Resistance in fall armyworm (Spodoptera frugiperda) populations from Puerto Rico to transgenic corn producing the Cry1Fa insecticidal protein resulted, for the first time in the United States, in practical resistance, and BT corn was withdrawn from the local market. The development of resistance to these insecticidal proteins is considered the most serious threat to the sustainability of BT crops. I would suggest that for armyworm you follow the minimum application intervals.Ĭould armyworm have developed a certain level of resistance to BT’s? I found this extract below There may be a scientific reason for this. Purely from observation I believe this sucker is harder to kill. However, the control it has on armyworm is much harder to evaluate. I understand there are several species of armyworm, but I believe this is the tropical armyworm.īacillus Thuringiensis (BT’s) have always controlled green cabbage caterpillars superbly. Army worm, in my experience, are much harder to control. Historically green cabbage caterpillars predominantly cause the most damage but this year I have noticed a lot more destruction from armyworm on multiple sites geographically far apart. If I see one caterpillar, I immediately activate a plan of action, with the appropriate tools. As an advisor I can only react to the problem, and the degree of the issue, once it is visible.

I am sure there is an explanation as to why some years it appears worse than others (see link 2 below). Predicting the amount of butterfly and moth pressure, that will enter your glasshouse, and the various locations is far harder to predict each year. Predicting the presence of caterpillars in glasshouse crops, at this time of the year, is normal.

I don’t recall, twelve months ago, caterpillars being as invasive. In March 2019 I published an article, when caterpillars were equally as difficult to control (see link 1 below to read the article again). Chewing their way through cucumber and tomato cropsĬaterpillars are back and causing damage to crops.

Download armyworm caterpillars