As the drydown period progresses the stalks of most crops will gradually change from green through shades of red to straw before drying off completely.

May occur a short time after black layer (R6) while the plant still has marked green leaf area. Monitor root strength in affected plants, assess frequency of symptoms. Factor this into future decisions.

Various pathogens can cause this reaction including anthracnose and nonspecific top dieback.

Most often caused by NLB at this late stage. As plant defences shut down this previously supressed disease takes over.

As the drydown period progresses the stalks of most crops will gradually change from green through shades of red to straw before drying off completely.

Usually accompanied with a complete loss of GLA as well as changes in stalk colour and strength. This can be the result of specific pathogens or combinations of pathogens.

Usually accompanied with complete loss of GLA as well as changes in stalk colour and strength. This can be the result of specific pathogens or combinations of pathogens.

Even the healthiest of stalks can break in extreme weather conditions. With stalk integrity naturally lower now than in previous growth phases, weather conditions capable of causing stalk lodging may be relatively moderate.

Often significant hybrid differences in plant integrity during drydown. Providing stalk strength below the ear is not overly compromised, upper canopy stalk breakage during this phase is not a major concern.

Even the healthiest of stalks can break in extreme weather conditions. With stalk integrity naturally lower now than in previous growth phases, weather conditions capable of causing stalk lodging may be relatively moderate. Upper canopy stalk breakage during this phase is not a major concern.

Currently not present in NZ but something all growers should be aware of in case of a future biosecurity incursion. This pest is also responsible for chewing holes in the ear peduncle/shank causing premature ear drop.

Stalks often redden during the drydown period caused by anthocyanin deposition, indicative of a surplus of photosynthates. Red stalks are an indicator of good stalk strength.

As the crop dries down plants naturally go through a period of senescence leading to plant death and natural reduction of plant integrity and ultimately, the collapse of the above ground vegetative parts. This process is sped up when saprophytic fungi move from the roots up the stems.

A rapid change in colour of the brace roots, relative to neighbouring plants is indicative of root rot. Test the root strength or resistance to root lodging by following the method described in the Root Problems overview.

As the crop dries down plants naturally go through a period of senescence leading to plant death and natural reduction of plant integrity and ultimately, the collapse of the above ground vegetative parts.

Test the root strength or resistance to root lodging by following the method described above. If weak, dig up a few plants to examine the roots. Compare the roots of these to a few of the stronger plants. Drought conditions during the previous growth phase predisposes crops to root rot.

Some hybrids tend to have stronger roots and/or stalks than others and are more capable of withstanding moderate to extreme weather events. If adverse weather events during this growth phase are common in your area, consider stalk and root strength as key factors in the hybrid decision making process. Also, planting at moderate populations of 95,000 seeds/ha or less will help reduce risk.

Corn earworm and cosmopolitan armyworm. Refer to Pests for more details on these insect pests.

Rodents often congregate in sheltered areas neighbouring crops so most damage is confined to the outside few rows. Bird damage is usually more widespread and can range from subtle to severe. Usually worse in years where alternative food sources are low.

Various fungi including Gibberella (white/pink discolouration), Penicillium (blue-green) and Aspergillus (black). See Diseases for more details on these cob diseases.

Various fungi including Gibberella (white/pink discolouration), Penicillium (blue-green) and Aspergillus (black). See Diseases for more details on these cob diseases.

Various fungi including Diplodia (white discolouration), Fusarium (white/salmon), Penicillium (blue-green) and Cladosporium (black).

Green vegetable bug (GVB) use their proboscis to penetrate the husks and pierce the kernels creating browny-grey discoloured marks on the kernel surface. Refer to Pests for more information on this insect pest.

Husks at cob tips appear shredded rather than chewed.

Corn earworm or cosmopolitan armyworm. Husks at tips appear more chewed than shredded, usually associated with caterpillar droppings. See Pests for more details on these insect pests.

Some hybrids have relatively short husks compared to others.

In some seasons, hybrids with usually decent husk cover can produce relatively short husks leaving the cob tips exposed. If this is a concern, and/or weather conditions favour certain cob rots, regularly scout your crop during the late-grain fill and drydown periods.