Helen Atthowe, Biodesign Farm
Alex Stone, Oregon State University
This article is part of the Biodesign Farm Organic System Description
Figure 1. Total pounds/acre of organic insecticides applied to brassica, pepper, and tomato crops, 1993–2010. Bt-K (Bacillus thuringiensis var kurstaki) was applied to brassicas for cabbageworms, 1994–1998. M-pede (soap) was applied to peppers for aphids, 1995–2000. Bt-SD (Bacillus thuringiensis var San Diego) was applied to eggplant for Colorado potato beetle, 1995 and 1997. All sprays were applied with a 3 gallon Solo backpack sprayer. No sprays were applied on any Biodesign crops from 2001 through 2010, yet crop damage was low and yields were good, according to farm pest damage, yield records, and on-farm research in 1995/1996 and 2006.
(1) Bt-K = DiPel dust Bt (Bacillus thuringiensis var kurstaki) applied at 2 tsp/gal of water
(2) M-Pede insecticidal soap concentrate applied at 4–6 Tbl (2.5 fl oz)/gal of water
(3) Bt-SD = Planet Natural Bt (Bacillus thuringiensis var San Diego), applied in 1995 and 1997 at 4–5 Tbl (2–2.5 fl oz)/gal of water. This product is no longer available.
Figure 2. Pepper yield and aphid/aphid parasite incidence on peppers 1996, 2006, and 2007. Yield and aphid (Myzus persicae) population densities were monitored in June 1996, 2006 and 2007 as part of on-farm experiments. Aphid parasites (Aphidius and Aphelinus species) were also monitored in 2006 and 2007. Aphid densities on 100 leaves from 10 sample plants were relatively consistent in June 1996 (272), 2006 (202), and 2007 (238). The percent parasitized aphids was 73 and 80% in 2006 and 2007, respectively. Lady beetle adults and larvae (Coleoptera: Coccinellidae), syrphid fly larvae (Diptera: Syrphidae), and aphid midge larvae (Aphidoletes aphidimyza) were also found on sample pepper leaves in 2006 and 2007, but in much lower numbers than parasitized aphids.
Figure 3. Average weekly predator/parasite incidence in living mulch row middles, 2006. On-farm research was conducted May–October 2006 in two 600-ft brussels sprouts rows and the living mulch row middles between crop rows. Weekly sweep net samples were collected for 11 weeks using a Gemplers® R13101 15” sweep net. Twenty pendular sweeps were completed through the red clover row middles and ten strokes in brussels sprouts rows in each of four randomized plots in no-spray treatments (4 samples per date). In this experiment, no-spray plots were designed to retain pest species, as well as arthropod predators and parasites, thus representing the natural pest-control capacity of Biodesign's system.
(1) Lady beetle adult and (2) Lady beetle larva (Coleoptera:Coccinellidae) population densities varied seasonally, but were highest earlier in the season (June and July). Adults were also observed in sweeps, but in lower densities than larvae.
(3) Nabid bug (Nabidae) population densities varied seasonally, but were highest later in the season, peaking in September.
(4) Minute pirate bugs (Anthocoridae) were abundant later in the season and were a major component of the living mulch predator community in August and September.
(5) Spiders (Araneae) and (6) Harvestmen (Opiliones) were a regular component of the living mulch predator community year-round.
(7) Wasp (various, including wasps in the Aphidiidae, Braconidae, and Aphelinidae families) population densities varied seasonally.
(8) Syrphid fly larvae (Diptera:Syrphidae) population densities varied seasonally.
Assassin bugs (Reduviidae), Syrphid fly adults (Diptera:Syrphidae), and lacewing adults and larvae (Chrysopidae) were also observed in sweeps, but in comparatively low density.
Figure 4. Average number of carabid beetles and spiders captured in pitfall traps on four sampling dates, 2006. On-farm research was conducted July–September 2006 to measure the incidence of ground-dwelling predators in Biodesign Farm's no-spray pest management system. One pitfall trap was placed in each of four randomized plots for one week on each of the four dates. (1) Carabid beetles (Carabidae) were observed in relatively high numbers throughout the crop growing season. (2) Spiders (Araneae) were a regular component of the living mulch predator community year-round.
Figure 5. Imported cabbageworm (ICW, Pieris rapae) adults (July 2004–2008) and larvae (at harvest, 1996 and 2004–2008) in broccoli. Adult ICW butterflies were monitored using sweep nets as part of an annual July butterfly count, 2004–2008. Population densities fluctuated from year to year, probably based on climate conditions. ICW larva population densities were monitored at harvest as part of on-farm experiments and during harvest field monitoring; average number per plant was low (< 0.08 / plant) 2004-2008. One hundred plants were sampled during harvest evaluations/field monitoring.
(1) ICW adults = Imported cabbageworm (Pieris rapae) moths
(2) ICW larvae = Imported cabbageworm (Pieris rapae) larvae
Figure 6. Brussels sprout yield and quality evaluation, 2006. On-farm research was conducted to study Biodesign Farm's natural enemy-based pest management system. Average pounds per plant of salable and unsalable sprouts were compared among three pest management treatments for imported cabbageworm (ICW, Pieris rapae): no-spray control (I), Bt-sprayed threshold (II), and pyrethrin/rotenone bimonthly sprays (III) . Treatments followed by different letters indicate significant differences (p<0.05).
(I) No-spray control: No treatment for ICW control. This treatment was designed to retain the pest species, as well as arthropod predators and parasites, and thus to be a measure of the natural pest-control capacity of Biodesign's natural enemy-based pest management system.
(II) Bt-sprayed threshold: selective sprays based on ICW population threshold: Eight applications of the insect-selective insecticides, Dipel dust Bt (Bacillus thuringiensis var. kurstaki) and Concern insecticidal soap, when pest density reached action thresholds based on the percentage of plants with one or more larvae. This threshold was adapted from the University of Minnesota Extension Service guidelines for cabbageworms (Pieris rapae) in cabbage (Hines, R. L., and W. D. Hutchison. 2001. Evaluation of action thresholds and spinosad for lepidopteran pest management in Minnesota cabbage. Journal of Economic Entomology 94: 190–196).
(III) Pyrethrin/rotenone bimonthly sprays: nonselective bimonthly sprays: Ten applications sprayed twice/month of the insect-non-selective insecticide Bonide liquid pyrethrin/rotenone (0.8% pyrethrin and 1.1% rotenone) at a rate of 2.6 ml/L of water, as labeled for control of ICW. Treatments were applied in the morning using a Solo 473P3 backpack-pump sprayer. Spraying began with the first appearance of ICW adults on 31 May and continued on a biweekly basis until 4 October.
This article is part of the Biodesign Farm Organic Systems Description.
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