Oregon Strawberry Newsletter

Transcription

1 Oregon Strawberry Newsletter Diane Kaufman North Willamette Research & Extension Center Oregon State University July, 2000 Dear Friends; It's hard to believe that we have just finished the fourth and final pick of Totems in our herbicide screening trial at NWREC. With harvest of Redcrest underway and renovation about to begin, this seemed a good time to discuss after-harvest activities. Because very few Oregon growers were able to make it to our Strawberry Field Day at NWREC on June 13, I have also included brief summaries of the presentations given that day. Hopefully, these summaries will provide a good overview of the main ideas presented, but they are pretty "bare-boned" (3 pages boiled down to 1 paragraph), so you may wish to contact the speakers for more detailed information. Strawberry Field Day Report Summaries: 1. Soil Applied Treatments to Control Root Weevils Joe DeFrancesco. A field trial was conducted in a 3 yr old field of Totem to evaluate the efficacy of soil-applied insecticides in controlling root weevil larvae. The 3 most common weevils found in this field were the black vine, strawberry, and rough strawberry root weevil. The following treatments were applied to pre-irrigated plots on August 19, 1999 and irrigated in immediately with 1.5 inches of water: Beauveria bassiana (Naturalis-L); Furadan; Meadowfoam meal; Enzone; Cruiser; untreated check. Treatments were evaluated on April 5, 2000 by digging 5 strawberry plants per plot and counting the number of live larvae per plot. Cruiser and Furadan provided the best level of control (73.5% and 71.8%, respectively). Naturalis-L and Enzone provided 0% and 8.6% control, respectively. Meadowfoam meal could not be evaluated because plants in those plots had died.. 2. Performance of New Fungicides for Control of Botrytis Pete Bristow, WSU. The following fungicides were applied in spring, 1999 to a vigorous 6 yr old planting of Hood strawberries in Lynden, WA: Elevate; Switch; Serenade (a new biological fungicide); Captan; Thiram; Flint; a standard rotation of Switch, Benlate+Captan, and Elevate; and a water check. Treatments were applied 5 to 6

2 times at 10 to 12 day intervals between May 14 and July 1. To evaluate the importance of application during bloom,the following treatments were also included: 1. a treatment in which Switch was applied 4 times between May14 and June 10 (Switch applied early); 2. a treatment in which Switch was not applied until after bloom (Switch applied late). There was no difference among treatments in total yield (healthy + rotten berries). The greatest amount of healthy fruit was in the Switch, Elevate, Switch applied early, and standard rotation plots. The lowest % rot was in the Elevate, Switch, Thiram, Switch applied early, and standard rotation plots. The % rot in the Switch applied late plots was similar to that in the water check, illustrating the importance of fungicide application during bloom. 3. Nitrogen Uptake and Movement in Strawberry/Granular and Foliar Fertilizers Bernadine Strik. The objective of this project is to help develop a better understanding of nitrogen fertilizer uptake and usage within the plant. Different methods and application times of nitrogen (N) fertilization are being compared using a labeled fertilizer that can be traced in the plant: foliar applications of urea at prebloom (April 21), green fruit (June 2), early post-renovation (Aug. 11), or late postrenovation (Sept. 8) and granular applications using ammonium nitrate at a rate of 25 lb N/A on April 21 or 50 lb N/A on July 28, at renovation. All the foliar treatments and the 25 lb N/A granular rate received an additional 50 lb N/A at renovation on July 22. Plants from each treatment were dug and sampled one day after fertilizer application and every 2 weeks through November 18, 1999 and again in Feb, April, and May, 2000 to determine total N and % labeled N in each plant part. In 1999, Bernadine found that there was no significant effect of additional foliar N fertilizer on yield, fruit size, % fruit rot, or fruit firmness. However, there was a trend for the additional 25 lb N/A in spring to produce a higher yield. Since berry size wasn't affected by fertilizer application, spring application of N may increase berry number. The treatments have been repeated this year to see if the same holds true for There is a risk to getting too much leaf growth with spring N, but that wasn't seen in these plots. In terms of N uptake and movement in the plant, it appears that plant growth in spring is mainly dependent on N reserves in roots and crowns. In spring, only 20% of the N in the leaves was from spring-applied N; based on yield results, though, Bernadine wants to see whether this small amount of fertilizer N impacts flower bud formation. Most of the fertilizer applied in spring was still in the leaves at the time of renovation and was, therefore, "lost" when leaves were mowed. In contrast, 55% of the N in the leaves and runners in September was from the granular fertilizer applied at renovation. The plant does not have many reserves at this time or does not rely on them. However, we know there is a lot of soil N available in summer due to mineralization. Bernadine would like to study whether the fertilizer N just replaces the mineralized N that would have been taken up otherwise. In the plant, N was exported from leaves to the crown and roots in late summer to replenish reserves.

3 Foliar feeding seems to be an inefficient way to supply N to the plant. At most, only 15% of the N applied foliarly (or to roots through run-off) got into the plant. 4. Strawberry Breeding Program Chad Finn. The cooperative breeding program (OR, WA, and British Columbia) has recently released the following new late season (after Redcrest) varieties: Firecracker (OR) fresh or processed market; excellent flavor Independence (OR) fresh market; won't cap, but plants durable; stand up to stresses well Puget Summer (WA) performed well at NWREC in the first year, but does not look good in the second year. Whonnock (BC) did not perform well at NWREC.This spring 13 selections were planted out in trials in grower fields. Approximately 60 selections are in trial at WSU and/or AgCanada. We have several California varieties planted at NWREC. The variety Diamonte is replacing Selva in CA, however, it has not looked good in OR; the fruit is large but light colored. 5. Alternative Herbicides for New and Established Strawberry Plantings Diane Kaufman. The planting established at NWREC on May 13, 1999 was divided into the following 2 separate experiments: 1. herbicides applied over the plants immediately after planting, with Simazine applied in September, and herbicides applied again in winter (Jan. 29, 2000). In this experiment, new herbicides (Milestone; Frontier; Axiom; Matrix; Authority; Visor) were compared to a chemical standard (Goal) and a weedy control. 2. Devrinol applied to all plots immediately after planting, with herbicides applied in fall (Sept. 29, 1999). In this experiment new herbicides (Milestone; Frontier; Gallery; Authority; Axiom+Gallery; Axiom+Authority; Matrix; Visor) were compared to a chemical standard (Simazine+Devrinol) and a weedy control. There was no apparent phytotoxicity from the new herbicides at either timing regime and no differences in strawberry plant growth. There were also no differences in yield among treatments (based on a total of 4 picks) at either timing regime. Quality of weed control in spring 2000 was better in winter applied plots than in fall applied plots. Milestone and Visor provide the broadest spectrum and longest period of weed control, but most herbicides evaluated thus far show promise for use in strawberries. The second planting, established on May 22, 2000, is also broken into 2 experiments (establishment+winter vs fall applications).and includes the same herbicides, with the exception of Matrix and the addition of Nortron and Valor.

4 Update on Pesticide Registrations Joe DeFrancesco. 1. The recent cancellation of Lorsban for home use has not affected the registration for strawberries. 2. Rohm and Haas has issued a supplemental label for Oregon And WA for use of Rally 40W fungicide on strawberry (for control of powdery mildew, leaf spot and leaf blight), caneberry (for control of cane and leaf rust, orange rust, yellow rust, and powdery mildew), gooseberry (for control of powdery mildew and anthracnose), and currant (for control of powdery mildew). 3. Elevate 50WDG is now permanently registered for use in strawberries. Brigade also has a permanent label for use in strawberries. 4. The Section 18 registration for use of Goal in strawberries (at planting and during renovation) expires on August 15, The tolerance for Ronilan use in strawberries was revoked in Jan, 2000, so strawberry growers can no longer use it. 6. Product with the old Rovral label can be used on strawberries in 2000 and 2001 (0 day PHI). However, the tolerance will change in Oct, 2001 and use of Rovral in strawberries will no longer be feasible. 7. A petition for establishment of tolerance for Stinger herbicide in strawberries will be submitted to EPA in Sept., Valero (cinnamaldehyde), a biopesticide by Mycotech, is now registered for use in berries for control of powdery mildew and mites. 9. A permanent label for the use of Savey miticide in strawberries is expected in July, Savey is effective on two spotted spider mite nymphs (immatures) and eggs. Renovation and Weevil Control Strategies Research by OSU Berry Specialist, Bernadine Strik suggests that the best time to renovate Totem and Redcrest is 2 to 4 weeks after harvest (early to mid-july this year). Since the presence of old leaves inhibits new growth, renovation (renovation= leaf removal, row narrowing, application of fertilizer and necessary fungicides, insecticides, herbicides, and irrigation) is important because it helps promote new growth. Vigorous leaf growth during late summer is important because next years flower buds are initiated from August through October (and possibly later during mild winters) in the axils of these newly formed leaves. Although the idea of a few weeks "rest period" (it is best if plants are not severely water stressed during this time) for strawberry plants has been generally accepted for many years, there is some thinking that leaf removal immediately after harvest would be an effective strategy in fields threatened by root weevils, particularly when there are newly planted berry plantings in adjacent areas of the field which need to be protected from weevil invasion.

5 There are 3 species of root weevil that attack strawberries: the black vine; rough strawberry; and strawberry root weevil. Of these, the black vine is earliest to emerge and began emerging from its pupal case in the soil this year around the third week in May. Newly emerged weevils feed for about 3-4 weeks before they begin laying eggs (weevils that emerge earlier in the season usually feed for a bit longer before they begin laying eggs; weevils that emerge later in the season usually feed for a slightly shorter period before they begin laying eggs.) Given these timings, black vine weevils will probably begin laying eggs in the field this year around the third week of June (as I write this newsletter). The rough strawberry and strawberry root weevil usually begin to emerge during strawberry harvest (early to mid-june) and would be expected to begin laying eggs around the first week of July. Given this scenario, the time immediately after the last pick is a strategic time for root weevil control. OSU Entomologist, Glenn Fisher, has found that early topping of strawberry plants can result in high mortality of root weevil adults from exposure to heat, dryness, and hunger, particularly when temperatures are high. A well timed application of Malathion, Guthion, or Brigade on a warm, still night and/or an application of Cryolite bait would reduce root weevil survival even more. Two-Spotted Spider Mites Spider mite populations have been higher in several fields this year than they have been in the last two years. Hot temperatures predicted for the next few weeks can be expected to increase spider mite pressure. Since heavy mite feeding can slow or stop growth of new leaves after renovation, it is a good idea to examine new leaves for spider mites every week. If populations exceed 5 crawler-stage mites per leaflet (3 leaflets per leaf) and no or few predators are present, application of a miticide is recommended. Chemical options include: Vendex; Kelthane; Danitol; Agri-Mek; M- Pede insecticidal soap. Vendex is relatively easy on predator mites and continues to be effective on adults and immatures. Kelthane is destructive to predator mites and can be of concern in terms of resistance. Danitol is a synthetic pyrethroid which has given somewhat disappointing results in WSU Entomologist, Lynell Tanigoshi's trials. It is best used when mite populations are low. Agri-Mek is considered effective, but destructive of predator mites. Insecticidal soaps kill only by direct contact, and, therefore, usually require several applications. Savey (label pending) has performed well in WSU trials. Unlike the materials listed above, which target adults and immatures, Savey targets eggs and immatures. In our lab trials evaluating the toxicity of chemicals to the predator mite Neosieulus fallacis, adult mortality from Savey was low and egg laying by N fallacis was not reduced.. However, because Savey is primarily toxic to eggs and immatures and we did not hold the eggs beyond 72 hours, we do not know the effect Savey may have on N. fallacis eggs or immatures.

6 Strawberry Crown Moth larvae are best controlled with an application of Lorsban 4E at a rate of 1 lb ai/a applied immediately after topping, when crowns are exposed. Since crown moth larvae are usually established inside crowns by mid-august and none of our registered insectides have any systemic activity, application of Lorsban can not be expected to provide good results past the first week in August. Adults fly from early June through July, and lay eggs on the underside of leaves near the crown.