by Wally Richards
Psyllidae, called the jumping plant lice or psyllids. (Note much of the following is from Internet research)
They are a family of small plant-feeding insects that tend to be very host-specific, each plant-louse species only feeds on one plant species or feeds on a few closely related plants.
Of current concern to tomato, potato, tamarillo, capsicum and chili gardeners is the new psyllid commonly known as the tomato/potato psyllid.
This psyllid comes from Central and North America where it breeds primarily on potatoes, tomatoes and other plants in the potato family, Solanaceace.
It also breeds on kumara, which is in the bindweed family, Convolvulaceae.
It was first found in New Zealand in 2006 and has spread throughout New Zealand.
This psyllid may transmit a bacterium, Candidatus Liberibacter solanacearum that causes a disease in its host plants.
The tomato potato psyllid occurs on its host plants in gardens, and crops in greenhouses and on farms.
The tomato potato psyllid breeds all year, though the time from egg to adult (generation time) is longer in the winter when it is cold, than in the summer or in a heated greenhouse.
Adult tomato potato psyllids are small insects similar in size to aphids. They have wings and look like small cicadas with a distinctive white band on the abdomen. The two pairs of transparent wings are held over their abdomen.
Tomato potato psyllid eggs are yellow and attached to leaves by a thin short stalk. The eggs may be laid on all parts of the leaf and plant stem, but are often found on the leaf edge where they are most easily seen.
Nymphs hatch from the eggs. They are flat and scale like, and have three pairs of legs and sucking mouthparts.
They settle on young leaves, mainly on the underside. Although they can walk, they spend much of their time motionless with their stylets inserted into the plant feeding on the plant sap.
There are five nymphal stages, each is called an instar. buds. Adults emerge from fifth instar nymphs.
The length of time needed for nymphal development depends on the temperature and is shorter when it is hotter.
The tomato potato psyllid inserts its maxillary stylets into the phloem, (the plant vessels for transmitting sap from the leaves to other parts of the plant.)
The sap has a high volume of water and sugars, more than the insect needs.
It excretes the excess water and sugar, which is called honeydew. The tomato potato psyllid coats the droplet of honeydew with white wax before ejecting it.
Leaves can become covered with these white wax coated droplets that are called psyllid sugars.
Like some other Hemiptera (sucking bugs), the tomato potato psyllid can transmit plant pathogens to plants.
Tomato potato psyllid is the primary vector (transmitter) of a bacterium, Candidatus Liberibacter solanacearum, which causes a disease that may weaken plants and reduce yields and quality of crops.
Plants infested with the psyllid may exhibit symptoms of a disease, psyllid yellows.
The disease symptoms initially appear in response to psyllid feeding and is presumably a physiological reaction to feeding and saliva secretions by the tomato potato psyllid.
On tomatoes, the disease symptoms are the yellowing and stunting of the growing tip and a cupping or curling of the leaves.
Many flowers may fall off the trusses of infected plants and fruit that develop may be small and misshapen.
On potatoes, the foliar symptoms are a stunting and yellowing of the growing tip and the edges of the curled leaves often have a pink blush or purple colour.
After a while infected potatoes develop a scorched appearance and plants may collapse prematurely.
Potato plants that are infected at an early stage, develop numerous small tubers. Tuber quality is also affected when the plants are infected at a later stage.
The disease is referred to as zebra chip because when the affected potatoes are fried they exhibit dark stripes where the areas high in sugar burn.
In New Zealand, the bacterial disease is usually less of a problem on outdoor capsicums, chilli and egg-plant.
Tomato potato psyllid breeds all year, especially in the warmer parts of the country and in greenhouses. In these situations, all life stages may be found all year round. In other areas, non-breeding adults may be found on plants.
Adults feed on leaves and can mate more than once. A female can lay up to 500 eggs over a 21-day period, but in the field it is more likely to be around 200 eggs.
The number of eggs laid also depends upon the host plant. The rate of development of nymphs is dependent on temperature.
The psyllid develops between 15°C and 32°C with optimum development at 27°C.
In a greenhouse with an average temperature of 18°C psyllids takes 33 days to complete their life cycle.
In New Zealand there are to 7-8 generations per year in the Auckland region.
In New Zealand’s winter, the numbers of psyllids are low and development is very slow.
Adults and nymphs can survive short periods of sub-zero temperatures. In New Zealand’s spring numbers on infested plants will begin to build up and reach a peak in late summer/early autumn.
Adult psyllids have wings and in North America can spread long distance by air. In New Zealand, dispersal tends to be more limited, 100 m or more in three days. They will invade new areas and plants, especially in summer.
From my experience its a temperature to numbers game, when given the ideal temperatures.
One adult laying 500 eggs can mean in about a month you have a population of 250,000 adults
Initially sprays will help control but as numbers rapidly increase you would need to spray every day and still lose the battle.
That was the point I reached about 3 years ago and watched my tomato plants and tamarillos die in front of my eyes.
The following season I treated my tomatoes and other host plants with silicon drench and sprays and in one season completely wiped out the psyllids from my glasshouse and gardens.
The silicon treatment which I call the ‘Cell Strengthening Kit’ makes the plant’s cells too tough for the psyllid nymphs to piece and feed and they soon starve to death after hatching.
This breaks the life cycle and there are no new adults to replace the old ones when they die.
Information on the kit is available on our mail order web site at www.0800466464.co.nz
More info on the pest is here
With our Silcon products you can once again grow tomatoes, potatoes and other affected plants.
or phone me for more information.