I'm curious about who here is affected by Japanese beetle, your experiences, and what strategies you use to deter them from eating all your plants. In bad Japanese beetle years, I think the phrase "You can't stop them; you can only hope to contain them" seems fitting.
The beetles have been in this area for at least 10 years, and their population has been high for maybe 5-7 years.
Here's my experience:
2011: Average beetle emergence – Fourth of July? It seemed like a particularly big year. I was working at a vineyard at the time, and within a few days of emerging, the beetles had completely covered the border rows. Their numbers were easily in the tens of thousands. We were working a few rows away, and any time we would touch a vine, the beetles would tumble off and fly in every direction. I got used to the feeling of pokey legs on my skin as the beetles fell down my shirt. Not exactly my idea of a fun time, but hey. Anyway, one particular row at the edge of the vineyard bordered a neighbor's hayfield, and that's where the damage was the worst. To me, it seems Japanese beetles tend to do the best in untilled ground (like hayfields) or fertile/irrigated grass (suburban lawns, golf courses). And they have clear preferences. It seems the more wine grape (
V. vinifera) in the plant's genetics, the better. These vines were Marechal Foch, a French hybrid, and the beetles loved them. Meanwhile, the leathery-leafed Concords were untouched. The combination of preferred plants in a border row adjacent to perfect beetle ground led to a perfect storm of beetles. At the vineyard, the strategy was simply to blast the orchard with Sevin, which created a rain of Japanese beetle carcasses. Not exactly a satisfactory approach when trying to grow healthy fruit.
Late summer/fall of 2011 was pretty dry in this area, which also happens to be when Japanese beetles are laying eggs, and larvae are feeding in the soil.
2012: Earliest beetle – June 15th, average 1-2 weeks later - the dry weather carried into spring, with below average rainfall, followed by basically no measurable rain from mid-May to mid-July. Japanese beetles were definitely present, but nowhere near previous levels. However, my observations were made about 100 miles south, and on apples, not grapes, so it’s difficult to compare. A combination of neem oil, surround coverage, and a couple sprays of PyGanic on border Honeycrisp seemed satisfactory (following Michael’s recommendations from The Holistic Orchard).
2013: Earliest beetle – June 26th – Average 2-3 weeks later – Low number of beetles, even compared to last year. Very minor damage on Honeycrisp, roses, basil, etc., but I just haven’t seen many beetles. Biweekly neem sprays, heavy surround coverage on Honeycrisp only, and a single spot spray of PyGanic on actively feeding beetles in Honeycrisp rows.
Anecdotal observations:
Drought/weather has major impacts on Japanese beetle population. I’m guessing the beetles have a difficult time emerging through dry, hard soil. During the drought, the ground here was like cement. Another effect could be desiccation of larvae and pupae in the soil, leading to fewer adults.
Border rows have the most feeding. This is especially true adjacent to hayfields, lawns, etc.
Surround is effective, but it needs to be layered and put on heavily. I totally covered the Honeycrisp trees this year (nonbearing, so didn’t need to worry about washing residues off), and I observed Japanese beetles walking sluggishly, not feeding, just sitting there, and reluctant to fly away unless I touched them (this is at all times of the day, so it’s not just their normal morning sluggishness).
Neem may have repellent/deterrent effects, but it’s difficult to measure. Sluggishness could be related to ingesting neem too. PyGanic seems to work fairly well for spot spraying border rows and preferred varieties, but I wouldn’t want to overuse it. I think it’s important to kill “clusters” of feeding beetles, otherwise they will attract more and defoliate individual trees, which can be a big setback.
I’d really like to see how the organic/holistic methods will do in a bad year for Japanese beetles, but for now, I’m counting myself lucky.
Anyone else have experiences with this bug?