Rabbiteye blueberries seem more tolerant of insect damage than highbush varieties. Although insect damage in blueberry plantings rarely reaches economic thresholds, regular monitoring by scouting and use of insect traps is advised. As discussed in the previous section, the use of beneficial insect habitats along crop field borders increases the presence of beneficial insects. If you are releasing purchased beneficial insects, these field-edge habitats will encourage them to remain and continue their life cycle in that location, helping reduce the pest populations. However, pests may also inhabit the field-edge habitats; therefore, these habitats should be monitored along with the crop field. For additional information, request ATTRA's publications Biointensive Integrated Pest Management and Farmscaping to Enhance Biological Control.
Depending on the locations of blueberry plantings and the insect pressure on them, sanitation, good cultural practices, vigorous plant growth, and natural biological control will handle most pests. However, when specific pests reach economically damaging levels, additional action is necessary. The following discussion identifies some common blueberry pests and allowed organic controls. This information was taken largely from Cornell University's Crop Profiles: Blueberries in New York (Harrington and Good, 2000), where more detailed information can be found.
The most common insect pest is the blueberry maggot, Rhagoletis mendax. It attacks the fruit in midsummer before harvest and feeds on all varieties of blueberries. It is found throughout the eastern U.S. and Canada. This pest overwinters in the pupae stage, buried 1 to 2 inches in the soil. The adult flies emerge over a period of a month or two during summer. They lay eggs in ripe berries, and the maggots eat the pulp of the fruits, causing many to drop, spoiling the sale of others, and creating difficulties in post-harvest care. Through degree-day calculations based on soil temperatures, one can predict the emergence of the flies — 934.3 degree days at the low temperature threshold of 41°F (Teixeira and Polavarapu, 2001) — and implement appropriate measures to prevent or control maggot damage.
The choice of blueberry varieties can influence the severity of blueberry maggot damage. In a Rhode Island study, the early ripening varieties Earliblue and Bluetta were found to have fewer maggots than late maturing varieties whose ripening periods were synchronized with the fly's egg-laying period. Of the mid- to late-season varieties, Northland and Herbert stood out with less damage.(Liburd et al., 1998)
The botanical insecticides rotenone and pyre-thrum can be effective in controlling blueberry maggots, but they can also be toxic to beneficial insects, fish, and swine. The spinosad-type insecticide Entrust™ (Dow AgroScience) is approved for use on organic crops including blueberries and has been reported effective against the blueberry maggot. Additionally, disking, cultivating, and off-season grazing by fowl can reduce pupa populations.
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