Fruit Crops

Yeast Knocks Out Blue Mold

The yeast Candida sake strain CPA-1 is an antagonist against many post-harvest pathogens of apple (and is being registered in Europe for this purpose). Two studies examined the biocontrol potential of this yeast for control of blue mold (Penicillium expansum) on apples.

One study compared the efficiency of pre- and post-harvest applications on Golden Delicious wounded before and after harvest and inoculated with blue mold prior to cold storage. Post-harvest treatment resulted in effective control of blue mold regardless of when wounds were made. The best disease control was > 80% reduction in lesion diameter and 50% reduction in the incidence of lesions. Pre-harvest applications were less effective and control was not improved by double applications (both pre- and post-harvest). C. sake population levels decreased more rapidly during cold storage for pre-harvest applications than for post-harvest applications. High populations of C. sake were present in post-harvest-treated apples, even after 90 days in cold storage. 

The second study investigated the interaction of blue mold and C. sake under different controlled atmosphere conditions typical of commercial cold storage. In a laboratory trial, control improved with increasing concentrations of C. sake. A 97% reduction in lesions was achieved at 3% oxygen, 3% carbon dioxide atmosphere. In a semi-commercial trial at 1C, C. sake reduced the size of lesions on wounded fruits by more than 80% after 60 days at 21% oxygen and 60% after 120 days of storage under controlled atmosphere conditions. Lesion size was reduced by more than 70% in all seven atmosphere conditions studied. Populations of C. sake decreased initially, followed by an increase to previous levels after 45 days and remained constant through 90 days. The yeast was able to colonize apples, especially those with wounds, under a variety of storage conditions and could provide effective control of blue mold.

Sources:

Teixido,  N., J. Usall, and I. Vinas. 1999. Efficacy of preharvest and postharvest Candida sake biocontrol treatments to prevent blue mould on apples during cold storage. International Journal of Food Microbiology 50(3):203-210.

Usall,  J., N. Teixido, E. Fons, and I. Vinas. 2000. Biological control of blue mould on apple by a strain of Candida sake under several controlled atmosphere conditions. International Journal of Food Microbiology 58(1-2):83-92.

Grape Leafhopper Egg Parasitoid In Vineyards

Several species of grape leafhoppers (primarily Erythroneura spp.) cause white flecking on grape leaves as they puncture cells on the underside of the leaves and suck out the sap. And several species of the wasp egg parasitoid Anagrus that can also be found in vineyards. A study in New York found the leafhopper E. comes and the wasp A. daanei to be the most abundant species on wild grape, while the E. vitifex-E.bistrata complex and A. erythroneurae were the most abundant species on cultivated grapes. Another wasp, A. tretiakovae, was reared from seven grape cultivars in equal proportions.

Although it appears that A. daanei and A. erythroneurae are more host specific than A. tretiakovae, this apparent host preference may actually be related to the associations of their leafhoppers for plant hosts. The wasps use alternate leafhopper hosts for overwintering that infest several plant species including maple, wild rose, and willow. The wasp adults are found mainly at the vineyard edge early in the season and gradually move into the interior so that by midseason or later they are more widely dispersed. Additional habitat management studies could be conducted to identify strategies to accelerate population growth of Anagrus in the spring and increase the rate of dispersal into vineyards.

 Source:

Williams, L. and T. E. Martinson. 2000. Colonization of New York vineyards by Anagrus spp. (Hymenoptera: Mymaridae): Overwintering biology, within-vineyard distribution of wasps, and parasitism of grape leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), eggs. Biol. Control 18(2):136-146.


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