Two young scientists from the Southern Fruit Research Institute, Master Le Quoc Dien and Engineer Do Hong Tuan, have successfully developed a simple solution to combat the yellow leaf greening disease in citrus trees: intercropping guava trees in orange and tangerine orchards.
This solution has been piloted in several orange and tangerine orchards in Tien Giang and Vinh Long, yielding very promising results…
In 2004, as the yellow leaf greening disease ravaged citrus orchards in the Mekong Delta, Dien and Tuan were tasked with finding a solution. They began by investigating the situation in various regions, in conjunction with a research project on the yellow leaf disease being conducted by experts from France, Australia, and Japan in Vietnam.
During a visit to the citrus orchard of farmer Le Van Bay in My Loi A hamlet, An Thoi Dong commune (Cai Be district, Tien Giang), they were surprised to see his orchard thriving while neighboring orchards were struggling. Upon closer inspection, they found that Mr. Bay had always intercropped guava trees to utilize the vacant land.
Further investigation at Mr. Nguyen Van Sang’s house in My Luong commune revealed that his citrus orchard had previously thrived when intercropped with guava, but suffered from disease after the guava was removed. The two scientists began to document this phenomenon and initially hypothesized that the psyllid (the pathogen causing yellow leaf greening) might dislike guava leaves.
They then experimented on a piece of land, planting 60 citrus trees interspersed with 60 guava trees. The results showed no signs of psyllid infestation. In the next phase of their experiment, they stripped all the guava leaves from the orchard, and just 2-3 days later, psyllids appeared. They had to wait for the guava leaves to regrow before the psyllids disappeared again.
At this point, it could be confirmed that guava leaves possess a special ability to repel psyllids. Dien and Tuan continued their trials on two models: one with intercropped guava and one without. After 11 months, the results indicated that the orchard without guava was 60% infected, while the orchard with guava showed no signs of disease at all. The two scientists concluded that intercropping guava in citrus orchards effectively prevents psyllid infestation, thereby preventing yellow leaf greening disease.
Since early 2006, the two young scientists have expanded this solution to over 34 plots belonging to farmers in Tam Binh and Binh Minh districts (Vinh Long). Results show that there has been no psyllid invasion. Meanwhile, the intercropped guava trees have started to mature, and they are expected to bear fruit in the upcoming August. Mr. Nguyen Van Hieu, a farmer in Tam Binh, expressed his excitement: “While waiting for the citrus to bear fruit, I can also harvest guava to sell for 2,000 VND/kg. This way, we manage to sustain our livelihood.”
Currently, these two scientists are analyzing the “special ability” of guava leaves to see how they repel psyllids. They are also researching the production of traps colored similarly to guava leaves, combined with extracting guava fragrance to introduce into the experimental citrus orchards. If the results are favorable, when the guava trees mature and need to be cut down, they may use “artificial guava leaves” as a replacement.
DUONG THE HUNG
