Gardening with Wilson

For the longest time, I was wondering what caused the young new growth of my peppermint plants to become distorted. The young leaves were consistently smaller, appeared to bunch together and leaf undersides were bronzed.

At first, I thought the culprit was either thrips or spider mites. I cut away most of the aerial growth and then sprayed either white summer oil or neem extract on my plants. Subsequent new growth still exhibited the same symptoms. I took a closer look at the distorted leaves and found no thrips or spidermites. I searched the herb growing books that I have in my possession as well as some websites on the internet but found no leads.

After some extensive searching using various keywords, I finally pounced on a website that offered an answer to what I have experiencing with my mint plants. The page entitled “Information on Peppermint – Verticillium Wilt” was found in an online resource called “An Online Guide to Plant Disease Control” that is maintained by the Oregon State University.

In that particular page, the symptoms of verticillium wilt were described as follows:

“First, upper leaves twist and curl. Leaves are bunched at the top of the plant. Infected plants are stunted yellowish to red or bronze. Lower leaves die first, then the aboveground part of the plant. With flowering or other stresses, stems or plants may die too rapidly for these symptoms to be observed.”

The page also shared that this fungal disease is soilborne and once established in soil is almost impossible to eradicate due to microsclerotia, which germinate and infect roots. The fungus grows throughout the vascular system and up into mint stems. After diseased plant parts die, microsclerotia form and remain several years in soil.

The disease is revealed on various other web resources to be transmitted during cultivation, transplanting, or by flowing water and soil moisture. Verticillium wilt can be transmitted from plant to plant by grafting and budding.

The solutions offered appeared to be either limited in terms of their efficacy or difficult to implement for an average gardener. I guess for now, I have to dump the diseased plants and infected soil. I will then use disease-free plant materials for propagation and sterilised soil mix to grow them from now on. There will be a need to dis-infect all cutting tools to prevent the spread as well.

Gardeners who grow food and medicinal plants would prefer not to use any harmful synthetic chemicals to control or cure pests and disease problems in their gardens. I recently came across an online resource that most organic gardeners and edible plant growers would be looking for.

The website termed “OISAT” (Online Information Service for Non-Chemical Pest Management in the Tropics) contains information on non-chemical pest management that can be used to minimise pest damage in a safe, effective and ecologically sound way in the tropics.

OISAT shares information on various non-chemical pest management practices which include preventive measures such as crop design and layout, cultural practices, management of natural enemies, and mechanical methods, as well as, curative measures such as pest-controlling plants, physical methods, the use of other substances such as soap, and other methods which include a diversity of types of methods not forming a particular category.

The term “non-chemical” for practices and products which exclude synthetic chemical pesticides and genetically altered substances. Non-chemical products, as they are used in the OISAT context, may be processed on the farm but also manufactured commercially. The non-chemical commercial products, which are not excluded, are biopesticides, which are permitted in organic agriculture.

Information is cateogrised into three main sections. Under the tab “Crops”, one would be able to find non-chemical pest management practices according to the cropping season of the major crops, indicating key pests for each growth stage and plant part.

To find methods specific to a particular pest or disease, one can click on the “Pest” tab. One can expect to see illustrations or photographs of a particular pest and disease and the recommended non-chemical management methods.

The actions of some non-chemical management methods cover a wide spectrum of pests or diseases, click the tab labelled “Control methods” to find out what other pests and diseases a particular method also help to treat or eradicate.

OISAT is brought to netizens by PAN (Pesticide Action Network). PAN is a network of over 600 participating nongovernmental organizations, institutions and individuals in over 90 countries working to replace the use of hazardous pesticides with ecologically sound and socially just alternatives. PAN was founded in 1982 and has five independent, collaborating Regional Centers that implement its projects and campaigns.

Click on the following URL to access OISAT:

http://oisat.org/