Lawn grubs are a common problem in South East Queensland during the period from November to May, more so to couch lawns rather than ‘Sir Walter’ lawns. They are easily treatable if required, early detection and prevention is the simplest way.
There are two main types of lawn grubs to look out for: – Armyworm and Sod Webworm
The armyworm is like a caterpillar, usually brown to dull grey, with black stripes on their body, size from 10mm to 30mm long, they are mostly active at night, feeding on the leaf blades of your lawn. They can devastate an entire lawn in 2 – 3 nights.
These sod webworms are commonly confused with cut worm, however both are treated the same and look very similar. They are transparent, but you can see the green materials they are eating so they can appear greenish. They are smaller than the army worm in size, about 10mm – 25mm, they are also active at night. The adult moth will lay eggs in flight; hatching should take place in 5-7 days’ time.
Patches of brown or thinning turf – may suggest there is grubs present, however you may need to use one of the methods below to be sure.
- A visual inspection of the leaf blade can be an effective method, you will actually see holes or part of the leaf missing like chew marks, in bad infestations there will be very little or no leaf at all to see.
- Use a hose to flood an area, they will come crawling out to the leaf tips, do this in a healthy part of the lawn near infected patches as they prefer the greenest areas.
- Try pouring a bucket of soapy water over your lawn & look for them.
- Check under the eaves of your house for furry brown patches, these are moth eggs waiting to hatch.
- Try parting the leaf blades and look for an accumulation of fresh small green pellets of excrement, these are their droppings.
- If there are orange / black wasps “The Ike Newman Wasp” (Leptobatopsis Indica) flying over your lawn, this will usually indicate that there are grubs present, as the wasp is looking for a host to lay its eggs.
Spray, spread or hose your lawn with an insecticide, there are various types- You must follow label instructions.
We suggest Sir Walter Pest Control (available from our Lawn Shop)
Now it is important to break the life cycle of the lawn grub by respraying in 7 – 10 days.
If your lawn was damaged by grubs you can fertilize the patches lightly to aid the recovery. – we suggest Sir Walter Fertilizer – slow release fertiliser (available from our Lawn Shop)
Tips on Spraying:
- Always spray in the evenings, the chemical you are using will breakdown in sunlight within 2 hours of application, which will be before the lawn grubs have a chance to come in contact with the chemical
- Don’t spray if rain is likely within 2 hours
- Read the label on the bottle and always follow label rates
- Only spray when protecting a new lawn or when they are in large damaging numbers
- Respray your lawn in 7 -10 days to help break the lifecycle
- Prevention is the best way to manage lawn grubs
- Over fertilized lawns are prone to frequent attacks so fertilize your lawn correctly. Avoid fertilizing during summer months (Dec-Feb); fertilize for growth not a deep green colour.
- Keep the eaves around the home free from moth’s eggs, remove with a broom or mop.
- Remember insecticides can kill lawn grubs and all other natural predators, the lawn grub will recover first, this may cause you to spray until nature (winter or extended cold weather) takes over again, there for only spray if necessary.
- Outdoor lights & street lights with lush lawns within close proximity will attract the moths, hence lawn grubs, and therefore will be a likely starting point.
White Curl Grub
Scarab beetle larvae, also known as white curl grub are a serious lawn pest. In subtropical areas, lawn damage is commonly seen from November through to January. The most common causal agent is the African black beetle. The African black beetle larvae grow to 20-25 mm in length before pupating in the soil. They have an orange-brown head capsule. Oval-shaped, shiny black adults, 12-15 mm long, emerge during February feeding on stems just below ground level. They are less active through winter and mate in spring.
White curl grubs (scarab beetle larvae – juvenile stage of lawn beetle) have a characteristic ‘C’ shape and three pairs of legs. They live underground, protected by soil. These develop into larger larvae and are voracious feeders on roots and underground stems. The adults also feed on turf but cause much less damage. A problem infestation is generally looked upon to be 25 or more white curl grubs per square metre. If few larvae are present, healthy turf is likely to outgrow the minor damage it will sustain. Under heat and drought stress, the problem may be exacerbated by reduced rates of regrowth and smaller numbers of larvae can cause major damage.
- Try pouring a bucket of soapy water over your lawn to move them to the surface
- Moisten a hessian bag or piece of carpet and place it on the lawn overnight to detect them the next morning
- Use garden lighting to attract and to detect adult beetles
- Chemical control measure are most effective on newly hatched larvae
- Prior to treatment, water the lawn well to bring the larvae closer to the surface
- Infiltration of chemical will also be improved by mowing and raking of out of thatch
- Spray, spread or hose your lawn with an insecticide, there are various types available – You must follow label instructions.
- We suggest Sir Walter Pest Control (available from our Lawn Shop)