Fruit Tree Problems Now

I think we can blame the drought for causing another problem, terrible insect pressure especially on our fruit trees. Most if not all fruit trees have made it through the winter, and most have survived the drought, if you watered. They have made it through freezes, and most are in bloom or have very small fruit, no small miracle for Texas fruit production! Now after making it through all these weather problems we have to add insects to the list!

Both the brown stink bug and the green stink bug overwinter in grassy areas and under brush or wood. They wait for warm weather to come out and begin looking for energy sources to replace lost body reserves and the plant of choice is fruit. The brown stink bug causes the fruit to deform, and the green stink bug causes the fruit to exude a resin or gummy mess that can accumulate on the fruit especially on peaches. Both insects have long snouts that they use to pierce the skin and suck out juices. In the case of the green stink bug this resin attracts wasps and bees so that they get the blame instead of the stink bug. Stink bugs are hard to control especially since they have piercing/sucking mouthparts.

Organic growers have a few choices including some plant oils, but effectiveness is not good many times.  Grandevo and PFR-97 have plant bugs on the label, but I have never seen them in action and a product I know will take care of plant bugs (stink bugs) is Venerate.  Also, there is Pyganic, but it is a last resort even if it is organic!

There is one major peach insect that everyone wants to get rid of, the Plum Curculio. This small worm or grub feeds inside the peach mostly near the seed and can cause anyone who has found one a real heartache. This worm or larva is laid by an adult snout beetle, similar in looks to the oak, pecan, or cotton weevil. This adult overwinters in the soil at the base of the fruit tree and comes out early with the plums and moves to peaches as plums mature early. The adult female will chew a small hole in the fruit skin and lay eggs just under the surface. The eggs hatch into small larva that feed in the fruit for 2 to 4 weeks and of course this is what causes the problems.

To control this insect spray must be made from shuck split (about the time the fruit is formed) and for two applications at two-week intervals and then 30 days before fruit harvest. This last spray is probably the most important since the eggs laid hatch out and the larva are still in the fruit at harvest. Recommended organic sprays include BoteGHA, Mycotrol or Botanigard MAXX all with Beauveria bassiana bacteria, Grandevo with Chromobacterum subtsugae, Venerate with the Burkholderia spp., Surround which is a kaolin clay product, and Pyganic. There is no insecticide to treat the soil with but keeping old fruit off the ground helps prevent next year’s problems. It might be interesting to see if a biological on the soil would help take out the overwintering adults, and if you do and it works let me know.

Another problem some homeowners have complained about is the gummy mess coming out of fruit tree limbs. This gum or resin is caused by a bacterial canker that has infected the limb. This canker develops in the fall and as the trees break dormancy in the spring, gum is formed by the infection and can break through the bark and flow down the tree limb. Stress in trees is the main culprit and treatments are not effective. Keep damaged wood trimmed out and supply water and nutrients to promote tree health.

Last, there is the ever-present issue of Brown Rot.  This disease is caused by four species of Monilinia with the predominant species being M. fructicola and M. laxa. Brown rot fungus has the ability to attack blossoms, fruit, spurs (flower- and fruit-bearing twigs), and small branches under favorable conditions in the spring. Disease severity is dependent upon environmental conditions. Blossom blight can be expected in humid, rainy weather with mild daytime temperatures (68°F–77°F; 20°C–25°C) and cool nights. Mature fruit rot occurs at high temperatures in conjunction with high humidity. Under the right conditions, the entire tree’s crop can be completely rotted.

Organic controls include Bacillus amyloliquefaciens sold by several companies, Polyoxin D zinc salt (OSO, sold by Certis), Botector/Blossom Protect (SAN Agrow), several copper products and possibly others not I have not seen or tested.  Again, I am open to hearing about your organic control for this disease or any others in fruit crops!

Author: Bob Whitney, Regents Fellow & Extension Organic Specialist

Agriculturalist, extension educator and researcher, organic agriculture enthusiast and promoter, international program developer, Christian, husband, father and friend.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: