The plant diseases we have in our crops are caused by
many different organisms, including fungi, bacteria, viruses, nematodes and
others. Fungicides are pesticides used
for controlling fungal and fungal-like diseases. This week, I wanted to bring a new M.S.U.
Extension MontGuide to your attention that is about fungicide use in field
crops and specifically talk about how to reduce the risk of fungicide
resistance developing.
When using fungicides for disease management, the
principles of integrated pest management should be used to avoid resistance
development. This includes such things
as preventative cultural practices, monitoring, acceptable pest levels,
mechanical controls, biological controls, and responsible use.
Preventative cultural practices include using high
quality, pathogen-free seed, crop rotation, using an adapted crop variety,
optimal seeding rate, planting date, irrigation practices where able,
fertilization and sanitation, such as breaking the “green” bridge.
Monitoring involves scouting crops for pests regularly
and getting them accurately identified.
You can then determine at what level the pest can or will be
tolerated.
Mechanical control methods include removing infected
plants from the crop to prevent reproduction and spread of the disease. Natural biological controls can also mitigate
pest damage. For plant diseases, these
can include beneficial insects predate on or parasitize insect vectors of plant
viruses.
When a pesticide is needed, be responsible and follow
all label restrictions and use the best application methods possible to target
the disease of interest. If a lack of
efficacy is suspected, leaved an untreated strip to compare with treated
areas. If the level of disease is the
same, then a symptomatic sample should be sent to the diagnostics lab. Other recommendations to prevent fungicide
resistance include selecting and using fungicides correctly, rotating the use
of fungicide modes of action, limiting the number of applications of fungicides
in a particular mode of action each season, mixing modes of action in blends or
tank mixes, using fungicides at the recommended rates and following all label
directions. Following these directions
should dramatically reduce your risk of developing resistance.
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