Heavy March rain in Texas’ citrus-production region brought both a sigh of relief and concerns, according to Texas A&M University-Kingsville Citrus Center researchers Veronica Ancona, Joel Cabrera and Madhurababu Kunta.
TEXAS FLOODING
“Receiving from 12 to 24 inches of rain across the region sounds great, except that it was in a short period of time, leaving areas flooded, including citrus orchards for several days,” the researchers reported. “Under these circumstances, poor drainage can stress citrus trees in different ways.”
The researchers noted that roots that are underwater for several days can start to decay, decreasing root mass that is needed for tree support and nutrient and water uptake. Excessive humidity can also exacerbate phytophthora pressure. Phytophthora thrives under flooding conditions and infects roots and tree trunks. This leads to root rots, gummosis and tree decline. Moreover, weakened root systems have a harder time maintaining tree growth and productivity during drought and heat stress.
GROWER STRATEGIES
There are several ways to promote healthy root systems, according to the researchers.
For new plantings, the use of raised beds has been shown to enhance root growth compared to flat beds. Moreover, raised beds protect the base of the young trees from being submerged in water during flooding events or irrigation.
Application of fungicides (mefenoxam, fosetyl-A) can be effective at reducing phytophtora and avoiding root infections, the researchers state. It is important to scout the area to look for symptoms of gummosis. This can cause rapid tree decline in young trees, especially if the trees are challenged by multiple stresses.
In flooded areas, a way to stop excessive root damage due to the lack of oxygen can be achieved by channeling water out of the orchard into ditches or other low areas, the researchers note.
It is important to develop a fertilization program that promotes root growth and development by incorporating phosphorous and potassium to adequate levels in accordance with an annual soil test.
The researchers say proper planning is key to minimizing the risks associated with unforeseen extreme weather events, whether it is excessive rain or drought. Transitioning from flood to pressurized irrigation systems (drip/micro-sprinklers) can be an orchard-saver in events of limited water availability, they report.
Read more on this topic on page 13 in the first edition of Texas A&M University-Kingsville Citrus Center’s Citrisphere newsletter.
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