Looking Back: Heavy Lessons on Thinning Young Fruits

Peaches in my garden - summer 2013 

Too much of anything is not a good thing.  There is balance to be observed between that which is beneficial and that which is permissible for a healthy life - plants included.   This year we were delighted to see a beautiful crop of peaches which is attributed to the absence of leaf curl infection.  The drier weather from late winter to early spring was not conducive for the proliferation of the pathogen Taphrina deformans.  In previous years, the tree would lose all its early leaves leaving the developing fruits to starve until the new set of healthy leaves come out.  Sometimes the fruits also get infected which results not only in low yield but poor quality crop.  

As the fruits grew larger under the summer sun, the problem slowly surfaced.  The slender stems laden with fruits began to hang straight downwards.  One of the larger branches was so heavy. I was afraid that it might break.  We had to prop it up with three pieces of 2x4x8 lumber.  I admit that my tree is not in its best form.  Pruning on this tree has been mainly for the purpose of making sure it does not arch into our neighbors' yard.  (I doubt they appreciate peaches falling into their swimming pool.)  This effort has led to the formation of a lop-sided tree.  It is a nice tree but it not strong enough to bear a heavy crop.  

   

A heavy fruit load can be detrimental to the tree.

Based on the situation described here, the problem that needed to be addressed is excessive fruits.
Under favorable growing conditions, such as what we had this year, fruit trees set more fruits than they can support adequately.  And this problem is magnified when trees have not been properly pruned in the previous season.  A heavy fruit load can result in branch breakage.  When there are too many fruits competing for carbohydrates, the fruits cannot reach their optimum size.  The tree also gets nutritionally deprived and weakened - making it more susceptible to pests and even sunburn damage.  Another possible effect of excessive fruits on trees is alternate bearing (the cycle in which the tree bears a heavy crop in one year and a skimpy or no yield in the next).  This phenomenon happens when the tree is nutritionally deprived while supporting its fruits - a situation that will continue to plague my tree until I will muster enough discipline to remove the excess fruits when they are young.  

Rule for fruit thinning:  Mature fruits should not be touching each other.

Peaches are among the fruit trees that require fruit thinning for best results - superior quality fruits are produced while maintaining a healthy tree.  As a general rule, allow room in between fruits so that at maturity fruits should not be touching each other.

For them - Water is Over-rated

Powdery Mildew on summer squash (Erysiphe cichoracearum)

These are no happy days for my summer squash - they are being "harassed" by powdery mildew.  There are different species of powdery mildew and they are plant-specific.  For example Erysiphe cruciferarum will infect crucifers while Erysiphe pisi prefers peas.  The pathogens that cause powdery mildew are unique from most leaf-infecting diseases because their spores do not require free water to germinate.  As a result they can infect their host plants in very dry condition such as ours. That is why in a time when blackspots and peach curl are all wiped off by the lack of moisture, powdery mildew is thriving happily.

The strength of this pathogen to withstand the lack of water can be totally reversed by water itself.  Hosing the leaves with water will do the trick depending on the severity or stage of the infection.  

Some literature on powdery mildew:

IPM-California

Powdery Mildew and  Resistant Varieties

Galls on the Peach Tree

Galls growing around the nodes of a peach tree

My peach tree suffered much from pest and diseases this season.  Due to the prolonged period of rains, the tree suffered much from leaf curl  (Taphrina deformans).  Now there are galls on the twigs (see picture).  The nature of these galls are unknown to me...if you know what they are please let me know.   They look like dark brown shiny beads with starch-like substance inside.  I have been doing research to identify them but I guess the most scientific step would have been to submit samples for pathological analysis.  It is my guess that these are caused by the fungal damage from the leaf curl.

Plant galls are not uncommon.  They are likened to a tumor that results from abnormal cell growth due to irritation caused by insect infestation and fungal or bacterial infection.  They grow on different plant tissues such as the roots, stems, branches, fruits and leaves.   The nature of the gall is not only affected by the organism that is causing it but also the location of gall formation on the plant.  Galls growing on leaves tend to be softer than those growing on bark of trees.   Galls growing on hairy leaves tend to be fuzzy while those growing on the branches are hard and shiny (such as the ones in the picture). 

Although they look very severe, galls are not detrimental to the plant.  They can interfere with the growth of the particular part where they are growing but not the whole plant.  

Detached galls.

Since I am not sure of the true nature of these galls,  I thought of removing them by hand to avoid further proliferation.   Luckily they were concentrated in a couple of branches only. 

If you know what these are please let me know.

Peach Leaf Curl

Distorted peach leaf

The Disease.  Leaf curl is a fungal disease that affects peaches.  It is caused by a pathogen called Taphrina deformans.  I guess that the word 'deformans' reflects the nature of damage on the plant instead of the fungus itself. Infected areas of the leaves appear thickened and reddish in color.  They turn into distorted or malformed leaves.

In My Garden.  Every year, this disease shows up on my one and only peach tree.  Right after the first set of leaves appear, infection follows.  When the leaves are all deformed and discolored, the tree seems hopeless and not fit for any serious photosynthesis.  Fortunately, the disease can only survive under cooler and spread with the aid of the rain.   As the temperatures rise, the infected leaves fall off.  In some previous years I also helped the tree by had-picking the infected leaves.  This reduces the chance of the disease spreading on new leaves and thus shortening the overall "leaf curl period".

Currently, the temperature here is about 58º F and raining.  The weather still favors the development of the disease.  However, I noticed that most of the infected leaves have fallen off the tree and the proportion of healthy leaves is now more than the red-distorted ones.

In Your Garden.   If you have this problem on your peach tree, don't despair.  Read and understand the life cycle of Peach Leaf Curl.   Acquaint yourself with your climatic condition in relation to the requirements of the pathogen.  Although the disease can affect the yield and growth of your tree, the potential extent of damage is controlled by nature itself with some preventive measures from you.

Stroll in your garden...get acquainted with your unseen enemies.  For it is much easier to subdue them when you know their secret life.