Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops

Published source details Nicholls C.I., Parrella M.P. & Altieri M.A. (2000) Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops. Agricultural and Forest Entomology, 2, 107-113.
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This study is summarised as evidence for the following.

	Action	Category
	Pest regulation: Plant or maintain ground cover in orchards or vineyards Action Link

Pest regulation: Plant or maintain ground cover in orchards or vineyards

A replicated, controlled study in 1996–1997 in two vineyards in northern California, USA, found greater pest regulation and fewer pests, but fewer natural enemies, in vine rows with cover crops, compared to vine rows without cover crops. Pest regulation: More parasitized eggs of Erythroneura elegantula western grape leafhoppers were found in vine rows with cover crops, compared to those without cover crops, in one of six comparisons (July 1997: 64% vs 55% parasitism). Pest numbers: Fewer leafhoppers and fewer Frankliniella occidentalis western flower thrips were found in vine rows with cover crops, compared to those without cover crops, in most comparisons (in most of 1996: 6–53 vs 8–75 leafhopper adults/trap; in most of 1997: 60–460 vs 90–690; from 30 May to 9 August 1996: 1–33 vs 3–38 leafhopper nymphs/leaf; from 25 July to 7 August 1997: 9–10 vs 21–22; in 1996: 70–920 vs 110–1,170 thrips/trap; in 1997: 8,200–12,900 vs 11,000–17,200). Natural enemy numbers: Fewer Anagrus epos parasitoids of grape leafhopper eggs were found vine rows with cover crops, compared to those without cover crops, in some comparisons (31 July–28 August 1996: 300–1,750 vs 450–2,200 parasitoids/trap; 24 July–28 August 1997: 400–3,650 vs 400–4,100). Implementation options: More predators and fewer leafhopper nymphs were found in rows with mown cover crops, one week after mowing, compared to before mowing (in 1996: 6 vs 2 predators/trap, 45 vs 53 leafhoppers/trap). Methods: In each of two vineyards, one block of vines had cover crops between the vine rows (in every other vine row), and one block was tilled and had no cover crops between the vine rows. Fagopyrum esculentum buckwheat and Helianthus anuus sunflower were grown as cover crops. Pests and natural enemies were sampled with sticky traps in April–September 1996–1997 (10 yellow and 10 blue traps/row, 10 rows/block). Leafhopper nymphs and parasitized eggs were sampled from 10 vine leaves/row. In one of the two vineyard blocks, three rows of cover crops were mown three times/year. In these rows and three unmown rows, pests and natural enemies were sampled (five sticky traps/row).