Fruit Pest News
September 17, 2001
An online newsletter whose goal is to update Extension agents and growers of commercial tree fruit and small fruit crops
on diseases and insects in Tennessee.
Fruit Pest News will be produced every two weeks until the end of the 2001 growing season. The weekly schedule will resume next spring.
Text appearing in blue or red can be clicked to link to other web sites. Be aware that much of the linked information is produced in other states and may not be applicable to Tennessee.
In This Issue:
1. Apples: Insect Update for Apples
2. Strawberries: Disease Control in the Fall
3. Stone Fruit: Plum Pox Update
4. Pumpkin Fruit Rots
1. INSECT UPDATE FOR APPLES
Oriental Fruit Moth on Apple
Oriental fruit moth (OFM) has become a more
important pest on apples in recent years. Third generation moths have emerged from
peach orchards (most fruit harvested and shoots no longer succulent and attractive
to larvae). These moths are laying their eggs on apple fruit. The trap catches
in Nashville have increased in late August through mid-September. Continue to monitor
your OFM pheromone traps. Since insecticides should give 2 weeks control do not be
concerned if trap catches remain high one week after spraying.
Codling Moth
Codling
moth should also be monitored using pheromone traps. Inspect fruit for codling moth
damage (messy excrement coming out of holes in the fruit). Treat if damage is found
or if trap catches for the third generation exceed 5 moths/trap/week which should
be,900 DD after biofix.
Evaluating Your Pest Control by Block
Evaluation
of pest control at harvest time lets you know the effectiveness of your pest control
program. Fruit should be sampled from each block and any factor that will reduce
the value of the fruit should be recorded. A sample of 100 fruit should be taken
from each of 5 trees or bins in a block (a total of 500 fruit per block). This will
give you an adequate sample size so that the pest control program can be evaluated.
Breakdowns in pest control may occur in certain parts of the block such as more
plum curculio injury near field borders, fence rows and woods or more codling moth
injury on areas of the block closer to abandoned orchards or bin storage areas.
You may also notice bruise injury at this time although it will probably show up
more in storage or even after packing. I think that it is a good idea to follow
a representative sample of fruit from each block from harvest through storage and
packout. I found in past studies that improved handling of fruit to reduce bruising
can be one of the best things that can be done. If sampling bins, you can track
fruit using a two-part card that has lines to record specific collected data. In
the bottom section of the two part card labeled "Storage" there are separate
lines to record the block name and cultivar, date picked/date stored, storage type
and building location, fruit pressure/sugar level, storage treatments used, and name
of picker (pickers that protect fruit should be rewarded while those that bruise
fruit should not). Each card has its unique identifying number on both the bottom
"Storage" section and the top "Packout" section. The Storage
section of the card is removed and kept on file when the bin is put into storage.
The Packout section remains on the bin through storage. It has lines to record
the block number and cultivar, packout date, fruit pressure/sugar level and notes.
Some type of plastic coated card that you can write on will be preferable to a plain
paper card due to moisture in storage. Additional sampling of culls at packout can
let the grower know what factors caused the most damage to the fruit. These records
can aid the grower in making marketing decisions and in assessing the crop production
and crop protection programs. It is important to collect data on each block of fruit
so that profitability by block can be determined. (FH)
2. STRAWBERRY DISEASE CONTROL IN THE FALL
Plasticulture strawberry fields are now being planted, and disease control is one of the many things that must be considered. Botrytis is thought to begin building up in fields in the fall, and an application of a Botrytis fungicide may be helpful, although there is not universal agreement as to when that application should take place. An application in early November would help prevent fungal colonization of plant parts that get killed by winter weather. Colonization could occur as early as the plant establishment stage, or even during rooting of the tips in the plug production beds. When planting in the field, the use of plug-type plants with water-wheel planters is advisable, as this practice would avert the need for sprinkler irrigation during establishment. Repeated wetting of the plants would encourage Botrytis colonization of the dead tissues. Botryticides that could be used in the fall include Elevate, Rovral, and the newly-registered Switch. Rovral may only be used one time.
Hopefully, you purchased anthracnose-free plants so that applications of anthracnose fungicides will not be needed. If anthracnose does appear (I would like to hear about it, if it does), a regular spray schedule that includes captan, Switch, or Quadris will be needed. The Section 18 label for Quadris expires on October 15.
Chandler strawberries generally have sufficient resistance to common leaf spot that chemical control is not needed. Some matted-row varieties occasionally require control measures. This disease is usually most likely during cool, wet weather. Nova is our most effective fungicide against common leaf spot. (SB)
3. PLUM POX UPDATE
No states other than Pennsylvania have reported stone fruit samples positive for plum pox virus. In Pennsylvania, the only positive samples from this year's survey have come from within the quarantine zone or from areas closely adjacent to the quarantine zone. The quarantine zone in Pennsylvania was established in 2000, encompassing the area in which plum pox was found. The survey results are encouraging, supporting our hopes that the virus has not become widespread. (SB)
4. PUMPKIN FRUIT ROTS
An article
on pumpkins in a fruit newsletter? Of course. Some apple growers grow pumpkins and
sell them at their stands to complement their apple sales. Other growers purchase
pumpkins for resale at their stands. In either case, post-harvest rots can be a problem.
Rotten pumpkins don't sell, and you don't want them to rot in Mrs. Customer's house,
either.
Most efforts to control post-harvest rots of pumpkins, gourds, and
winter squash should have already taken place. Most of the rots that appear in storage
actually began in the field, during the production of the fruit. However, there are
some steps you can take to lessen the development of rots after harvest.
Pre-harvest
control measures. Rots develop when disease-causing organisms, mostly fungi,
enter the fruit surface. The best defense against this invasion is fruit rind tissue
with strong cell walls. To obtain such "tough" fruit, the plant must be
kept healthy during the growing season. Healthy leaves provide carbohydrates to the
fruit, which strengthens the cell walls. Provide adequate calcium, avoid excessive
nitrogen, and irrigate during dry periods. Follow a recommended spray program to
control diseases and insects. Controlling foliar diseases helps maintain healthy
leaves and reduces the populations of organisms that can infect the fruit. Crop rotation
is very important in reducing the populations of fruit-rotting organisms. Certain
pathogens, such as the Fusarium fruit rot fungus, are not controlled by fungicides.
Two years in a non-cucurbit crop should be allowed between pumpkin crops.
Post-harvest
control measures. Damaged pumpkin skin allows easier entrance of the fruit-rotting
pathogens. Handle fruit carefully to avoid injuries. It is helpful to wash the fruit
after harvest and allow to dry. Some growers dip or spray the pumpkins in a 10 percent
bleach solution. This practice can reduce infections in storage, but will not stop
the development of infections that occurred in the field. Holding the pumpkins at
80-85 degrees F and 80-85% relative humidity for 7 to 10 days allows scratched areas
to cure. After the curing period, the temperature and humidity must be lowered to
the levels recommended for storage (50-55 degrees F and 50-70% relative humidity),
to reduce the disease potential.
Store pumpkins in a dry, shaded area, out
of contact with the soil (straw or hay works well). Avoid piling pumpkins, as this
practice decreases air circulation around them. Check stored fruits regularly for
rots, and discard affected ones. Storage life of pumpkins is typically two to three
months. (SB)
The Fruit Pest News URL is: http://web.utk.edu/~extepp/fpn/fpn.htm
Contacts:
Steve Bost, Professor and Extension Plant Pathologist
Frank Hale, Associate Professor and Extension Entomologist
Both authors available at:
615-832-6802
fax 615-781-2568
Plant and Pest Diagnostic Center
5201 Marchant Drive
Nashville, TN 37211