Ding Dong Merrily On IPM

Whether you celebrate Christmas or not, this time of year it’s cold and dark and the shops are full of lights and food. But it’s not just farmers and producers we have to thank for Christmas dinners, biological control agents are helping to put food on our table all whilst enabling traditional pesticide use to be reduced. Let’s take a walk through some traditional Christmas fare, their pests, and the solutions available.

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Love them or hate them, sprouts are an iconic part of Christmas dinner and have well-studied pests and therefore require a many-faceted pest management strategy. Intercropping and companion plants can be used to control the cabbage moth (Mamestra brassicae) and the garden pebble (Evergestis forficalis). Intercropping of mustard with the brussels sprout crop reduced levels of the mealy cabbage aphid Brevicoryne brassicae to levels where they can be adequately controlled by predatory syrphid larvae, without reducing sprout yield. Rove beetles (Aleochara spp.) can be used as predators to control the cabbage root fly, Delia radicum, once pest numbers have been reduced to an appropriate level.

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Garden pebble larvae on broccoli

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Mealy cabbage aphid infestation on a Brassica leaf



It’s important, with all this indulgence, not to forget to leave some carrots out for any reindeer which might be passing this part of Shropshire. One study found that by growing carrot varieties with natural carrot root fly (Psila rosae) resistance, smaller amounts of insecticidescan be used, in turn allowing natural predators and parasitoids to work through the crop. It also found that sowing brassicas underneath the carrot crop can further reduce insecticide usage. This is the perfect example of how integrated pest management strategies can be used to deliver an effective alternative to traditional pesticides to secure sustainable production of my second favourite vegetable (spot the IPM student).



A carrot root fly larvae emerging from an infected carrot


Port, sherry, Buck’s Fizz, whatever your tipple at Christmas is, if it’s wine-based, the likelihood is it’s made from the European grape Vitis vinifera, which is incredibly susceptible to pests and diseases, not least the Japanese beetle, Popillia japonica, which can feed on all parts of the plant both as a larva and an adult, causing dramatic damage in vineyards. Japanese beetle numbers can be reduced by up to 100% using the nematode worm Heterorhabditis bacteriophora which infect the beetle larvae and release Protorhabdus bacteria which kills them, without affecting non-target organisms in the soil.


The life cycle of the Japanese beetle


UK residents consume the 4th most chocolate in the world, consuming on average 6.8kg of chocolate in 2015, and Christmas is a peak time for chocolate coins, Toblerone, and Terry’s Chocolate Oranges (not sponsored, sadly). One of the most important pests of chocolate is the cocoa pod borer moth (Conopomorpha cramerella): the larvae tunnel into the pod and feed on the seeds for two to three weeks before chewing their way out of the fruit to pupate. The damage they cause to the cocoa pods causes an enormous economic impact on cocoa industries, especially impacting Indonesia, Malaysia, the Philippines, Papua New Guinea and Western Samoa. The presence of the black cocoa ant (Dolichoderus thoracicus) has been observed to increase the amount of cocoa pod damage seen, with the ants entering previously damaged pods to attack the moth larvae. The presence of the ants also reduces the amount of rat damage normally found on up to 90% cocoa pods, showing the wide-reaching impacts of beneficial invertebrates.

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A cocoa pod showing damage from the larvae of the cocoa pod borer moth



For many people, a satsuma in the toe of your stocking is a classic feature of Christmas, and even if not, a bit of fresh fruit can really help cleanse the palate as well as bringing a bit of welcome vitamin C in the cold, dark months. The chili thrips, Scirthothrips dorsalis Hood, is a significant pest of tropical fruits and ornamental crops, including causing silver scar damage to satsuma mandarin fruit. Luckily, however, the thrips can be controlled using phytoseiid mites as predators, including Neoseiulus cucmeris and Amblyseius swirskii, with A. swirskii being able to reduce the thrips level to one per leaf, where they’re no longer damaging to the plant.

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Chili thrips damage on rose leaves

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Thrips damage on young oranges


All these fun and games aside, it must be remembered that food security is a difficult and ever-changing issue, especially with the growing global population. The work which goes in to developing alternate solutions to traditional chemicals and ensuring that we can enjoy many Christmases to come, is an important facet of modern applied entomology.

Happy Christmas from the EntoBlog gang!

Britain’s Next Top Pest

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Our Entomology MSc gang have just had two weeks hearing from some of the key players in the biological control industry. While there were many invasive insect pests mentioned that are currently giving UK growers cold sweats in the middle of the night, a few names kept cropping up.

Without further ado, here’s a run-down of just a few of the headline crop-hungry taxa posing new threats on these shores.

Spotted wing drosophila (Drosophila suzukii)


Not the most appetizing plum, thanks to D. suzukii (photo: Martin Hauser/ Wikimedia Commons)

Despite its catchy name, nobody hopes to catch this fruit fly on their crop. Originally from South East Asia, it’s been rapidly expanding its range in Europe, and was first seen in the UK in August 2012. Unlike like other Drosophila, which tend to go in for decaying and rotten fruit, D. suzukii uses its serrated ovipositor to lay its eggs through the skins of otherwise undamaged fruit. A neat evolutionary advantage for it, really bad news for growers of soft fruit.

The pest control industry is very much all over trying to get the better of this species, though there is no perfect formula. Research has suggested that using biological methods, in this case entomopathic nematodes and fungi, can reduce population development, but can’t stop outbreaks.

South American tomato moth (Tuta absoluta)

Another great name, another insect to strike fear into growers. Unsurprisingly, it’s massively into tomatoes, and can do enormous damage to crops when left unchecked – to the point when they can finish off the lot. Although numbers of outbreaks in the UK are still relatively small, the potential to penetrate all parts of the tomato plant means that any arrivals, such as in imports of Spanish tomatoes, must be taken very seriously indeed.

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The tomato isn’t looking great either (Photo: TNAU Agritech Portal)

Full development from egg to adult has been seen in a wide range of temperatures, and a 2013 study concluded that Tuta is “well able to develop under temperatures that would commonly be experienced in UK glasshouses”.

Other research has highlighted the potential of natural enemies to counter this tomato-loving moth, with Macrolophus and Nesidiocoris tenuis, two Hemipteran egg predators, now seen as having the best potential to make inroads into populations. The problem with this approach is that sometimes a beneficial insect can become a pest, and in this case, the biocontrols have been known to do plant damage themselves. Nothing is ever completely straightforward in the world of pest management, it seems.

Diamondback moth (Plutella xylostella)

There have been recent spikes in numbers of this lover of cabbage and cauliflowers, sparking natural concern among growers. Evidence is mounting that it’s surviving winter here, as well as resistant to pesticides.1280px-Plutella_xylostella1

The fight is by no means over, however. Intercropping – growing a different crop in proximity to the main one – looks like a promising tactic in taking on the pest. A 2010 study showed that planting onion, tomato or pepper with cabbage was as effective as spraying.

Melon thrips (Thrips palmi)


Photo: Forestry Images/ Wikimedia Commons

Although this thrips species can’t survive the British winter, it can establish with protected crops, and is extremely unfussy in its choice of meal. As such, it’s as much a threat to growers of ornamental plants as it is to those in the fruit and veg business.

What’s more, it’s another insect known for being highly pesticide resistant, so effective biological controls are certainly what’s called for here. It seems likely that a mix of entomopathic nematodes and fungi may well be the dream team for tackling both the larval and adult stages.


Is that it?

Far, far from it. The insects featured here are certainly not the only ones that could potentially do significant harm in UK agriculture, should they both get the chance to arrive and find a way to consolidate their numbers here.

DEFRA’s top six of the very latest potentially damaging pests and diseases features a pair of longhorn beetles from the east, while the UK Plant Health Risk Register is a fascinating and somewhat frightening source of information about potential threats to the flora of this island. Currently listing 1,024 pests (not just insects, however), it serves to highlight that amidst the great advantages to global trade come some pretty serious pitfalls.

The prizes for pests that manage to establish themselves in the UK’s famously un-tropical climes are significant – and in an agricultural environment of reducing pesticide effectiveness and use, controlling their proliferation is a multi-faceted and often complex game.

Successful pest management has to take into account factors like the temperatures insects operate in, where they operate in the crop canopy, the need to tackle both adult and juvenile stages, and compatibility of biological control methods with insecticides and fungicides. It also needs to factor in a comprehensive clean-up after the pest has been beaten, to prevent an immediate repeat of the nightmare all over again.

While there are plenty of checks in place to try and prevent invasive pests getting the chance to test their resolve against the UK climate, it’s practically impossible to prevent every insect of potential harm making it past the border. The prerogative is that when they do show up, they are reported quickly, and expert advice sought when needed. If the last fortnight’s lecturers were anything to go by, there certainly is the expertise out there to nip most comers in the bud before scares become crises.