Potato Grower

November 2017

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WWW.POTATOGROWER.COM 37 beetles becomes questionable, starving them to death may be another option. Obviously, I do not advocate that potato farmers switch to growing something else. Potato is the most nutritionally valuable staple crop grown by humans, and I have dedicated most of my career to finding better ways to protect it from insect pests. One way to make beetles hungry is to make potato plants inedible to them. Unfortunately, as mentioned above, breeding attempts carried out in this direction have been largely unsuccessful. One big challenge is that potato tuber is a modified potato stem. Therefore, changing stems (and the leaves they carry) to make them inedible to beetles while keeping tubers edible to humans is a challenge. Another approach to inducing starvation in Colorado potato beetles is moving food away from them. Temporary food withdrawal in the form of crop rotations has been repeatedly shown to be useful in reducing beetle populations. When the need arises, Colorado potato beetles can be highly mobile and fly over long distances. Nevertheless, although some of them will eventually find a rotated field, most will not. The ones that will are likely to be delayed in the onset of feeding and laying eggs compared to the beetles that simply need to re-emerge within the previous year's crop. Interestingly, our recent study shows that Colorado potato beetles that are deprived of food and water turn on each other, start fighting, and eventually cannibalize weaker and smaller individuals in the group. It has been long known that larvae in this species cannibalize eggs. Furthermore, female beetles often lay special non-viable eggs that are specifically designated as food for neonate larvae hatching from viable eggs. However, we demonstrated that when faced with starvation, adults also resort to cannibalism. Under natural conditions, this potentially means an additional source of mortality for the beetles that find themselves on rotated fields planted to unsuitable crops. Not only will they deplete their energy reserves in the often futile search for edible host plants, they can also be devoured by larger and more aggressive members of their own species. It is tempting to envision a world where desperate hordes of hungry Colorado potato beetle cannibals roam post- Magnesium (Mg) 11% Intrepid Trio ® boosts yield and avoids magnesium deficiency caused by high rates of potassium and ammonium- nitrogen fertilizers. Sulfur (S) as Sulfate 22% Intrepid Trio ® provides sulfate in a 100% readily available, pH neutral form to boost disease resistance and improve nitrogen use efficiency. Potassium (K 2 O) 22% Intrepid Trio ® granules deliver sustained, low-chloride potassium to prevent blackspot bruising, moisture loss and disease. Intrepid Trio ® is 100% natural langbeinite, a unique mineral with three essential nutrients in every granule. Trio readily dissolves in the soil for sustained plant nutrition. Make Trio part of your perfectly balanced potato fertilizer program. Call us at 1.800.451.2888 or learn more at info.intrepidTRIO.com Essential Minerals for Success BY INTREPID Naturally Balanced Nutrition in Every Granule 168930IntPot12v.indd 1 9/8/17 9:44 AM apocalyptic landscapes of current-season barley fields, while lush, green, undamaged potato crops are blossoming on rotated fields nearby. Unfortunately, such a fantasy world is unlikely to materialize. While reducing overall beetle numbers, cannibalism will actually help the largest and strongest of them to survive and eventually migrate to potato fields. With a single Colorado potato beetle females producing 600 or more eggs, subsequent perpetuation of the species is very likely. Throughout my career as an applied agricultural entomologist, I have often encountered an expectation that either I, or my more intelligent and hardworking colleagues, ought to discover a silver-bullet solution to a particular insect problem. The entire history of Colorado potato beetle control proves that such an expectation is often unrealistic, at least in the medium- to long-term. It also highlights the importance of practicing integrated pest management. While neither insecticides nor crop rotation will solve the beetle problem once and for all, their combined use is likely to provide more sustainable crop protection compared to each technique used alone.

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