If I could charge a dollar for every question I answer on talkback radio concerning spittlebugs and passionvine hoppers, I’d be retired and lying on a beach in the Bahamas – or perhaps more likely in Namibia or Amazonia, the high desert of Arizona. Characteristic patches of bubbles up (spittle) and down the stems of lavender, Coprosma and a heap of other host plants. Many of these are caused by the so-called meadow spittle bug (an exotic species from Europe. We have about 15 species in NZ - many native – few introduced ones. 
Most gardeners in southern regions will know these frothy bubble-houses and most gardeners think they are “disgusting”. I reckon they’re a marvel of engineering! The larval critters suck sap/fluids from the plant, excrete this through their bottom and add some glue-y excretion from a gland on the abdomen. Then they use their abdominal contractions as a “bellows” and pump air into the watery mixture, causing fine and coarse bubbles to form. Try that in the bath, next time!  
When you wipe away the bubble, the green-ish creature is exposed and immediately starts “repairing” it’s home – that way it will remain in a moist environment and – more importantly: hidden from predator’s view!  Damage and consequences to the plants?  NIL  Ecosystem service: the adult froghoppers emerge with wings from that bubble, jump around the garden and usually end up as food for insectivorous birds. All good! 
The Passionvine hopper is a more northern sap-sucker, found Northland to Marlborough/Nelson. It can become very numerous indeed on some desirable plants, often climbers like wisteria and passionfruit vines, as well as perennials like salvia, hydrangeas, and camellias. Huge numbers can debilitate these hosts as both nymphs and adults relentlessly such phloem juices from the stems and lianes. 
They excrete honeydew which can cause a bout of black sooty mould deposit all over the plants. When that honeydew is splattered all over or native tutu vine in the bush, bees can pick some serious poisons, which are then incorporated in the honey produced! Very poisonous to people! 
In early November the nymphs hatch from their eggs. I call them fluffy bums – as their “nylon-filament tails” are prominent features.  Slowly they grow larger and larger shedding skins along their journey, until they reach adulthood: moth-like insects with delta-shaped wings, showing prominent vein-markings; they, too, suck plant sap. These insects have the ability to jump quickly and far and the adult passionvine hoppers also flick and fly very smartly, avoiding the insecticides you may want to spray at them! 
But there is some other trick you can play right now, to control the numbers of hoppers in your garden, this summer: The babies are just hatching now and climb to new growth in the top of their host plants. On still mornings, you can simply cull their numbers by using an aerosol spray can (that emits fine mist of insecticide) and spray the tiny nymphs in a misty cloud of spray. They can jump all they like, but won’t be able to avoid contact with that aerosol in the still of the morning; those new-borns are far more susceptible to insecticide sprays than in a week or so now’s the time! LISTEN TO AUDIO ABOVE