Now that Pawnees have shell hardened and we approach shell hardening on most other varieties in the next week, it is time to start thinking seriously about managing stink bugs and weevils. Prior to shell hardening these pests simply knock nuts off the trees as they feed or lay eggs. Going forward after shell hardening, they will cause damage to the nuts that you will not be able to see until you harvest.
With this in mind, a spray or two following shell hardening is advisable where these pests are a concern. Pyrethroids are the best option for these pests. Of the pyrethroids, Bifenthrin provides the best and most long-lasting control on the complex of stink bugs we generally face and will work well on weevil.
A common question is, “When should I spray?” There are pheromone lures and traps available from various suppliers like Great Lakes IPM on-line which will allow you to monitor stink bugs closely if you wish. However, it may be getting late in the season for that. Knock down sprays can help locate stink bugs and weevil but they can be time consuming and are a shot in the dark. Circle traps on the trees or tedders traps (also available from the same sources on line) in the orchard can help you monitor weevil emergence if you want to pin-point this activity.
Weevils emerge following rain when the soil is a little more soft. Heaven knows, we’ve had plenty of that and soil conditions are ripe for weevil emergence. If you have an orchard which has had weevil in the past, you need to prepare to spray when shell hardening arrives (which should be within the next week on most varieties). Though weevil are not as much of a problem in young orchards, those young orchards adjacent to older orchards or those which used to be old orchards should be monitored closely for weevil. For most situations 2-3 weevil sprays will be plenty.
Bifentrhin has the longest residual on some of our major stink bug pests and will last 10-14 days. This is very important because stink bugs are highly mobile and fly around the landscape from field to field and orchard to orchard, which is why multiple sprays (2-3) are a good idea. If you have row crops nearby, pay attention to what is going on in those crops. When cotton cuts out and bolls open, stink bugs often look for a new home. When peanuts are dug, they can attract stink bugs which will also look around for other places to go and pecan orchards are very appealing. Timing one of your orchard sprays for stink bug with these critical periods of the row crops around you is a good idea.
Aphids and mites have been relatively light to date. Most likely because of the rain. As it turns hot and dry we will likely see these pests escalate. Bifenthrin and all pyrethroids will flare aphids and mites so be prepared for these pests following your pyrethroid sprays. This is one reason I prefer to wait until as late as possible to begin spraying for weevil or stink bug. Many growers include an aphicide like imidacloprid, Carbine, or Transform in their pyrethroid spray to minimize the blow back from aphids. But, in my experience you may be just as well to spray the pyrethroid and then come back with the aphicide and/or miticide if you can get back around in time because they will be coming whether you include it in with the pyrethroid or not.