 | |  | |  |
 | |  |
Citrus Scarring Pest Control by Tim Braun
It has often been said that citrus, oranges and lemons, are easy to market to the public consumer because there is no
packaging involved. The packages for Arizona and California citrus is mighty expensive to produce. If the citrus
package, the rind, that covers the citrus product isn’t treated and protected with great care a lot of money and effort is
lost. Citrus that can only be marketed as juice reduces the grower’s income.
Much of the money spent on that package is used to control one insect, citrus thrips. In Arizona citrus thrips is
considered the number one pest. There are a number of causes that produce rind damage. Biological damage includes:
insects, mites, diseases or snails. The mechanical damage includes: equipment, hail, sand or wind. Chemical scarring is
caused by some spray materials. Under certain circumstances citrus fruit can exude juices out onto their own rind which
usually washes off..
The small insects with fringed wings that are an orange yellow color and are found flying around citrus trees in
warm weather probably are citrus thrips adults. When temperatures rise above 58 F citrus thrips develop. Adult female
citrus thrips lay around 25 to 250 eggs in green citrus twigs, young fruit or new leaves. Eggs are oviposited under the
cuticle of the plant. When the larvae hatch they begin feeding by puncturing the epidermal cells of the fruit leaving
scabby gray or silver scars on the rind. The same feeding on young leaves can disfigure, scar or kill the leaves.
The larvae hatch during the spring and summer months. In the warmer desert areas of California and Arizona the egg
laying begins earlier and lasts to early winter months. The eggs that overwinter are layed in the last flush of growth. The
overwinter eggs hatch when new spring growth emerges due to warmer temperatures. The first instar larvae are
noticeably smaller than the second instar. The adult sized second instar does a great deal of scarring of the fruit and can
damage young leaves. The first and second instars feed on leaves and fruit. Under the sepals of the young fruit is where
thrips feeding does the greatest damage to the citrus fruit. As the small fruit becomes larger, the scarring enlarges with
the growth causing a scar that circles the top of the fruit.
During their third and fourth instars thrips move to the ground or crevices on the tree to become prepupa (third instar)
and pupa (fourth instar). The adults that emerge move around the foliage of the trees. In California and central Arizona 8
to 10 generations of citrus thrips are common. In the Yuma area on the border between Arizona and California as much
as 10 to 12 generations of citrus thrips are produced.
Tapping the flush of new growth leaves against a dark colored sheet or a wallet will give you an indication of the thrips
infestation. The fruit should be examined with a hand lens. There are several methods of counting thrips nymph
depending on the area and the experience of the sampler. Some people take up to twenty five samples in each quadrant of
the grove. In the Yuma area when a count of 10 thrips per leaf flush is counted spraying is usually recommended.
Thrips predators include: predaceous mites, spiders, lacewings, minute pirate bugs and lady bugs to name a few. The
predators are able to hold the numbers down when infestations are low, but these predators do not bring the infestations
under control in warm or hot conditions. Pesticides are usually required in these conditions.
Sabadilla, a botanical insecticide, spinosad (Success), the natural product and Agri-Mek which are all fairly nontoxic to
beneficials are used. The harsher chemicals on predators include; Dimethoate, carbamates and pyrethroids. These
pesticides have been used long enough that there is resistance to most of them in many citrus growing areas.
Because of the need for these harsh pesticides in the control of thrips the Arizona Citrus Research Council in
cooperation with the University researchers has done a great deal of research on the need for thrips control determined
by the size of the fruit. Arizona citrus researchers found that if thrips treatment is discontinued at 1 inch diameter fruit
size the harvested fruit lacked yield reducing scarring. This may save a treatment. In the Yuma area as many as five
treatments per season are used. This last treatment may not be needed. Some growers now use this method, but other
growers keep treating to insure scar free fruit.
If there is an insect born to scar citrus fruit, it has to be the “Citrus Peel Miner“. The citrus peel minor is common in
the California San Joaquin Valley, Coachella area and the Desert citrus growing areas. In Arizona citrus peel minor is
found throughout the state’s citrus areas. It occasionally reaches damaging levels in central Arizona. In California the
more susceptible crops are grapefruit, pumelos, and smooth-skinned navel varieties (Fukumoto, Atwood, TI).
Susceptible citrus varieties can have 20-80% citrus peel minor fruit scarring damage. Other less susceptible varieties
rarely get damage of 5%.
Citrus peelminors have a complete life history. The adult moths each lay 10 to 50 eggs on the cuticle of the stems and
fruit of citrus. The larva hatches in 4 or 5 days and feeds on the peel of the fruit below the egg shell. It then bores a hole
and begins feeding while mining below the epidermal cells. The semitransparent larvae are yellowish in color and goes
through four to five instars. Each instar lasts for 3 to 4 days. The larvae then stops feeding and becomes a non feeding
form. Then the next larval form is a spinning form with spinning mouth parts. The reddish brown spinning form of the
citrus peel miner exits the mined leaf, stem or fruit for a niche in the axial of the stem, crevasse in the bark or in the
ground trash. Then the citrus peelminor will spin a silken cocoon covered with small white or silver balls and pupate.
After 10 to 12 days the peel miner moth will emerge from the cocoon. The dark gray moths are mottled with brown and
cream colored wing markings. Moths exist for about 11 days. The entire life cycle from egg to egg is about 30 days with
6 to 8 generations.
August through November is the time to check for peelminer. Checking surrounding vegetation, cotton and oleander,
as well as the lower 4 ft on the citrus canopy for mined stems, leaves or fruit. Citrus peelminers have a number of
predators therefore when checking look for live peelminers. The mining scarring is easily seen on the rinds. If treatment
is required Lorsban is effective if applied with thorough coverage. Spinosad is also effective with thorough spray
coverage. When a citrus peelminers’ infestation starts the treatment of two to three flights with a mixture of Micromate
for eggs and a pyrethroid or organophosphate for adults and larvae should give control.
With the use of soft pesticides, Esteem and Success for thrips in citrus, Katydids are becoming a serious problem in the
San Joaquin Valley. Some growers mix light dosages of organophosphates or pyrethroids with Success to get control.
The insect growth regulator, Micromite, is slower (7 to 10 days), but a drawback exists. Micromite will kill the predator,
vedalia beetle.
When non-selective pesticides are replaced with selective pesticides katydid can become a damaging citrus pest.
Selective pesticides like Success are effective and control katydids on stone fruits, but populations of katydids in citrus
last longer than the applied Success residues and katydid become a problem pest.
Katydids look similar to grasshoppers except that katydid antennae are very long. Two kinds of katydids exist on citrus,
angular winged and forktailed. The angular winged are larger, have a humpback appearance, broader wings and feeds
only on leaves. The forktailed katydid nymph is more abundant and feeds on citrus fruit as well as leaves. When they
feed on fruit they do it right after petal fall. The young first instar nymphs chew on the entire small fruit causing a large
misshapen scar as the fruit enlarges. The larger second through fourth instar nymphs have large mouth parts. Katydid
2nd -4th instar nymphs take a single bite that expands into a large round scar as the fruit matures. A single katydid will
take one bite out of several small fruit as it moves about the tree. They will also feed on larger fruit and leaves. They can
scar a great deal of fruit over the petal fall period and for the next two months as they mature into adults.
Katydids have one generation per year. They lay their gray, oval, flat eggs in two overlapping rows on citrus twigs and
leaves. Looking for katydid eggs inside the edges of leaves in the fall will indicate the size of the coming spring
infestation. If predators are abundant infestations are reduced. Treatment is recommended if high populations are found
at petal fall when previous damage has been found.
Larger nymph instars of katydids will survive a cryolite or Success treatment used for thrips control. Adding some
organophosphates to the thrips spray mix will control the larger instar katydid nymphs. Other pesticides used in katydid
control include: Micromite (Insect Growth Regulator); Dibrom; Lorsban; Dimethoate; Baythroid and Danitol;
Back in the 1970’s I was traveling with a new member of the company that I was working for up on the coastal
highway above Santa Barbara. He wanted me to look at a crop of young citrus that was during petal fall. The young fruit
and leaves were showing signs of feeding. The grower had been applying sabadilla for the thrips, but the damage was of
an irregular chewing type both on the leaves and fruit. We found no thrips on the flush or on the young fruit. When we
checked the trash around the trunk of the trees we found earwigs. The field near it had two year old plantings with the
same damage. The young seedlings had tree wraps present. We found large numbers of earwigs in this field under the
paper wraps. We treated specifically for earwigs and controlled them.
Earwigs are a pest in citrus that is another pest that has emerged since the softer pesticides have been used to reduce
uses of the less selective materials like organophosphates and carbamates. The scarring caused by their chewing can
cause the citrus fruit to be turned down for the fresh market. Adult female European earwigs lay 50 to 90 eggs in the soil
during the fall hatching in the spring. Spring laid eggs hatch in about 14 days. Any predators that bother the earwig eggs
are attacked by the mother earwigs who guards the eggs aggressively.
The nymphs grow through five instars in 45 days during the warm months. Earwigs only have one generation. Because
this one generation overlaps, all sizes of earwigs are present during warm weather. Adults mate and eggs are laid after
about 11 days. The nymph and adults have pincer-like projections on their abdomen. The female forceps are straight and
the male’s are curved. Earwigs feed at night. When inspecting injured citrus fruit or leaves check the leaf litter on the
ground or under the paper wraps used for sunburn control. Removing the paper wraps is one form of earwig control.
When thrips are present and control includes some of the non-selective pesticides like the organophosphates the earwigs
will be controlled at the same time.
In some of the warmer areas of California the potato leafhopper can be a pest that causes citrus fruit scarring. Potato
leafhopper can migrate in the fall from field crops that are drying up. The potato leafhopper will winter in the citrus
groves. The potato leafhopper damage is most evident on green fruit as yellowish to light brown scars. The scarring is
done by the hopper’s piercing sucking form of feeding on the rind surface. Potato leaf hopper damage is random
clustered puncturing with no particular pattern.
The potato leafhopper is slender and green with bristle like antennae. It has rows of spines on its hind legs. If the
leafhopper is in a crop next to the citrus field a hydrated lime spray to repel the leafhoppers can be applied as a
preventative measure of control.
I live in an area of Yuma, Arizona where the landscaping is maintained by an association. In the early spring of the year
I noticed omnivorous leafroller infestations on some of the full grown bushes. By the early spring all the leaves were
gone from these large plants. In November the plants had to be replaced. When omnivorous leafroller lay their eggs in
Arizona and California citrus during February and March. The thrips control measures with non selective pesticides will
control earwig infestations.
Back during the 1950’s untreated groves in Southern California lost 70 to 80 % of the crop to fruit drop due to
omnivorous leafroller. Now major pest control sprays control omnivorous leafroller. Arizona has omnivorous leafroller in
the citrus, but it is only treated occasionally in nursery stock. Some omnivorous leafroller damage still occurs
occasionally. When omnivorous leafrollers tie their leaves that they are feeding on to fruit with webbing and feed on the
citrus rinds scarring occurs. They will also feed under the button at petal fall causing scar damage similar to thrips.
The omnivorous leafroller has a complete lifecycle. Eggs are laid in masses and covered with a clear adhesive material.
100 to 500 eggs are laid in five days. The larvae that hatch have five instars in 13 to 50 days. The first stage instars have
white tubercles at the base of the bristles on their back and sides of their body. The older instar stages have a brown
head and a prothoracic shield. The larvae moves to the midrib of a leaf where it rolls the leave over itself with silk like
threads and begins feeding. When the leaf is consumed the omnivorous leafroller moves to another leaf. In a rolled leaf
they will pupate for about 4 to 9 days and the winged adults will emerge. Omnivorous leafrollers have about six
generations per year. In Southern California and Arizona omnivorous leafrollers can be found in all stages throughout the
year.
Several predators feed on omnivorous leafrollers, but when they become a problem pesticides that are used include:
Lorsban, Lannate, Prokil Cryolite, Sevin, Dibrom and Bt’s. As mentioned before the thrips sprays usually occur when
omnivorous leafroller is at its most damaging period and both insects are controlled.
Another cause of scarring especially in the desert citrus is the citrus flat mite. Often when inspections of citrus has
found fruit scarring with low to no thrips infestations of citrus flat mite has been found in the grove. This is often the
case for citrus in the desert regions of California and Arizona. Citrus flat mite can tolerate hot summer temperatures
found in the desert. Some of the citrus pesticides do not control mites. The flat mite is hard to locate with the naked eye.
Even hand lens will miss them. Flat mite are usually classified as a secondary scarring pest. They feed on citrus rinds
that have been damaged by either thrips, some other pest or wind or sand damage.
The flat mite is amber in color with dark markings. The very young flat mites are red. The predators include other
predacious mites as well as lace wing and lady beetles. Dicofol is selective for mites and when added to thrips sprays it is
effective. Other pesticides include: sulfur and Agri-Mek.
Citrus cut worm scars citrus fruit and is sometimes a problem in the San Joaquin Valley. Variegated cutworm is found
in just about all citrus fields in California and Arizona and is not a scarring insect to citrus. The damage that citrus
cutworm causes is serious because the larvae move around while feeding on the young fruit after petal fall. A small
number of citrus cutworm can do a great deal of damage. They drop to the ground during the day only feeding at night.
Bt’s and Cryolite are used as well as Lorsban, Lannate, Sevin and Dibrom.
Blowing sand can scar fruit. Branches moving against the fruit can scar it. Some pesticide sprays will burn the rind and
scar it. Snails will feed on the rind and scar it. Equipment moving through the orchard will scar fruit when the fruit is
tender.
Citrus fruit scarring can occur anytime during the year. Monitoring the fruit all year for scarring as well as infestations
and finding the cause of the problem is the only way to prevent citrus fruit scarring.
The use of trade names in this course is solely for the purpose of providing specific information. It is not a guarantee
or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable
composition. Use pesticides safely. Read and follow directions on the manufacturer’s label.
Acknowledgements:
Article written by Susan McGinley, ECAT, College of Agriculture
citrusent.uckac.edu’PeelminerDD07.
As reported in the UC Citrus Entomology Program Citrus E-Newsletter May 2007.
://cekern.ucdavis.edu/Custom_Program143/Earwigs_Flying_Under_Radar_of_Many_httpCitrus_Pest_Control_Advisors.
htm
Penn State College of Agricultural Sciences, Cooperative Extension European Earwigs, Insect: Dermaptera, Jacobs,
Steve, Sr. Extension Associate.
Compiled by: Ken Agnew
Pesticide Information and Training Office
University of Arizona Crop Profile For Citrus In Arizona
Susceptibility of Lemons to Citrus Thrips Scarring Based on Fruit Size
David L. Kerns, Assistant Specialist, Entomology, Yuma Agricultural Center
Tony Tellez, Research Specialist, Yuma Agricultural Centert
It has often been said that citrus, oranges and lemons, are easy to market to the public consumer because there is no
packaging involved. The packages for Arizona and California citrus is mighty expensive to produce. If the citrus
package, the rind, that covers the citrus product isn’t treated and protected with great care a lot of money and effort is
lost. Citrus that can only be marketed as juice reduces the grower’s income.
Much of the money spent on that package is used to control one insect, citrus thrips. In Arizona citrus thrips is
considered the number one pest. There are a number of causes that produce rind damage. Biological damage includes:
insects, mites, diseases or snails. The mechanical damage includes: equipment, hail, sand or wind. Chemical scarring is
caused by some spray materials. Under certain circumstances citrus fruit can exude juices out onto their own rind which
usually washes off..
The small insects with fringed wings that are an orange yellow color and are found flying around citrus trees in
warm weather probably are citrus thrips adults. When temperatures rise above 58 F citrus thrips develop. Adult female
citrus thrips lay around 25 to 250 eggs in green citrus twigs, young fruit or new leaves. Eggs are oviposited under the
cuticle of the plant. When the larvae hatch they begin feeding by puncturing the epidermal cells of the fruit leaving
scabby gray or silver scars on the rind. The same feeding on young leaves can disfigure, scar or kill the leaves.
The larvae hatch during the spring and summer months. In the warmer desert areas of California and Arizona the egg
laying begins earlier and lasts to early winter months. The eggs that overwinter are layed in the last flush of growth. The
overwinter eggs hatch when new spring growth emerges due to warmer temperatures. The first instar larvae are
noticeably smaller than the second instar. The adult sized second instar does a great deal of scarring of the fruit and can
damage young leaves. The first and second instars feed on leaves and fruit. Under the sepals of the young fruit is where
thrips feeding does the greatest damage to the citrus fruit. As the small fruit becomes larger, the scarring enlarges with
the growth causing a scar that circles the top of the fruit.
During their third and fourth instars thrips move to the ground or crevices on the tree to become prepupa (third instar)
and pupa (fourth instar). The adults that emerge move around the foliage of the trees. In California and central Arizona 8
to 10 generations of citrus thrips are common. In the Yuma area on the border between Arizona and California as much
as 10 to 12 generations of citrus thrips are produced.
Tapping the flush of new growth leaves against a dark colored sheet or a wallet will give you an indication of the thrips
infestation. The fruit should be examined with a hand lens. There are several methods of counting thrips nymph
depending on the area and the experience of the sampler. Some people take up to twenty five samples in each quadrant of
the grove. In the Yuma area when a count of 10 thrips per leaf flush is counted spraying is usually recommended.
Thrips predators include: predaceous mites, spiders, lacewings, minute pirate bugs and lady bugs to name a few. The
predators are able to hold the numbers down when infestations are low, but these predators do not bring the infestations
under control in warm or hot conditions. Pesticides are usually required in these conditions.
Sabadilla, a botanical insecticide, spinosad (Success), the natural product and Agri-Mek which are all fairly nontoxic to
beneficials are used. The harsher chemicals on predators include; Dimethoate, carbamates and pyrethroids. These
pesticides have been used long enough that there is resistance to most of them in many citrus growing areas.
Because of the need for these harsh pesticides in the control of thrips the Arizona Citrus Research Council in
cooperation with the University researchers has done a great deal of research on the need for thrips control determined
by the size of the fruit. Arizona citrus researchers found that if thrips treatment is discontinued at 1 inch diameter fruit
size the harvested fruit lacked yield reducing scarring. This may save a treatment. In the Yuma area as many as five
treatments per season are used. This last treatment may not be needed. Some growers now use this method, but other
growers keep treating to insure scar free fruit.
If there is an insect born to scar citrus fruit, it has to be the “Citrus Peel Miner“. The citrus peel minor is common in
the California San Joaquin Valley, Coachella area and the Desert citrus growing areas. In Arizona citrus peel minor is
found throughout the state’s citrus areas. It occasionally reaches damaging levels in central Arizona. In California the
more susceptible crops are grapefruit, pumelos, and smooth-skinned navel varieties (Fukumoto, Atwood, TI).
Susceptible citrus varieties can have 20-80% citrus peel minor fruit scarring damage. Other less susceptible varieties
rarely get damage of 5%.
Citrus peelminors have a complete life history. The adult moths each lay 10 to 50 eggs on the cuticle of the stems and
fruit of citrus. The larva hatches in 4 or 5 days and feeds on the peel of the fruit below the egg shell. It then bores a hole
and begins feeding while mining below the epidermal cells. The semitransparent larvae are yellowish in color and goes
through four to five instars. Each instar lasts for 3 to 4 days. The larvae then stops feeding and becomes a non feeding
form. Then the next larval form is a spinning form with spinning mouth parts. The reddish brown spinning form of the
citrus peel miner exits the mined leaf, stem or fruit for a niche in the axial of the stem, crevasse in the bark or in the
ground trash. Then the citrus peelminor will spin a silken cocoon covered with small white or silver balls and pupate.
After 10 to 12 days the peel miner moth will emerge from the cocoon. The dark gray moths are mottled with brown and
cream colored wing markings. Moths exist for about 11 days. The entire life cycle from egg to egg is about 30 days with
6 to 8 generations.
August through November is the time to check for peelminer. Checking surrounding vegetation, cotton and oleander,
as well as the lower 4 ft on the citrus canopy for mined stems, leaves or fruit. Citrus peelminers have a number of
predators therefore when checking look for live peelminers. The mining scarring is easily seen on the rinds. If treatment
is required Lorsban is effective if applied with thorough coverage. Spinosad is also effective with thorough spray
coverage. When a citrus peelminers’ infestation starts the treatment of two to three flights with a mixture of Micromate
for eggs and a pyrethroid or organophosphate for adults and larvae should give control.
With the use of soft pesticides, Esteem and Success for thrips in citrus, Katydids are becoming a serious problem in the
San Joaquin Valley. Some growers mix light dosages of organophosphates or pyrethroids with Success to get control.
The insect growth regulator, Micromite, is slower (7 to 10 days), but a drawback exists. Micromite will kill the predator,
vedalia beetle.
When non-selective pesticides are replaced with selective pesticides katydid can become a damaging citrus pest.
Selective pesticides like Success are effective and control katydids on stone fruits, but populations of katydids in citrus
last longer than the applied Success residues and katydid become a problem pest.
Katydids look similar to grasshoppers except that katydid antennae are very long. Two kinds of katydids exist on citrus,
angular winged and forktailed. The angular winged are larger, have a humpback appearance, broader wings and feeds
only on leaves. The forktailed katydid nymph is more abundant and feeds on citrus fruit as well as leaves. When they
feed on fruit they do it right after petal fall. The young first instar nymphs chew on the entire small fruit causing a large
misshapen scar as the fruit enlarges. The larger second through fourth instar nymphs have large mouth parts. Katydid
2nd -4th instar nymphs take a single bite that expands into a large round scar as the fruit matures. A single katydid will
take one bite out of several small fruit as it moves about the tree. They will also feed on larger fruit and leaves. They can
scar a great deal of fruit over the petal fall period and for the next two months as they mature into adults.
Katydids have one generation per year. They lay their gray, oval, flat eggs in two overlapping rows on citrus twigs and
leaves. Looking for katydid eggs inside the edges of leaves in the fall will indicate the size of the coming spring
infestation. If predators are abundant infestations are reduced. Treatment is recommended if high populations are found
at petal fall when previous damage has been found.
Larger nymph instars of katydids will survive a cryolite or Success treatment used for thrips control. Adding some
organophosphates to the thrips spray mix will control the larger instar katydid nymphs. Other pesticides used in katydid
control include: Micromite (Insect Growth Regulator); Dibrom; Lorsban; Dimethoate; Baythroid and Danitol;
Back in the 1970’s I was traveling with a new member of the company that I was working for up on the coastal
highway above Santa Barbara. He wanted me to look at a crop of young citrus that was during petal fall. The young fruit
and leaves were showing signs of feeding. The grower had been applying sabadilla for the thrips, but the damage was of
an irregular chewing type both on the leaves and fruit. We found no thrips on the flush or on the young fruit. When we
checked the trash around the trunk of the trees we found earwigs. The field near it had two year old plantings with the
same damage. The young seedlings had tree wraps present. We found large numbers of earwigs in this field under the
paper wraps. We treated specifically for earwigs and controlled them.
Earwigs are a pest in citrus that is another pest that has emerged since the softer pesticides have been used to reduce
uses of the less selective materials like organophosphates and carbamates. The scarring caused by their chewing can
cause the citrus fruit to be turned down for the fresh market. Adult female European earwigs lay 50 to 90 eggs in the soil
during the fall hatching in the spring. Spring laid eggs hatch in about 14 days. Any predators that bother the earwig eggs
are attacked by the mother earwigs who guards the eggs aggressively.
The nymphs grow through five instars in 45 days during the warm months. Earwigs only have one generation. Because
this one generation overlaps, all sizes of earwigs are present during warm weather. Adults mate and eggs are laid after
about 11 days. The nymph and adults have pincer-like projections on their abdomen. The female forceps are straight and
the male’s are curved. Earwigs feed at night. When inspecting injured citrus fruit or leaves check the leaf litter on the
ground or under the paper wraps used for sunburn control. Removing the paper wraps is one form of earwig control.
When thrips are present and control includes some of the non-selective pesticides like the organophosphates the earwigs
will be controlled at the same time.
In some of the warmer areas of California the potato leafhopper can be a pest that causes citrus fruit scarring. Potato
leafhopper can migrate in the fall from field crops that are drying up. The potato leafhopper will winter in the citrus
groves. The potato leafhopper damage is most evident on green fruit as yellowish to light brown scars. The scarring is
done by the hopper’s piercing sucking form of feeding on the rind surface. Potato leaf hopper damage is random
clustered puncturing with no particular pattern.
The potato leafhopper is slender and green with bristle like antennae. It has rows of spines on its hind legs. If the
leafhopper is in a crop next to the citrus field a hydrated lime spray to repel the leafhoppers can be applied as a
preventative measure of control.
I live in an area of Yuma, Arizona where the landscaping is maintained by an association. In the early spring of the year
I noticed omnivorous leafroller infestations on some of the full grown bushes. By the early spring all the leaves were
gone from these large plants. In November the plants had to be replaced. When omnivorous leafroller lay their eggs in
Arizona and California citrus during February and March. The thrips control measures with non selective pesticides will
control earwig infestations.
Back during the 1950’s untreated groves in Southern California lost 70 to 80 % of the crop to fruit drop due to
omnivorous leafroller. Now major pest control sprays control omnivorous leafroller. Arizona has omnivorous leafroller in
the citrus, but it is only treated occasionally in nursery stock. Some omnivorous leafroller damage still occurs
occasionally. When omnivorous leafrollers tie their leaves that they are feeding on to fruit with webbing and feed on the
citrus rinds scarring occurs. They will also feed under the button at petal fall causing scar damage similar to thrips.
The omnivorous leafroller has a complete lifecycle. Eggs are laid in masses and covered with a clear adhesive material.
100 to 500 eggs are laid in five days. The larvae that hatch have five instars in 13 to 50 days. The first stage instars have
white tubercles at the base of the bristles on their back and sides of their body. The older instar stages have a brown
head and a prothoracic shield. The larvae moves to the midrib of a leaf where it rolls the leave over itself with silk like
threads and begins feeding. When the leaf is consumed the omnivorous leafroller moves to another leaf. In a rolled leaf
they will pupate for about 4 to 9 days and the winged adults will emerge. Omnivorous leafrollers have about six
generations per year. In Southern California and Arizona omnivorous leafrollers can be found in all stages throughout the
year.
Several predators feed on omnivorous leafrollers, but when they become a problem pesticides that are used include:
Lorsban, Lannate, Prokil Cryolite, Sevin, Dibrom and Bt’s. As mentioned before the thrips sprays usually occur when
omnivorous leafroller is at its most damaging period and both insects are controlled.
Another cause of scarring especially in the desert citrus is the citrus flat mite. Often when inspections of citrus has
found fruit scarring with low to no thrips infestations of citrus flat mite has been found in the grove. This is often the
case for citrus in the desert regions of California and Arizona. Citrus flat mite can tolerate hot summer temperatures
found in the desert. Some of the citrus pesticides do not control mites. The flat mite is hard to locate with the naked eye.
Even hand lens will miss them. Flat mite are usually classified as a secondary scarring pest. They feed on citrus rinds
that have been damaged by either thrips, some other pest or wind or sand damage.
The flat mite is amber in color with dark markings. The very young flat mites are red. The predators include other
predacious mites as well as lace wing and lady beetles. Dicofol is selective for mites and when added to thrips sprays it is
effective. Other pesticides include: sulfur and Agri-Mek.
Citrus cut worm scars citrus fruit and is sometimes a problem in the San Joaquin Valley. Variegated cutworm is found
in just about all citrus fields in California and Arizona and is not a scarring insect to citrus. The damage that citrus
cutworm causes is serious because the larvae move around while feeding on the young fruit after petal fall. A small
number of citrus cutworm can do a great deal of damage. They drop to the ground during the day only feeding at night.
Bt’s and Cryolite are used as well as Lorsban, Lannate, Sevin and Dibrom.
Blowing sand can scar fruit. Branches moving against the fruit can scar it. Some pesticide sprays will burn the rind and
scar it. Snails will feed on the rind and scar it. Equipment moving through the orchard will scar fruit when the fruit is
tender.
Citrus fruit scarring can occur anytime during the year. Monitoring the fruit all year for scarring as well as infestations
and finding the cause of the problem is the only way to prevent citrus fruit scarring.
The use of trade names in this course is solely for the purpose of providing specific information. It is not a guarantee
or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable
composition. Use pesticides safely. Read and follow directions on the manufacturer’s label.
Acknowledgements:
Article written by Susan McGinley, ECAT, College of Agriculture
citrusent.uckac.edu’PeelminerDD07.
As reported in the UC Citrus Entomology Program Citrus E-Newsletter May 2007.
://cekern.ucdavis.edu/Custom_Program143/Earwigs_Flying_Under_Radar_of_Many_httpCitrus_Pest_Control_Advisors.
htm
Penn State College of Agricultural Sciences, Cooperative Extension European Earwigs, Insect: Dermaptera, Jacobs,
Steve, Sr. Extension Associate.
Compiled by: Ken Agnew
Pesticide Information and Training Office
University of Arizona Crop Profile For Citrus In Arizona
Susceptibility of Lemons to Citrus Thrips Scarring Based on Fruit Size
David L. Kerns, Assistant Specialist, Entomology, Yuma Agricultural Center
Tony Tellez, Research Specialist, Yuma Agricultural Centert