User:Michael.C.Wright/sandbox/CLR notes

Control

Recent studies and research papers have shown that 1. CLR is under-researched compared to pathogens of other cash crops and 2. there are many factors that can influence the incidence and severity of the disease. Therefore an integrated approach that includes genetic, chemical, and cultural controls is the best course of action.

Resistant cultivars

The most effective and durable strategy against CLR is the use of resistant cultivars. The use of resistant cultivars has a number of benefits beyond disease control and can include the reduction in use of agrochemicals as control. A reduction in chemical application also has positive economic effects for farmers by reducing the cost of production. However, in lieu of deploying new, resistant plant stock, or in the interim between initiation of a renewal program and complete renewal, other methods of control are available.

Chemicals

There are social, environmental, and economical concerns associated with any chemical control of plant diseases and some of these have a more direct and immediate impact than others on a farmer's decision to use chemicals. The use of chemicals must first and fore-most make economic sense and the cost of their use can be as much as 50% of the total cost of production. For smallholder farmers this can be cost-prohibitive. Copper-based fungicides such as Bordeaux mixture have proven to be effective and economical, and work best when applied at inoculum levels below 10%.

Typically copper-based mixtures are used as preventative measures and systemic fungicides are used as curative measures.

Cultural

Understanding that the extended presence of water on the leaves allows H vastatrix to infect can help decide what can be done to prevent infection. Cultural methods like pruning the branches back to allow more air circulation and light penetration can dry the moisture on the leaves, hindering urediniospore germination, and preventing favorable conditions that the pathogen needs to successfully infect. Planting coffee trees in wide rows and preventing weed growth also allows for more air circulation. The goal is to create an environment that is not conductive to development of the pathogen.

Plant Nutrition

The correct amount of plant nutrients can also play a role in host resistance. Adequate nutrition allows the plant's natural, biochemical defenses to perform at optimal levels. For example, nitrogen and potassium are two critical, macronutrients that assist a coffee tree to resist infection. Nitrogen is a critical component of chlorophyll, which is central to photosynthesis. Potassium helps to increase the thickness of a leaf's epidermis, which acts as a barrier to pathogen attack. It also aids in recovery of tissues after an attack by H. Vastatrix.

Pruning

Experiments have shown that removal of infected leaves can possibly reduce the final amount of the disease by a significant amount.

Fruit Thinning

Fruit thinning combined with chemical application (cyproconazole and epoxiconazole for example) can increase effective control.

Shade

There is a complex interaction between shade, meteorological effects such as rainfall or dry periods, and aerial dispersal of rust. Researchers have found that shade may suppress spore dispersal under dry conditions but assist spore dispersal during wet conditions. The researchers acknowledge the need for further research on the topic.

Notes and quotes

Light can have negative impact on the development of latent rust areas on leaves. The mechanism for this effect is could be light-activated plant protection compounds.

Fruit load increases rust intensity at the branch, plant, and plot levels.