Pests

Pests sub-sections:

Lawn Grub

The main grub in the area is the Lawn Army worm. They can advance in mass across a field, consuming the grass as they go hence the name army worm. This grub only affects lawns in summer. Lawn grub, (Armyworm), is a moth caterpillar that feeds on the turf foliage at night. The grubs come in large numbers and can cause rapid damage as they move across the turf area.

The Life Cycle :
The moths emerge from the pupae and crawl to the soil surface. They mate from the first night after emergence and egg laying may commence two nights later. Most eggs are deposited between dusk and midnight with individual moths laying up 4000 eggs with and average of 1700. Egg masses are seldom laid directly on the host plants, and are more commonly found on adjacent vegetation. Citrus, eucalypt, papaya etc leaves are favoured backyard oviposition sites but eggs may be laid on the walls and under the eaves of buildings. Egg masses occur on both upper and lower surfaces of the leaves, usually within a few metres of the ground. Eggs hatch more or less simultaneously.

Young armyworms have well developed ‘silk glands’ and may use silk threads to lower themselves to the ground. They prefer sheltered feeding sites. Feeding commences immediately after hatching and continues at night until larval maturity.

Eggs hatch in 2 to 3 days at 27oC and the whole lifecycle from egg to adult can take as little as a month. The larval stage may take as little as 2 to 3 weeks.

Apart from areas of dying lawn, the main indicator of the presence of Army worm is a red wasp with a long sting hovering over the lawn (these are predators of the army worm), birds (ibis or plover pecking into the lawn), or a build-up of yellow cocoons on your house eaves.

To actually identify army worms either put a wet bag on the lawn in the evening then turn it over in the morning -brown, greenish brown or black coloured caterpillar-like grub and sometimes with a striped or triangular markings- this is an army worm; or you can flood a small patch of your lawn and they will come to the surface. They feed on lawns in large groups then when the food supply is exhausted they move off together, a bit like an army on the march.

Particularly affected are Kikuyu and couch lawns and less affected are the buffalo grasses. Be vigilante with newly laid down turf and watch out for the army worm. You should spray the army worm as soon as you are aware of them as they love the new root shoots of new turf and can do great damage very quickly thus please seek out assistance from your local nursery immediately.

To control army worm at this stage the only effective way is with insecticides. Purchase a lawn grub killer form you garden shop. Follow all instructions and safety directions. It is very important to spray in the evening and quite often helps if insecticide is washed in with a light sprinkler.

The bad news is that it is possible for lawns to be attacked several times in Summer and early Autumn If this happens retreat with Insecticide. The roots of the lawn should still be intact despite the damage to the leaf area, it is possible to get regrowth by applying a fast acting fertilizer. Also there is some indication that crusher dust used as base for lawn may retard army worm.

As a prevention, we recommend you maintain your lawn with regular mowing during the warmer months. The eggs are laid in masses of 600-700 eggs that are covered with long, light brown hair, these felt-like egg masses are cemented to leaves of trees and shrubs or on building close to light and are often found on eaves and open ceilings. Brushing the egg masses of helps to physically control the insect,

The lawn armyworm is a serious problem and loves feeding on just about any lawn variety. Severe damage to lawns is characterised by a completely strip a circular area sharply defined by a front of undamaged turf. With heavy populations of actively feeding larvae, this destruction may advance about 30cm each night.

Top

Fungal diseases

Fungal diseases usually occur in the lawn when conditions are damp and the strength of the grass is low. The appearance of fungus is probably the most common symptom of “run-down” turf arising from such causes as over compaction of soil, nutrient and pH imbalance, inadequate drainage, poor soil aeration, dense shade, over close mowing and a shallow depth of topsoil.

The following can be found in lawns:

  • Liverwort (tiny coloured flowers on long stems)
  • Dry Rot ( Fusariuim spp)
  • Dollar Spot (Sclerotinia homeocarpa) in turf (appears as small freckles across the lawn (about the size of a 50 cent piece))
  • Fairy Rings – toadstools (either toadstools or an outline of a cloud shape and the outline is darker green than the rest of the lawn.

The eradication of fungal diseases can only be achieved effectively when the cause can be correctly identified and conditions rectified. The removal of the cause results in a slow disappearance of the fungus and prevention of its return. Attention to general maintenance such as the improvement of drainage, the application of fertiliser to improve the turf quality and aeration will have obvious benefits.
The most common type of fungal disease is Dollar Spot -

DOLLAR SPOT IN TURFGRASS (Sclerotinia homoeocarpa)
Dollar spot originally was a major concern on bentgrass in where it formed spots the size of silver dollars, consequently the name “dollar spot” and in lawns the fungi may infect large areas. Infected areas 10 cm or larger may run together, causing great patches of dollar spot over the turf area. Irregular patches to 3 metres wide can occur in blue couch, and saltine varieties of lawns.

Dollar spot fungi can be spread by mowers, feet, hoses, travelling sprinklers and other maintenance equipment. Keeping your equipment clean will help prevent the fungi from spreading, .Strains of dollar spot fungi grow within a wide range of temperatures, so this turf disease may be active from late spring to late autumn. Although, most problems develop when temperatures are tolerably warm and change rapidly, as with warm days and cool nights.

A Dollar spot fungus is complex and is often serious during the hot weather, many home gardeners perceive the resulting bleached grass is caused by lack of water. They don’t understand that the problem is caused by a fungus and then flood the area with water and the disease gets exceedingly multiplies.

IDENTIFICATION
Affected leaves will show yellow-green blotches or bands that generally can go undetected. These lesions gradually bleach to a white or straw colour. On finer-textured turf grasses, individual lesions on the leaves often bridge the width of the grass blade, producing a constricted area resembling an hourglass. On coarser grasses, the spots caused by dollar spot may not span the blade.

The tip of the leaf blade may show the characteristic lesion, or the lesion may be in the middle of the blade, leaving the leaf tip green. When the turf grass is wet from early morning dew, a fine, white cobweb-like mycelial growth (strands of fungus) may be visible on the diseased leaves. As the grass dries out the mycelium disappears. Be sure not to confuse this with spider webs.

Heavy layers of a thatch can encourage Dollar spot because water, air and nutrients cannot penetrate to the underlying soil and grass roots. This results in shallow and poorly developed roots that are highly susceptible to drought stress.

CONTROL
If you want to water during daylight hours, allow grass to dry for at least one hour before watering. When watering very late in the day, allow time for grass blades to dry before nightfall. Early morning watering (before sunrise) helps remove dew from the leaf surface.

  1. Spray the lawn area with Mancozeb. Plus twice more at 6 day intervals if you notice Dollar spot.
  2. Never water the lawn in the late afternoon or at night as this enhances the growth disease.
  3. Cut the lawn at least once every 6 day. Wash the underside cutting area and wheels of the mower. Then spray with a solution of one part White King mixed with nine parts of water to sterilize.

POINTS TO REMEMBER
Turf grass under stress is more susceptible to infection.
Proper lawn management, such as aeration, proper watering and fertilization, will reduce dollar spot problems.
Use fungicides only in situations with recurrent dollar spot problems.
Ensure nitrogen levels are sufficient to sustain a moderate rate of shoot growth

Top

Weeds

Healthy turf should be able to eradicate most weed infestations. Regular moving will remove most weed heads before they can set seed. This generally alleviates the need for chemical application in a lot of cases and can dramatically reduce the appearance of weeds. The right height for your grass helps to shade weeds out of existence.

By mowing both often and regular you remove the seed heads of weeds making it harder for them to seed their next crop. Dry, wet or compact soils all promote weed growth because your grass usually struggles under these conditions. The weaker your grass condition is then the more chance weeds have of surviving multiplying. Practicing good lawn maintenance procedure is the best policy you can adopt to assist in the eradication of weeds and ensure you maintain good condition for your turf to survive.

There are two types of weeds, broad leafed weeds and narrow leafed weeds. – grass weeds.

Broad Leaf weeds
Broad leafed weeds are usually the main problem. These include the burrs, pig weeds and sensitive weed. Generally anything that is not a grass weed (a grass having a leaf that is basically the same width at the bottom and the top), is a broad leafed weed.

Purchase a broad leaf weedkiller from a garden shop. They may have different names but the active ingredients should be M.C.P.A. and Dicamba. Make sure your grass weeds are growing well, this may mean fertilizing them a couple weeks before spraying, and watering them the day before you spray. Mix up spray to manufacturers recommendations, observing all safety procedure.

Generally it is best to spray in the morning after the dew has gone and do not spry if rain is expected within 4 hours. You can spot spray the weed or spray the whole areas. Remember most of your gardens plants are broad leafed plants so avoid spray drift. Usually you will see weeds start to brown off in a week. Also do not mow for a week after spraying.

Grass weeds
Grass weeds are a bit harder to control but are generally not so unslightly in your lawn. The decision must be made whether to bother to get rid of them as in grass like broad leafed carpet grass they do not stand out. Some grasses weeds are only annuals i.e. will grow, put out a seed head, then die. These may be the prevalent grass weed in some lawns that have suffered badly from the drought. To get rid of these weeds keep moving and fertilising to get your lawn thick and healthy so they cannot germinate next year.

And last but not least the cheapest and most efficient and most environmentally friendly, is to pull the weeds out. Ideally wait for some wet weather and get stuck in with the whole family.

Bindi 
These form from the stem at the base of the leaves tiny flowers which are produced in spring and these turn into burrs of sharp spines.  This is best sprayed with Roundup or Zero. (Please be careful and follow instructions very carefully).

Be careful with Buffalo what chemicals you use and use ones that are specifically for broad leafed lawns.

Nutgrass
A weed that spreads by a tough wirey root system with small nutlike tubers that from on the roots It is a perennial weed with grass like leaves in the shape of triangular flowers stems which bear flowers and seeds in umbrella like heads with a reddish-purple or brown appearance. Nut grass is extremely difficult to kill, and the best way to rid this nasty weed is by digging out the whole plat ensuring you remove all the toots and bulbs (any root or bulbs left will reproduce.) Registered products include Monument and Sempra will kill it. Again please read and follow the instructions as directed.

Others: 
Other intrusive seeds include: crowsfoot, summer grass, wintergrass and catsear and again the best way to rid each of these weeds is to dig out and also ensure the roots are dug up a well.

Top