Orange Pests, Diseases, and Other Problems
Oranges are prone to pests like spider mites, borers, and aphids.
For bugs, the gardener can either apply an organic or non-invasive pesticide or consider making their own natural pesticide.
For larger animals attacking the crops, the fence and/or networks well.
Published: June 28, 2022.
Orange Pests
Aphids
Aphids are small green insect pests that damage many types of plants. If one’s orange trees are infested with them, the grower should wash them off with soapy water.
A strong jet of water or rainstorm too can remove them from the trees.
The growers can even remove them with their hands.
Another solution is to spray flour on the affected parts. This will constipate aphids.
Yet another solution is to encourage the entry of beneficial insects like lacewings and ladybirds/ladybugs by growing herbs like clover, dill, and mint. These insects eat aphids.
The beneficial insects can even be bought from a farming supplier and released in one’s yard. Even one can attract bug-eating birds like chickadees, titmice, and wrens to their garden and they will eat aphids.
Ants
Ants and other insects that feed on the plant should be removed but it’s quite difficult.
In the case of a potted plant, one can keep the plant in a pot filled with water. This makes it impossible for the ants to reach the plant.
One can also apply the insecticide permethrin to the soil. They should read and follow the instructions on the pack carefully.
Or they can use a bait containing the insecticide along with sugars, proteins, and oils to which ants are easily attracted.
They can even apply the organic insecticide Diatomaceous Earth (DE) using an applicator bulb.
Note: When applying the chemicals always be sure to read the instructions and act accordingly. If unsure, contact the local garden center(s) and ask for professional help.
Diseases and Other Problems
Sweet Orange Scab
Sweet orange scab disease mainly affects sweet oranges, mandarins, and tangerines. It’s a relatively harmless fungal disease that doesn’t kill trees, but considerably affects the looks of the fruits, although the flavor is not affected.
Some growers even use the damaged fruits to make juice.
The disease is caused by a fungus Elsinoe australis which is spread by water usually by splashing, overhead watering, or wind-driven rain. 3 to 4 hours of wet conditions can cause this disease.
Affected fruits show raised, wart-like corky pustules that arise as grayish pink or tan, typically turning dark gray or yellowish brown.
These bumps become smoother as the disease progresses. There may even be lesions on twigs and small, wrinkled leaves.
Sometimes, the disease may even result in premature fruit drop and sometimes even stunted growth of young trees.
To prevent the disease, one should water the trees with a soaker hose or drip irrigation system and should avoid overhead irrigation since the disease spreads in water droplets. The grower should also use good sanitation practices and tools and growing areas should be kept clean.
One should treat affected trees with a copper-based fungicide.
Typically, a minimum of two treatments are needed, 2 to 3 weeks apart. One should even consult their local cooperative extension office or agricultural expert about the best products for their area.
Alternaria Blotch
This is a fungal disease caused by Alternaria citri and is also called Alternaria rot or black rot when it attacks navel oranges. The fungus is non-toxic and affects lemons and oranges.
While the rot is softer on lemons, it’s more prominent on oranges and causes hard black spots on the peel that extend into the orange core. It can cause the fruits to drop from the tree and form rotten areas.
Sometimes, the rot can develop after harvest during storage, but can still be identified in the orchard.
For treating Alternaria blotch, it’s important to grow healthy fruit. Damaged or stressed fruit, especially split navel oranges are particularly vulnerable to this fungal infection.
Avoiding water and nitrogen stress can decrease the quantity of split oranges. The gardener should provide sufficient water and nutrients to their trees. Thus, taking good care of one’s orange trees is a way to prevent and treat Alternaria rot.
It’s also important to regularly maintain the orchard. The fungus causing Alternaria rot grows in the tissue of fallen fruits in humid weather. Removing orchard debris regularly can prevent this.
According to experts, there is no effective chemical treatment for this fungal disease. Still, one can control it to some extent with imazalil and/or 2,4-D.
Note: Again, when applying the chemicals always be sure to read the instructions and act accordingly. If unsure, contact the local garden center(s) and ask for professional help.
Leaves Turning Yellow
Yellow leaves may indicate alkalinity. In that case, the grower should test the soil to check if the pH is too high. If it is so, they should apply an acidic (low pH) fertilizer and wash the soil heavily to leach out alkaline salts.
Growers should remember that excessive manure fertilizer or manure used during the dry season can cause alkalinity.
Small Oranges
Although orange is an ornamental tree with its rich foliage and lovely flowers, most growers are interested in the fruits and can be disappointed when the fruits are small. Small fruits can result from a variety of causes.
If the fruit is small early in the season, it may be a normal situation. Oranges are known for dropping many tiny fruits early on when the tree has produced too many.
However, if mature oranges are undersized, there may be a problem. The causes may include water stress, nutrient stress, and insect pests or infection.
In the case of nutrient stress, a likely cause may be zinc deficiency. When citrus trees don’t receive sufficient zinc, the leaves develop irregular green bands along the veins.
The growth of leaves may be affected and fruit can become discolored and small. To deal with the problem, one should apply a micronutrient spray that contains zinc, manganese, and iron, in spring and again at the end of the summer.
In case of water stress, orange trees need sufficient irrigation as it produces juicy fruits. When watering is improper or inadequate, water stress can cause small fruit. Even everyday watering may not be sufficient if the grower is not doing it properly.
Citrus trees need their entire root system irrigated. The roots may extend 2 feet (60 cm) deep and many feet (up to 1 m) beyond the canopy. When one waters oranges, they should wait till the top 3 inches (8 cm) are dry; then they should water thoroughly enough to let all of the roots get a drink.
In case of insect pests or infections, citrus rust mites are one of the major pests that attack orange trees. These mites are of several types, including the ones that cause small oranges.
They may even cause premature fruit drop and leaf loss. The grower should look for leaves that are bronzed and with necrotic spots. Annual miticide application can help prevent these bugs.
Another insect pest that can cause mature oranges to be small are leafhoppers. They can spread the pathogen Spiroplasma citri that can cause a disease named Stubborn disease.
This disease can lead to an orange tree that bears no fruit or abnormally small fruit. The fruit may be lopsided with a green blossom end. The only solution is to remove and destroy the affected trees.
Melon aphid is another insect pest that indirectly causes small oranges. Its feeding results in the tristeza disease complex.
The symptoms include light green leaves, early leaf drop, and an abundant crop of small oranges. The only remedy is to prevent it by taking care to control aphid populations (introducing natural enemies of aphids in one’s garden, like ladybugs and lacewings, removing ants naturally that defend aphids, etc.).
No Oranges
There may be several reasons why an orange tree doesn’t bear oranges. When an orange tree has flowers but no fruit, the problem may be that the flowers aren’t pollinated. This happens especially when the plant is grown in a sheltered area such as a greenhouse or sunroom.
Sometimes the tree won’t flower in the first place. In that case, the grower should check the location of the tree and the care they’re giving to the tree. Orange trees need sun, adequate water, and regular fertilization.
Also, the age of the plant should be considered. Fruit can be expected 3 o 5 years after planting the tree.
If a grower is wondering why their orange tree is not producing fruit, they should check if one of the following is the situation:
- The tree is not old enough to bear fruit
- The tree is not receiving adequate sunlight
- Cold temperatures are killing flower buds
- Flowers are not being pollinated
- Watering, fertilization, or pruning is not proper
How to Make an Orange Tree Fruit More?
If one’s flowers are not being pollinated, they should shake the tree while the tree blooms, in order to shake loose pollen and make it fall onto the pistil. This should be done regularly for several days.
If the grower has unusually cold temperatures or warm spells suddenly followed by cold temperatures, this can cause loss of flower buds or prevent buds from opening.
In that case, covering the canopy with a blanket may help prevent crop loss.
Proper maintenance results in a healthy tree t
hat can produce a good crop. The grower should water the trees weekly if there is no rain. They should either use drip irrigation or water slowly by hand to allow the soil to absorb as much water as possible. If the soil is heavy clay and doesn’t absorb water well, the grower should water often but in smaller quantities.
Orange trees need a lot of nitrogen, but if it’s given too much, flowering is prevented.
Providing the tree with a fertilizer specially made for citrus trees is the best way to make sure one is giving the right amount of fertilizer to their tree.
The instructions on the label should be carefully read and followed. If one’s tree is standing on the lawn, they should remember that when they fertilize the lawn, they give the tree an extra dose of high-nitrogen fertilizer.
This can be avoided by covering the soil over the tree’s root system with mulch so they won’t have grass to fertilize in that area.
The grower should also prune their trees to provide them with good shape and structure. If this is done correctly, the tree will need very little pruning when it’s mature enough to fruit.
The grower should prune old trees to remove dead and damaged branches. They should remove branches from the canopy every 3 to 4 years so as to see dappled sunlight under the tree.
An open canopy that receives adequate light gets a boost for good production. Pruning only a part of a branch known as heading back encourages new growth at the cost of flowers and fruits.
Splitting Fruit
If the grower is upset because their oranges are split open and become inedible, they should understand that they can prevent the problem by applying correct cultural and nutritional conditions.
Causes: The most common victim of split fruit is navel oranges. One of the main causes is that water and plant sugars reach the fruit too soon for it to produce adequate rind to hold the pulp.
The excess fluids cause the skin to burst. Especially young trees have the highest events of oranges splitting. Mostly oranges split open from July to November.
Cracked rinds start at the blossom end of the fruit. While most of the splitting occurs at the end of the season, it can start as early as July.
Trees having the highest crop load are the most affected. Split oranges occur seasonally and basically caused by plant care, but also due to temperature changes and humidity.
The extent of the split may vary. It may be short and slim or may expose the pulp inside. Navel oranges crack open more, maybe due to the rind’s thickness and the large stylar.
The splitting of citrus fruits is caused due to cultural activities. Water problems may cause it when the tree receives too much water. E.g., in winter the tree needs only 1/8 to ¼ inch (3-6 mm) of rain per week.
From March to June, this need increases to ½ inch (1 cm) and in the warm season, the tree needs 1 inch (2.5 cm) of water per week. Anything more than this is excessive.
The problem can be caused even due to over-fertilization. Orange trees should need 1 to 2 pounds (453.5 to 907 g) of nitrogen annually. The grower should split the application into 3 or 4 periods. This will prevent overfertilization that causes split rind.
Another cause is believed to be tree stress. Hot, dry winds dry the tree out and take moisture away from the fruit which shrinks. Then when water is available, it first goes to the fruit, which swells too much.
Young plants with a small root system are most vulnerable as they don’t have a sufficiently wide root area to collect moisture.
Curling Leaves
Leaf curl is one of the most obvious signs of an orange tree being in distress. There are four major reasons for leaf curl – pests, diseases, water stress, and weather. Sometimes, it can be a combination of all four.
Pests: Insect pests may be a culprit for leaf curl. They like the sap flowing through the foliage of the orange trees.
These insects include aphids, spider mites, scale, citrus psyllid, mealybugs, and citrus leaf miners.
The grower should check their trees for signs of these insects. If insects are causing one’s leaves to curl, the treatment can have 2 levels – firstly, a number of predatory insects such as green lacewings, predatory wasps, and ladybugs can be introduced in the garden.
They will reduce the harmful insect within no time.
Secondly, the gardener can use an insecticide. Neem oil, insecticidal soap, or horticultural oil should be used on a cool, calm day.
Diseases: A disease can also be a cause of leaf curl.
Both botrytis disease and bacterial blast can cause leaf curl.
Botrytis disease penetrates trees that have open wounds. The affected area of the tree develops a grey, velvety mold which is followed by leaf discoloration, curling, and twig dieback.
This disease can be prevented by preventing injuries to the tree from frost, rot, and machinery. As a treatment, one can apply a copper fungicide before the arrival of wet weather to prevent fungus from reaching the blossom or fruit stage.
The bacterial blast starts with black spots on the petiole and progresses onto the axil. In the end, the leaves curl, wither and drop. The grower can deal with this disease by applying the copper spray to the infected orange.
Other Reasons: The most obvious reason for leaf curl in citruses is water stress.
Shortage of water will ultimately affect the flowers and fruit causing their premature drop. The correct amount of water needed by an orange tree depends on its type, weather, time of the year, and size of the tree.
For example, an orange tree with a 14-foot (4 m) canopy needs 29 gallons (53 L) of water per day in July and in dry periods. But even overwatering can cause leaf curl. The gardener should make sure the area of the plantation has excellent drainage.
They should remember that citruses don’t like wet feet.
Another factor is the weather. Extreme hot spells will cause the tree to dry out, so one should water more often, particularly if it’s a potted plant.
Citruses are even susceptible to sunburn which too cause leaves to curl and also yellow or brown blotches on fruits. But even cold weather may cause leaves to curl. The grower should keep the plant covered if a cold snap is expected.
Lastly, sometimes orange leaves will cup downward in the late fall or early winter. However, this is normal and the grower need not worry about it, because new growth will appear in the form of ordinary shaped leaves in the spring.
