ANNUAL GROWERS MEETING
‘Brown Spot’ Issue in Almonds: Potential Causes and Solutions The annual meeting’s second pest management session covered a relatively new challenge facing almond growers, Brown Spot, produced by the feeding of several species of Plant Bugs. Mel Machado, VP of Member Relations noted that for several years, Blue Diamond had been identifying Brown Spot damage in almonds from orchards that growers and their Pest Control Advisors had not observed Leaf- Footed Plant Bugs, LFPB, the “traditional” cause of Brown Spot. Using data from Blue Diamond ’s delivery testing
are available for native Stink Bug, the typically observed Green or Brown Stink Bugs and LFPB. While growers and PCA’s may use beat trays, knocking the insects from the trees onto pans or trays to detect their presence and search for egg masses on the leaves. For many the first sign of the insect’s presence is the gummy exudate emitting from the feeding puncture on the hulls. Plant bugs also exhibit a varietal preference, which growers may take advantage of when surveying their orchards. LFPB is known to strike Sonora, Price, Aldrich, and Fritz varieties first. LFPB is also very attracted to pomegranate and junipers in the farmstead landscape and BMSB is very attracted to Tree of Heaven. It was noted that while Stink Bugs appear to have taken up residence within orchards, growers should also monitor the edges of orchards to detect Plant Bugs that may be moving into the orchards from other croplands. Lures and traps have been developed for BMSB and are available for grower use. Parasitic wasps have also been identified that lay their eggs within the Stink Bug and BMSB eggs. However, Dr. Rijal noted that the egg parasites cannot control juvenile or adult Plant Bugs and that effective biological tools are still far in the future. Blue Diamond Growers is proud to assist the member/grower community improve the quality of their crop through vehicles such as the Annual Meeting Seminars. Through cooperative efforts between growers, researchers, and Blue Diamond staff, reducing reject levels within the crop enhances grower returns, reduces costs, and improves the quality of almond delivered to customers around the world. Dr. Rijal presenting
process, Machado documented the increase in Brown Spot and gum, which is associated with Brown Spot observed in recent years. He also noted that in extreme cases, Brown Spot has created reject levels in excess of 30%, rendering the deliveries as Oil Stock with no value. Focusing on work conducted by Dr. Rijal, several species of Stink Bugs, including the newly invasive Brown Marmorated Stink Bug, BMSB, have been identified as the cause of Brown Spot. Several of the Stink Bug species have established residence within almond orchards and have become an increasing source of crop damage and financial loss. Increasing damage caused by Plant Bugs in recent years is thought to the be the result of reduced usage of broad-spectrum control measures in favor of more finely targeted materials aimed at other orchard pests. Plant Bugs damage almonds through their feeding on the nut, probing deep into the kernel using their piercing- sucking mouthparts. If probed prior to kernel solidification and hardening, almonds typically fall from the tree. This early season feeding can be quite dramatic with a significant proportion of the crop cast to the ground. After kernel hardening, the nuts are retained by the tree and the damage typically manifests itself as sunken lesion and/or brown discoloration on the kernel, rendering it inedible, adding to the level of rejects in the crop. The number of gummy nuts in the crop further increases the losses. Dr. Rijal noted that there are currently no economic thresholds established for control and no effective traps
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ALMOND FACTS
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