You may remember in my very first article I mentioned the surreal moment after harvest of looking out over an empty farm. Now into the fourth instalment of my hop farm diaries, the exact opposite moment has arrived. A wall of hop plants now greets you from every side of the farm. Everything happens so quickly.

How great are hops? From almost no sign of a plant in September to a plant chock-full of resiny goodness by February. A lot of work has to be done in between that time though.

The days are longer, the frosts are gone, and I can finally get out and ride my bike to work. It’s a great way to start the working day. The temperatures in the area did take quite a while to warm up through spring though. This meant we had the slowest start to the season since I have been working on the farm and a late start to hop training. Just to remind you if you missed the last article, hop training is the process of winding our hop bines onto the string. That’s right, still not a typo, they are called bines. Hop training began a week later than expected and with unusually slow-growing plants. We are catching up though! The days and nights warmed up and it is now a sea of green reaching to the sky.

Luckily, we were able to find work for our seasonal crew elsewhere while we waited for some more growth. Our RSE workers arrived for their third season on the farm and it’s always a pleasure to have them back. Even better for them, they moved into our brand new accommodation that was built during winter. Our seven workers from Vanuatu will stay for hop training and return for harvest in late February after some time away working on apple orchards.

diary of a hop farmer
Seasonal workers from Vanuatu, plus an Italian backpacker, at Hinetai Hops

Work continues around the farm outside of hop training. Our ‘babies’ have been a big success so far and have grown stronger than a lot of other varieties. Trial hop NZH-102 has grown especially strong early on and my expectations are high for this variety in its first year. The grass has begun to grow faster and faster so there’s lots of mowing in between the plant rows. Here’s continued cultivation in our organic blocks to keep the weeds under control. For the first time this year, we will be seeding a grass crop in our organic blocks with the aim to improve soil structure and health. Unexpected leaks and irrigation control system issues need urgent attention as the weather warms up and the hops begin to need more water.

Now I understand that’s quite a limited update so far, but in a slight change from the norm, I managed to catch up with Chris Thompson, general manager of Bioforce, to discuss one of my main roles on the farm during summer. Pest control. Hops in New Zealand have one main pest issue, the two-spotted spider mite. This dominates a lot of my time in summer and is so vital in protecting the crop. Before I go into our techniques for managing this issue, I will let Chris give you some in-depth expert knowledge.

Firstly, who is Bioforce?

Bioforce is a second-generation family business based south of Auckland. We were originally a spinoff from Crop and Food (now Plant and Food Research) and saw the need to create bio-controls to help combat insecticide resistance and enable pollinating insects to thrive in crops. 

From humble beginnings, with only a parasitoid for whitefly and a predator for spider mites we now produce three parasitoids, four predatory mites, two ladybirds, a lacewing, anthocoridae and distribute three species of nematodes (which are imported from Germany). Throughout the course of the year, we are involved in around 30 sectors ranging from flowers, vegetables, and hops to chicken farms. 

What is your role in helping hop farms?

Hops in New Zealand are reasonably blessed compared with hops in other countries like the USA. In New Zealand we only have to worry about spider mites, however, this may change in the future if other pest insects develop a resistance to the compounds in hop plants and adapt to the local environment. For instance, in the US they deal with aphids and caterpillars as well. 

Our involvement with New Zealand Hops is to provide millions of predatory mites to enable hop farmers to combat these pests throughout the summer growing season. Each week in summer we will be busy packaging them up and running them out to Auckland Airport to take direct flights to Nelson.

What are the mite species that affect hops?

Tetranychus urticae, also known as the two-spotted spider mite. Phytoseiulus persimilis — known to our customers as Mite E — is the predominant predator of Tetranychus urticae. It is considered a specialist predatory mite as it will walk past anything else which will fit in its mouth to the point of death on its mission to eradicate the pest mite.

How do these pest mites affect hop plants, and how does the predator take control back?

T. urticae is a plant-feeding mite which chews away at the surface of the leaves and, in severe cases, flower buds and fruit. This feeding damage reduces photosynthesis and increases plant stress which can lead to reduced yields and the death of the plant. However, on the brighter side, new research in the past 12 months into the effect of T. urticae on other crops such as medical cannabis has found a benefit to yields if a low population of pests colonises the plant (note: an optimal mite pressure has not been determined). The stresses induced by spider mite feeding stimulate plant defence mechanisms such as metabolite production which are often the compounds which affect the taste of produce and in the medical cannabis case are the compounds pharmaceutical companies wish to extract from the plant. 

To ensure T. urticae numbers do not reach damaging levels, hop farmers introduce P. persimilis, the bright red predatory mites which have claimed fame as being the most voracious predators of spider mites known. Persimilis or as we call them Mite E can feed on every stage of T. urticae. They do have a preference to eat the eggs first rather than adults. If you could imagine being on a desert island with a few chickens, we would even search out the eggs first before trying to chase and wrestle down an adult chicken. 

How do you grow your different species on site?

We must produce billions of spider mites on large beds of plants as a food source for our predators. Once the predator population on a bed of plants is sufficiently high we are able to collect adults and nymphs then pack them into an inert media and send them off on flights to our customers. 

We are actively researching and prototyping new techniques which may extend the shelf life of the predators in transit or enable sachets to be used early in the season when pest numbers are very low.

Using a magnifying glass to find pests

The work for us to control the pest issue starts around mid-December. My magnifying glass will be in my pocket all summer long. If you look up a row you may see me on the ladder fixing a sprinkler but also taking a good look at the underside of the leaves of our plants checking for mite activity. Any pest activity is quickly acted on. The first sign of a pest mite outbreak is a yellow/gold tinge on the leaves of a plant. Generally higher up on the plant. We occasionally take a trip up the hill behind the farm with binoculars to assess the canopy from above.

The predator mites from Bioforce arrive to us in cardboard tubes which we then take around the farm to release into ‘hot spots’ of pest mite activity. We either release these by hand by simply sprinkling the predators onto leaves or via blowing via a leaf blower mounted on a quad bike. This way we can spread predators into a larger area to deal with a wider spread outbreak.

As Chris mentioned above, the two-spotted spider mite thrives in hot low-humidity conditions. We often experience over 30C temperatures during summer and an outbreak can occur quickly and spread fast. As well as spreading predator mites we also run our irrigation regularly throughout the day to increase the humidity to create an environment to counter the pest mites. This also helps our predator mites that thrive in higher humidity environments.

Once we have control of hot spots and have a strong predator population, we are able to transport our own plant leaves around the farm to take care of any other outbreaks that may occur.

The results of all our effort to control this issue are evident at harvest when we get a good look at our healthy-looking plants at ground level in the shed. Last season was a more widespread issue with pest mites than ever before on the farm, but our response was extremely effective and we had control of the issue throughout the season.

Outside of the farm and delving into the craft beer scene a bit here, we said goodbye to our good friends Nigel and Jackie at The Workshop bar and brewery in Nelson. It was a great last night we had with them at the bar, and we wish them all the best for the future of Test Lab brewery. A night in Nelson was a welcome break from small-town country life here in Tapawera! And of course, you can’t go to Nelson without a visit to The Free House! Duty manager and brewer at the new on-site Flavourtorium brewery, Rhys, was on hand to lace some hazies with some chilli sauce for an interesting taste experience.

Looking ahead to the next issue and we will be getting closer to harvest. We will have a better idea of what we expect from harvest and how the crop is looking. So, I look forward to giving the readers a pre-harvest update. For now, grow you beauties!