Barley Farming Guide

What you will see

Net form: dark brown lesions with a distinctive net-like pattern of cross-hatched lines visible with a hand lens. Spot form: dark brown oval spots without the net pattern, often with a yellow halo. Both forms cause premature leaf death, starting from lower leaves and progressing upward.

Conditions that favor it

Cool, wet weather (15-25°C). Spread from infected stubble and seed. Continuous barley cropping dramatically increases inoculum. The most common and damaging disease of barley worldwide.

What you will see

Pale green to gray, water-soaked lesions on leaves, often with a distinctive dark brown margin. Lesions are irregularly shaped and tend to start at the leaf tip or edge. Severe infections cause leaves to look "scalded" — gray-green and papery.

Conditions that favor it

Cool (10-20°C), wet weather with frequent rain or heavy dew. The most important foliar disease in cool, maritime climates (UK, Northern Europe, Pacific Northwest). Spread by rain splash from lower to upper leaves.

What you will see

White-gray, fluffy fungal growth on upper leaf surfaces, stems, and heads. Pustules can be rubbed off the leaf surface with a finger. Leaves underneath the mildew turn yellow and die. Severe infection reduces grain size and number.

Conditions that favor it

Dense canopy, moderate temperatures (15-22°C), high humidity. More common in early-sown, high-nitrogen, lush crops with dense canopies. Barley-specific mildew strains — does not cross-infect wheat.

What you will see

Premature bleaching of spikelets, pink-orange mold at the base of infected spikelets. Infected kernels are shriveled, chalky, and may have a pinkish color. Produces DON (vomitoxin) mycotoxin that contaminates grain. Malting barley with FHB is rejected — DON affects beer quality and gushing.

Conditions that favor it

Warm (25-28°C), wet weather during heading and flowering. Corn stubble in the rotation is the primary inoculum source. Devastating for malting barley quality — zero tolerance at many maltsters.

What you will see

Stunting, with leaves turning yellow (in barley) or purple-red (variable). Discoloration starts at the leaf tips and margins of older leaves and spreads inward. Root growth is reduced. Plants may tiller excessively but produce small, poorly filled heads.

Conditions that favor it

Transmitted by cereal aphids (bird cherry-oat aphid, grain aphid). Most damaging when infection occurs early (before tillering). Fall-planted barley in warm autumns with high aphid flights is most at risk. No cure once infected.

Damage

Direct feeding damage is minimal, but aphids transmit Barley Yellow Dwarf Virus (BYDV), which causes significant yield losses. Heavy populations also produce honeydew and reduce grain quality. Early-season aphid flights into fall-planted barley are the highest risk.

How to identify

Small (2-3mm), soft-bodied insects. Bird cherry-oat aphid is dark olive-green with a rusty-red patch near the tailpipes. Grain aphid is larger, green. Check stems, undersides of leaves, and developing heads. Threshold: 25% of plants infested in fall for BYDV risk; 5 aphids per head during grain fill for direct damage.

Damage

Larvae bore into the central shoot of seedlings, killing the main stem (deadheart). Tillers may compensate partially but maturity is delayed and yield reduced. Most damaging in late-sown spring barley where plants are at a vulnerable stage when frit fly adults are active.

How to identify

Small (2-3mm), shiny black flies. Larvae are white maggots (4-5mm) found inside the stem at the growing point. Deadhearts in seedlings that can be pulled out easily. Most common after grass leys where frit fly populations build up.

Damage

Both adults and larvae skeletonize leaves, scraping the upper surface and leaving only the lower epidermis (appears as transparent "windows" on leaves). Larvae are more damaging — each can consume 30+ square mm of leaf per day. Heavy feeding on the flag leaf reduces grain fill.

How to identify

Adults: small (5mm), metallic blue-black with orange-red thorax and legs. Larvae: slug-like, covered with a shiny, wet-looking dark mass of their own excrement (which they carry on their backs as protection). Threshold: 3 larvae per stem.

Damage

Feed on germinating seeds and emerging seedlings, shredding leaves and sometimes destroying the growing point. Most damaging in no-till and minimum-till systems where surface residue provides slug habitat. Can reduce plant stands by 20-40% in severe cases.

How to identify

Slime trails on soil surface and on damaged leaves. Gray or brown slugs (20-50mm) found under residue and clods during the day. Most active at night and in wet conditions. Threshold: 4+ slugs per trap in slug pellet assessment before planting.

Damage

Feed inside the boot on the developing head, causing white or silver discoloration on the awns and glumes. Kernel weight is reduced by 5-15% in moderate infestations. Malting quality may be affected through reduced kernel plumpness.

How to identify

Very small (1-2mm), slender, dark-bodied insects found inside the leaf sheath or boot. Peel back the flag leaf sheath during the boot stage — thrips are inside feeding on the developing head. Most common in hot, dry conditions. Threshold: 10 thrips per head.