Something hit the citrus trees of Riverside in late December 2017. Some vandal spraying herbicide? It was too widespread. It was all over town, orchards and backyards. It was on the north and east sides of trees. It didn't happen in Ventura or Santa Barbara. It probably happened to a lot of other plant species, but our correspondent had eyes only for citrus.
It sure looks like it could have been a cold, freezing wind, but on closer consultation with our Citrus Specialist, Peggy Mauk who also directs the Agricultural Operations at UC Riverside – it was the demon wind. The Satan Wind. The Santa Ana that dried out the trees that had not gotten sufficient water to cool themselves and had dried out on the windward side of the tree and orchard. Burned, in effect. This is the side of the orchard that dries out the most. It's what's called the “clothes line” effect. The margins that dry first because of the greater exposure to wind, sun and usually lower humidity. In this case, way lower. And by the time the damage was noticed a week later, the winds had been forgotten. Expect more water stress in our future.
The USDA's Farm Service Agency and Natural Resources Conservation Service will have workshops to aid agricultural producers; including cattle, tree, nursery, vegetable, and berry farmers in filing for federal assistance programs. Appointments can be arranged now for filing applications during these workshops.
You come on a leaf with the margins munched on. It's got to be a beetle or a looper or some insect doing the damage, right? Not necessarily. It's not time to drag out the Raid. Look at the damage closely. In the photos below you can see the dead leaf margins caused by either salt damage or more likely leaf blight. Leaf blight is a disease that shows up with water stress and is caused by a fungus, one of the Botryoshpaerias. It causes an uneven marginal necrosis that goes along the margin in a somewhat irregular pattern and often not at the leaf tip. In this case it does affect the leaf tip, and since salt burn and leaf blight are caused by the same conditions of water stress, it's probably a bit of both.
Lepidopteran larvae will more commonly feed in a smooth pattern, not the rough pattern seen here. Now with this dead tissue, the wind blows it out, and what's left is the uneven margin. No it's not time to spray an insecticide. It's time to reflect on irrigation. There's a lot of this damage out there now. On avocados, citrus, landscape plants. It's going away until the leaves drop and are replaced with new ones, that will hopefully be well hydrated by rain and proper irrigation.
Top photo is salt/leaf blight damage
Bottom is necrotic tissue that the wind has blown out
The first years of a tree's life are for building a structure for the future. Many varieties of trees are precocious and will bear fruit when they should be building structure. Letting a tree carry fruit when it is too young (under 2 years of age in the ground and some say 5 depending on the tree species) delays future good production and distorts the tree's architecture. A young avocado tree can be completely humbled (brought to ground literally) by the weight of the 12 ounce fruit. ‘Lamb Hass' wants to grow upright, but if the young tree is burdened with fruit early on, it will grow squat and twisted.
Another problem with precocious trees recently came up with ‘Meyer' lemon. Along the coast, this is a tree that will carry fruit throughout the year. It is a small tree naturally, but also because it puts so much energy into fruit production. If allowed to fruit to its full potential early, the canopy development is delayed and the fruit grows unprotected from winds. It is much more subject to wind scarring. Imagine the wind flailing the fruit around with no branches or leaves to protect it. Now the grower has a small, twisted fruit tree and fruit that can't be sold.
Give your young trees a chance to grow without the burden of carrying fruit to early. They are your children.
Imagine all this fruit on a one year old canopy
And this fruit is fully exposed to the elements and wind scarring