Q. We’ve noticed leaf
damage this year on our rose bushes, apple and pear trees. More than previous
years. But, peach, apricot, and pomegranate seem unaffected. Some of our roses
were decimated. Any idea what pest causes this and how to control it?
damage this year on our rose bushes, apple and pear trees. More than previous
years. But, peach, apricot, and pomegranate seem unaffected. Some of our roses
were decimated. Any idea what pest causes this and how to control it?
 |
| Leaf damage from chewing insects. Very typical of adult June beetle damage. |
A. The picture of leaves
you sent show uneven missing parts, many areas with parts missing down to the
veins of the leaf. This type of damage is
from insects that have mouths specialized for chewing leaves. Heavy damage
means there is a large population you have not seen in the past.
you sent show uneven missing parts, many areas with parts missing down to the
veins of the leaf. This type of damage is
from insects that have mouths specialized for chewing leaves. Heavy damage
means there is a large population you have not seen in the past.
 |
| Typical June beetle |
Unless you see this type of damage throughout the year,
there is no reason to spray chemicals now. Damage from these types of insects
is probably over. Instead, concentrate on getting the plant producing
replacement leaves. Let me explain why.
there is no reason to spray chemicals now. Damage from these types of insects
is probably over. Instead, concentrate on getting the plant producing
replacement leaves. Let me explain why.
Common insects that chew leaves include grasshoppers,
many different types of beetles, weevils, and others. Some of these insects
chew leaves throughout their entire lifecycle (e.g. grasshoppers) and others
only during part of their lifecycle (most of beetles). Sometimes the damage
progressively gets worse (grasshoppers and some weevils) and other times it
lasts only two or three weeks and it’s gone (many beetles).
many different types of beetles, weevils, and others. Some of these insects
chew leaves throughout their entire lifecycle (e.g. grasshoppers) and others
only during part of their lifecycle (most of beetles). Sometimes the damage
progressively gets worse (grasshoppers and some weevils) and other times it
lasts only two or three weeks and it’s gone (many beetles).
 |
| Metallic Green June Bettle |
Most of this type of damage that begins in summer lasts
perhaps three weeks and stops. This is because the damaging stage of this
insect is over. The lifecycle of this insect has moved to another stage of
development and most likely will not be a problem. If you spray now, you wasted
your money and time.
perhaps three weeks and stops. This is because the damaging stage of this
insect is over. The lifecycle of this insect has moved to another stage of
development and most likely will not be a problem. If you spray now, you wasted
your money and time.
 |
| Grape fleabeetle |
When this type of damage suddenly occurs this time of
year, it is usually from the adult stage of large insects like scarab beetles. They
feed for two or three weeks before they die. An example are June beetles.
Chewing damage from smaller beetles, like flea beetles, occurs earlier in late
spring. Smaller insects like flea beetles can produce a second “crop” of adults
so sometimes damage is seen in the fall as well. But the damage comes on fast
and it’s over fast.
year, it is usually from the adult stage of large insects like scarab beetles. They
feed for two or three weeks before they die. An example are June beetles.
Chewing damage from smaller beetles, like flea beetles, occurs earlier in late
spring. Smaller insects like flea beetles can produce a second “crop” of adults
so sometimes damage is seen in the fall as well. But the damage comes on fast
and it’s over fast.
 |
| Grape fleabeetle damage |
Exceptions are grasshoppers where all stages of its
lifecycle have chewing mouthparts. With insects like grasshoppers, we see leaf
damage early in the season that progressively gets worse as the season wears on.
Grasshopper control is best done as soon as possible if there have been
problems in the past.
lifecycle have chewing mouthparts. With insects like grasshoppers, we see leaf
damage early in the season that progressively gets worse as the season wears on.
Grasshopper control is best done as soon as possible if there have been
problems in the past.
 |
| Probably root weevil damage |
Chemical pesticides reduce damage next year if you
kill the chewing adults as soon as damage starts. If you wait until the damage
is extensive, it’s too late. The leaf-damaging adults are gone, the damage has
been done and have laid their eggs for next year.
kill the chewing adults as soon as damage starts. If you wait until the damage
is extensive, it’s too late. The leaf-damaging adults are gone, the damage has
been done and have laid their eggs for next year.
Instead, concentrate your efforts in rebuilding what was
lost. Apply fertilizers to the soil and water them in. During hot summer
months, use half of the recommended rate on the bag or container. Apply it
twice, four weeks apart. Avoid applying fertilizers after August 1 to plants
that are tender during cold winter months.
lost. Apply fertilizers to the soil and water them in. During hot summer
months, use half of the recommended rate on the bag or container. Apply it
twice, four weeks apart. Avoid applying fertilizers after August 1 to plants
that are tender during cold winter months.