as well as sturdy enough. Most folks kind of just deal.
Thanks again for studying with me!
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