Monday, March 22, 2021

Citrus Leafminer and Leaf Gall


Horticulture Hotline 03/22/21

By Bill Lamson-Scribner


If you have a citrus tree, now is the time to put out Citrus Leafminer Pheromone Traps. If you have had leafminers in the past, you know that they love to attack that new spring flush of growth. Leafminers’ larvae feed by creating shallow tunnels in young leaves that eventually kill the leaves. In severe cases the leafminers can defoliate the tree and the tree will decline. The traps we sell (Possum’s) contain no pesticides, are safe for organic use and last up to 15 weeks.


I guess in the restaurant (“Foodie”) world they call them “pairings.” Most of the customer base I deal with calls them “cocktails.” Basically, when you get a synergistic effect from adding two or more items together – when 1 + 1 = 5 not 2. When the two or more items together act better than the two or more items act individually, you have synergy. If you have a dead spot or dead area in your lawn, try some cotton burr compost (10  2 cubic foot bags per thousand square feet) and SeaHume (15 pounds per thousand square feet). You will thank me later!


Have you noticed an azalea or a camellia whose leaves are 2-3 times the normal size and are really thick and fleshy?


They have leaf gall. Leaf gall is a very common disease that affects camellias and azaleas while they are putting on new leaves in the spring. This disease affects Camellia sasanqua (the small leaf camellia that blooms in the fall) more than Camellia japonica (the large leaf camellia that blooms in the winter).  The cool nights, overhead irrigation and rains in the early spring make this disease flourish.  This disease is caused by the fungus Exobasidium camelliae. Sometimes galls can be caused by insects or mites as well. There is another Exobasidium fungus that affects azaleas in a very similar way. 


Leaf gall is the common name for this fungus.  The leaves become very large and fleshy.  The new growth is much thicker than normal and then the leaves break apart and release spores.  When the leaf breaks apart, you can see the lower part of the leaf turns white.  The disease spreads by wind and splashing water. A good layer of mulch will help with the splashing water.


The best control for leaf gall is to pick the infected leaves off as soon as you see them in the spring.  If you can pull them off before the spores develop, you can prevent the disease from spreading.  Once you pull them off, place them in a plastic bag (the one your newspaper comes in is handy, a dog poop bag, or any other plastic bag you might have around the house) and throw them away in the garbage or burn them in the ever so popular backyard fire pit. 


Usually, this disease does not require chemical treatment.  The manual pulling off of leaves and limiting overhead irrigation in the spring, when the nights are cool, will keep it in check.  If you have a severe problem year after year, you could apply Mancozeb at bud break.  This control should be your last resort, and only used in severe cases. 


For this year, pull off as many infected leaves as you can.  Soon your plants should go back to producing its normal size leaves.  The leaves that were affected by leaf gall will soon wither, turn brown and fall off the shrub.


Soil test taken to Possum’s (check), preemergent product on lawn and beds (check), SeaHume on lawn and beds (check), 17-00-09 in beds (check), Perk on lawn (check), Citrus Leafminer Pheromone Traps in citrus (check), irrigation gone through and adjustments made (check), Dominion drench on plants with history of insect pest (check), lawnmower serviced (check), Cutless growth regulator for shrubs I don’t want to trim (check), Intice Perimeter around outside of house for roaches and other uninvited guest (check) …


Always read, understand and follow product label. The product label is a Federal Law.