Thrips can multiply quickly and be tough to root out

Rose Buitenhuis is the director of the biological crop protection program at Vineland Research and Innovation Centre and was one of the presenters at last month’s Ontario Fruit and Vegetable Convention, where she discussed thrips and their impact on nectarine crops. ~ VRIC photo

By Luke Edwards

When Sun Tzu wrote about the importance of knowing one’s enemy, he probably didn’t have stone fruit on his mind.

But it’s just as important for growers and the pests that disrupt their crops as it is for generals who wage war on the battlefield. And though thrips may be a familiar foe for many, we may not know quite as much about the insect as we previously thought.

At last month’s Ontario Fruit and Vegetable Convention Rose Buitenhuis, director of the biological crop protection program at Vineland Research and Innovation Centre, and Justin Renkema, a research scientist in entomology with Agriculture and Agri-Food Canada, shared some research on how thrips impact nectarines and some options to control and limit their populations.

“We don’t have a solution yet, but we are thinking a lot about what solutions there could be,” said Buitenhuis.

While she said thrips are “pest number one” in greenhouses, they can also be found in orchards. Their feeding and egg laying can injure buds and flowers, and lead to fruit surface russeting.

Some of the challenges growers face include the fact that when they enter buds they’re more or less protected, and due to the Ontario Bee Act sprays can’t be applied during bloom.

Additionally, a single thrip can lay seven eggs a day and live for a month.

“One thrip can multiply to 200 thrips in a really short time,” Buitenhuis said. And even a single larva can cause significant damage.

When most people think of thrips they tend to think of the western flower thrip. However, Buitenhuis said research shows Ontario has a much more diverse population.

“We have a whole bunch of thrips species in Ontario,” she said.

Integrated pest management follows a fairly simple process, starting with forecasting, then prevention, and finally curative control.

Renkema shared a few options to help control the populations. Trap plants can act as a sink for thrips, he said. The use of reflective mulch in New Zealand has also shown promise.

Spraying entomopathogenic nematodes on trees may also be effective, but it’s failed in other crops.

There are also some native predators, but Renkema said they don’t tend to come out as early as growers would prefer. Similarly, there are three sprays available, though they can also harm the beneficial bugs.