Dear Coffee Farmers and Friends,
The Coffee Leaf Rust (CLR), Hemileia vastratix was officially reported here in Hawaii during this week. This is a new issue that is expecting to affect the coffee industry in Hawaii. The best strategy for control is by planting coffee plants resistant to CLR. However, right now we do not have this kind of plants available to coffee growers in Hawaii. This does not mean that the coffee industry is expecting to disappear due to CLR. There are alternatives of management of this plant pathogen in coffee plants susceptible such as Typica, Caturra and Bourbon.
A combination of agronomic practices (control of weeds, fertilisation, pruning, regulation of shadow and number of trees per area) and sprays of fungicides (protectant and systemic) can help coffee farmers to keep CLR infection with low incidence (< 5 % infection) and low severity. Keep records of flowering (high, meddle and low intensity) help to establish a program for sprays of fungicides according with the phenology of the coffee plant. The goal is keep coffee leaves healthy and clean from CLR during the early coffee season (March - July ) when berries are growing and support the growing of foliage all time.
Defoliations caused by CLR not just affect the current production, but also the coffee production for the next year season. This is the reason why is very relevant to keep coffee plants with enough foliage that guarantee the fill-up of the berries. Therefore, a good program for control weeds, which reduce competition of nutrients and an adequate fertilisation program are key aspects to help in the regulation of CLR.
Here in Hawaii, we do not have information about how the CLR is going to affect coffee plantations and how weather conditions could be facilitate the dispersal of this pathogen and its infection. However, we know that some weather conditions such as temperature, relative humidity, sun radiation and precipitation play a relevant role in CLR survival, (dissemination, germination, colonisation and reproduction), which are the four stages of its life cycle.
Optimum temperatures for CLR ranging between 60 and 83 Fahrenheit (16-28 Centigrades). Locations with frequent precipitations especially during the afternoons are appropriate for the development of CRL. Coffee plantations at low elevation with optimum temperatures and precipitations for CLR are expecting to be more affected.
The use of fungicides have to be during the early development of the disease (low infection), which in many places is related with the phenology of coffee plant. The first spray is recommended 50-60 days after the high intensity flowering has occurred (Colombia situation). Addtional sprays are recommended at 4-6 weeks intervals during the development of green berries. Four to six sprays of fungicides during coffee season are recommended (Colombia situation). Since, we do not have information about the development of CLR in Hawaii, we cannot give an specific recommendation. However, we can see alternatives of control that have worked in other coffee producer countries to give an idea about how we can address this issue here in Hawaii before we can get resistant coffee plants.
For sprays of fungicides two relevant aspects are: (moment of spays and coverage). Taming means, sprays before the disease have disseminated all the plantation (low infection < 5%) and guarantee a very good coverage at the moment of spray. Most of sprays are focus in prevention.
Three is a long way to start to walk, but we have to be optimist and proactive to keep producing on of the best specialty coffees in the world, despite the fact that right now we have CLR in Hawaii.
Luis F. Aristizabal