Dec 2020

8 Yield Killers to Watch out for

With only a few weeks until Christmas, I’m sure you’re looking forward to enjoying lots of good food with the family!?

Well, there’s a few critters that can’t wait that long – they have already started.


We get it… they are small… BUT, they can steal so much of your hard earned $$ if they find a liking to your crop.

So you might be asking:

  • What insects might I come across?
  • What signs do I look for?
  • How much damage will it make to the crop?
  • When should I consider controlling them?

Here’s a basic insight, based on what we’ve seen/expect this season:


  • Cause damage to germinating and newly emerged seedlings (Looks like the leaf has been hit by a shotgun)
  • Very small brown insects about the size of a pin head
  • Jump when disturbed
  • Detected most easily by placing a white card or cloth on ground and gently disturbing soil.


  • Cause damage to young seedlings and mature plants
  • Larvae are small maggots that live in the leaf tissue, in mines they create as feed.
  • Pictured is early Leaf Miner damage in Turnips


  • Damage is done at early emergence stage, in Maize and Brassica
  • Losses of well over 10,000 plants/ha can occur at populations of 3 caterpillars/100 plants before the two leaf stage or 6 caterpillars/100 plants at the two to four leaf stage.
  • The larger caterpillars are the most damaging, cutting the plant off at the stem.
  • Dig near a dying plant to find the caterpillar as pictured.


  • Damage is caused to newly planted seedlings, they often wilt and die as a result.
  • You will find holes eaten at the base of the plant, below soil level.
  • The caterpillar is white as below, and grows into a Click Beetle.


  • Common in warm dry areas, prefer open ground
  • can be very damaging to germinating crops, particularly those direct drilled
  • Adults are often seen on sunny days when their silvery wings reflect.
  • These bugs are between 2 – 4mm long, as pictured.
  • Also pictured is Nysius damage to a swede crop.


  • Moths are around 10mm long, have diamond shape on their wings
  • Larvae burrow into leaf and feed on the tissue.
  • Caterpillars feed on underside of leaves, and are a yellow grey/green colour


  • Butterflies are white with one or two black spots on their wings
  • Caterpillars are green with a narrow orange strip down their backs
  • Caterpillars may reach 25 mm long, and feed on the leaves only, leaving the veins.
  • Its rare to get severe damage from White Butterfly, but it can happen.


  • Adults are 2 – 3mm long and are difficult to see
  • On hatching the white legless larvae tunnel into the stem where they usually remain until ready to pupate
  • Most damage is done when the larvae mine the stem, causing the plant to yellow and often die.


Early control is key – so early detection is critical.

Take a photo and send it to your Smart Agronomist, or just call, and you’ll have a recommendation sorted real quick. 


Until next time, all the best and keep smiling!

The Smart Team