Leafminer
Class: Insects
Common Name
Leafminer
Scientific name
A group of insects from several different orders. An important genus is the liriomyza.
Potential Hosts
Wide range of ornamental and cultural crops: cucumber, basil, mint, parsley and other fresh herbs, tomato, citrus, eggplant, bean, pea, watermelon, melon and other cucurbitaceae members, decorative flowers like chrysanthemum and roses
Who am I?
Leafminers are insects belonging to different orders: sawflies belong to hymenoptora, flies belong to the order of diptera, and moths that belong to the order lepidoptera. Together, they form a large group of plant pests that are important to cultural crops around the world. Standing out are three flies species: liriomyza trifolii, liriomyza nuidobrensis, and liriomyza bryoniae. Another famous member of the group, but perhaps less intimidating, is the citrus leafminer (phyllocnistis citrilla.)
Feeding patterns are important in helping identify the genus and the species, and it is quiet characteristic. Leafminers are year-long pests that favors warm environments.
The first signs of infestation are tiny yellow dots upon leaves upper surfaces. The spots depict where the female laid her eggs. A week after, maggots begin eating their way inside the leaf tissue thus creating those complex tunnels we recognize so easily. The tunnel provides sufficient living conditions for the larvae. In the following 10 days, the tunnel gets wider and longer. Eventually maggots pop out and fall to the ground where they'll complete their metamorphosis and turn into a fly after another 10 days.
It's larvae stage is the one responsible for the actual damage. In a large enough population, it can cause a significant drop in yields due to sabotaging photosynthesis. Another form of damage occurs when the beauty of ornamental plants is ruined or when the look of fresh herbs is degraded, thus making it hard for growers to market them.
Control measures
Cultural
Growing inside structures: The most effective way to protect your crop from leafminers is simply (but costly) to grow it inside a greenhouse or a dense (50 Mesh) net structure.
The sooner the better: It’s easier and more cost effective to eradicate leafminers while infestation is still in its initial stage. Make it a routine to monitor the field regularly and search plants for leafminer symptoms on a weekly basis.
Conventional (chemical)
The efficiency of insecticides greatly depends on the different orders leafminers belong to. Luckily for us, different types of leafminers come from different orders that attack different crops. Decisions for using pesticides depends on the crop.
It is harder to completely eliminate infestations in vegetables and field crops compared to citrus crops. Citrus leafminer, phyllocnistis citrilla, is a kind of moth that creates tunnels upon foliage and causes noticeable leaf deformation. The following pesticides are used in one or more parts of the world for leafminer of citrus: imidacloprid, abamectin, and acetamiprid.
The following pesticides are used in one or more parts of the world for leafminer of vegetables: cyromazine, thiocyclam hydrogen oxalate, milbemectin, and chlorantraniliprole-based products.
Organic
Spinosad-based products
Biological
For citrus leafminer, use the commercially available parasitoid ageniaspis citricola. For vegetables, ornamental, and fresh herbs use parasitoid wasp diglyphus, a natural enemy of dipteran leafminers and a successful commercially available biological product against leafminers.
Caution and careful notice should be taken when using any plant protection products (insecticides, fungicides, and herbicides). It is the grower’s sole responsibility to keep track of the legal uses and permissions with respect to the laws in their country and destination markets. Always read the instructions written on labels, and in a case of contradiction, work in accordance to the product label. Keep in mind that information written on the label usually applies to local markets. Pest control products intended for organic farming are generally considered to be less effective in comparison to conventional products. When dealing with organic, biologic, and to some extent a small number of conventional chemical products, a complete eradication of a pest or disease will often require several iterations of a specific treatment or combination of treatments.