1 - Natural fruit thinning is not uncommon when temperatures rise and winds increase in New Mexico.

Yard and Garden May 24, 2014

Q.

I have noticed small apples falling from my apple tree. Is something wrong? I hope I will be able to harvest some apples this year. I had no crop at all last year.

A.

There are several things that can cause apples to drop from the tree. Insects, such as codling moth larvae feeding in the apples can cause them to fall early, but that usually happens later in the year.

Some chemical applications can cause fruit thinning and drop. Some chemicals are intended for this purpose, but some insecticides, such as carbaryl insecticide, have a secondary effect of causing fruit thinning. Have you sprayed fruit thinner or insecticides?

The most likely causes at this time of year are environmental factors can cause natural thinning of fruit. These factors are a change from cool weather to warm/hot weather. Wind can cause fruit drop, and lack of moisture can also cause fruit drop. All of these factors have been present in New Mexico recently. This natural fruit thinning is usually beneficial, allowing larger fruit to form. Such natural thinning usually does not cause too many fruit to fall. You may still need to do some manual thinning if too many fruit remain. This should be done while the fruit are small.

As temperatures rise in the early summer and late spring, water loss by apple trees increases. Even when trees are well watered, the increased water loss is enough to cause increased fruit drop, but in dry years this can be a greater problem. Proper irrigation can help. Proper irrigation means providing moisture to the soil outside the dripline of the tree to a depth appropriate for the type of tree and soil conditions. This means moistening the soil to a depth of 3 feet for apple trees if there is that depth of soil. This should be done two or three times a month during the growing season. Periodically irrigating more deeply, or directing roof runoff from rains to the trees, can help prevent accumulation of harmful mineral salts at the bottom of this zone of irrigated soil.

Irrigation outside the dripline, starting at the dripline and extending several feet outward is important for providing water to the small absorbing roots. Inside the dripline of the tree, there are fewer absorbing roots, so irrigation inside the dripline is not necessary.

Wind can physically remove fruit by bashing them against the stems, or by increasing water loss. As in the case of increased water loss from temperature change, proper irrigation is the best method for reducing fruit drop.

For more information about growing fruit trees in New Mexico, irrigating trees, and proper fruit thinning, contact your local NMSU Cooperative Extension Service office.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!