Pest Management

Colorado potato beetle adult and eggs

 

Colorado Potato Beetle Larvae.

 

Citrus Red Mite

 

 Lemon fruit distortion caused by the Citrus Bud Mite 

 

My approach toward pest management follows from my interest in quantifying the impact of herbivorous insects on plant fitness. The first step toward managing a pest is to know when pest populations cause significant economic reductions in crop value. My early work in this area was on the Colorado potato beetle in New England. I was among the first to show seasonal variation in the sensitivity of potato plants to defoliation and when the need for pest suppression was most critical. After assuming my position at UC Riverside, I applied the same approach toward developing realistic economic treatment thresholds for two mite pests of citrus, the Citrus red mite, and the Citrus bud mite.

In the first case, there is no density of Citrus red mites that causes significant economic loss if the trees are well managed. The Citrus red mite can cause some fruit abortion early in their development and reduce total yield. However, such fruit thinning often is beneficial economically, for the remaining fruit often grow to a larger size. The price structure of fresh-market citrus favors larger fruit, thus, the economic effect of increased fruit size often offsets the effect of reduced yield. Trees where Citrus red mite populations were suppressed often had lower crop values than trees where Citrus red mite populations were unmanged. These results greatly improved the management of citrus pests because growers save about $250 per acre in pesticide costs. The reduction in pesticide applications also indirectly benefits the management of other citrus pests by preserving populations of beneficial species.

For the Citrus bud mite the oil sprays that are used to suppress mite populations caused greater reductions in crop value than the mites did. This probably was the result of fruit abortion after oil sprays were applied. Once again, aggressive pest management not only was unnecessary, but actually reduced crop value.

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