The natural enemy of my enemy is my friend! We start seeing increased activity of beneficial insects this time of year. Everyone can identify a ladybug, a select few know what a lacewing looks like, but did you know that certain flies, beetles, and even yellowjackets also help to regulate pest populations?
CLICK TO VIEW a newly revised OSU Extension publication about natural enemies
Three years ago, my field season was so affected by yellowjackets (FIG. 1) that I decided to find out what I could learn about them. Their abundance, activity, what influences populations, etc. It was actually harder than I thought to find information! This was noted by a 2018 paper , where the team investigated 908 published papers over almost 40 years and yep – less than 3% of them were wasp-related (FIG. 2).
“Despite the importance of both taxa, bees are universally loved whilst wasps are universally despised.”
Some growers tend to think of birds as chronic annoyances. Solutions range from preventative tactics (netting and birddogs) to scare tactics such as artificial predator calls and driving around the farm firing empty shells at murders – sound familiar?
But a new study suggests that certain birds can – and should – be welcomed as a part of an overall sustainable farming strategy. The link below explains:
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Notable trends during the week of June 24th include:
Cabbage Looper moth counts continue to be extremely high, we are likely seeing the 2nd generation, which is considered the most damaging for brassica crops.
Armyworms have wide host ranges but can be especially damaging in grasses, pastures, and field crops.
One species, in particular, seems to be booming this year. It is called the “Thoughtful Apamea“, which is closely related to glassy cutworm, but habits and host range are largely unknown.
Conversely, True Armyworm is well-studied and we have been collaborating on a project to monitor them in Tillamook County. So far, counts are low, but if you’re interested, trap counts will always be posted here: https://beav.es/ZQM
Beneficial Insects include pollinators, predators, and parasitoids that provide some type of ecosystem service. As natural enemies of pests, their activity tends to lag slightly. We have noted an increase in Syrphidae and Tachinidae flies this week, as monitored by passive sampling techniques.
ANSWER: A lady beetle pupa, which is the life stage between larva and adult. Ladybug pupae affix themselves to a leaf surface to complete development. Do not try to control them – these are good guys!
All this talk about crop PEST insects should not go unaccompanied by at least a brief mention and applaud for those silent heroes, the BENEFICIALS!
Biological control by generalist predators can be quite effective at mitigating pest insect populations, depending on the circumstance.
Two of the most common predators that we see in vegetable crops are ladybird beetles (ladybugs) and lacewings. I decided to track activity of these two groups this year, just to see if any activity patterns would be evident.
Ladybugs and lacewings can be passively sampled with yellow sticky traps. Although, for a more detailed study, one would want to incorporate sweep net sampling, increase trap numbers per acre, etc.
The convergent lady beetle (Hippodamia convergens) is a native species. They overwinter as adults, mate, and then lay eggs in the spring. A study from Corvallis using field-collected H. convergens found that 228 growing degree-days (above a threshold) are required for development from egg to adult, and that this heat-unit requirement is rather consistent throughout North American populations (Miller 1992 Env. Ent. 21).
These graphs show a clear pattern of increased ladybug activity (adults on sticky cards) beginning around late June-early July. Sure enough, the increase correlates with published heat-unit requirements, and is confirmed by a degree-day model and online phenology tool (uspest.org, check it out!)
Cool! But what does all this mean? Well, it suggests that passive sampling is a good way to estimate ladybug phenology, and could provide us with comparative data on predator activity differences between years.
Perhaps more importantly: recognize that while it takes ~230GDD to detect ADULT ladybugs, the larvae are predacious too and have been busy in your fields and gardens all spring!!