by johnah on October 31, 2020
What is Pear Tree Leaf Curl?
Pear tree leaf curl is a common problem in trees, especially those with young growth. Most commonly it occurs when there are too many branches growing at one time. This causes the trunk to bend or twist. Leaves may turn brownish yellow and fall off their stems (Figure 1). If left untreated, this condition will eventually cause the tree to die from rot or other problems caused by lack of water and nutrients.
Figure 1: A branch bending over.
How Do You Diagnose It?
The first step to diagnosing this condition is to look at the leaves themselves. They should not have turned black yet, but they may start to do so if the tree is stressed due to drought or other factors. Look for any signs of insect damage such as dead insects on the leaves (Figure 2). Also look for small white spots on the leaves (Figure 3). These are called grain spot and they indicate that there is mold on the tree. Mold can grow anywhere on a tree, but usually appears in areas where moisture is lacking.
Figure 2: Insect damage to a leaf.
Figure 3: Grain spotting on a leaf.
Mold grows quickly and can cause other problems such as stunted growth or even death of the affected tree.
What Do They Look Like?
Normally, the leaves of pear trees are a dark green color and roughly teardrop-shaped (Figures 4, 5). Normally, they have jagged edges. There are also small teeth at the bottom of each leaf (see Figures 6, 7).
If pear tree leaf blister mite is the problem, the leaves will be covered in white spots that look like blisters (see Figure 8). The blisters will grow until they burst and ooze a substance that is important for the growth of the mite.
The leaves will also turn yellowish and wilt if there are too many mites. For this reason, if you notice this symptom, you should destroy all infested leaves and dispose of them so that the mites cannot spread to other plants.
Figure 4: A healthy pear tree leaf.
Figure 5: Another healthy pear tree leaf.
Figure 6: A pear tree leaf with teeth at the base.
Figure 7: You can see the teeth at the bottom of the leaf.
How Do You Get Rid Of It?
There are several ways to get rid of this condition including:
Destroying infested leaves: This is important because you do not want the mites to feed on the trees anymore.
Sources & references used in this article:
Pear decline in Spain by L Avinent, G Llacer, J Almacellas, R Tora – Plant Pathology, 1997 – Wiley Online Library
The properties of terrestrial laser system intensity for measuring leaf geometries: a case study with conference pear trees (Pyrus Communis) by MAF Balduzzi, D Van der Zande, J Stuckens… – Sensors, 2011 – mdpi.com
Characterization of a phytoplasma associated with pear decline in Iran by M Salehi, K Izadpanah, SM Taghavi… – Journal of …, 2008 – Wiley Online Library
Disease resistance in apple, pear and peach germplasm originating from the Balkan Peninsula by V Ognjanov, D Vujanic-Varga, K Gasic… – … Congress, Part 3: Culture …, 1998 – actahort.org
Transmission of pear decline by using naturally infected Cacopsylla pyri L. by L Carraro, N Loi, P Ermacora, A Gregoris… – … of Temperate Fruit Crops …, 1997 – actahort.org
Detection and characterization of phytoplasmas in diseased stone fruits and pear by PCR-RFLP analysis in Turkey by G Sertkaya, M Martini, P Ermacora, R Musetti, R Osler – Phytoparasitica, 2005 – Springer
Occurrence, symptom expression and characterization of phytoplasma associated with pear decline disease in Catalonia (Spain) by M Garcia‐Chapa, A Lavina, I Sanchez… – Journal of …, 2003 – Wiley Online Library