IPM: Back To Basics In Almonds
Pest monitoring is the heart of any orchard integrated pest management (IPM) program and is cost-effective and easy to implement. Traps and lures are relatively inexpensive and the effort it takes to hang, read, and maintain traps is minimal. Accessing degree-day data and keeping records adds a little more time, but all in all, you get your money’s worth. Pest monitoring allows you to effectively time sprays and to skip sprays when they are not needed. The following is a brief guide to the basics of hands-on pest monitoring.
There are many traps available for monitoring pests. The disposable wing trap is good for snaring peach twig borer (PTB) and other moth pests in almonds, other nuts, and tree fruit. This trap consists of a paper top and a gridded sticky bottom, folded and assembled with a wire hanger and two plastic spacers. A pheromone lure or “cap” is dropped onto the sticky surface and the trap is hung inside the canopy in the northeast (shaded) quadrant of the tree, secured to a limb 6 to 8 feet high. A higher trap, placed with a pole or attached to a loop of tree rope, might catch more moths but a lower trap is easier to secure and service.
Traps for monitoring different pest species can be hung in adjacent trees. To establish a “trapping station” within the orchard, pick a row that is marked on the edge with a utility pole or some other landmark and cluster the traps a good distance within the orchard, perhaps 10 to 15 trees.
Trap Early And Often
Different types of traps are used for monitoring different almond pests. A navel orangeworm (NOW) egg trap is a small, black plastic canister that is half filled with almond meal/almond oil bait and hung in the tree like the wing trap. The adult NOW moth lays her eggs on the surface of the canister.
To trap San Jose scale (SJS), a sticky card with a secured pheromone lure is hung at eye level well within the canopy, attached with a wire twist tie to a small limb. The trap attracts the male flyers as well as some beneficial wasps that parasitize immobile scale. The trapped SJS flyers, scale parasites and the developing NOW eggs on the egg traps are, when viewed through a hand lens, easily recognizable after you have seen them once.
Traps should be placed out in the orchard early in the season before the pests are active. The date that a trap starts catching a targeted pest is the “biofix” for that pest. Treatment timing recommendations are based on degree-day accumulations starting at the biofix, so the better you pinpoint that date, the more effective a treatment can be. Checking a trap at least twice a week to establish the biofix is recommended. Once this is established, it can be informative to continue checking the traps weekly, counting and removing moths as the season progresses, and checking more often when a new generation biofix is expected.
The grid simplifies the counting of moths when there are many in the trap. The bottom is replaced when it is full or dirty but the wing trap top should last the whole season. Counting the tiny male scale insects on a sticky card is time consuming. If the scale population is high (hundreds per card), count only those in the highlighted grid squares, estimate the total, and replace the sticky card. With the NOW egg trap, it is relatively easy to count the eggs as you remove them with a small brush or the tip of a pocket knife. Lures and bait should be replaced periodically, usually every four weeks. Neglected traps will still catch pests but the numbers can be misleading.
No Traps For Ants
A few almond pests can be monitored without traps. Two species of ants — fire ants in the south and pavement ants in the north — can damage nuts that are drying on the orchard floor at harvest time. Monitor ants by identifying and counting ant mounds between trees. Count these in the spring because ants spend the hot summer months below ground. Be aware that some ant species are beneficial. Native gray ants eat PTB larvae and other insect pests and leave almonds alone. If a pest ant population is high, treat before harvest or be prepared to limit how long the nuts dry on the orchard floor. The latter may not be possible if you practice early harvest for NOW control.
Mites are monitored starting in early summer (or earlier) by observing leaves for damaging spider mites and their predators. Pick leaves from trees on the dry orchard edges or in other known orchard hot spots. Observe both sides of the leaves with a hand lens. Often, trees can withstand some mite presence if predators are also present. Sampling protocols for mites and ants, as well as trap placement dates and treatment timings for all the major almond pests, can be found in the Almond Pest Management Guidelines at ucipm.ucdavis.edu.
A “May Spray” can be an effective treatment in almonds with the newer reduced-risk materials. Insecticide treatment decisions should be based on previous years’ harvest evaluation and mummy nut load in not only your orchard but adjacent orchards. If harvest reject levels were acceptable and mummy nuts are fewer than two per tree, treatment with insecticide might not be warranted. When treatment is necessary, timing sprays using trap catch data, shoot strike observations, and other field scouting methods can greatly increase treatment efficacy. Be aware that use of pyrethroid insecticides at this time can flare mites later and necessitate a mite treatment.