As the temperature rises, so does the potential for citrus leafminer (CLM) attack on citrus crops. Citrus leafminer is a consistent and serious pest on citrus, resulting in feeding damage to young shoots and leaves. Damaged leaves are often curled, and the presence of dead tissue, combined with reduced leaf area, could compromise the plant’s overall health and photosynthetic capacity. The damaged leaves will eventually mature and remain for a long period of time. Multiple infestation events can damage leaves throughout the branch, making the branch visually unappealing (Figure 2). The indirect risk of CLM damage in citrus is the potential incidence of citrus canker, a serious disease caused by a bacterial pathogen (Figure 1). This bacterial pathogen can spread through various routes, such as human movement, contaminated equipment, and irrigation, and to cause infection, it requires a moist environment and an opening in plant tissues to enter. Citrus leafminer damage can provide that opening for the bacterial pathogen and aid in the spread of citrus canker disease. For all these reasons, it is important to manage citrus leafminer in commercial citrus groves.
Citrus leafminers preferentially attack only the new growth of the plant- shoots, leaves, buds, etc. The new growth in citrus, often called “flush,” is a distinct event that occurs periodically during the year. In South Georgia, there are typically three major flushing events in most citrus cultivars. However, there may be some minor flushing between these events, and depending on the weather, irrigation, fertilizer, and the use of plant growth regulators, all of which might influence the flushing frequency and load. Most major insect pests, including citrus leafminer and Asian citrus psyllid, take advantage of the new flush, increasing the risk of these pests in citrus groves.
In the last two years, we have continuously monitored citrus leafminers in three commercial citrus groves in Tift, Berrien, and Worth Counties in Georgia. Based on our observations and field evaluations, it is typical for citrus leafminers to become active sometime in mid-May and remain present until the end of the year (Figure 3). However, the peak population of citrus leafminers occurs in July and September. The population appears to dip in August, likely due to the intense heat during that period.
Based on our field observations, we have not seen any leafminer damage until recently. This confirms the fact that although we had a spring flush on citrus trees during April, there was no damage to that growth since citrus leafminers were not active. Now that we are beginning to see the summer flush, and the leafminer population is picking up, we should expect to see damage from leafminer feeding now onwards. So, every time there is new growth on the plant, it will be attacked by leafminers unless any insecticide treatments are made to manage the population.
Here are some considerations in managing citrus leafminer damage on citrus trees. Not all varieties are equally susceptible or equally valued from a production perspective. For example, grapefruit varieties (Ruby Red, Star Ruby) and Shuranui mandarin appear to be more susceptible than other citrus varieties such as Sansumas, Tango and Naval. However, almost all varieties suffer some level of damage from leafminer attack. The second important point is to prepare early for the leafminer attack, especially for the summer flush onwards. Leafminer attack can be cryptic, meaning they may lay eggs and the larvae will be making the tunnel before you know it. So, as soon as you expect to see new growth, treatment should go out without any delay. A field trial conducted to evaluate a few insecticide products in a commercial citrus grove in Tift County during 2025 indicated that Exirel (Cyantraniliprole) and Admire Pro (Imidacloprid) are effective against citrus leafminer. Movento (Spirotetramat) and Sivanto (Flupyradifurone) are moderately effective. The best management approach for citrus leafminer starts with monitoring of moth activity by using pheromone traps (Figure 4). While there is no definite number of moths on the traps that should determine application of insecticide, we have seen the number of moths increasing rapidly after mid-May. So, fewer moths (10-20 per trap) in early May should be considered an indicator that an insecticide application is needed in the following weeks.
I would like to acknowledge GDA’s funding support through the Specialty Crop Block Grant Program to conduct this research and share information on citrus leafminer management to citrus growers. Additionally, I thank the graduate students (Madhav Koirala and Oludare Odumuyiwa) and postdoctoral researchers (Dr. Rajendra Acharya and Dr. Vishal Patil) for their hard work in conducting the experiments and field observations.
