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Project description

Evaluation of wheat straw mulches for pest and disease control in cucurbit production systems. (01FE021)
Program UC IPM competitive research grants program
J.P. Mitchell, Vegetable Crops, UC Davis
C.G. Summers, Entomology, UC Davis, Kearney Agricultural Center
J.J. Stapleton, UC IPM, Kearney Agricultural Center
Host/habitat Squash; Melons; Vegetable Crops; Cucurbits
Pest Cotton Aphid Aphis gossypii; Green Peach Aphid Myzus persicae; Silverleaf Whitefly Bemisia argentifolii; Aphids and Aphid-Vectored Diseases; Unspecified Weeds
Disciplines Entomology, Plant Pathology, Weed Science
Field Ecology
Start year (duration)  2001 (Two Years)
Objectives Evaluate the effectiveness of wheat straw residue mulches for insect pest, disease, and weed control in cucurbit crop production systems.

Determine the spectral reflectivity properties of wheat straw residues as a possible mechanism for insect repulsion.

Assess the utility of these surface mulches in reducing the need for pesticides in these cropping systems.

Determine the potential economic benefits of using crop residue mulches for squash and melon production in California.

Final report Plastic reflective mulch and wheat straw mulch delayed colonization by Bemisia argentifolii and the incidence of aphid-borne viruses in zucchini squash. The mulches were compared to a preplant treatment of imidacloprid and an untreated, unmulched control. In the first year, yield of marketable fruit in the plastic and straw-mulched plots was approximately twice that from the imidacloprid plot. In the second year, yield from the straw mulch plots was twice that of the imidacloprid and plastic mulch plots. Yields from both mulched plots and from the imidacloprid plots were higher than those from the control plots. The mulches were more effective than a preplant application of imidacloprid in reducing the incidence of both B. argentifolii and aphid-borne viruses. Plants growing over the plastic and straw mulches grew more rapidly and reached a larger size than did those growing over bare soil. Both plastic and straw mulch were effective in reducing aphid and whitefly numbers as well as the incidence of virus diseases in cantaloupe. Cartons per acre were significantly higher in plants growing over reflective mulch. Yields from plants growing over straw mulch were equal to those from plants growing over bare soil. Plants growing over reflective plastic produced larger-sized melons than those growing over the other treatments. The spectral quantum flux from the plastic averaged between 80 and 90% of ambient values in the ultraviolet range. Spectral quantum flux values of straw were similar to those of the reflective mulch near 300 nm but were virtually identical to bare soil beyond 320 nm. The plastic reflected 94% of the incoming photosynthetically active radiation (PAR) while the straw reflected 85% and bare soil reflected 41%.
Two field experiments were conducted in 2002 at the Kearney Research and Extension Center in Parlier, CA to evaluate the effectiveness of wheat straw mulches for insect and disease control in squash and cantaloupe melon. In the melon study, silverleaf whitefly nymph and adults, alate aphids and virus infection symptoms were consistently lower over both the wheat straw and the reflective plastic mulches relative to the bare ground control throughout the month-long sampling period. Melon fruit in this year's study were generally quite small due most likely to the late season planting, however, total yields were significantly higher over the silver plastic relative to the other treatments. In our 2002 squash experiment, the percent of plants presenting silverleaf whitefly symptoms and the percent of plants with virus infection were generally highest in the fallow control, machine-harvested wheat, and fallow + AdmireÒ plots relative to either the silver plastic or the hand-scattered wheat mulches. Yields, however, were only higher from plants above the silver reflective plastic mulch.
A field experiment was conducted in 2001 at the Kearney Agricultural Center to evaluate the effectiveness of wheat straw mulches for insect and disease control in squash production. Experimental treatments included 1) untreated (no insecticide) control, 2) Admire insecticide treated, injected into the soil 1-day before planting 3) silver reflective plastic mulch, 4) chopped wheat residue from fall planted wheat as a surface mulch, and 5) hand-scattered wheat residue from baled straw. The wheat mulch treatments were selected based on our successful use of them in tomato production systems. In general, squash silverleaf and virus symptoms tended to be lower over the silver reflective plastic, the scattered straw mulches and the Admire-treated plots than in either the harvested wheat residue or the control plots. Similarly, plants in these treatments produced both earlier and higher cumulative yields than plants growing over the planted wheat mulch or the untreated control. These preliminary finding indicate considerable promise of the alternative mulch systems for nonchemical management of late season insect and disease pests of this crop.

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