Dealing with Grasshoppers and Locusts in Australian Gardens

Introduction: Understanding Grasshoppers and Locusts in Australian Gardens

Grasshopper pressure peaks in eastern Australian summers. Learn exclusion netting for precious plants, Eco-Neem spray timing, and which plants they tend to leave alone. This guide is written specifically for Australian gardeners, covering local varieties, climate-specific timing, and techniques that work in Australian soils and conditions. Whether you're in Queensland subtropical heat or Tasmanian cool temperate, you'll find actionable advice tailored to your region.

Grasshoppers and locusts represent one of the most challenging pest management issues facing Australian gardeners, particularly during the warmer months. These voracious insects can devastate vegetable patches, strip foliage from ornamental plants, and cause significant economic loss to both home gardeners and agricultural operations. Understanding the lifecycle, behaviour patterns, and effective control strategies specific to Australia's climate and geography is essential for maintaining a healthy, productive garden.

Identifying Grasshoppers and Locusts: Australian Species

Australia is home to numerous grasshopper and locust species, each with distinct characteristics and seasonal patterns. The most commonly encountered varieties in home gardens include:

• Migratory Locusts (Locusta migratoria) – These are the most destructive species in Australia, capable of forming massive swarms. They typically appear in eastern Australia from spring through to autumn, with peak activity during the warmer months.
• Australian Plague Locust (Chortoicetes terminifera) – Native to inland Australia, this species occasionally migrates eastward during outbreak years, particularly affecting Queensland and New South Wales gardens.
• Mountain Grasshopper (Phaulacridium vittatum) – Common in cooler regions of Victoria and Tasmania, this species prefers temperate conditions and can cause damage in autumn and early winter.
• Short-horned Grasshoppers (Acrididae family) – Various species throughout Australia, typically smaller than locusts but equally damaging to garden plants.

Key differences between grasshoppers and locusts include body size, colouration patterns, and gregarious behaviour. Locusts are generally larger, possess longer antennae, and demonstrate the remarkable ability to change behaviour and appearance when crowded – a phenomenon called phase polyphenism. In their gregarious phase, locusts form destructive swarms; in their solitary phase, they behave more like typical grasshoppers.

Seasonal Timing and Climate-Specific Patterns Across Australia

Eastern Australian Patterns (Queensland and Northern NSW)

Queensland gardeners face some of Australia's most intense grasshopper pressure. In subtropical regions, grasshoppers may remain active throughout the year, with peak populations occurring between December and March (summer). Spring (September to November) marks the beginning of breeding season, making this an ideal time to implement preventative measures.

The warm, humid conditions in coastal Queensland favour rapid grasshopper reproduction. Garden damage typically intensifies in January and February when juvenile grasshoppers mature and increase feeding activity. Irrigation systems common in Queensland gardens may inadvertently create ideal breeding conditions, so careful water management becomes essential.

Southern Regions (Victoria and Tasmania)

Tasmanian and southern Victorian gardeners experience a compressed grasshopper season. Peak activity occurs during the relatively brief warm period of December through February. Cool temperate conditions mean grasshopper populations remain lower overall, though the Mountain Grasshopper can still cause significant damage during autumn (March to May).

The advantage of cooler climates is that grasshoppers enter dormancy earlier, allowing gardeners a longer pest-free period. However, early spring warming in September can trigger unexpected population surges if conditions align favourably.

Inland and Central Australia

Gardeners in inland NSW, parts of South Australia, and central Australia must monitor for Australian Plague Locusts, particularly during drought-breaking rainfall events. These conditions trigger explosive population growth, potentially leading to swarms that migrate toward coastal agricultural areas and gardens. The unpredictable nature of inland rainfall means grasshopper outbreaks can occur suddenly and intensely.

Exclusion Netting: Physical Barriers for Precious Plants

Exclusion netting represents one of the most reliable, chemical-free methods for protecting high-value plants. This approach works exceptionally well in Australian gardens where summer heat can intensify during peak grasshopper season.

Selecting the Right Netting Material

Quality exclusion netting should have a mesh size no larger than 2mm to effectively exclude even juvenile grasshoppers. In Australia, several options are readily available:

• Insect mesh netting – Lightweight, UV-stabilised mesh specifically designed for insect exclusion. Australian brands typically withstand harsh UV exposure and can last multiple seasons.
• Fine agricultural netting – Heavier duty options suitable for larger garden areas, though more expensive than lightweight alternatives.
• Shade cloth modifications – Repurposing fine-mesh shade cloth (commonly available at Australian nurseries) as an economical alternative, though less durable than dedicated insect netting.

Installation Best Practices

Proper installation is crucial for exclusion netting effectiveness. The netting must be secured tightly to the soil or garden bed edges to prevent grasshoppers from finding gaps. Use pegs, rocks, or soil to weigh down the netting perimeter completely.

Consider the height of your plants when installing netting. As plants grow through summer, ensure adequate space remains between plant foliage and the netting. Installing netting on frames or hoops allows easier plant access for watering and harvesting whilst maintaining complete protection.

In high-wind areas (common in parts of inland NSW and South Australia), reinforce all attachment points and consider using heavier-duty netting that can withstand gusty conditions typical of Australian summers.

Maintenance During the Growing Season

Inspect netting regularly, particularly after windy periods or heavy rain. Small tears can become entry points for grasshoppers, so repair damage promptly using garden tape or replacement patches. Remove netting during flowering periods if pollinator access is necessary, then replace it immediately afterward to prevent grasshopper damage to developing fruits and seeds.

Organic Spray Solutions: Timing and Application

Eco-Neem Spray Protocols

Neem oil-based products like Eco-Neem contain azadirachtin, a natural insecticide derived from neem tree seeds. These products are particularly valuable in Australian organic gardening because they disrupt insect feeding and reproduction without harming beneficial insects when applied correctly.

Timing is critical for neem spray effectiveness. Apply when grasshopper populations are still in juvenile stages (nymphs) during September and October in most of eastern Australia. Juvenile grasshoppers are more susceptible to neem's effects than mature adults. A single application to mature grasshoppers is rarely sufficient; plan for multiple applications across the season.

Application Guidelines for Australian Conditions

Australian summer heat affects neem spray efficacy significantly. Apply Eco-Neem early in the morning (before 8 AM) or in late evening (after 5 PM) to avoid the intense midday heat that can reduce the product's effectiveness. Never apply during peak heat in January or February midday hours, as the heat will cause the neem oil to evaporate too rapidly.

Thorough coverage is essential – spray both upper and lower leaf surfaces where grasshoppers feed and hide. In Queensland's humid conditions, repeat applications every 7-10 days. In drier inland regions, the interval can extend to 10-14 days as the product persists longer without being washed away by moisture.

Follow all label directions carefully, as commercial neem products vary in concentration. Always dilute according to manufacturer specifications, and wear appropriate protective equipment including gloves and a mask during application. Store neem products in cool, dark conditions – the hot Australian summer can degrade these products if left in sheds or garages.

Alternative Organic Sprays

Several other organic options work well in Australian gardens:

• Spinosad-based products – Derived from naturally occurring soil bacteria, spinosad is highly effective against grasshoppers. Apply in early morning or evening, as UV light breaks down the active ingredient.
• Pyrethrin sprays – Natural insecticides from chrysanthemum flowers, effective for heavy grasshopper infestations. Use only as a last resort due to potential impacts on beneficial insects.
• Garlic and chilli sprays – Homemade deterrents with limited but measurable effectiveness. These work best as preventative measures when populations are still low.

Plant Selection: Identifying Grasshopper-Resistant Plants

Strategic plant selection can significantly reduce grasshopper damage. Some plants possess natural chemical defences or structural characteristics that make them less palatable to grasshoppers and locusts.

Plants Grasshoppers Tend to Avoid

• Aromatic herbs – Lavender, rosemary, thyme, and oregano contain essential oils that deter grasshoppers. These Mediterranean herbs thrive in Australian gardens and provide dual benefits of pest management and culinary use.
• Tough-leaved plants – Aucuba, pittosporum, and many native Australian shrubs have tough, waxy leaves that are difficult for grasshoppers to consume. Native species like wattle and grevillea are particularly resistant.
• Plants with hairy foliage – Verbascum, lamb's ear, and similar plants with dense hair coverage tend to be avoided by grasshoppers.
• Plants with toxic compounds – Foxglove, digitalis, and many native plants containing alkaloids are naturally avoided by most herbivorous insects.

High-Risk Plants: Most Attractive to Grasshoppers

Conversely, certain plants are particularly attractive to grasshoppers and should receive extra protection during peak season:

• Legumes – peas, beans, and clover are highly preferred grasshopper foods
• Brassicas – cabbage, broccoli, and cauliflower are consistently targeted
• Young seedlings and tender growth on any plant
• Soft-leaved ornamentals like hydrangea and deciduous shrubs
• Vegetable crops during fruiting and seed development stages

Prioritise protection of these high-risk plants through netting or organic sprays whilst allowing grasshoppers to feed on less valuable, less palatable species in your garden.

Common Mistakes Australian Gardeners Make

Waiting too long to act: Many gardeners delay intervention until grasshopper populations are established and mature. By then, damage is severe and control becomes difficult. Begin preventative measures in spring (September) before populations peak.

Inconsistent spray application: A single neem spray application rarely controls grasshoppers completely. Commit to a regular spray schedule every 7-14 days depending on your location and weather conditions.

Improper netting installation: Leaving gaps at the base of netting or failing to secure edges properly allows grasshoppers to access plants. Take time to seal all potential entry points thoroughly.

Ignoring water management: Over-watering creates lush, tender plant growth that grasshoppers prefer. Additionally, moisture around garden beds provides ideal breeding habitat. Water deeply but less frequently to reduce grasshopper breeding conditions.

Neglecting garden hygiene: Dense plant debris, mulch piles, and overgrown weeds provide shelter for grasshoppers. Regular garden tidying reduces suitable breeding habitat.