Weekly Pest Alerts for May through September 2019

Douglas County OSU Extension Service  -   Horticulture Program 

Weekly Pest Alert Comments - 2019 by Steve Renquist

Questions? Contact Steve Renquist.

July 30

The weather during the last week of July turned hot with several daytime high temperatures in the low 90’s.  Night time low temperatures continued to be in the 50’s to low 60’s which has helped minimize any leaf scorch or serious plant stress.  The high temperatures have also helped to control the Spotted Wing Drosophila activity. The SWD damage in berry crops has been very minor despite the fact that the past two weeks has been the main ripening period for raspberries in our region. Damage to blueberry fruit has also been minimal. Fig harvest is really going strong so keep harvesting fruit quickly when ripe to prevent the SWD infestation. The longer the figs hang on the tree the thinner the skin gets so it is easy for the SWD to lay their eggs in very ripe figs.

It has been 14 days since our last spray recommendation for codling moth in pears and apples. Even though we have not seen many catches in our pheromone traps during that time, it is a good idea not to push the spray interval any further. I will be making a codling moth spray now with Spinosad. If you used Spinosad on your last spray, I would recommend rotating to either Cyd-X or Malathion. I would not use horticultural oil with temperatures around 90 degrees. This time of year any week with a catch of two codling moths is a signal to spray.  In my orchard I am seeing very clean fruit so far with just a few apples and pears with surface stings and only 3-4 apples with a worm hole. It is always a good idea to inspect the fruit on your trees closely to make sure your trap lures are still working. If you find quite a few fruit with worm holes, it may be time to add new lures to your sticky trap.

With the hot temps and no rain over the past week or two, there is no reason to be spraying any fungicide on the apple or pear trees. As we get into the months of September and October you will want to consider making a fungicide spray to stop shot hole fungus in peaches, plums, apricots, nectarines, and cherries. This is a fungus that leaves lots of small holes in the leaves that look like someone shot buckshot through the leaves. Do this before leaf fall and fall rains. With apple and pear trees a fall fungicide spray for Nectria canker on the branches or trunk of trees is very helpful to minimize elliptical shaped cankers that can eventually lead to branch dieback and the invasion of wood rotting fungi into the wounds.    

July 15

The weather in late June and early July has turned nearly perfect with daytime high temps in the 80’s and nighttime low temps around 60 degrees. If you have made a two well timed codling moth sprays, one in late May and a second in mid-June, you should see your apple and pear crop maturing nicely with very little damage. When you have a spray program that alternates Spinosad with Cyd-X you may notice a few codling stings that look like an entry point for the larvae. If you cut into those stings you will often notice they don’t enter the apple or pear very far, and there is no sign of the larvae. There is no deep feeding tunnel or larvae present because the larvae has eaten some of the Cyd-X or Spinosad and has died before getting far. The Cyd-X works by slowing infecting the larvae from the inside of their digestive track.

Despite the relatively dry mild weather of late June and early July we have not seen any serious outbreak of powdery mildew on tree fruit or wine grapes until the past week. With cooler temps and increased humidity in our area I am starting to see signs of powdery mildew on roses and grapes. Make sure to get a fungicide cover spray on your susceptible crops like grapes, squash, ornamental shrubs and roses, and some varieties of apple. You know which crops tend to get powdery mildew in your yard, get out there and protect them. Captan, sulfur, Immunox, and Kaligreen or Armicarb are products that will work for homeowners.

With blueberry, strawberry, and raspberry harvest winding down, it is not quite as critical to be controlling the Spotted Wing Drosophila in berry crops unless you have late maturing varieties. If you still have fruit ripening, stay vigilant and keep picking fruit as it matures so the pests don’t have time to damage the fruit. If you are getting soft mushy fruit when picking, you will need to make a spray of Spinosad about a week before picking or Malathion at least a day before picking to adhere to the label. So far this summer I have noticed very light vinegar trap catches of late and very little damage to the soft fruit.

My fig crop is ripening presently. Be alert to protect your fig crop from the Spotted Wing Drosophila. The SWD really like figs so as the figs ripen, harvest them daily and if the figs need to hang for any length of time, you may need to make one spray of either Spinosad or Malathion.

June 17

Codling moth traps in orchards that were sprayed within the past two weeks had no catches. One home orchard that does not spray has been averaging 15 moth catches in each of the past two weeks. It is very important to be consistent with your pest control monitoring and control applications. This time of year with no rain and warm temperatures is beneficial to insect pests so don’t stretch your control application beyond two weeks. I continue to follow a spray rotation alternating between Spinosad, Cyd-X, and horticultural oil (not dormant oil) when high temperatures are below 85 degrees. Don’t use oil sprays on plants when temps are above 85 degrees or you will burn leaves.

Disease pressure with apples so far this year is pretty light. I made three fungicide sprays in spring on apples, pears, and plums. I have seen no apple or pear scab and no powdery mildew. The timing of my Captan spray around late bloom was very good this year and I have not seen any scab lesions on the apples and pears. The second fungicide spray of Immunox did a good job of knocking out any mildew I might have missed early season. The early season fungicide spray is really critical to prevent what can be a full summer fight against apple scab.

The recent hot weather in the first half of June has put a lot of pressure on the SWD. So far I have not seen any big catches in my vinegar traps. With both blueberries and raspberries coloring though it is that time of year to monitor the SWD population closely. I advise you when the berry crops are ready to harvest, don’t delay or the SWD will be laying eggs in the fruit. If you have a lot of nearly ripe fruit hanging on the canes, and you are about a week away from harvest, making a spray with Spinosad or Malathion is allowable. If you prefer to go without the spray, remember to pick the fruit nearly every day after the fruit tastes good, to minimize feeding damage.

Hopefully you have finished your fruit thinning on the fruit trees to reduce pest pressure and improve the size and quality of the fruit. Fruit thinning is also good for the fruit tree to lessen moisture and nutrient demand which allows the tree to make good fruit buds for next year’s crop.

June 3

SWD catches in cherry orchards continue to be very large with counts over 50 again. Anyone with cherry crops that are starting to color need to make their first control spray this week if they did not spray last week. If you sprayed a week ago and your cherry crop is not ripening quickly because of the cool weather this week, you may need to make another spray next week.

The most critical spray for codling moth control is often the first one that usually falls in late May for the Umpqua Valley. This spray will work to keep a lid on the overall codling moth population as the summer progresses. It is also important to keep monitoring your traps all summer into September and when you catch two moths in one week, make another spray. Remember to clean out your traps each time you record the weekly catch numbers. Always rotate your chemical sprays after each application to minimize resistance buildup.

I noticed pretty heavy pressure from flea beetles on new seedlings in my vegetable garden again this year following the mowing and shredding of the cover crop. Cover crops are great for the soil but during the decomposition phase in the new garden, the insects that aid organic matter decomposition can start chewing on new seedlings. If you have problems with new seedlings being eaten, one application of Spinosad will usually be all that is needed to give them time to grow past the pests.

If you have grapevines that are not hybrids or concords with powdery mildew resistance, it is a good time to make your first fungicide spray. There are a number of fungicides that work well for homeowners but the easiest to find is sulfur. Sulfur is also good for homeowners since you can use it several times in a row without worrying about resistance developing.

May 

A mild winter pushed all the fruit trees to bloom about 2-3 weeks earlier than the last couple of years. The mild winter was followed by a snow storm that dropped about 20 inches of snow on crops coming out of dormancy.  The snow slowed crop progress a little for both berry crops and tree fruit. As May began to warm up with temperatures around 90 degrees during the first half of the month, insect emergence accelerated and ended the month right on the twenty year averages. One of my codling moth traps did pick up 20 moths during the first three weeks of May.

We are working with a little different strategy now to begin the summer monitoring period for codling moth. Now we like to wait until we hit 250 degree days accumulation from January 1 before making our first spray.  This gives time for both male and female to congregate and be active and vulnerable to controls before the female lays eggs.  This year we made our first codling moth sprays for apples, pears, and plums in the last week of May but you can make your first spray now if you did not make one yet.

As we go forward always remember to clean out the traps so your new weekly monitoring will be accurate. From this point going forward as we move into the new week any trap with 2 or more moth catches should be followed with another spray.  For organic growers we started our codling moth spray program with Spinosad this year. We plan to use Cyd-X with our second spray. You can use Surround or horticultural oil, or superior oil if you prefer, but remember if the temperature is in the upper 80’s or hotter do not use the oil sprays. If you are not an organic grower you can use non organic products like sevin or malathion.

We are also monitoring for apple or pear scab presently. I made two fungicide sprays one with Captan and one with Immunox during May. With our relatively dry May I have noticed no scab infection on leaves, even on Gala which is very vulnerable to apple scab. It is important to put fungicides on your fruit trees, grapevines and berry crops to protect them from powdery mildew, scab, or other fungal diseases. You should always put on a fungicide spray to prevent these diseases so get the spray on pre-bloom and post-bloom if the weather forecast looks dry for a day or two. Organic growers are restricted to using dusting sulfur or wettable sulfur.  Conventional growers can use captan, or immunox. 

Always buy 2 or more insecticide products, and alternate their use as I advise the timing in the weeks ahead to prevent resistance by insects. Sulfur is a product that has not experienced disease resistance issues.

Remember to get vinegar traps out in your orchard and berry crops to monitor for Spotted Wing Drosophila. These small vinegar flies have been laying eggs in berry, cherry, and peach crops the past few seasons and will need to be controlled as your fruit crop gets near full size. I will advise you when to apply controls, however it is important to know if they are around your fruit crops presently.

Researchers have been trapping Brown Marmorated Stink Bugs (BMSB) around much of western Oregon during the past year. These insects can cause a major amount of damage to fruit and vegetable crops so look up what they look like and keep alert. These pests especially like English holly and Tree of Heaven (Ailanthus altissima) to gather and live in. Researchers have been getting good control of these pests by treating the ornamental host plants with systemic insecticides. I have put out some traps in several areas of Garden Valley to follow the population buildup of the BMSB.

With a good set of fruit on apple trees you should plan to finish fruit thinning by June 15.  We saw petal fall from most tree fruit crops in mid to late April. Apples, pears, peaches, and plums often set way to much fruit. Thinning fruit will improve size and quality, plus keep your tree branches from breaking. When you are thinning off fruit look for damaged fruit and remove them.

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