The Tomato-Potato Psyllid
Tomato-Potato Psyllid aka TPP (Bactericera cockerelli)
If you want to grow tomatoes, peppers, aubergines, tamarillosand/or kumara in your garden this summer, this is important reading!
The TPP has been in New Zealand since 2005 and affects a wide range of crops including tomatoes, peppers, potatoes, eggplants, cape gooseberry and tamarillos, all in the solanaceous family, as well as kumara. It will also overwinter on weedy solanaceous plants such as the nightshades, as well as convolvulus.
The TPP first got to Tryphena on Aotea about 7 years ago, probably via infected plants being brought over from the mainland. In the summer of 2020-2021, Okiwi Passion lost their entire crop of 700 tomato plants within a month to the psyllid, having had no previous incursions, showing how quickly and devastatingly this insect can spread.
These pests build up numbers from spring to summer when they are at their peak- the hotter the better.
All stages of the insect’s lifecycle are problematic.
Adult: adult psyllids suck sap from the leaves of their host, and lay eggs on the leaf margins, leaf surfaces and stalks.
Nymphs: these are the larvae of the adult and suck vast quantities of sap, stunting plant growth.
Both adult and juvenile psyllids can carry a deadly bacterial disease called Candidatus Liberibacter solanacearum which they inject into the plant as they suck sap, causing plants to deteriorate and die very fast (see below).
Signs and Symptoms of the TPP on Tomatoes:
yellow patches on leaves (psyllid yellows), then purpling and cupping of leaves, reduced yields and sudden decline of the plant resulting in death
white powder on leaves: these are honeydew or “psyllid sugars” - crystals of excess sugars from the tomato sap, excreted by the psyllid nymphs. It looks just like icing sugar.
tomato fruit may be fully coloured but have no flavour
green/slightly orange nymphs at different stages of development on underside of leaves: at first glance they look like aphids but they move very little. Psyllids go through 5 stages of development called instars before becoming adults. They look like fat greenish scales with 3 pairs of legs and a stylet which they use to suck plant sap. During this phase they live mostly on the underside of the leaves- there can be dozens on each leaf in various stages. They excrete honeydew and move very little.
yellowish 1mm eggs on short stalk, found on leaf margins, under leaves and on stalks
adult TPP on the leaf surfaces. Adult TPP are easily recognised, looking like a cross between a miniature cicadas and a mosquito. They are only about 3mm long with a white band across the abdomen (see fact sheet link below) . Only the front pair of legs are visible from above as they keep the back legs ready to hop on disturbance. They live mostly on the leaf surface and hop/move/fly quickly when disturbed.
Signs and Symptoms of the TPP on Potatoes
In potatoes, the psyllid causes the same "psyllid yellows" of the leaves, eventual collapse of the plant, zebra-chipping of tubers with black marks, and often only marble-sized tubers if the infection happens early in the growth cycle. Tubers do not cook properly, and if eaten, are extremely bitter.
Monitoring
Hang yellow sticky traps among the tomato leaves and at the entrance to your hothouse if you have one. Check regularly.
Protection
Protect plants with fine insect mesh at planting time. Make sure edges are closed down with planks or soil to stop psyllids finding their way in. Be aware that if there are already psyllids on the plants, they will party in an enclosed protected environment!
Do your best to attract the following psyllid-control insects into your garden. They are incredibly effective and most of them do a wide range of other useful pest-control functions in the garden!
Minute Pirate Bugs (Orius insidiosis): These beneficial insects can be found in most gardens and are attracted with pollen bearing flowering plants like cosmos and the daisies. Orius kills its prey by piercing them with its mouthparts, and sucking out the body fluids. Nymphs and adults feed on a variety of small prey, including thrips, mites, aphids, whiteflies, scale insects, small caterpillars, and eggs of various insects. They have also been shown to eat eggs and nymphs of the Psyllid. Read more in the links below.
Dusky Ladybird (Scymnus loewii): these are small predatory ladybirds that feed mostly on aphids, but will also feed on a wide range of alternative prey, including psyllid and whitefly eggs as well as eggs of butterflies and moths. Both adults and larvae are predators. Read more in the links below.
Tamarixia triozae - this is a small parasitic wasp which originated in the US (where the psyllid originated too) which exclusively parasitises psyllid nymphs and adults by laying its eggs inside them. Tamarixia also feed on on the earlier nymph stages of the TPP. Tamarixia is a 100% safe, tiny wasp which will not sting you! Read more in the links below.
Tasmanian Lacewing: both adults and larvae of these small predatory insects are voracious consumers of aphids but also eat psyllids, starting to predate soon after hatching. These little guys will be in your garden already if you have plenty of flowers. Read more in the links below.
If you have a big psyllid problem or grow alot of susceptible crops, you can buy in the above natural psyllid predators from BioForce. Order on a Friday and ask to be sent out on a Monday so they don't get held up in transit over the weekend. Release either at dusk or just before dawn on a calm day and spread them throughout your garden.
Attracting and keeping psyllid predators and parasites into your garden:
Plant the following to provide an ongoing source of pollen as well as nectar for our helpful friends. Remember these are only useful once they flower, so plant them ahead of time!
Daisy family: Calendula, cosmos, sunflower, zinnia, rudbeckia etc
Carrot family: coriander, fennel, dill, parsley, carrots, parsnips
Others: nasturtium, alyssum, yarrow, tansy, chives
For the winter, consider building a bug hotel to keep these insects close by.
Remove TPP host weeds around your garden:
Nightshades, brugmansia, cape gooseberries (yes they can be weedy!), and poroporo are among the weeds that can host TPP adults through the cooler months.
Further Reading/Watching
this is a good quick guide to what the TPP looks like at all stages
https://www.facebook.com/watch/?v=684290078916282
In depth fact sheet on the TPP: https://interestinginsects.landcareresearch.co.nz/taxa/57c9a6fd-2c93-4e07-bc0c-9c0ea1e6c679
https://interestinginsects.landcareresearch.co.nz/taxa/828fc76c-2ba3-4222-806c-c24b9d566e45
This is the content of an IPM workshop on whitefly but illustrates how an IPM programme works in the real world https://a-lighter-touch.co.nz/wp-content/uploads/2023/09/Whitefly-IPM-Workshop-2023.pdf
