April 2003

Oregon State UniversityNorth Willamette Research & Extension Center15210 NE Miley RoadAurora, Oregon 97002-9543Diane Kaufman 503-678-1264 ext 23 Damage from hot weather immediately before harvest coupled with disappointing prices from processors and spotty labor shortages have made this a pretty difficult year for manystrawberry growers. This was a good year to have at least some fresh market opportunitiesfor selling fruit, and for having varieties that were able to withstand the heat better than‘Totem’. It’s difficult to feel very enthusiastic after such a season. However, with the finalpicks of ‘Totem’ drawing to a close and renovation upon us, this seemed a good time todiscuss after-harvest activities.
the winter and spring was mild, soils were very wet. Waterlogged soils at this timeprovided poor aeration for root growth.
It was painful to watch some fields that had As wet soils warmed, fungi that attack roots (Phytophthora causing red stele; Pythium, few days in the 90’s. What happened? Even Rhizoctonia, Fusarium, Cylindrocarpon caus- look at the roots revealed serious problems.
we add all this together, we come up with When I dug some very healthy looking plants little opportunity for good root growth.
in May, I was shocked to find very few new Add to this any nibbling on roots by root white roots under those plants. Because last year’s black roots are not very effective at plants that looked good when temperatures supplying water, it is very important that strawberry plants produce a good flush of to heat stress. All-in-all, this was the worst new milky-white roots each year. This usu-ally occurs in the fall. Good root develop-ment during this time is crucial to a goodcrop the following June. Our problems probably began last fall, when it was warm and dry resulting in poor new root devel- only measured 0.56 and 3.22 inches of pre- cipitation in October and November, respec- tively. This is well below the 30 year aver- age of 3.85 and 6.85 inches for Octoberand November, respectively. Even though Oregon State University Extension Service offers educational programs, activities, and materi-als without discrimination based on race, color, religion, sex, sexual orientation, national ori-gin, age, marital status, disability, or disabled veteran or Vietnam-era veteran status. Oregon State University Extension Service is an Equal Opportunity Employer.
possible year for record-breaking hot tem- immediately after harvest would be an effec-peratures in late May and early-June.
tive strategy in fields threatened by root wee-vils, particularly when there are newly planted There are also probably differences among berry plantings in adjacent areas of the field varieties in their ability to stand up to heat. which need to be protected from weevil in- In looking at the varieties at NWREC, it is vasion.
apparent that some varieties appear to havefared better than others. The newly released There are 3 species of root weevil that attack varieties ‘Tillamook’ and ‘Pinnacle’ look very strawberries: the black vine, rough strawberry, impressive at the Station this year. The later and strawberry root weevil. Of these, the varieties ‘Firecracker’ and ‘Independence’ also black vine is earliest to emerge and usually look impressive, although they are early in begins emerging from its pupal case in the their fruiting cycle. If you are growing any soil around the end of May. Newly emerged new or experimental varieties, I would ap- weevils feed for about 3-4 weeks before they preciate a call to let me know how they per- begin to lay eggs (weevils that emerge earlier in the season usually feed for a slightly shorterperiod before they begin laying eggs). Giventhese timings, black vine weevils probablybegan laying eggs around the second to thirdweek of June. The rough strawberry and Renovation and Weevil or strawberry root weevil usually begin to emerge during strawberry harvest (early to mid June) and would be expected to begin laying eggs around the last week of June/first week ofJuly. In our “pit traps” in strawberries atNWREC this year, we saw our first newly Research by OSU Berry Specialist, Bernadine emerged adult strawberry root weevil on 6/Strik suggests that the best time to renovate 13. Given this scenario, the time immediately‘Totem’ and ‘Redcrest’ is 2 to 4 weeks after after the last pick is a strategic time for rootharvest (early to mid-July). Since the pres- weevil control. OSU Entomologist, Glennence of old leaves inhibits new growth, reno- Fisher has found that early topping of straw-vation (renovation = leaf removal, row nar- berry plants can result in high mortality ofrowing, application of fertilizer and necessary root weevil adultsfungicides, insecticides, herbicides, and irriga- from exposure to tion) is important because it helps promote heat, dryness, and new growth. Vigorous leaf growth during hunger, particu-late summer is important because next years larly when tem- flower buds are initiated from August through peratures are October (and possibly later during mild win- high. A well-ters) in the axils of these newly formed leaves. timed application Although the idea of a few weeks “rest pe- gade on a warm,riod” (it is best if plants are not severely wa- still night wouldter stressed during this time) for strawberry reduce root weevil survival even more. Be-plants has been generally accepted for many cause root weevils can burrow under the soilyears, there is some thinking that leaf removal surface to escape the heat, it is advisable to apply the insecticide at night and within 1 or important. The PNW Handbook recommends2 days of mowing, when weevils are still ex- application of Thiodan in 400 gallons of wa-posed.
ter per acre. In research conducted by GinaKoskela and myself in the mid-1990’s, we Early mowing of strawberry leaves would also found 200 gallons to be as effective as 400increase mortality of the cyclamen mite, which gallons. High pressure (60 to 80 psi) is alsois once again apparent in many fields. The necessary. Applications made later in thecyclamen mite is usually only a problem ev- spring, once the canopy is full are not gener-ery few years. Evidence suggests that cycla- ally effective because it is difficult to get ad-men mites come in on the plants. Growers equate penetration to the crown and the dam-first begin to see symptoms of damage around age has already been done (remember thatthe time of the first picking year. Affected the actual feeding damage occurred whenleaves look crinkled, thick and leathery; leaf flowers were in buds deep in the crown).
petioles often have small bumps or tooth-like Although the 2 lb ai rate of Thiodan provides projections on good control of the cyclamen mite, that ratethem. Although we is harmful to the predator mite Neosieulus don’t become fallacis. Because of this, it may be a good aware of cyclamen idea to scout for two-spotted spider mites inmites until we see late summer and/or the following spring.
come in on the tual damage oc- Growers interested in biological control of cy- curred many clamen mites may wish to consider purchas- months prior (dur- ing one of the following predators:ing fall – early Amblysieus cucumeris, Neosieulus fallacis; or spring) when these leaves were nestled in buds the predatory six-spotted thrip (Scolothripsdeep in the crown. The cyclamen mite does sexmaculatus). The first two are predatorynot like bright light, heat, or dryness and, mites. N fallacis is native here, thrives in straw-therefore, lives in bud scales deep within the berries, and is an excellent two-spotted spidercrown. Cyclamen mites damage cells of leaves mite predator. Many strawberry growers havewhile still in the bud; as leaves expand the already had experience with N. fallacis fordamage becomes apparent. By the second two-spot control. N. fallacis definitely pre-year, leaves begin to become small and fers two-spots to cyclamen mites, but it willcrinkled and fruit size is reduced.
kill and eat cyclamen mites if hungry enough.
The 2 lb ai rate of Thiodan is highly toxic to N. fallacis, so it may be advisable to wait a The 2 lb ai rate of Thiodan has proven effec- week or two after an application before re- tive at reducing cyclamen mite populations. leasing N. fallacis or any other predator.
However, for the insecticide to be effective, Good results on cyclamen mite have been re- it must be able to penetrate deep into the ported in California with A. cucumeris and crown where cyclamen mites live. For this the six-spotted thrip. I tried a release of A.
reason, the best time to apply Thiodan is cucumeris for biocontrol of cyclamen mite in within a few days after mowing. Another field plots a few years ago and found them to application may be necessary in early spring be somewhat effective (compared to the un- (before new leaf growth has begun), espe- treated controls).
cially if the winter has been mild. Becausepenetration is the key to control of the cycla-men mite, use of adequate water is extremely control. Select should be applied with a cropoil concentrate to actively growing weeds.
Although we can apply up to 32 fl. oz. ofSelect 2 EC per season, growers should notapply more than 8 fl. oz. per application.
Another option for growers with heavy grassy Renovation is also a good time to apply her- weed pressure would be to tank-mix Spartan bicides. The Section 18 label for Spartan 4F with Devrinol; however, Devrinol is a root- vation. Spartan is a pre-emergence (to be ably the safest time of application.
applied before weeds emerge) herbicide withlittle or no burn back of existing weeds. It iseffective on a wide range of broadleaf weeds.
In our research with Spartan at NWREC andat our plots in Corvallis, we saw very littlephytotoxicity (e.g., 1 or 2 small red spots)when it was applied the day after planting.
Threat of phyto increases as plants begin toproduce new growth. Application of Spartan22 days after planting caused quite a bit ofdamage in research conducted in California.
We have also not seen any problems from application of 0.125 lb ai to strawberry plantsat renovation. However, Ed Peachey has re- ported some damage from the 0.25 lb ai rate(8 oz) applied in winter in our Corvallis plots. The strawberry crown moth (SCM) is once We did not observe any phyto from the 0.25 again becoming a serious problem in some lb ai rate winter application at NWREC, but fields. Although this insect is usually associ- we have higher organic matter content at ated with strawberries, it also can attack NWREC (4-5%) than in our Corvallis plots. caneberries, and has a great affection for black Soil organic matter content and cation ex- raspberries, to which it can cause a great deal change capacity (CEC) are always important of damage. The strawberry crown moth ap- factors with pre-emergence herbicides.
pears to have thrived during our last five mild Because Spartan is not very effective on grasses, winters.
growers with pressure from crabgrass,barnyardgrass, or annual bluegrass may alsouse the renovation/late summer or fall timing The damage is done by the larva, which boresto apply Select 2 EC herbicide for grassy weed and tunnels in crowns and roots. Larvae over- winter within strawberry crowns and resume damaged, the tops of these plants usually comefeeding in spring. Larvae pupate within the off easily when pulled.
crowns and roots. Adults emerge betweenMay and July; they fly and mate in June 3. Infested fields which are being removed through July. Pheromone traps put out in should be thoroughly plowed as described late May/early June will attract males. These above.
pheromone traps can be used to monitor adultpopulations in strawberry and black cap fields. 4. New plantings should not be placed adja- cent to infested fields. Grain planted between Eggs are laid on stems and leaves of straw- a new field and an infested one can serve as a berry plants and new larvae emerge within barrier to the flight of adult moths. Although 10-14 days and begin feeding in the crown SCM are strong fliers, they do not fly very and roots. SCM larvae are best controlled high, so a grain barrier can help prevent in- with an application of Lorsban 4E at a rate of festation of a new field.
1 lb ai/A applied immediately after topping,when crowns are exposed. As with the cycla-men mite, water and pressure are very im-portant. Insecticides will be most effectiveapplied in 200 gallons of water at high pres-sure. Since the larvae are usually establishedinside the crowns by mid-August and none ofour registered insecticides has any systemicactivity, application of Lorsban can not be expected to provide good results past the first Some additional strategies for SCM con- - Monitor fields for two-spotted spider mites.
trol include: If populations exceed 5 crawler-stage mitesper leaflet (3 leaflets per leaf) and no or fewpredators are present, application of a miti- 1. In fields topped early, before SCM flight cide is recommended. Use of Brigade (root has occurred (use pheromone traps to deter- weevils), Lorsban (strawberry crown moth), mine this), one may leave a few border rows or the 2 lb ai/A rate of Thiodan (cyclamen untopped. Egg-laying females will be attracted mites) may reduce predator mite (Neosieulus to those rows and deposit most of their eggs fallacis) populations and result in higher spi- there. These rows can then be disked under der mite populations. For this reason, July/ in the fall. Thorough shredding of all roots August (after all insecticides/miticides have and crowns followed by deep plowing is nec- been applied) is also a good time to purchase essary to kill SCM larvae and pupae.
and release predator mites so they have timeto get established before winter.
2. Because infestations usually begin near fieldborders and damaged plants occur in clumps, - Apply Aliette or other phosphorus acid these plants can be removed and destroyed. based material for Phytophthora root rot con- Plants damaged by SCM will be stunted and trol once the new flush of leaves is present, if the foliage will turn a reddish color earlier necessary. Because last winter was wetter than than uninfested plants. Because the crown is normal, root rot is once again a factor.
In case you would like to see the fall-spring rainfall pattern over the last few years, I have Monthly rainfall in inches, October through May, 1999/2000; 2000/2001; 2002/2003 99-00 2.46 4.74 4.35 6.21 5.15 3.46 2.14 2.48 30.99 00-01 3.21 3.04 3.16 1.55 1.28 3.51 2.43 1.05 19.23 3.85 6.85 7.57 7.41 5.48 4.86 3.36 2.64 42.02 OSU Strawberry NewsletterNorth Willamette Research & Extension Center Return Service Requested

Source: http://berrygrape.org/files/newsletters/strawberry/2003-06.pdf


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