One of the many advantages of growing hydroponically is that your plants are less susceptible to pests and diseases than they would be in conventional soil gardening. With this being said, less susceptible doesn’t mean untouchable, and unfortunately, leaf curl is one of the most common hydroponic nuisances we talk about in-store. So let’s talk about what leaf curl is, what crops are most affected, and how you can put it to a stop. 

Many stressors can cause leaf curl affecting various crops, from beans, capsicum, and beetroot to pumpkin. The most impacted crop, however, is none other than tomatoes, which makes sense, given that, as Australians, we produce 550 million kilos of the crop each year.

In today’s newsletter, we will focus on two viral causes of leaf curl; Beet Curly Top Virus and Tomato Yellow Leaf Curl Virus. First, however, it’s important to remember that environmental stressors can also cause leaf curl. For example, overwatering, underwatering, over-fertilising, or even herbicide use can trigger the dreaded leaf curl.

While it can be hard to differentiate between environmental stressors and diseases, one surefire indicator is the spread of the leaf curl. Because insect carriers spread viral infections, they are less thorough than environmental stressors. Therefore, if every plant and leaf is affected, you are likely dealing with stress. On the other hand, if some leaves or plants are affected and others seem healthy, the likely cause is disease. 

Let’s start with Beet Curly Top Virus. 

Beet Curly Top Virus (BCTV) is carried from plant to plant by the beet leafhopper (surprise, surprise). Once a leafhopper catches BCTV, it will carry the virus for the rest of its life. Adult leafhoppers may feed on a variety of crops; however, given a preference for egg-laying on beets and tomatoes, these crops are most at risk of contracting BCTV.

In recent years there have been many attempts to breed tomatoes that are resistant to curly top. Unfortunately, none of these attempts have been successful, meaning all nightshade varieties are currently susceptible. 

In addition, it’s important to note that spraying with insecticide will not control BCTV. This is because leafhoppers can migrate long distances and don’t remain in tomato fields after reproduction. Therefore, when symptoms are evident in your crop, the leafhopper has moved on. 

As goes for most viral garden infections, a good defence is the best offence. The stronger your plants are, the less they will be impacted by BCTV. We recommend hardening off your crop before planting, fertilising regularly and adding netting over any crop that pests or viral infections have hit in the past. For more information about hardening off your crop, read our newsletter on the subject, which we’ll link below. 

If BCTV impacts your crop, it’s unlikely to recover. Your best bet is to remove and discard the infected plants before starting fresh with some additional contingencies in place. 

Moving on to another cause of viral leaf curl, let’s talk about Tomato Yellow Leaf Curl Virus. 

Tomato Yellow Leaf Curl Virus (TYLCV) is another disease transmitted via insects, this time sap-sucking insects such as aphids and whitefly. Plants that have been infected will exhibit stunted growth and inhibited fruit production along with pale, cupped foliage.  

TYLCV tends to impact hydroponic growers more than traditional gardeners, as the virus thrives in the conditions offered by indoor or greenhouse garden set-ups. 

TYLCV can target a range of crops such as chilli, potato and eggplant, but as the name of the virus suggests, tomato is a clear favourite. 

As with BCTV, prevention is critical to controlling a TYLCV infestation. Once again, a regular nutrient regime and hardening off crops before planting will go a long way in preparing them to cope with and bounce back from infection. In addition, you can apply a garlic barrier around common plant targets, which will work to repel insects and lower the overall pest count in your garden. 

The treatment of TYLCV is much the same as BCTV except, unlike Beet Curly Top Virus, a plant can contract TYLCV without being symptomatic. Because of this, if your cop is impacted, you’ll need to be extra diligent in removing and discarding diseased plants, especially weeds.

In both cases, you, as a gardener, may also be responsible for spreading disease around your garden. Ensure you thoroughly clean tools between each use to prevent the spread of viral infections. We love Sleeps With The Fishez for sterilising our gardening tools in-house or a mixture of 1:20 bleach to water. 

Prevention is worth its weight in gold when it comes to viruses that cause leaves and foliage to curl. Use the information in this newsletter to prepare your garden for a potential infestation, and if the dreaded leaf curl targets your garden, we wish you the best of luck. As always, thanks for tuning in to this month’s newsletter and from the whole team at Aquaponics WA; happy growing!