Insect Control

Grass Grub

Grass Grub (Costelytra zealandica) also known as Brown Beetle is a native species that like many biting and chewing insects has a distinct annual life cycle. The adults emerge from October through until February and lay eggs in the soil. They also feed on foliage and may occasionally strip the leaves of cherry and plum trees. The larvae hatch from the eggs after 2 weeks and then inhabit the root zone (20mm – 30mm deep) from March until June eating the roots of susceptible species. After this time they descend to a depth of 150mm – 300mm where they overwinter. The damage they cause to plant roots reduces the plants ability to uptake water and the outcome is patches of dead grass particularly through times of drought or sustained moisture stress. The grubs vary in size from 10mm – 15mm in length and are creamy white colouration with a black abdomen. Flocks of birds particularly starlings feeding in turf often indicate a heavy infestation of grass grub.

Survey the lawn by take spade width squares in a variety of area preferably before damage is noticeable. This is best to occur during the period December or March. Tip the sod upside down and inspect the soil. If two or more grubs are found then apply Pyrifos G granules at label rates. Please treat this compound as a poison and take all necessary precautions to ensure that there is no skin contact. Apply 25mm of water within 7 days of application

Argentine Stem Weevil

Argentine Stem Weevil (Listronotus bonariensis) like other weevils are distinguishable from beetles by their long snouts and their legless grubs or larvae. Adults are small being approximately 5-10mm long and greyish brown in colour whilst the larvae are creamy white. This is mainly a pest of ryegrass in particular with the larvae feeding within the grass stem whilst the adults feed on expanded leaves. The damage caused by adults in particular is noticeable by the windows they chew in the leaves. Damage from Argentine Stem Weevil can occur throughout the warmer months from September through until late April.

Black African Beetle Adult

Black Beetle(Heteronuchus arator) It is generally found in the top half of the north island though it has been reported as far south as Wellington. Originally it was a native from South Africa although it has now been in both NZ for a long time. The adult black beetle is approximately 15mm long and has a shiny, black and sturdy in appearance. As an adult it can be found throughout the year but most predominantly from the months of February through until October. The adults burrow into the soil where they also consume the roots of grasses. The larvae which are larger than the larvae of the grass grub are creamy white in colour with a black head and abdomen. They live in the top 20mm – 50mm of the soil profile where they eat the roots of susceptible species with the majority of the damage done from October through until March. The damage is obvious after a period of hot, dry conditions when the affected plants struggle to uptake sufficient moisture as a result of their impaired root function. Without regular irrigation these plants will desiccate and die. For that reason treatment is recommended in October and November prior to the worst of the damage occurring.

Survey the lawn by take spade width squares in a variety of area preferably before damage is noticeable. This is best to occur in November or December. Tip the sod upside down and inspect the soil. If two or more grubs are found then apply Pyrifos G granules at label rates. Please treat this compound as a poison and take all necessary precautions to ensure that there is no skin contact.

Black African Beetle

Black Beetle(Heteronuchus arator) ) It is generally found in the top half of the north island though it has been reported as far south as Wellington. Originally it was a native from South Africa although it has now been in NZ for a long time. The adult black beetle is approximately 15mm long and has a shiny, black and sturdy appearance. As an adult it can be found throughout the year but most predominantly from the months of February through until October. The adults burrow into the soil where they also consume the roots of grasses. The larvae which are larger than the larvae of the grass grub are creamy white in colour with a black head and abdomen. They live in the top 10mm – 50mm of the soil profile where they eat the roots of susceptible species with the majority of the damage done from October through until March. The damage is obvious after a period of hot, dry conditions when the affected plants struggle to uptake sufficient moisture as a result of their impaired root function. Without regular irrigation these plants will desiccate and die. For that reason treatment is recommended in October and November prior to the worst of the damage occurring.

Apply Pyriphos 10G granules in October – December as per label instructions. This is an insecticide and precautions should be taken to avoid contact and to avoid inhaling any dust whilst applying this product. Ensure that at least 25mm of water is applied within 7 days of application. If the infestation is acute a second application may be required in January or February. An approved Handlers certificate is now required to purchase this product. Alternatively, a treatment using Acelypron at label rates will control black beetle in both adult and larval form.

Black Cricket

These are also known as Black Field Crickets or simply field crickets. They are generally found on clay soil types over summer when cracks in the ground profile create an ideal environment for them to live. The crickets live in these cracks or holes in the ground and emerge to feed on the leaves of the grasses often severing leaves and taking them back to their burrow to eat. They take the closest plants first and as a result a bare patch around their home is very evident. The majority of the damage is visible over the summer months from January until April. They are visible during the day and move quickly when disturbed by foot traffic.

Increase the watering regime to swell the soil and decrease the incidence of cracks on the soil surface. Apply bait. This is normally in the form of treated wheat or barley. Care should be taken as the bait is poisonous.

Porina Caterpillar

Porina (Wiseana spp.) comprises several species of native moth whose caterpillars are common pest of turf. These large caterpillars are approximately 50 – 75mm long when mature and are grey to greyish yellow in colouration. They live in shallow vertical tunnels and emerge at night to feed on grass leaves. Turf damage around the tunnels is particularly noticeable from autumn onwards.

Place boards on the lawn over an evening. Once the boards are removed the following morning the porina burrows will have been clearly exposed. If five (5) or more burrows are apparent per square metre then control will be necessary.

Sod Webworm

The term Sod Webworm is used to denote the species that includes Eudonia spp., Orocrambus spp. and Scoparia spp. The adults emerge as moths from September through until December. These adult moths feed on clover and the flowers of native plants. Egg laying continues until late February. The resultant caterpillars live in shallow burrows in the ground and emerge to eat the foliage of surrounding grass plants. Damage is known to occur from January until as late as October however typically the majority of the damage is seen occurring during the period February – June. The caterpillars range from 10 – 20mm in size and are generally green with dark green spots located in lines down the length of the body. Because they live in shallow burrows, heavy rain on flat ground is known to reduce numbers through drowning of the caterpillars. No pesticides are registered specifically for sod webworm control after cultivation, however, any products containing chlorpyriphos or pyrethroid should provide effective control if applied in autumn when their activity is at a peak.

Apply Pyriphos granules at label rates from late March to June. Ensure that at least 25mm of water is applied within 7 days of application.

Tasmanian Grass Grub

Tasmanian Grass Grub (Acrossidius tasmaniae). This species is often confused with Black Beetle as both the adults and the grubs look similar. However, the grubs which unlike Black Beetle live in small burrows near the surface and emerge to eat foliage near the tunnel entrance. They create damage from the period May through until November, with the adults emerging in December and January.

Survey the lawn by taking spade width squares in a variety of areas preferably before damage is noticeable. This is best to occur in November or December. Tip the sod upside down and inspect the soil. If two or more grubs are found then apply Pyrifos G granules at label rates. Please treat this compound as a poison and take all necessary precautions to ensure that there is no skin contact. This product requires 25mm of water applied within 7 days of application.