Naval orange worm
Navel orange worm is a primary pest of almonds in California, more severe in mid- and southern San Joaquin Valley. Overwinters in the unshaken nuts (mummy nuts) from last year. larvae feeds on nuts and may cause severe damage in the next season if not taken care of.
Management
1. Mummy Nuts
Count the overwintering nuts on 20 trees per block on or before February 1 to determine the average number of mummies. When sampling, be sure to evaluate trees from all varieties since mummy counts can be quite different from one variety to the next. If an average of 2 or more mummies per tree are found, then remove mummies by shaking or hand poling the entire block. Remove mummy nuts from trees before bud swell by mechanically shaking the tree or hand poling, or both. Blow or sweep fallen mummy nuts to the row centers and destroy them by discing or flail mowing by March 15.
2. Early Harvest (to be kept in mind for next season harvesting)
Early harvest with rapid removal of nuts from the orchard floor. Harvest nuts as soon as good removal can be achieved; this is when 100% of nuts are at hullsplit at the 6- to 8-foot level of tree canopy. Risk of navel orangeworm infestation in early-harvested varieties such as Nonpareil can be greatly reduced if nuts are harvested before third-generation eggs are laid.
3. Varietal Selection (for new growers/plantations)
Hard-shelled varieties and those with a tight shell seal are resistant to navel orangeworm.
*Insecticide treatments are often needed if these practices are not carried out/when navel orangeworm may immigrate in from neighboring orchards.
Being the above measures not undertaken carefully, damage could range from 2% to 6% of the produce leading to substantial loss. Data reported by almond processors by region.
Above does not include rejection in ranch and hulling rejects. Overall loss could be 3%-8%
Financial Impact assessment based upon yield at 2500 lbs/acre and almond pricing at $1.70 , $2.0 and $2.50 per pound.
Cost to remove mummies and orchard treatment.
Farmers own shaker/sweeper make sense to shake mummies with almond price $2.0 and yield impact is over 3%. For custom hire shaking/sweeping break even point is 5%.
Please go the link for visuals: https://www.youtube.com/watch?v=mGsoV5ceFeo
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