Leafminer Larvae Can Destroy Young Citrus Trees

Author: Meera, November 7, 2014
Satsuma is heavy bearing and nearly seedless

Satsuma tangerine trees such as this one are loveliest during late fall and early winter



The new leaves on nearly all our citrus trees show signs of the presence of the citrus leafminer. The local garden center representative explained this pest is ravaging trees in our area. The pest’s name is fitting–its larvae tunnel into new leaves creating mining tunnels.



This pest came to California in 2000 by way of Florida, where it showed up in 1993 and began steadily moving westward. The citrus leafminer is native to Asia, but in the 1940s, it showed up in Australia. From there, it began to appear in other citrus-growing regions of the world.



The citrus leafminer is a small, light-colored moth. Its forewings are irridescent. The wing tips have a black spot. The hind wings and its body are white. Look for a serpentine tunnel on a new leaf and inside the tunnel is thin dark line, the frass (or feces) trail.



The citrus leafminer burrows into new leaves, creating tunnels

The citrus leafminer burrows into new leaves, creating tunnels that, in turn, make for an exotic mosaic appearance on the leaves




In its last stage before adulthood, the larva causes the leaf the curl up. The curling is the result of the larva rolling the leaf end around itself in order to pupate as it becomes an adult moth.



Older, hardened citrus leaves are not at risk.  The citrus leafminer attacks only young, shiny, green, new leaves. Young trees are perhaps at greatest risk.



Citrus growers should prune their trees only once each year because pruning causes a flush of new growth, open for attack. Because of the difficulty of getting the product inside the tunnels, chemical control is not recommended. Also, traps using a pheromone attracts only the male moth. It gets stuck inside, but this won’t eliminate the citrus leafminer population.



The dark line inside a tunnel is the frass (feces) trail

The dark line inside each thread of a tunnel is the frass (feces) trail of the larvae



Biological control is accomplished through parasites and predators. The non-stinging wasps, Cirrospilus and Pnigalio species are particularly effective against citrus leafminer since the parasites lay eggs inside the leafminer tunnels, either inside or on the top of the citrus leafminer larvae. The parasite egg hatches and the parasite larvae eat the leafminer larva.  You don’t have to put these pests in your garden. They are attracted to citrus just like the leafminer is.



Nature has a powerful checks-and-balance ecosystem that works best when growers do not spray insecticides. Pesticides and insecticides disrupt predator activity and nature’s inherent balance.




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