Sampling combines two key elements central to continual IPM improvement – evaluation and adaptation.
“A damage report from your handler won’t tell you everything and can miss some key takeaways you can observe before the product leaves the orchard,” said Lauren Fann, pest management specialist for the Almond Board of California. “Before sending that product off to the processor, growers and PCAs can sample nuts to determine what pest programs and practices were effective and which ones were not.”
Sampling is different from the grade sheets growers receive from handlers. Though grade sheets may specify damage to nuts, they don’t identify what caused the problems. Sampling, on the other hand, allows growers to pinpoint the specific kind and percentage of pest damage among the nuts tested. This has two distinct advantages:
- Accuracy: Knowing what caused nut damage during the last growing season allows growers to better assess their management decisions, including the efficacy of the material applied, the timing of those treatments and how well any monitoring programs worked.
- Record keeping: Through this evaluation process, growers can develop historical records for each block. Over time, this provides valuable context and information – such as where infestations may be coming from and the location of perennial orchard hot spots. This information allows growers to adapt management programs according to the orchard’s specific patterns and pressure.
How to Conduct Harvest Sampling
UC IPM guidelines for harvest sampling recommend that 500 nuts per block should be taken; however, not every block has the same layout, pressure, size and neighboring conditions and the total number of samples should be adjusted accordingly. Fann said larger blocks may require additional sampling to provide an accurate representation of that location’s true pressure and damage. The primary is to obtain a representative sample from multiple areas within a block.
If growers know a block has historically shown high pressure, they can partition and denote which rows samples were taken from to gain more precise information. For example, five 100-nut samples can be taken from five evenly spaced rows within a block. Because insect populations build over time and space in orchards, this method should give growers more detailed information regarding where pressure is coming from.
Fann said that if growers don’t have time to crack out samples at harvest, they can store them in a cold room or freezer until activities wind down and the analysis can be completed.
Tips to Identify Damage
The main pests to keep an eye out for during damage assessments include navel orangeworm (NOW), ants, leaffooted bugs and stink bugs. Fann offered these recommendations for what to look for:
- NOW: Signs include deep feeding tunnels throughout the kernel. Also, white frass and webbing on the kernel.
- Ants: Kernels often are shriveled, with sanded or stripped kernel skins and sawdust-like residue, without the presence of webbings and white frass. In severe cases, nut meat will be hollowed out, leaving only the kernel skin.
- Leaffooted bugs and stink bugs: Feeding from these pests can result in dark spots on the surface of kernels. Early season feeding can cause gumming (gummosis) of the fruit and kernel abortion. Stink bugs can feed later into the season, creating black necrotic tissue on the kernel that appears sunken. Pitting, stippling and dark necrotic tissue often are present. Soft shell varieties such as Fritz, Sonora, Aldrich, Livingston, Monterey and Peerless are the most susceptible to bug damage
