Insect and Disease Control in August
In the July Growing tips, I wrote about the spotted wing drosophila, a recently introduced fruit fly that has been observed along the western seaboard of the U.S. and into Canada, west of the Rocky Mountains. The female fly deposits her eggs in berries and soft fruit as they approach ripening (other fruit flies wait until the fruit is full ripe). It is valuable to put out monitoring traps to determine if this pest is in your back yard. For more information on this new pest and directions to make a monitoring trap go to spottedwing.org.
APPLE MAGGOT/ CODLING MOTH: Continue monitoring for apple maggot flies and codling moths if using sprays as your control measure. Reapply sprays when the number of flies trapped increases, or if you are using Surround, re-apply when growth of the fruit or rain fall has reduced the white coverage.
Sanitation is an important cultural tool for reducing the over-all insect population of both apple maggot and codling moth, or any other fruit infesting insects in your orchard. Pick up any fruit that falls early in the ripening season (within a couple days of falling) and discard or destroy it, before the developing maggot or larvae is mature enough to crawl out of the fruit and continue its life cycle. The first fruit drops following pollination are the most important to pick up, but cleaning up the fruit in August will help reduce the over-wintering population. The more isolated your orchard is the more effective picking up the fruit will be. If your neighbors are not picking up their fallen fruit you might consider putting up extra monitoring traps between your orchard and theirs, to trap some of the migrating insects before they arrive in your orchard. You can find apple maggot and codling moth traps on our Pest Control page.
Spinosad (#T177), a quick acting broad spectrum natural insecticide spray derived from the metabolites of a common soil bacterium and neem oil based insecticides (Safer Bioneem Botanical Insecticide #T172) are both effective against codling moth, plum curculio, and currant worm caterpillars before they enter the fruit. Use Spinosad for heavier infestations, and follow label instructions on timing to avoid damage to beneficial insects, up to 6 sprays per year. Use neem oil based products when you prefer a more gentle approach. The first spray would be applied 2-4 weeks after bloom, or when you started seeing pin hole scars in the fruit (from the little caterpillars chewing their way into the fruit). Applying spray in August is helpful in controlling second or third generations of these pests. Start looking for the scars a week or so after catching increased numbers of adults in your monitoring traps, when you start seeing new scars it is time to spray.
Some varieties of grapes, apples, gooseberry, currants and other fruiting plants are susceptible to powdery mildew. There are chemical fungicide sprays available at your local nursery, or you may want to try the recipe on page 16 in our Raintree Plant Owner’s manual . You can achieve a reasonable level of control using fatty-acid soap, oil (such as Neem), and powdered milk, but you will need to apply repeated sprays throughout the typical infection period, from June through August or September. To avoid having to spray, choose varieties listed as being resistant or immune to powdery mildew.
Grapes that are born in tight clusters can be susceptible to botrytis (bunch rot). Thin fruit clusters to maintain better air circulation in the bunch. Serenade, a biological fungicide derived from Bacillus subtilis strain, may be effective as a spray. Botrytis also affects other fruits, including strawberry, raspberry, blackberry, blueberry, cherry, and pear. Keeping the fruit dry, and not in contact with other fruit will help minimize spread of the disease. Sanitation is very important. Clean up and discard infected fruit (compost piles are generally not hot enough to destroy the organism), as well as old leaves that have died back or have fungal lesions on them, to remove as much source of innoculum as you can.
STONE FRUITS: Spray cherries, peaches, plums, and other stone fruits for brown rot, botrytis (gray mold) and other fruit infesting fungi if rain threatens or occurs just prior to harvest with a fungicide. Inspect for fruits that are showing evidence of infection, brown water-soaked looking lesions on the surface of the fruit in concentric rings or irregular patches, brown or gray fuzzy dots or patches. Pick and burn or discard infected fruits to help control the spread of fungal diseases. Apple, pear, and quince should also be inspected for possible infections.
Check CAMELLIAS, CITRUS, and other SMOOTH LEAVED EVERGREENS for black sooty growth on leaves and stems. Sooty mold grows on the sugary honeydew secretions of sucking insects (aphid, scale, or mealy bug), turning the leaf surfaces black. You can remove the sooty mold by spraying with the fatty-acid soap / light oil /milk mixture on pg 16 of Raintree Plant Owner's Guide, then wipe or forcefully spray the mold away. Be careful with the water spray, test a few leaves first to be sure you are not damaging them with too hard a spray. This mixture makes the sooty mold easier to remove and kills the sucking insects at the same time. One spray will not be sufficient to fully control the insects, see the Raintree Plant Owners Manual for more information.
* NOTE: Your local co-operative extension office should be able to provide you with pest and disease identification assistance, as well as pesticide and their use recommendations. Look in your local phone book under county listings, or go to our Helpful Links page, in Growers Info in the top tool bar, to find your local office along with other helpful resources.