Shothole
Registered against on 4 crops
Shothole (caused by the fungal pathogen Wilsonomyces carpophilus) is a damaging foliar and fruit disease primarily affecting stone fruit crops such as cherries. In susceptible orchards, unmanaged infections lead to severe canopy defoliation, weakened flower bud development for subsequent seasons, and direct fruit blemishes that render harvested produce unmarketable for fresh retail markets.
While shothole is classically recognized as a high-priority disease in cherry production, Australian APVMA registration data also covers specific treatments across citrus crops including oranges, lemons, and limes. Rain-splashed spores can spread rapidly through wet microclimates, making proactive canopy management essential.
Where it matters in Australia
Shothole is a major seasonal concern across temperate stone fruit districts in southern Australia, including the Goulburn Valley, Young, Orange, the Adelaide Hills, and Tasmania, where wet spring weather drives rapid spore germination. In citrus-growing districts such as Sunraysia and the Riverland, APVMA registrations exist for specific protective treatments, though stone fruit blocks—particularly cherries—remain the core focus of seasonal shothole management.
Symptoms
Foliar symptoms begin as small, circular, purplish to reddish-brown spots on expanding foliage. As the lesion expands, the center dries out, turns papery brown, and drops away clean from the healthy tissue, leaving characteristic round 'shot holes' with dark margins. Severe leaf infection leads to premature defoliation.
On developing cherry fruit, lesions appear as small, raised, brown spots surrounded by a reddish margin, often exudating clear droplets of gum. Unlike bacterial spot, which creates water-soaked, irregular margins, shothole leaf lesions are distinctly neat and circular. Twig infections show sunken, purplish-black lesions that may girdle smaller lateral shoots.
Life cycle
The pathogen overwinters as dormant mycelium or spores within infected buds, stem lesions, and fallen leaf litter from the previous season. In spring, rising temperatures combined with rain events or overhead irrigation trigger spore release.
Spores travel short distances via rain splash and wind-blown droplets to land on expanding leaves, blossom tissue, and young green fruit. If free moisture persists on the canopy, infection occurs rapidly. Secondary cycles of spore production continue throughout warm, wet spring and summer conditions, building up disease pressure within the canopy until autumn leaf drop.
Monitoring
Begin orchard monitoring during winter pruning by inspecting dormant buds and twigs for dark, sunken lesions and dried gumming. From bud swell through to shuck fall and early fruit development, inspect 10 to 20 trees per block weekly.
Focus scouting efforts on the lower and inner canopy, low-lying orchard sections, and sheltered blocks where leaf wetness persists. Look for tiny purplish spots on expanding leaves and young fruit immediately following spring rain events. Decision-making relies on applying protective cover prior to forecast rainfall during sensitive growth stages rather than waiting for visible shot-hole symptoms to appear.
Management
Effective shothole control relies on an integrated approach combining winter hygiene, canopy architecture management, and targeted chemical protectants.
Prune out dead wood, blighted twigs, and canopy hotspots during winter to reduce overwintering inoculum and open the canopy for rapid leaf drying and improved spray penetration. Ensure irrigation systems avoid wetting the leaf canopy where possible.
Chemical management should focus on protective sprays applied ahead of predicted rainfall events during critical early-season growth windows. Rotate fungicide mode-of-action groups across the season to manage pathogen resistance risks. Always consult the approved APVMA product label for crop safety, harvest WHPs, and application directions.
Crops with registered control options
Common questions
- Why does the registered use table show 139 products for cherry but only 1 for citrus crops?
- Shothole is a primary fungal pathogen of stone fruit, which is why cherry growers have access to a wide spectrum of multi-site protectants and systemic options. The single registration across orange, lemon, and lime reflects a specific dual-registered or minor-use compound. Always verify that your intended target crop and pest combination is explicitly stated on the product label.
- How do I decide between protectant and systemic fungicides for shothole?
- Protectant fungicides must be applied before rain events to establish a surface barrier that prevents spore germination. Systemic treatments offer limited curative activity if applied immediately following an infection window. Choose based on weather forecasts, canopy growth stage, and your spray diary rotation strategy; always check the label for specific timing directions.
- Where do I check withholding periods (WHP) and spray re-entry intervals?
- All statutory WHPs, maximum seasonal application limits, and re-entry intervals are detailed in the Directions for Use section of the APVMA-approved product label. Because these values vary by crop, rate, and chemical class, do not estimate them—always read the physical label affixed to the container.
- Why is autumn orchard sanitation important for spring shothole control?
- The pathogen overwinters in twig lesions, infected buds, and leaf litter on the orchard floor. Managing fallen leaves in late autumn via flail mowing or leaf-breakdown treatments speeds up tissue decomposition, significantly reducing the spore population ready to infect the emerging spring flush.
- How do I manage fungicide resistance when spraying for shothole?
- Continuous reliance on single-site systemic fungicides creates selection pressure for resistant fungal strains. To preserve chemical efficacy, rotate between different fungicide mode-of-action groups (identified by the group letters/numbers on the product label) and incorporate multi-site protectants where registered.