Location: Crop Improvement and Protection Research2009 Annual Report
1a. Objectives (from AD-416)
1. Develop controlled atmosphere treatments for postharvest pest control on perishable commodities. A) Develop semi-commercial scale storage and ultralow oxygen combination treatment for control of western flower thrips on head lettuce. B) Develop semi-commercial scale storage and ultralow oxygen combination treatment for control of western flower thrips on broccoli. C) Develop controlled atmosphere treatment for control of mealybugs and black widow spiders on table grapes. D) Develop ultralow oxygen treatment for control of vine mealybug on grape rootstocks. 2. Develop pure phosphine funigant treatments for highly perishable commodities. A) Develop fumigation treatment with pure phosphine for control of western flower thrips on lettuce, broccoli, asparagus, and strawberries. B) Develop fumigation treatment with pure phosphine for control of lettuce aphid and leafminer on lettuce. C) Develop fumigation treatments with pure phosphine for control of mealybugs and spiders on table grapes.
1b. Approach (from AD-416)
The minimum duration of pre-treatment cold storage needs to be determined in order to reduce the overall duration for completing ULO treatment and make it possible for pre-export ULO treatments. Effectiveness of ULO treatments for thrips control and their effect on postharvest quality of lettuce needs to be determined in large-scale tests. Oxygen consumption rates and oxygen demands by lettuce need to be determined in large-scale trials for commercial application. Efficacy and safety of ULO treatment for control of western flower thrips on broccoli.
3. Progress Report
Following the successful development of ultralow oxygen (ULO) treatment for control of black widow spiders last year, vine mealybug was found to be susceptible to ULO treatment. However, grape mealybug was very tolerant to ULO treatment and required ULO treatment up to two weeks to achieve close to complete control. The research is continuing in order to achieve better understanding of mealybugs in response to ULO treatments as well as species specific variation in susceptibility to ULO treatment. Low temperature fumigation with pure phosphine was studied as an alternative treatment for control of grape mealybug, vine mealybug, and black widow spiders are important pests on harvested table grapes. Effective treatments were identified for control of all life stages of both mealybugs and black widow spiders. Crawlers, nymphs, and adults of both mealybugs, however, were more susceptible to phosphine fumigation at low temperature than mealybug eggs and black widow spiders. These results showed that low temperature phosphine fumigation was effective against mealybugs and black widow spiders and set a foundation for further study on effects of phosphine fumigation on table grape quality.
1. Ultra-low oxygen (ULO) treatment for postharvest control of western flower thrips on lettuce. Presence of western flower thrips on U.S. fresh commodities including lettuce is a major obstacle to their exportation to Taiwan. ARS researchers at Salinas, California developed an efficacious, ultralow oxygen treatment to control the pest on harvested lettuce. A 3-day storage period immediately prior to ultralow oxygen treatment of different lettuce cultivars achieved complete control of thrips without any negative effects on lettuce quality in a pallet scale study. The research reduced overall time needed to complete ULO treatment and thereby made the ULO treatment more practical for commercial adaptation.
2. Ultra-low oxygen treatment for control of Vine mealybug on grape rootstocks. Vine mealybug, a major pest of vineyards, is difficult to control on grape rootstocks with foliar pesticides and the currently used method of hot water dipping of dormant rootstocks after harvest is labor intensive. ARS researchers at Salinas, California successfully developed an efficacious, ultralow oxygen treatment to solve this vine mealybug problem. The pest was controlled by storing rootstocks with vine mealybug under ultralow oxygen treatment for 3 or 4 days at 25 or 15°C, respectively. The treatments caused 100% mortality of all life stages of vine mealybug and had no negative effects on rootstock growth. The ULO treatments provide a safe, effective, and economical alternative to the hot water immersion treatment for control of vine mealybug.